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use super::SoftF32;

/// Floor (SoftF32)
///
/// Finds the nearest integer less than or equal to `x`.
pub const fn floor(x: SoftF32) -> SoftF32 {
    let mut ui = x.to_bits();
    let e = (((ui >> 23) as i32) & 0xff) - 0x7f;

    if e >= 23 {
        return x;
    }
    if e >= 0 {
        let m: u32 = 0x007fffff >> e;
        if (ui & m) == 0 {
            return x;
        }
        // force_eval!(x + SoftF32::from_bits(0x7b800000));
        if ui >> 31 != 0 {
            ui += m;
        }
        ui &= !m;
    } else {
        // force_eval!(x + SoftF32::from_bits(0x7b800000));
        if ui >> 31 == 0 {
            ui = 0;
        } else if ui << 1 != 0 {
            return SoftF32(-1.0);
        }
    }
    SoftF32::from_bits(ui)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn sanity_check() {
        assert_eq!(floor(SoftF32(0.5)).0, 0.0);
        assert_eq!(floor(SoftF32(1.1)).0, 1.0);
        assert_eq!(floor(SoftF32(2.9)).0, 2.0);
    }

    /// The spec: https://en.cppreference.com/w/cpp/numeric/math/floor
    #[test]
    fn spec_tests() {
        // Not Asserted: that the current rounding mode has no effect.
        assert!(floor(SoftF32(f32::NAN)).0.is_nan());
        for f in [0.0, -0.0, f32::INFINITY, f32::NEG_INFINITY]
            .iter()
            .copied()
        {
            assert_eq!(SoftF32(f).floor().0, f);
        }
    }
}