use std::{
    collections::{hash_map::Entry, HashMap},
    env, iter, mem,
    sync::{Arc, Mutex},
};

use wayland_backend::{client::InvalidId, smallvec::SmallVec};
use wayland_client::{
    protocol::{
        wl_pointer::{self, WlPointer},
        wl_seat::WlSeat,
        wl_shm::WlShm,
        wl_surface::WlSurface,
    },
    Connection, Dispatch, Proxy, QueueHandle, WEnum,
};
use wayland_cursor::{Cursor, CursorTheme};
use wayland_protocols::wp::cursor_shape::v1::client::wp_cursor_shape_device_v1::WpCursorShapeDeviceV1;

use crate::{
    compositor::{SurfaceData, SurfaceDataExt},
    error::GlobalError,
};

use super::SeatState;

#[doc(inline)]
pub use cursor_icon::{CursorIcon, ParseError as CursorIconParseError};

pub mod cursor_shape;

use cursor_shape::cursor_icon_to_shape;

/* From linux/input-event-codes.h - the buttons usually used by mice */
pub const BTN_LEFT: u32 = 0x110;
pub const BTN_RIGHT: u32 = 0x111;
pub const BTN_MIDDLE: u32 = 0x112;
/// The fourth non-scroll button, which is often used as "back" in web browsers.
pub const BTN_SIDE: u32 = 0x113;
/// The fifth non-scroll button, which is often used as "forward" in web browsers.
pub const BTN_EXTRA: u32 = 0x114;

/// See also [`BTN_EXTRA`].
pub const BTN_FORWARD: u32 = 0x115;
/// See also [`BTN_SIDE`].
pub const BTN_BACK: u32 = 0x116;
pub const BTN_TASK: u32 = 0x117;

/// Describes a scroll along one axis
#[derive(Default, Debug, Clone, Copy, PartialEq)]
pub struct AxisScroll {
    /// The scroll measured in pixels.
    pub absolute: f64,

    /// The scroll measured in steps.
    ///
    /// Note: this might always be zero if the scrolling is due to a touchpad or other continuous
    /// source.
    pub discrete: i32,

    /// The scroll was stopped.
    ///
    /// Generally this is encountered when hardware indicates the end of some continuous scrolling.
    pub stop: bool,
}

impl AxisScroll {
    /// Returns true if there was no movement along this axis.
    pub fn is_none(&self) -> bool {
        *self == Self::default()
    }

    fn merge(&mut self, other: &Self) {
        self.absolute += other.absolute;
        self.discrete += other.discrete;
        self.stop |= other.stop;
    }
}

/// A single pointer event.
#[derive(Debug, Clone)]
pub struct PointerEvent {
    pub surface: WlSurface,
    pub position: (f64, f64),
    pub kind: PointerEventKind,
}

#[derive(Debug, Clone)]
pub enum PointerEventKind {
    Enter {
        serial: u32,
    },
    Leave {
        serial: u32,
    },
    Motion {
        time: u32,
    },
    Press {
        time: u32,
        button: u32,
        serial: u32,
    },
    Release {
        time: u32,
        button: u32,
        serial: u32,
    },
    Axis {
        time: u32,
        horizontal: AxisScroll,
        vertical: AxisScroll,
        source: Option<wl_pointer::AxisSource>,
    },
}

pub trait PointerHandler: Sized {
    /// One or more pointer events are available.
    ///
    /// Multiple related events may be grouped together in a single frame.  Some examples:
    ///
    /// - A drag that terminates outside the surface may send the Release and Leave events as one frame
    /// - Movement from one surface to another may send the Enter and Leave events in one frame
    fn pointer_frame(
        &mut self,
        conn: &Connection,
        qh: &QueueHandle<Self>,
        pointer: &WlPointer,
        events: &[PointerEvent],
    );
}

#[derive(Debug)]
pub struct PointerData {
    seat: WlSeat,
    pub(crate) inner: Mutex<PointerDataInner>,
}

impl PointerData {
    pub fn new(seat: WlSeat) -> Self {
        Self { seat, inner: Default::default() }
    }

    /// The seat associated with this pointer.
    pub fn seat(&self) -> &WlSeat {
        &self.seat
    }

    /// Serial from the latest [`PointerEventKind::Enter`] event.
    pub fn latest_enter_serial(&self) -> Option<u32> {
        self.inner.lock().unwrap().latest_enter
    }

    /// Serial from the latest button [`PointerEventKind::Press`] and
    /// [`PointerEventKind::Release`] events.
    pub fn latest_button_serial(&self) -> Option<u32> {
        self.inner.lock().unwrap().latest_btn
    }
}

pub trait PointerDataExt: Send + Sync {
    fn pointer_data(&self) -> &PointerData;
}

impl PointerDataExt for PointerData {
    fn pointer_data(&self) -> &PointerData {
        self
    }
}

#[macro_export]
macro_rules! delegate_pointer {
    ($(@<$( $lt:tt $( : $clt:tt $(+ $dlt:tt )* )? ),+>)? $ty: ty) => {
        $crate::delegate_pointer!(@{ $(@< $( $lt $( : $clt $(+ $dlt )* )? ),+ >)? $ty }; pointer: []);
        $crate::delegate_pointer!(@{ $(@< $( $lt $( : $clt $(+ $dlt )* )? ),+ >)? $ty }; pointer-only: $crate::seat::pointer::PointerData);
    };
    ($(@<$( $lt:tt $( : $clt:tt $(+ $dlt:tt )* )? ),+>)? $ty: ty, pointer: [$($pointer_data:ty),* $(,)?]) => {
        $crate::delegate_pointer!(@{ $(@< $( $lt $( : $clt $(+ $dlt )* )? ),+ >)? $ty }; pointer: [ $($pointer_data),* ]);
    };
    (@{$($ty:tt)*}; pointer: []) => {
        $crate::reexports::client::delegate_dispatch!($($ty)*:
            [
                $crate::reexports::protocols::wp::cursor_shape::v1::client::wp_cursor_shape_manager_v1::WpCursorShapeManagerV1: $crate::globals::GlobalData
            ] => $crate::seat::pointer::cursor_shape::CursorShapeManager
        );
        $crate::reexports::client::delegate_dispatch!($($ty)*:
            [
                $crate::reexports::protocols::wp::cursor_shape::v1::client::wp_cursor_shape_device_v1::WpCursorShapeDeviceV1: $crate::globals::GlobalData
            ] => $crate::seat::pointer::cursor_shape::CursorShapeManager
        );
    };
    (@{$($ty:tt)*}; pointer-only: $pointer_data:ty) => {
        $crate::reexports::client::delegate_dispatch!($($ty)*:
            [
                $crate::reexports::client::protocol::wl_pointer::WlPointer: $pointer_data
            ] => $crate::seat::SeatState
        );
    };
    (@$ty:tt; pointer: [$($pointer:ty),*]) => {
        $crate::delegate_pointer!(@$ty; pointer: []);
        $( $crate::delegate_pointer!(@$ty; pointer-only: $pointer); )*
    }
}

#[derive(Debug, Default)]
pub(crate) struct PointerDataInner {
    /// Surface the pointer most recently entered
    pub(crate) surface: Option<WlSurface>,
    /// Position relative to the surface
    pub(crate) position: (f64, f64),

    /// List of pending events.  Only used for version >= 5.
    pub(crate) pending: SmallVec<[PointerEvent; 3]>,

    /// The serial of the latest enter event for the pointer
    pub(crate) latest_enter: Option<u32>,

    /// The serial of the latest enter event for the pointer
    pub(crate) latest_btn: Option<u32>,
}

impl<D, U> Dispatch<WlPointer, U, D> for SeatState
where
    D: Dispatch<WlPointer, U> + PointerHandler,
    U: PointerDataExt,
{
    fn event(
        data: &mut D,
        pointer: &WlPointer,
        event: wl_pointer::Event,
        udata: &U,
        conn: &Connection,
        qh: &QueueHandle<D>,
    ) {
        let udata = udata.pointer_data();
        let mut guard = udata.inner.lock().unwrap();
        let mut leave_surface = None;
        let kind = match event {
            wl_pointer::Event::Enter { surface, surface_x, surface_y, serial } => {
                guard.surface = Some(surface);
                guard.position = (surface_x, surface_y);
                guard.latest_enter.replace(serial);

                PointerEventKind::Enter { serial }
            }

            wl_pointer::Event::Leave { surface, serial } => {
                if guard.surface.as_ref() == Some(&surface) {
                    guard.surface = None;
                }
                leave_surface = Some(surface);

                PointerEventKind::Leave { serial }
            }

            wl_pointer::Event::Motion { time, surface_x, surface_y } => {
                guard.position = (surface_x, surface_y);

                PointerEventKind::Motion { time }
            }

            wl_pointer::Event::Button { time, button, state, serial } => {
                guard.latest_btn.replace(serial);
                match state {
                    WEnum::Value(wl_pointer::ButtonState::Pressed) => {
                        PointerEventKind::Press { time, button, serial }
                    }
                    WEnum::Value(wl_pointer::ButtonState::Released) => {
                        PointerEventKind::Release { time, button, serial }
                    }
                    WEnum::Unknown(unknown) => {
                        log::warn!(target: "sctk", "{}: invalid pointer button state: {:x}", pointer.id(), unknown);
                        return;
                    }
                    _ => unreachable!(),
                }
            }
            // Axis logical events.
            wl_pointer::Event::Axis { time, axis, value } => match axis {
                WEnum::Value(axis) => {
                    let (mut horizontal, mut vertical) = <(AxisScroll, AxisScroll)>::default();
                    match axis {
                        wl_pointer::Axis::VerticalScroll => {
                            vertical.absolute = value;
                        }
                        wl_pointer::Axis::HorizontalScroll => {
                            horizontal.absolute = value;
                        }
                        _ => unreachable!(),
                    };

                    PointerEventKind::Axis { time, horizontal, vertical, source: None }
                }
                WEnum::Unknown(unknown) => {
                    log::warn!(target: "sctk", "{}: invalid pointer axis: {:x}", pointer.id(), unknown);
                    return;
                }
            },

            wl_pointer::Event::AxisSource { axis_source } => match axis_source {
                WEnum::Value(source) => PointerEventKind::Axis {
                    horizontal: AxisScroll::default(),
                    vertical: AxisScroll::default(),
                    source: Some(source),
                    time: 0,
                },
                WEnum::Unknown(unknown) => {
                    log::warn!(target: "sctk", "unknown pointer axis source: {:x}", unknown);
                    return;
                }
            },

            wl_pointer::Event::AxisStop { time, axis } => match axis {
                WEnum::Value(axis) => {
                    let (mut horizontal, mut vertical) = <(AxisScroll, AxisScroll)>::default();
                    match axis {
                        wl_pointer::Axis::VerticalScroll => vertical.stop = true,
                        wl_pointer::Axis::HorizontalScroll => horizontal.stop = true,

                        _ => unreachable!(),
                    }

                    PointerEventKind::Axis { time, horizontal, vertical, source: None }
                }

                WEnum::Unknown(unknown) => {
                    log::warn!(target: "sctk", "{}: invalid pointer axis: {:x}", pointer.id(), unknown);
                    return;
                }
            },

            wl_pointer::Event::AxisDiscrete { axis, discrete } => match axis {
                WEnum::Value(axis) => {
                    let (mut horizontal, mut vertical) = <(AxisScroll, AxisScroll)>::default();
                    match axis {
                        wl_pointer::Axis::VerticalScroll => {
                            vertical.discrete = discrete;
                        }

                        wl_pointer::Axis::HorizontalScroll => {
                            horizontal.discrete = discrete;
                        }

                        _ => unreachable!(),
                    };

                    PointerEventKind::Axis { time: 0, horizontal, vertical, source: None }
                }

                WEnum::Unknown(unknown) => {
                    log::warn!(target: "sctk", "{}: invalid pointer axis: {:x}", pointer.id(), unknown);
                    return;
                }
            },

            wl_pointer::Event::Frame => {
                let pending = mem::take(&mut guard.pending);
                drop(guard);
                if !pending.is_empty() {
                    data.pointer_frame(conn, qh, pointer, &pending);
                }
                return;
            }

            _ => unreachable!(),
        };

        let surface = match (leave_surface, &guard.surface) {
            (Some(surface), _) => surface,
            (None, Some(surface)) => surface.clone(),
            (None, None) => {
                log::warn!(target: "sctk", "{}: got pointer event {:?} without an entered surface", pointer.id(), kind);
                return;
            }
        };

        let event = PointerEvent { surface, position: guard.position, kind };

        if pointer.version() < 5 {
            drop(guard);
            // No Frame events, send right away
            data.pointer_frame(conn, qh, pointer, &[event]);
        } else {
            // Merge a new Axis event with the previous event to create an event with more
            // information and potentially diagonal scrolling.
            if let (
                Some(PointerEvent {
                    kind:
                        PointerEventKind::Axis { time: ot, horizontal: oh, vertical: ov, source: os },
                    ..
                }),
                PointerEvent {
                    kind:
                        PointerEventKind::Axis { time: nt, horizontal: nh, vertical: nv, source: ns },
                    ..
                },
            ) = (guard.pending.last_mut(), &event)
            {
                // A time of 0 is "don't know", so avoid using it if possible.
                if *ot == 0 {
                    *ot = *nt;
                }
                oh.merge(nh);
                ov.merge(nv);
                *os = os.or(*ns);
                return;
            }

            guard.pending.push(event);
        }
    }
}

/// Pointer themeing
#[derive(Debug)]
pub struct ThemedPointer<U = PointerData, S = SurfaceData> {
    pub(super) themes: Arc<Mutex<Themes>>,
    /// The underlying wl_pointer.
    pub(super) pointer: WlPointer,
    pub(super) shm: WlShm,
    /// The surface owned by the cursor to present the icon.
    pub(super) surface: WlSurface,
    pub(super) shape_device: Option<WpCursorShapeDeviceV1>,
    pub(super) _marker: std::marker::PhantomData<U>,
    pub(super) _surface_data: std::marker::PhantomData<S>,
}

impl<U: PointerDataExt + 'static, S: SurfaceDataExt + 'static> ThemedPointer<U, S> {
    /// Set the cursor to the given [`CursorIcon`].
    ///
    /// The cursor icon should be reloaded on every [`PointerEventKind::Enter`] event.
    pub fn set_cursor(&self, conn: &Connection, icon: CursorIcon) -> Result<(), PointerThemeError> {
        let serial = match self
            .pointer
            .data::<U>()
            .and_then(|data| data.pointer_data().latest_enter_serial())
        {
            Some(serial) => serial,
            None => return Err(PointerThemeError::MissingEnterSerial),
        };

        if let Some(shape_device) = self.shape_device.as_ref() {
            shape_device.set_shape(serial, cursor_icon_to_shape(icon));
            Ok(())
        } else {
            self.set_cursor_legacy(conn, serial, icon)
        }
    }

    /// The legacy method of loading the cursor from the system cursor
    /// theme instead of relying on compositor to set the cursor.
    fn set_cursor_legacy(
        &self,
        conn: &Connection,
        serial: u32,
        icon: CursorIcon,
    ) -> Result<(), PointerThemeError> {
        let mut themes = self.themes.lock().unwrap();

        let scale = self.surface.data::<S>().unwrap().surface_data().scale_factor();
        for cursor_icon_name in iter::once(&icon.name()).chain(icon.alt_names().iter()) {
            if let Some(cursor) = themes
                .get_cursor(conn, cursor_icon_name, scale as u32, &self.shm)
                .map_err(PointerThemeError::InvalidId)?
            {
                let image = &cursor[0];
                let (w, h) = image.dimensions();
                let (hx, hy) = image.hotspot();

                self.surface.set_buffer_scale(scale);
                self.surface.attach(Some(image), 0, 0);

                if self.surface.version() >= 4 {
                    self.surface.damage_buffer(0, 0, w as i32, h as i32);
                } else {
                    // Fallback for the old old surface.
                    self.surface.damage(0, 0, w as i32 / scale, h as i32 / scale);
                }

                // Commit the surface to place the cursor image in the compositor's memory.
                self.surface.commit();

                // Set the pointer surface to change the pointer.
                self.pointer.set_cursor(
                    serial,
                    Some(&self.surface),
                    hx as i32 / scale,
                    hy as i32 / scale,
                );

                return Ok(());
            }
        }

        Err(PointerThemeError::CursorNotFound)
    }

    /// Hide the cursor by providing empty surface for it.
    ///
    /// The cursor should be hidden on every [`PointerEventKind::Enter`] event.
    pub fn hide_cursor(&self) -> Result<(), PointerThemeError> {
        let data = self.pointer.data::<U>();
        if let Some(serial) = data.and_then(|data| data.pointer_data().latest_enter_serial()) {
            self.pointer.set_cursor(serial, None, 0, 0);
            Ok(())
        } else {
            Err(PointerThemeError::MissingEnterSerial)
        }
    }

    /// The [`WlPointer`] associated with this [`ThemedPointer`].
    pub fn pointer(&self) -> &WlPointer {
        &self.pointer
    }

    /// The associated [`WlSurface`] with this [`ThemedPointer`].
    pub fn surface(&self) -> &WlSurface {
        &self.surface
    }
}

impl<U, S> Drop for ThemedPointer<U, S> {
    fn drop(&mut self) {
        if let Some(shape_device) = self.shape_device.take() {
            shape_device.destroy();
        }

        if self.pointer.version() >= 3 {
            self.pointer.release();
        }
        self.surface.destroy();
    }
}

/// Specifies which cursor theme should be used by the theme manager.
#[derive(Debug)]
pub enum ThemeSpec<'a> {
    /// Use this specific theme with the given base size.
    Named {
        /// Name of the cursor theme.
        name: &'a str,

        /// Base size of the cursor names.
        ///
        /// Note this size assumes a scale factor of 1. Cursor image sizes may be multiplied by the base size
        /// for HiDPI outputs.
        size: u32,
    },

    /// Use the system provided theme
    ///
    /// In this case SCTK will read the `XCURSOR_THEME` and
    /// `XCURSOR_SIZE` environment variables to figure out the
    /// theme to use.
    System,
}

impl<'a> Default for ThemeSpec<'a> {
    fn default() -> Self {
        Self::System
    }
}

/// An error indicating that the cursor was not found.
#[derive(Debug, thiserror::Error)]
pub enum PointerThemeError {
    /// An invalid ObjectId was used.
    #[error("Invalid ObjectId")]
    InvalidId(InvalidId),

    /// A global error occurred.
    #[error("A Global Error occured")]
    GlobalError(GlobalError),

    /// The requested cursor was not found.
    #[error("Cursor not found")]
    CursorNotFound,

    /// There has been no enter event yet for the pointer.
    #[error("Missing enter event serial")]
    MissingEnterSerial,
}

#[derive(Debug)]
pub(crate) struct Themes {
    name: String,
    size: u32,
    // Scale -> CursorTheme
    themes: HashMap<u32, CursorTheme>,
}

impl Default for Themes {
    fn default() -> Self {
        Themes::new(ThemeSpec::default())
    }
}

impl Themes {
    pub(crate) fn new(spec: ThemeSpec) -> Themes {
        let (name, size) = match spec {
            ThemeSpec::Named { name, size } => (name.into(), size),
            ThemeSpec::System => {
                let name = env::var("XCURSOR_THEME").ok().unwrap_or_else(|| "default".into());
                let size = env::var("XCURSOR_SIZE").ok().and_then(|s| s.parse().ok()).unwrap_or(24);
                (name, size)
            }
        };

        Themes { name, size, themes: HashMap::new() }
    }

    fn get_cursor(
        &mut self,
        conn: &Connection,
        name: &str,
        scale: u32,
        shm: &WlShm,
    ) -> Result<Option<&Cursor>, InvalidId> {
        // Check if the theme has been initialized at the specified scale.
        if let Entry::Vacant(e) = self.themes.entry(scale) {
            // Initialize the theme for the specified scale
            let theme = CursorTheme::load_from_name(
                conn,
                shm.clone(), // TODO: Does the cursor theme need to clone wl_shm?
                &self.name,
                self.size * scale,
            )?;

            e.insert(theme);
        }

        let theme = self.themes.get_mut(&scale).unwrap();

        Ok(theme.get_cursor(name))
    }
}