1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
use indexmap::IndexMap;
/// the compose module allows construction of shaders from modules (which are themselves shaders).
///
/// it does this by treating shaders as modules, and
/// - building each module independently to naga IR
/// - creating "header" files for each supported language, which are used to build dependent modules/shaders
/// - making final shaders by combining the shader IR with the IR for imported modules
///
/// for multiple small shaders with large common imports, this can be faster than parsing the full source for each shader, and it allows for constructing shaders in a cleaner modular manner with better scope control.
///
/// ## imports
///
/// shaders can be added to the composer as modules. this makes their types, constants, variables and functions available to modules/shaders that import them. note that importing a module will affect the final shader's global state if the module defines globals variables with bindings.
///
/// modules must include a `#define_import_path` directive that names the module.
///
/// ```ignore
/// #define_import_path my_module
///
/// fn my_func() -> f32 {
///     return 1.0;
/// }
/// ```
///
/// shaders can then import the module with an `#import` directive (with an optional `as` name). at point of use, imported items must be qualified:
///
/// ```ignore
/// #import my_module
/// #import my_other_module as Mod2
///
/// fn main() -> f32 {
///     let x = my_module::my_func();
///     let y = Mod2::my_other_func();
///     return x*y;
/// }
/// ```
///
/// or import a comma-separated list of individual items with a `#from` directive. at point of use, imported items must be prefixed with `::` :
///
/// ```ignore
/// #from my_module import my_func, my_const
///
/// fn main() -> f32 {
///     return ::my_func(::my_const);
/// }
/// ```
///
/// imports can be nested - modules may import other modules, but not recursively. when a new module is added, all its `#import`s must already have been added.
/// the same module can be imported multiple times by different modules in the import tree.
/// there is no overlap of namespaces, so the same function names (or type, constant, or variable names) may be used in different modules.
///
/// note: when importing an item with the `#from` directive, the final shader will include the required dependencies (bindings, globals, consts, other functions) of the imported item, but will not include the rest of the imported module. it will however still include all of any modules imported by the imported module. this is probably not desired in general and may be fixed in a future version. currently for a more complete culling of unused dependencies the `prune` module can be used.
///
/// ## overriding functions
///
/// virtual functions can be declared with the `virtual` keyword:
/// ```ignore
/// virtual fn point_light(world_position: vec3<f32>) -> vec3<f32> { ... }
/// ```
/// virtual functions defined in imported modules can then be overridden using the `override` keyword:
///
/// ```ignore
/// #import bevy_pbr::lighting as Lighting
///
/// override fn Lighting::point_light (world_position: vec3<f32>) -> vec3<f32> {
///     let original = Lighting::point_light(world_position);
///     let quantized = vec3<u32>(original * 3.0);
///     return vec3<f32>(quantized) / 3.0;
/// }
/// ```
///
/// override function definitions cause *all* calls to the original function in the entire shader scope to be replaced by calls to the new function, with the exception of calls within the override function itself.
///
/// the function signature of the override must match the base function.
///
/// overrides can be specified at any point in the final shader's import tree.
///
/// multiple overrides can be applied to the same function. for example, given :
/// - a module `a` containing a function `f`,
/// - a module `b` that imports `a`, and containing an `override a::f` function,
/// - a module `c` that imports `a` and `b`, and containing an `override a::f` function,
/// then b and c both specify an override for `a::f`.
/// the `override fn a::f` declared in module `b` may call to `a::f` within its body.
/// the `override fn a::f` declared in module 'c' may call to `a::f` within its body, but the call will be redirected to `b::f`.
/// any other calls to `a::f` (within modules 'a' or `b`, or anywhere else) will end up redirected to `c::f`
/// in this way a chain or stack of overrides can be applied.
///
/// different overrides of the same function can be specified in different import branches. the final stack will be ordered based on the first occurrence of the override in the import tree (using a depth first search).
///
/// note that imports into a module/shader are processed in order, but are processed before the body of the current shader/module regardless of where they occur in that module, so there is no way to import a module containing an override and inject a call into the override stack prior to that imported override. you can instead create two modules each containing an override and import them into a parent module/shader to order them as required.
/// override functions can currently only be defined in wgsl.
///
/// if the `override_any` crate feature is enabled, then the `virtual` keyword is not required for the function being overridden.
///
/// ## languages
///
/// modules can we written in GLSL or WGSL. shaders with entry points can be imported as modules (provided they have a `#define_import_path` directive). entry points are available to call from imported modules either via their name (for WGSL) or via `module::main` (for GLSL).
///
/// final shaders can also be written in GLSL or WGSL. for GLSL users must specify whether the shader is a vertex shader or fragment shader via the `ShaderType` argument (GLSL compute shaders are not supported).
///
/// ## preprocessing
///
/// when generating a final shader or adding a composable module, a set of `shader_def` string/value pairs must be provided. The value can be a bool (`ShaderDefValue::Bool`), an i32 (`ShaderDefValue::Int`) or a u32 (`ShaderDefValue::UInt`).
///
/// these allow conditional compilation of parts of modules and the final shader. conditional compilation is performed with `#if` / `#ifdef` / `#ifndef`, `#else` and `#endif` preprocessor directives:
///
/// ```ignore
/// fn get_number() -> f32 {
///     #ifdef BIG_NUMBER
///         return 999.0;
///     #else
///         return 0.999;
///     #endif
/// }
/// ```
/// the `#ifdef` directive matches when the def name exists in the input binding set (regardless of value). the `#ifndef` directive is the reverse.
///
/// the `#if` directive requires a def name, an operator, and a value for comparison:
/// - the def name must be a provided `shader_def` name.
/// - the operator must be one of `==`, `!=`, `>=`, `>`, `<`, `<=`
/// - the value must be an integer literal if comparing to a `ShaderDef::Int`, or `true` or `false` if comparing to a `ShaderDef::Bool`.
///
/// shader defs can also be used in the shader source with `#SHADER_DEF` or `#{SHADER_DEF}`, and will be substituted for their value.
///
/// ## error reporting
///
/// codespan reporting for errors is available using the error `emit_to_string` method. this requires validation to be enabled, which is true by default. `Composer::non_validating()` produces a non-validating composer that is not able to give accurate error reporting.
///
use naga::EntryPoint;
use regex::Regex;
use std::collections::{hash_map::Entry, BTreeMap, HashMap, HashSet};
use tracing::{debug, trace};

use crate::{
    compose::preprocess::{PreprocessOutput, PreprocessorMetaData},
    derive::DerivedModule,
    redirect::Redirector,
};

pub use self::error::{ComposerError, ComposerErrorInner, ErrSource};
use self::preprocess::Preprocessor;

pub mod comment_strip_iter;
pub mod error;
pub mod parse_imports;
pub mod preprocess;
mod test;
pub mod tokenizer;
pub mod util;

#[derive(Hash, PartialEq, Eq, Clone, Copy, Debug, Default)]
pub enum ShaderLanguage {
    #[default]
    Wgsl,
    #[cfg(feature = "glsl")]
    Glsl,
}

#[derive(Hash, PartialEq, Eq, Clone, Copy, Debug, Default)]
pub enum ShaderType {
    #[default]
    Wgsl,
    #[cfg(feature = "glsl")]
    GlslVertex,
    #[cfg(feature = "glsl")]
    GlslFragment,
}

impl From<ShaderType> for ShaderLanguage {
    fn from(ty: ShaderType) -> Self {
        match ty {
            ShaderType::Wgsl => ShaderLanguage::Wgsl,
            #[cfg(feature = "glsl")]
            ShaderType::GlslVertex | ShaderType::GlslFragment => ShaderLanguage::Glsl,
        }
    }
}

#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
pub enum ShaderDefValue {
    Bool(bool),
    Int(i32),
    UInt(u32),
}

impl Default for ShaderDefValue {
    fn default() -> Self {
        ShaderDefValue::Bool(true)
    }
}

impl ShaderDefValue {
    fn value_as_string(&self) -> String {
        match self {
            ShaderDefValue::Bool(val) => val.to_string(),
            ShaderDefValue::Int(val) => val.to_string(),
            ShaderDefValue::UInt(val) => val.to_string(),
        }
    }
}

#[derive(Clone, PartialEq, Eq, Hash, Debug, Default)]
pub struct OwnedShaderDefs(BTreeMap<String, ShaderDefValue>);

#[derive(Clone, PartialEq, Eq, Hash, Debug)]
struct ModuleKey(OwnedShaderDefs);

impl ModuleKey {
    fn from_members(key: &HashMap<String, ShaderDefValue>, universe: &[String]) -> Self {
        let mut acc = OwnedShaderDefs::default();
        for item in universe {
            if let Some(value) = key.get(item) {
                acc.0.insert(item.to_owned(), *value);
            }
        }
        ModuleKey(acc)
    }
}

// a module built with a specific set of shader_defs
#[derive(Default, Debug)]
pub struct ComposableModule {
    // module decoration, prefixed to all items from this module in the final source
    pub decorated_name: String,
    // module names required as imports, optionally with a list of items to import
    pub imports: Vec<ImportDefinition>,
    // types exported
    pub owned_types: HashSet<String>,
    // constants exported
    pub owned_constants: HashSet<String>,
    // vars exported
    pub owned_vars: HashSet<String>,
    // functions exported
    pub owned_functions: HashSet<String>,
    // local functions that can be overridden
    pub virtual_functions: HashSet<String>,
    // overriding functions defined in this module
    // target function -> Vec<replacement functions>
    pub override_functions: IndexMap<String, Vec<String>>,
    // naga module, built against headers for any imports
    module_ir: naga::Module,
    // headers in different shader languages, used for building modules/shaders that import this module
    // headers contain types, constants, global vars and empty function definitions -
    // just enough to convert source strings that want to import this module into naga IR
    // headers: HashMap<ShaderLanguage, String>,
    header_ir: naga::Module,
    // character offset of the start of the owned module string
    start_offset: usize,
}

// data used to build a ComposableModule
#[derive(Debug)]
pub struct ComposableModuleDefinition {
    pub name: String,
    // shader text (with auto bindings replaced - we do this on module add as we only want to do it once to avoid burning slots)
    pub sanitized_source: String,
    // language
    pub language: ShaderLanguage,
    // source path for error display
    pub file_path: String,
    // shader def values bound to this module
    pub shader_defs: HashMap<String, ShaderDefValue>,
    // list of shader_defs that can affect this module
    effective_defs: Vec<String>,
    // full list of possible imports (regardless of shader_def configuration)
    all_imports: HashSet<String>,
    // additional imports to add (as though they were included in the source after any other imports)
    additional_imports: Vec<ImportDefinition>,
    // built composable modules for a given set of shader defs
    modules: HashMap<ModuleKey, ComposableModule>,
    // used in spans when this module is included
    module_index: usize,
    // preprocessor meta data
    // metadata: PreprocessorMetaData,
}

impl ComposableModuleDefinition {
    fn get_module(
        &self,
        shader_defs: &HashMap<String, ShaderDefValue>,
    ) -> Option<&ComposableModule> {
        self.modules
            .get(&ModuleKey::from_members(shader_defs, &self.effective_defs))
    }

    fn insert_module(
        &mut self,
        shader_defs: &HashMap<String, ShaderDefValue>,
        module: ComposableModule,
    ) -> &ComposableModule {
        match self
            .modules
            .entry(ModuleKey::from_members(shader_defs, &self.effective_defs))
        {
            Entry::Occupied(_) => panic!("entry already populated"),
            Entry::Vacant(v) => v.insert(module),
        }
    }
}

#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct ImportDefinition {
    pub import: String,
    pub items: Vec<String>,
}

#[derive(Debug, Clone)]
pub struct ImportDefWithOffset {
    definition: ImportDefinition,
    offset: usize,
}

/// module composer.
/// stores any modules that can be imported into a shader
/// and builds the final shader
#[derive(Debug)]
pub struct Composer {
    pub validate: bool,
    pub module_sets: HashMap<String, ComposableModuleDefinition>,
    pub module_index: HashMap<usize, String>,
    pub capabilities: naga::valid::Capabilities,
    preprocessor: Preprocessor,
    check_decoration_regex: Regex,
    undecorate_regex: Regex,
    virtual_fn_regex: Regex,
    override_fn_regex: Regex,
    undecorate_override_regex: Regex,
    auto_binding_regex: Regex,
    auto_binding_index: u32,
}

// shift for module index
// 21 gives
//   max size for shader of 2m characters
//   max 2048 modules
const SPAN_SHIFT: usize = 21;

impl Default for Composer {
    fn default() -> Self {
        Self {
            validate: true,
            capabilities: Default::default(),
            module_sets: Default::default(),
            module_index: Default::default(),
            preprocessor: Preprocessor::default(),
            check_decoration_regex: Regex::new(
                format!(
                    "({}|{})",
                    regex_syntax::escape(DECORATION_PRE),
                    regex_syntax::escape(DECORATION_OVERRIDE_PRE)
                )
                .as_str(),
            )
            .unwrap(),
            undecorate_regex: Regex::new(
                format!(
                    r"(\x1B\[\d+\w)?([\w\d_]+){}([A-Z0-9]*){}",
                    regex_syntax::escape(DECORATION_PRE),
                    regex_syntax::escape(DECORATION_POST)
                )
                .as_str(),
            )
            .unwrap(),
            virtual_fn_regex: Regex::new(
                r"(?P<lead>[\s]*virtual\s+fn\s+)(?P<function>[^\s]+)(?P<trail>\s*)\(",
            )
            .unwrap(),
            override_fn_regex: Regex::new(
                format!(
                    r"(override\s+fn\s+)([^\s]+){}([\w\d]+){}(\s*)\(",
                    regex_syntax::escape(DECORATION_PRE),
                    regex_syntax::escape(DECORATION_POST)
                )
                .as_str(),
            )
            .unwrap(),
            undecorate_override_regex: Regex::new(
                format!(
                    "{}([A-Z0-9]*){}",
                    regex_syntax::escape(DECORATION_OVERRIDE_PRE),
                    regex_syntax::escape(DECORATION_POST)
                )
                .as_str(),
            )
            .unwrap(),
            auto_binding_regex: Regex::new(r"@binding\(auto\)").unwrap(),
            auto_binding_index: 0,
        }
    }
}

const DECORATION_PRE: &str = "X_naga_oil_mod_X";
const DECORATION_POST: &str = "X";

// must be same length as DECORATION_PRE for spans to work
const DECORATION_OVERRIDE_PRE: &str = "X_naga_oil_vrt_X";

struct IrBuildResult {
    module: naga::Module,
    start_offset: usize,
    override_functions: IndexMap<String, Vec<String>>,
}

impl Composer {
    pub fn decorated_name(module_name: Option<&str>, item_name: &str) -> String {
        match module_name {
            Some(module_name) => format!("{}{}", item_name, Self::decorate(module_name)),
            None => item_name.to_owned(),
        }
    }

    fn decorate(module: &str) -> String {
        let encoded = data_encoding::BASE32_NOPAD.encode(module.as_bytes());
        format!("{DECORATION_PRE}{encoded}{DECORATION_POST}")
    }

    fn decode(from: &str) -> String {
        String::from_utf8(data_encoding::BASE32_NOPAD.decode(from.as_bytes()).unwrap()).unwrap()
    }

    fn undecorate(&self, string: &str) -> String {
        let undecor = self
            .undecorate_regex
            .replace_all(string, |caps: &regex::Captures| {
                format!(
                    "{}{}::{}",
                    caps.get(1).map(|cc| cc.as_str()).unwrap_or(""),
                    Self::decode(caps.get(3).unwrap().as_str()),
                    caps.get(2).unwrap().as_str()
                )
            });

        let undecor =
            self.undecorate_override_regex
                .replace_all(&undecor, |caps: &regex::Captures| {
                    format!(
                        "override fn {}::",
                        Self::decode(caps.get(1).unwrap().as_str())
                    )
                });

        undecor.to_string()
    }

    fn sanitize_and_set_auto_bindings(&mut self, source: &str) -> String {
        let mut substituted_source = source.replace("\r\n", "\n").replace('\r', "\n");
        if !substituted_source.ends_with('\n') {
            substituted_source.push('\n');
        }

        // replace @binding(auto) with an incrementing index
        struct AutoBindingReplacer<'a> {
            auto: &'a mut u32,
        }

        impl<'a> regex::Replacer for AutoBindingReplacer<'a> {
            fn replace_append(&mut self, _: &regex::Captures<'_>, dst: &mut String) {
                dst.push_str(&format!("@binding({})", self.auto));
                *self.auto += 1;
            }
        }

        let substituted_source = self.auto_binding_regex.replace_all(
            &substituted_source,
            AutoBindingReplacer {
                auto: &mut self.auto_binding_index,
            },
        );

        substituted_source.into_owned()
    }

    fn naga_to_string(
        &self,
        naga_module: &mut naga::Module,
        language: ShaderLanguage,
        #[allow(unused)] header_for: &str, // Only used when GLSL is enabled
    ) -> Result<String, ComposerErrorInner> {
        // TODO: cache headers again
        let info =
            naga::valid::Validator::new(naga::valid::ValidationFlags::all(), self.capabilities)
                .validate(naga_module)
                .map_err(ComposerErrorInner::HeaderValidationError)?;

        match language {
            ShaderLanguage::Wgsl => naga::back::wgsl::write_string(
                naga_module,
                &info,
                naga::back::wgsl::WriterFlags::EXPLICIT_TYPES,
            )
            .map_err(ComposerErrorInner::WgslBackError),
            #[cfg(feature = "glsl")]
            ShaderLanguage::Glsl => {
                let vec4 = naga_module.types.insert(
                    naga::Type {
                        name: None,
                        inner: naga::TypeInner::Vector {
                            size: naga::VectorSize::Quad,
                            scalar: naga::Scalar::F32,
                        },
                    },
                    naga::Span::UNDEFINED,
                );
                // add a dummy entry point for glsl headers
                let dummy_entry_point = "dummy_module_entry_point".to_owned();
                let func = naga::Function {
                    name: Some(dummy_entry_point.clone()),
                    arguments: Default::default(),
                    result: Some(naga::FunctionResult {
                        ty: vec4,
                        binding: Some(naga::Binding::BuiltIn(naga::BuiltIn::Position {
                            invariant: false,
                        })),
                    }),
                    local_variables: Default::default(),
                    expressions: Default::default(),
                    named_expressions: Default::default(),
                    body: Default::default(),
                };
                let ep = EntryPoint {
                    name: dummy_entry_point.clone(),
                    stage: naga::ShaderStage::Vertex,
                    function: func,
                    early_depth_test: None,
                    workgroup_size: [0, 0, 0],
                };

                naga_module.entry_points.push(ep);

                let info = naga::valid::Validator::new(
                    naga::valid::ValidationFlags::all(),
                    self.capabilities,
                )
                .validate(naga_module)
                .map_err(ComposerErrorInner::HeaderValidationError)?;

                let mut string = String::new();
                let options = naga::back::glsl::Options {
                    version: naga::back::glsl::Version::Desktop(450),
                    writer_flags: naga::back::glsl::WriterFlags::INCLUDE_UNUSED_ITEMS,
                    ..Default::default()
                };
                let pipeline_options = naga::back::glsl::PipelineOptions {
                    shader_stage: naga::ShaderStage::Vertex,
                    entry_point: dummy_entry_point,
                    multiview: None,
                };
                let mut writer = naga::back::glsl::Writer::new(
                    &mut string,
                    naga_module,
                    &info,
                    &options,
                    &pipeline_options,
                    naga::proc::BoundsCheckPolicies::default(),
                )
                .map_err(ComposerErrorInner::GlslBackError)?;

                writer.write().map_err(ComposerErrorInner::GlslBackError)?;

                // strip version decl and main() impl
                let lines: Vec<_> = string.lines().collect();
                let string = lines[1..lines.len() - 3].join("\n");
                trace!("glsl header for {}:\n\"\n{:?}\n\"", header_for, string);

                Ok(string)
            }
        }
    }

    // build naga module for a given shader_def configuration. builds a minimal self-contained module built against headers for imports
    fn create_module_ir(
        &self,
        name: &str,
        source: String,
        language: ShaderLanguage,
        imports: &[ImportDefinition],
        shader_defs: &HashMap<String, ShaderDefValue>,
    ) -> Result<IrBuildResult, ComposerError> {
        debug!("creating IR for {} with defs: {:?}", name, shader_defs);

        let mut module_string = match language {
            ShaderLanguage::Wgsl => String::new(),
            #[cfg(feature = "glsl")]
            ShaderLanguage::Glsl => String::from("#version 450\n"),
        };

        let mut override_functions: IndexMap<String, Vec<String>> = IndexMap::default();
        let mut added_imports: HashSet<String> = HashSet::new();
        let mut header_module = DerivedModule::default();

        for import in imports {
            if added_imports.contains(&import.import) {
                continue;
            }
            // add to header module
            self.add_import(
                &mut header_module,
                import,
                shader_defs,
                true,
                &mut added_imports,
            );

            // // we must have ensured these exist with Composer::ensure_imports()
            trace!("looking for {}", import.import);
            let import_module_set = self.module_sets.get(&import.import).unwrap();
            trace!("with defs {:?}", shader_defs);
            let module = import_module_set.get_module(shader_defs).unwrap();
            trace!("ok");

            // gather overrides
            if !module.override_functions.is_empty() {
                for (original, replacements) in &module.override_functions {
                    match override_functions.entry(original.clone()) {
                        indexmap::map::Entry::Occupied(o) => {
                            let existing = o.into_mut();
                            let new_replacements: Vec<_> = replacements
                                .iter()
                                .filter(|rep| !existing.contains(rep))
                                .cloned()
                                .collect();
                            existing.extend(new_replacements);
                        }
                        indexmap::map::Entry::Vacant(v) => {
                            v.insert(replacements.clone());
                        }
                    }
                }
            }
        }

        let composed_header = self
            .naga_to_string(&mut header_module.into(), language, name)
            .map_err(|inner| ComposerError {
                inner,
                source: ErrSource::Module {
                    name: name.to_owned(),
                    offset: 0,
                    defs: shader_defs.clone(),
                },
            })?;
        module_string.push_str(&composed_header);

        let start_offset = module_string.len();

        module_string.push_str(&source);

        trace!(
            "parsing {}: {}, header len {}, total len {}",
            name,
            module_string,
            start_offset,
            module_string.len()
        );
        let module = match language {
            ShaderLanguage::Wgsl => naga::front::wgsl::parse_str(&module_string).map_err(|e| {
                debug!("full err'd source file: \n---\n{}\n---", module_string);
                ComposerError {
                    inner: ComposerErrorInner::WgslParseError(e),
                    source: ErrSource::Module {
                        name: name.to_owned(),
                        offset: start_offset,
                        defs: shader_defs.clone(),
                    },
                }
            })?,
            #[cfg(feature = "glsl")]
            ShaderLanguage::Glsl => naga::front::glsl::Frontend::default()
                .parse(
                    &naga::front::glsl::Options {
                        stage: naga::ShaderStage::Vertex,
                        defines: Default::default(),
                    },
                    &module_string,
                )
                .map_err(|e| {
                    debug!("full err'd source file: \n---\n{}\n---", module_string);
                    ComposerError {
                        inner: ComposerErrorInner::GlslParseError(e),
                        source: ErrSource::Module {
                            name: name.to_owned(),
                            offset: start_offset,
                            defs: shader_defs.clone(),
                        },
                    }
                })?,
        };

        Ok(IrBuildResult {
            module,
            start_offset,
            override_functions,
        })
    }

    // check that identifiers exported by a module do not get modified in string export
    fn validate_identifiers(
        source_ir: &naga::Module,
        lang: ShaderLanguage,
        header: &str,
        module_decoration: &str,
        owned_types: &HashSet<String>,
    ) -> Result<(), ComposerErrorInner> {
        // TODO: remove this once glsl front support is complete
        #[cfg(feature = "glsl")]
        if lang == ShaderLanguage::Glsl {
            return Ok(());
        }

        let recompiled = match lang {
            ShaderLanguage::Wgsl => naga::front::wgsl::parse_str(header).unwrap(),
            #[cfg(feature = "glsl")]
            ShaderLanguage::Glsl => naga::front::glsl::Frontend::default()
                .parse(
                    &naga::front::glsl::Options {
                        stage: naga::ShaderStage::Vertex,
                        defines: Default::default(),
                    },
                    &format!("{}\n{}", header, "void main() {}"),
                )
                .map_err(|e| {
                    debug!("full err'd source file: \n---\n{header}\n---");
                    ComposerErrorInner::GlslParseError(e)
                })?,
        };

        let recompiled_types: IndexMap<_, _> = recompiled
            .types
            .iter()
            .flat_map(|(h, ty)| ty.name.as_deref().map(|name| (name, h)))
            .collect();
        for (h, ty) in source_ir.types.iter() {
            if let Some(name) = &ty.name {
                let decorated_type_name = format!("{name}{module_decoration}");
                if !owned_types.contains(&decorated_type_name) {
                    continue;
                }
                match recompiled_types.get(decorated_type_name.as_str()) {
                    Some(recompiled_h) => {
                        if let naga::TypeInner::Struct { members, .. } = &ty.inner {
                            let recompiled_ty = recompiled.types.get_handle(*recompiled_h).unwrap();
                            let naga::TypeInner::Struct {
                                members: recompiled_members,
                                ..
                            } = &recompiled_ty.inner
                            else {
                                panic!();
                            };
                            for (member, recompiled_member) in
                                members.iter().zip(recompiled_members)
                            {
                                if member.name != recompiled_member.name {
                                    return Err(ComposerErrorInner::InvalidIdentifier {
                                        original: member.name.clone().unwrap_or_default(),
                                        at: source_ir.types.get_span(h),
                                    });
                                }
                            }
                        }
                    }
                    None => {
                        return Err(ComposerErrorInner::InvalidIdentifier {
                            original: name.clone(),
                            at: source_ir.types.get_span(h),
                        })
                    }
                }
            }
        }

        let recompiled_consts: HashSet<_> = recompiled
            .constants
            .iter()
            .flat_map(|(_, c)| c.name.as_deref())
            .filter(|name| name.ends_with(module_decoration))
            .collect();
        for (h, c) in source_ir.constants.iter() {
            if let Some(name) = &c.name {
                if name.ends_with(module_decoration) && !recompiled_consts.contains(name.as_str()) {
                    return Err(ComposerErrorInner::InvalidIdentifier {
                        original: name.clone(),
                        at: source_ir.constants.get_span(h),
                    });
                }
            }
        }

        let recompiled_globals: HashSet<_> = recompiled
            .global_variables
            .iter()
            .flat_map(|(_, c)| c.name.as_deref())
            .filter(|name| name.ends_with(module_decoration))
            .collect();
        for (h, gv) in source_ir.global_variables.iter() {
            if let Some(name) = &gv.name {
                if name.ends_with(module_decoration) && !recompiled_globals.contains(name.as_str())
                {
                    return Err(ComposerErrorInner::InvalidIdentifier {
                        original: name.clone(),
                        at: source_ir.global_variables.get_span(h),
                    });
                }
            }
        }

        let recompiled_fns: HashSet<_> = recompiled
            .functions
            .iter()
            .flat_map(|(_, c)| c.name.as_deref())
            .filter(|name| name.ends_with(module_decoration))
            .collect();
        for (h, f) in source_ir.functions.iter() {
            if let Some(name) = &f.name {
                if name.ends_with(module_decoration) && !recompiled_fns.contains(name.as_str()) {
                    return Err(ComposerErrorInner::InvalidIdentifier {
                        original: name.clone(),
                        at: source_ir.functions.get_span(h),
                    });
                }
            }
        }

        Ok(())
    }

    // build a ComposableModule from a ComposableModuleDefinition, for a given set of shader defs
    // - build the naga IR (against headers)
    // - record any types/vars/constants/functions that are defined within this module
    // - build headers for each supported language
    #[allow(clippy::too_many_arguments)]
    fn create_composable_module(
        &mut self,
        module_definition: &ComposableModuleDefinition,
        module_decoration: String,
        shader_defs: &HashMap<String, ShaderDefValue>,
        create_headers: bool,
        demote_entrypoints: bool,
        source: &str,
        imports: Vec<ImportDefWithOffset>,
    ) -> Result<ComposableModule, ComposerError> {
        let mut imports: Vec<_> = imports
            .into_iter()
            .map(|import_with_offset| import_with_offset.definition)
            .collect();
        imports.extend(module_definition.additional_imports.to_vec());

        trace!(
            "create composable module {}: source len {}",
            module_definition.name,
            source.len()
        );

        // record virtual/overridable functions
        let mut virtual_functions: HashSet<String> = Default::default();
        let source = self
            .virtual_fn_regex
            .replace_all(source, |cap: &regex::Captures| {
                let target_function = cap.get(2).unwrap().as_str().to_owned();

                let replacement_str = format!(
                    "{}fn {}{}(",
                    " ".repeat(cap.get(1).unwrap().range().len() - 3),
                    target_function,
                    " ".repeat(cap.get(3).unwrap().range().len()),
                );

                virtual_functions.insert(target_function);

                replacement_str
            });

        // record and rename override functions
        let mut local_override_functions: IndexMap<String, String> = Default::default();

        #[cfg(not(feature = "override_any"))]
        let mut override_error = None;

        let source =
            self.override_fn_regex
                .replace_all(&source, |cap: &regex::Captures| {
                    let target_module = cap.get(3).unwrap().as_str().to_owned();
                    let target_function = cap.get(2).unwrap().as_str().to_owned();

                    #[cfg(not(feature = "override_any"))]
                    {
                        let wrap_err = |inner: ComposerErrorInner| -> ComposerError {
                            ComposerError {
                                inner,
                                source: ErrSource::Module {
                                    name: module_definition.name.to_owned(),
                                    offset: 0,
                                    defs: shader_defs.clone(),
                                },
                            }
                        };

                        // ensure overrides are applied to virtual functions
                        let raw_module_name = Self::decode(&target_module);
                        let module_set = self.module_sets.get(&raw_module_name);

                        match module_set {
                            None => {
                                // TODO this should be unreachable?
                                let pos = cap.get(3).unwrap().start();
                                override_error = Some(wrap_err(
                                    ComposerErrorInner::ImportNotFound(raw_module_name, pos),
                                ));
                            }
                            Some(module_set) => {
                                let module = module_set.get_module(shader_defs).unwrap();
                                if !module.virtual_functions.contains(&target_function) {
                                    let pos = cap.get(2).unwrap().start();
                                    override_error =
                                        Some(wrap_err(ComposerErrorInner::OverrideNotVirtual {
                                            name: target_function.clone(),
                                            pos,
                                        }));
                                }
                            }
                        }
                    }

                    let base_name = format!(
                        "{}{}{}{}",
                        target_function.as_str(),
                        DECORATION_PRE,
                        target_module.as_str(),
                        DECORATION_POST,
                    );
                    let rename = format!(
                        "{}{}{}{}",
                        target_function.as_str(),
                        DECORATION_OVERRIDE_PRE,
                        target_module.as_str(),
                        DECORATION_POST,
                    );

                    let replacement_str = format!(
                        "{}fn {}{}(",
                        " ".repeat(cap.get(1).unwrap().range().len() - 3),
                        rename,
                        " ".repeat(cap.get(4).unwrap().range().len()),
                    );

                    local_override_functions.insert(rename, base_name);

                    replacement_str
                })
                .to_string();

        #[cfg(not(feature = "override_any"))]
        if let Some(err) = override_error {
            return Err(err);
        }

        trace!("local overrides: {:?}", local_override_functions);
        trace!(
            "create composable module {}: source len {}",
            module_definition.name,
            source.len()
        );

        let IrBuildResult {
            module: mut source_ir,
            start_offset,
            mut override_functions,
        } = self.create_module_ir(
            &module_definition.name,
            source,
            module_definition.language,
            &imports,
            shader_defs,
        )?;

        // from here on errors need to be reported using the modified source with start_offset
        let wrap_err = |inner: ComposerErrorInner| -> ComposerError {
            ComposerError {
                inner,
                source: ErrSource::Module {
                    name: module_definition.name.to_owned(),
                    offset: start_offset,
                    defs: shader_defs.clone(),
                },
            }
        };

        // add our local override to the total set of overrides for the given function
        for (rename, base_name) in &local_override_functions {
            override_functions
                .entry(base_name.clone())
                .or_default()
                .push(format!("{rename}{module_decoration}"));
        }

        // rename and record owned items (except types which can't be mutably accessed)
        let mut owned_constants = IndexMap::new();
        for (h, c) in source_ir.constants.iter_mut() {
            if let Some(name) = c.name.as_mut() {
                if !name.contains(DECORATION_PRE) {
                    *name = format!("{name}{module_decoration}");
                    owned_constants.insert(name.clone(), h);
                }
            }
        }

        let mut owned_vars = IndexMap::new();
        for (h, gv) in source_ir.global_variables.iter_mut() {
            if let Some(name) = gv.name.as_mut() {
                if !name.contains(DECORATION_PRE) {
                    *name = format!("{name}{module_decoration}");

                    owned_vars.insert(name.clone(), h);
                }
            }
        }

        let mut owned_functions = IndexMap::new();
        for (h_f, f) in source_ir.functions.iter_mut() {
            if let Some(name) = f.name.as_mut() {
                if !name.contains(DECORATION_PRE) {
                    *name = format!("{name}{module_decoration}");

                    // create dummy header function
                    let header_function = naga::Function {
                        name: Some(name.clone()),
                        arguments: f.arguments.to_vec(),
                        result: f.result.clone(),
                        local_variables: Default::default(),
                        expressions: Default::default(),
                        named_expressions: Default::default(),
                        body: Default::default(),
                    };

                    // record owned function
                    owned_functions.insert(name.clone(), (Some(h_f), header_function));
                }
            }
        }

        if demote_entrypoints {
            // make normal functions out of the source entry points
            for ep in &mut source_ir.entry_points {
                ep.function.name = Some(format!(
                    "{}{}",
                    ep.function.name.as_deref().unwrap_or("main"),
                    module_decoration,
                ));
                let header_function = naga::Function {
                    name: ep.function.name.clone(),
                    arguments: ep
                        .function
                        .arguments
                        .iter()
                        .cloned()
                        .map(|arg| naga::FunctionArgument {
                            name: arg.name,
                            ty: arg.ty,
                            binding: None,
                        })
                        .collect(),
                    result: ep.function.result.clone().map(|res| naga::FunctionResult {
                        ty: res.ty,
                        binding: None,
                    }),
                    local_variables: Default::default(),
                    expressions: Default::default(),
                    named_expressions: Default::default(),
                    body: Default::default(),
                };

                owned_functions.insert(ep.function.name.clone().unwrap(), (None, header_function));
            }
        };

        let mut module_builder = DerivedModule::default();
        let mut header_builder = DerivedModule::default();
        module_builder.set_shader_source(&source_ir, 0);
        header_builder.set_shader_source(&source_ir, 0);

        let mut owned_types = HashSet::new();
        for (h, ty) in source_ir.types.iter() {
            if let Some(name) = &ty.name {
                // we need to exclude autogenerated struct names, i.e. those that begin with "__"
                // "__" is a reserved prefix for naga so user variables cannot use it.
                if !name.contains(DECORATION_PRE) && !name.starts_with("__") {
                    let name = format!("{name}{module_decoration}");
                    owned_types.insert(name.clone());
                    // copy and rename types
                    module_builder.rename_type(&h, Some(name.clone()));
                    header_builder.rename_type(&h, Some(name));
                    continue;
                }
            }

            // copy all required types
            module_builder.import_type(&h);
        }

        // copy owned types into header and module
        for h in owned_constants.values() {
            header_builder.import_const(h);
            module_builder.import_const(h);
        }

        for h in owned_vars.values() {
            header_builder.import_global(h);
            module_builder.import_global(h);
        }

        // only stubs of owned functions into the header
        for (h_f, f) in owned_functions.values() {
            let span = h_f
                .map(|h_f| source_ir.functions.get_span(h_f))
                .unwrap_or(naga::Span::UNDEFINED);
            header_builder.import_function(f, span); // header stub function
        }
        // all functions into the module (note source_ir only contains stubs for imported functions)
        for (h_f, f) in source_ir.functions.iter() {
            let span = source_ir.functions.get_span(h_f);
            module_builder.import_function(f, span);
        }
        // // including entry points as vanilla functions if required
        if demote_entrypoints {
            for ep in &source_ir.entry_points {
                let mut f = ep.function.clone();
                f.arguments = f
                    .arguments
                    .into_iter()
                    .map(|arg| naga::FunctionArgument {
                        name: arg.name,
                        ty: arg.ty,
                        binding: None,
                    })
                    .collect();
                f.result = f.result.map(|res| naga::FunctionResult {
                    ty: res.ty,
                    binding: None,
                });

                module_builder.import_function(&f, naga::Span::UNDEFINED);
                // todo figure out how to get span info for entrypoints
            }
        }

        let module_ir = module_builder.into_module_with_entrypoints();
        let mut header_ir: naga::Module = header_builder.into();

        if self.validate && create_headers {
            // check that identifiers haven't been renamed
            #[allow(clippy::single_element_loop)]
            for language in [
                ShaderLanguage::Wgsl,
                #[cfg(feature = "glsl")]
                ShaderLanguage::Glsl,
            ] {
                let header = self
                    .naga_to_string(&mut header_ir, language, &module_definition.name)
                    .map_err(wrap_err)?;
                Self::validate_identifiers(
                    &source_ir,
                    language,
                    &header,
                    &module_decoration,
                    &owned_types,
                )
                .map_err(wrap_err)?;
            }
        }

        let composable_module = ComposableModule {
            decorated_name: module_decoration,
            imports,
            owned_types,
            owned_constants: owned_constants.into_keys().collect(),
            owned_vars: owned_vars.into_keys().collect(),
            owned_functions: owned_functions.into_keys().collect(),
            virtual_functions,
            override_functions,
            module_ir,
            header_ir,
            start_offset,
        };

        Ok(composable_module)
    }

    // shunt all data owned by a composable into a derived module
    fn add_composable_data<'a>(
        derived: &mut DerivedModule<'a>,
        composable: &'a ComposableModule,
        items: Option<&Vec<String>>,
        span_offset: usize,
        header: bool,
    ) {
        let items: Option<HashSet<String>> = items.map(|items| {
            items
                .iter()
                .map(|item| format!("{}{}", item, composable.decorated_name))
                .collect()
        });
        let items = items.as_ref();

        let source_ir = match header {
            true => &composable.header_ir,
            false => &composable.module_ir,
        };

        derived.set_shader_source(source_ir, span_offset);

        for (h, ty) in source_ir.types.iter() {
            if let Some(name) = &ty.name {
                if composable.owned_types.contains(name)
                    && items.map_or(true, |items| items.contains(name))
                {
                    derived.import_type(&h);
                }
            }
        }

        for (h, c) in source_ir.constants.iter() {
            if let Some(name) = &c.name {
                if composable.owned_constants.contains(name)
                    && items.map_or(true, |items| items.contains(name))
                {
                    derived.import_const(&h);
                }
            }
        }

        for (h, v) in source_ir.global_variables.iter() {
            if let Some(name) = &v.name {
                if composable.owned_vars.contains(name)
                    && items.map_or(true, |items| items.contains(name))
                {
                    derived.import_global(&h);
                }
            }
        }

        for (h_f, f) in source_ir.functions.iter() {
            if let Some(name) = &f.name {
                if composable.owned_functions.contains(name)
                    && (items.map_or(true, |items| items.contains(name))
                        || composable
                            .override_functions
                            .values()
                            .any(|v| v.contains(name)))
                {
                    let span = composable.module_ir.functions.get_span(h_f);
                    derived.import_function_if_new(f, span);
                }
            }
        }

        derived.clear_shader_source();
    }

    // add an import (and recursive imports) into a derived module
    fn add_import<'a>(
        &'a self,
        derived: &mut DerivedModule<'a>,
        import: &ImportDefinition,
        shader_defs: &HashMap<String, ShaderDefValue>,
        header: bool,
        already_added: &mut HashSet<String>,
    ) {
        if already_added.contains(&import.import) {
            trace!("skipping {}, already added", import.import);
            return;
        }

        let import_module_set = self.module_sets.get(&import.import).unwrap();
        let module = import_module_set.get_module(shader_defs).unwrap();

        for import in &module.imports {
            self.add_import(derived, import, shader_defs, header, already_added);
        }

        Self::add_composable_data(
            derived,
            module,
            Some(&import.items),
            import_module_set.module_index << SPAN_SHIFT,
            header,
        );
    }

    fn ensure_import(
        &mut self,
        module_set: &ComposableModuleDefinition,
        shader_defs: &HashMap<String, ShaderDefValue>,
    ) -> Result<ComposableModule, ComposerError> {
        let PreprocessOutput {
            preprocessed_source,
            imports,
        } = self
            .preprocessor
            .preprocess(&module_set.sanitized_source, shader_defs, self.validate)
            .map_err(|inner| ComposerError {
                inner,
                source: ErrSource::Module {
                    name: module_set.name.to_owned(),
                    offset: 0,
                    defs: shader_defs.clone(),
                },
            })?;

        self.ensure_imports(imports.iter().map(|import| &import.definition), shader_defs)?;
        self.ensure_imports(&module_set.additional_imports, shader_defs)?;

        self.create_composable_module(
            module_set,
            Self::decorate(&module_set.name),
            shader_defs,
            true,
            true,
            &preprocessed_source,
            imports,
        )
    }

    // build required ComposableModules for a given set of shader_defs
    fn ensure_imports<'a>(
        &mut self,
        imports: impl IntoIterator<Item = &'a ImportDefinition>,
        shader_defs: &HashMap<String, ShaderDefValue>,
    ) -> Result<(), ComposerError> {
        for ImportDefinition { import, .. } in imports.into_iter() {
            // we've already ensured imports exist when they were added
            let module_set = self.module_sets.get(import).unwrap();
            if module_set.get_module(shader_defs).is_some() {
                continue;
            }

            // we need to build the module
            // take the set so we can recurse without borrowing
            let (set_key, mut module_set) = self.module_sets.remove_entry(import).unwrap();

            match self.ensure_import(&module_set, shader_defs) {
                Ok(module) => {
                    module_set.insert_module(shader_defs, module);
                    self.module_sets.insert(set_key, module_set);
                }
                Err(e) => {
                    self.module_sets.insert(set_key, module_set);
                    return Err(e);
                }
            }
        }

        Ok(())
    }
}

#[derive(Default)]
pub struct ComposableModuleDescriptor<'a> {
    pub source: &'a str,
    pub file_path: &'a str,
    pub language: ShaderLanguage,
    pub as_name: Option<String>,
    pub additional_imports: &'a [ImportDefinition],
    pub shader_defs: HashMap<String, ShaderDefValue>,
}

#[derive(Default)]
pub struct NagaModuleDescriptor<'a> {
    pub source: &'a str,
    pub file_path: &'a str,
    pub shader_type: ShaderType,
    pub shader_defs: HashMap<String, ShaderDefValue>,
    pub additional_imports: &'a [ImportDefinition],
}

// public api
impl Composer {
    /// create a non-validating composer.
    /// validation errors in the final shader will not be caught, and errors resulting from their
    /// use will have bad span data, so codespan reporting will fail.
    /// use default() to create a validating composer.
    pub fn non_validating() -> Self {
        Self {
            validate: false,
            ..Default::default()
        }
    }

    /// specify capabilities to be used for naga module generation.
    /// purges any existing modules
    pub fn with_capabilities(self, capabilities: naga::valid::Capabilities) -> Self {
        Self {
            capabilities,
            validate: self.validate,
            ..Default::default()
        }
    }

    /// check if a module with the given name has been added
    pub fn contains_module(&self, module_name: &str) -> bool {
        self.module_sets.contains_key(module_name)
    }

    /// add a composable module to the composer.
    /// all modules imported by this module must already have been added
    pub fn add_composable_module(
        &mut self,
        desc: ComposableModuleDescriptor,
    ) -> Result<&ComposableModuleDefinition, ComposerError> {
        let ComposableModuleDescriptor {
            source,
            file_path,
            language,
            as_name,
            additional_imports,
            mut shader_defs,
        } = desc;

        // reject a module containing the DECORATION strings
        if let Some(decor) = self.check_decoration_regex.find(source) {
            return Err(ComposerError {
                inner: ComposerErrorInner::DecorationInSource(decor.range()),
                source: ErrSource::Constructing {
                    path: file_path.to_owned(),
                    source: source.to_owned(),
                    offset: 0,
                },
            });
        }

        let substituted_source = self.sanitize_and_set_auto_bindings(source);

        let PreprocessorMetaData {
            name: module_name,
            mut imports,
            mut effective_defs,
            ..
        } = self
            .preprocessor
            .get_preprocessor_metadata(&substituted_source, false)
            .map_err(|inner| ComposerError {
                inner,
                source: ErrSource::Constructing {
                    path: file_path.to_owned(),
                    source: source.to_owned(),
                    offset: 0,
                },
            })?;
        let module_name = as_name.or(module_name);
        if module_name.is_none() {
            return Err(ComposerError {
                inner: ComposerErrorInner::NoModuleName,
                source: ErrSource::Constructing {
                    path: file_path.to_owned(),
                    source: source.to_owned(),
                    offset: 0,
                },
            });
        }
        let module_name = module_name.unwrap();

        debug!(
            "adding module definition for {} with defs: {:?}",
            module_name, shader_defs
        );

        // add custom imports
        let additional_imports = additional_imports.to_vec();
        imports.extend(
            additional_imports
                .iter()
                .cloned()
                .map(|def| ImportDefWithOffset {
                    definition: def,
                    offset: 0,
                }),
        );

        for import in &imports {
            // we require modules already added so that we can capture the shader_defs that may impact us by impacting our dependencies
            let module_set = self
                .module_sets
                .get(&import.definition.import)
                .ok_or_else(|| ComposerError {
                    inner: ComposerErrorInner::ImportNotFound(
                        import.definition.import.clone(),
                        import.offset,
                    ),
                    source: ErrSource::Constructing {
                        path: file_path.to_owned(),
                        source: substituted_source.to_owned(),
                        offset: 0,
                    },
                })?;
            effective_defs.extend(module_set.effective_defs.iter().cloned());
            shader_defs.extend(
                module_set
                    .shader_defs
                    .iter()
                    .map(|def| (def.0.clone(), *def.1)),
            );
        }

        // remove defs that are already specified through our imports
        effective_defs.retain(|name| !shader_defs.contains_key(name));

        // can't gracefully report errors for more modules. perhaps this should be a warning
        assert!((self.module_sets.len() as u32) < u32::MAX >> SPAN_SHIFT);
        let module_index = self.module_sets.len() + 1;

        let module_set = ComposableModuleDefinition {
            name: module_name.clone(),
            sanitized_source: substituted_source,
            file_path: file_path.to_owned(),
            language,
            effective_defs: effective_defs.into_iter().collect(),
            all_imports: imports.into_iter().map(|id| id.definition.import).collect(),
            additional_imports,
            shader_defs,
            module_index,
            modules: Default::default(),
        };

        // invalidate dependent modules if this module already exists
        self.remove_composable_module(&module_name);

        self.module_sets.insert(module_name.clone(), module_set);
        self.module_index.insert(module_index, module_name.clone());
        Ok(self.module_sets.get(&module_name).unwrap())
    }

    /// remove a composable module. also removes modules that depend on this module, as we cannot be sure about
    /// the completeness of their effective shader defs any more...
    pub fn remove_composable_module(&mut self, module_name: &str) {
        // todo this could be improved by making effective defs an Option<HashSet> and populating on demand?
        let mut dependent_sets = Vec::new();

        if self.module_sets.remove(module_name).is_some() {
            dependent_sets.extend(self.module_sets.iter().filter_map(|(dependent_name, set)| {
                if set.all_imports.contains(module_name) {
                    Some(dependent_name.clone())
                } else {
                    None
                }
            }));
        }

        for dependent_set in dependent_sets {
            self.remove_composable_module(&dependent_set);
        }
    }

    /// build a naga shader module
    pub fn make_naga_module(
        &mut self,
        desc: NagaModuleDescriptor,
    ) -> Result<naga::Module, ComposerError> {
        let NagaModuleDescriptor {
            source,
            file_path,
            shader_type,
            mut shader_defs,
            additional_imports,
        } = desc;

        let sanitized_source = self.sanitize_and_set_auto_bindings(source);

        let PreprocessorMetaData {
            name,
            defines,
            imports,
            ..
        } = self
            .preprocessor
            .get_preprocessor_metadata(&sanitized_source, true)
            .map_err(|inner| ComposerError {
                inner,
                source: ErrSource::Constructing {
                    path: file_path.to_owned(),
                    source: sanitized_source.to_owned(),
                    offset: 0,
                },
            })?;
        shader_defs.extend(defines);

        let name = name.unwrap_or_default();

        // make sure imports have been added
        // and gather additional defs specified at module level
        for (import_name, offset) in imports
            .iter()
            .map(|id| (&id.definition.import, id.offset))
            .chain(additional_imports.iter().map(|ai| (&ai.import, 0)))
        {
            if let Some(module_set) = self.module_sets.get(import_name) {
                for (def, value) in &module_set.shader_defs {
                    if let Some(prior_value) = shader_defs.insert(def.clone(), *value) {
                        if prior_value != *value {
                            return Err(ComposerError {
                                inner: ComposerErrorInner::InconsistentShaderDefValue {
                                    def: def.clone(),
                                },
                                source: ErrSource::Constructing {
                                    path: file_path.to_owned(),
                                    source: sanitized_source.to_owned(),
                                    offset: 0,
                                },
                            });
                        }
                    }
                }
            } else {
                return Err(ComposerError {
                    inner: ComposerErrorInner::ImportNotFound(import_name.clone(), offset),
                    source: ErrSource::Constructing {
                        path: file_path.to_owned(),
                        source: sanitized_source,
                        offset: 0,
                    },
                });
            }
        }
        self.ensure_imports(
            imports.iter().map(|import| &import.definition),
            &shader_defs,
        )?;
        self.ensure_imports(additional_imports, &shader_defs)?;

        let definition = ComposableModuleDefinition {
            name,
            sanitized_source: sanitized_source.clone(),
            language: shader_type.into(),
            file_path: file_path.to_owned(),
            module_index: 0,
            additional_imports: additional_imports.to_vec(),
            // we don't care about these for creating a top-level module
            effective_defs: Default::default(),
            all_imports: Default::default(),
            shader_defs: Default::default(),
            modules: Default::default(),
        };

        let PreprocessOutput {
            preprocessed_source,
            imports,
        } = self
            .preprocessor
            .preprocess(&sanitized_source, &shader_defs, self.validate)
            .map_err(|inner| ComposerError {
                inner,
                source: ErrSource::Constructing {
                    path: file_path.to_owned(),
                    source: sanitized_source,
                    offset: 0,
                },
            })?;

        let composable = self
            .create_composable_module(
                &definition,
                String::from(""),
                &shader_defs,
                false,
                false,
                &preprocessed_source,
                imports,
            )
            .map_err(|e| ComposerError {
                inner: e.inner,
                source: ErrSource::Constructing {
                    path: definition.file_path.to_owned(),
                    source: preprocessed_source.clone(),
                    offset: e.source.offset(),
                },
            })?;

        let mut derived = DerivedModule::default();

        let mut already_added = Default::default();
        for import in &composable.imports {
            self.add_import(
                &mut derived,
                import,
                &shader_defs,
                false,
                &mut already_added,
            );
        }

        Self::add_composable_data(&mut derived, &composable, None, 0, false);

        let stage = match shader_type {
            #[cfg(feature = "glsl")]
            ShaderType::GlslVertex => Some(naga::ShaderStage::Vertex),
            #[cfg(feature = "glsl")]
            ShaderType::GlslFragment => Some(naga::ShaderStage::Fragment),
            _ => None,
        };

        let mut entry_points = Vec::default();
        derived.set_shader_source(&composable.module_ir, 0);
        for ep in &composable.module_ir.entry_points {
            let mapped_func = derived.localize_function(&ep.function);
            entry_points.push(EntryPoint {
                name: ep.name.clone(),
                function: mapped_func,
                stage: stage.unwrap_or(ep.stage),
                early_depth_test: ep.early_depth_test,
                workgroup_size: ep.workgroup_size,
            });
        }

        let mut naga_module = naga::Module {
            entry_points,
            ..derived.into()
        };

        // apply overrides
        if !composable.override_functions.is_empty() {
            let mut redirect = Redirector::new(naga_module);

            for (base_function, overrides) in composable.override_functions {
                let mut omit = HashSet::default();

                let mut original = base_function;
                for replacement in overrides {
                    let (_h_orig, _h_replace) = redirect
                        .redirect_function(&original, &replacement, &omit)
                        .map_err(|e| ComposerError {
                            inner: e.into(),
                            source: ErrSource::Constructing {
                                path: file_path.to_owned(),
                                source: preprocessed_source.clone(),
                                offset: composable.start_offset,
                            },
                        })?;
                    omit.insert(replacement.clone());
                    original = replacement;
                }
            }

            naga_module = redirect.into_module().map_err(|e| ComposerError {
                inner: e.into(),
                source: ErrSource::Constructing {
                    path: file_path.to_owned(),
                    source: preprocessed_source.clone(),
                    offset: composable.start_offset,
                },
            })?;
        }

        // validation
        if self.validate {
            let info =
                naga::valid::Validator::new(naga::valid::ValidationFlags::all(), self.capabilities)
                    .validate(&naga_module);
            match info {
                Ok(_) => Ok(naga_module),
                Err(e) => {
                    let original_span = e.spans().last();
                    let err_source = match original_span.and_then(|(span, _)| span.to_range()) {
                        Some(rng) => {
                            let module_index = rng.start >> SPAN_SHIFT;
                            match module_index {
                                0 => ErrSource::Constructing {
                                    path: file_path.to_owned(),
                                    source: preprocessed_source.clone(),
                                    offset: composable.start_offset,
                                },
                                _ => {
                                    let module_name =
                                        self.module_index.get(&module_index).unwrap().clone();
                                    let offset = self
                                        .module_sets
                                        .get(&module_name)
                                        .unwrap()
                                        .get_module(&shader_defs)
                                        .unwrap()
                                        .start_offset;
                                    ErrSource::Module {
                                        name: module_name,
                                        offset,
                                        defs: shader_defs.clone(),
                                    }
                                }
                            }
                        }
                        None => ErrSource::Constructing {
                            path: file_path.to_owned(),
                            source: preprocessed_source.clone(),
                            offset: composable.start_offset,
                        },
                    };

                    Err(ComposerError {
                        inner: ComposerErrorInner::ShaderValidationError(e),
                        source: err_source,
                    })
                }
            }
        } else {
            Ok(naga_module)
        }
    }
}

static PREPROCESSOR: once_cell::sync::Lazy<Preprocessor> =
    once_cell::sync::Lazy::new(Preprocessor::default);

/// Get module name and all required imports (ignoring shader_defs) from a shader string
pub fn get_preprocessor_data(
    source: &str,
) -> (
    Option<String>,
    Vec<ImportDefinition>,
    HashMap<String, ShaderDefValue>,
) {
    if let Ok(PreprocessorMetaData {
        name,
        imports,
        defines,
        ..
    }) = PREPROCESSOR.get_preprocessor_metadata(source, true)
    {
        (
            name,
            imports
                .into_iter()
                .map(|import_with_offset| import_with_offset.definition)
                .collect(),
            defines,
        )
    } else {
        // if errors occur we return nothing; the actual error will be displayed when the caller attempts to use the shader
        Default::default()
    }
}