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/*
 * Copyright 2023 Alberto Ruiz <aruiz@gnome.org>
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

#![feature(core_intrinsics)]

use std::mem::transmute;

pub trait Swappable {}

impl Swappable for u128 {}
impl Swappable for u64 {}
impl Swappable for u32 {}
impl Swappable for u16 {}

impl Swappable for i128 {}
impl Swappable for i64 {}
impl Swappable for i32 {}
impl Swappable for i16 {}

impl Swappable for usize {}
impl Swappable for isize {}

impl Swappable for f32 {}
impl Swappable for f64 {}

pub struct LittleEndian<T: Swappable> {
    data: T,
}

pub struct BigEndian<T: Swappable> {
    data: T,
}

macro_rules! into_from {
    ($type: ident, $end: ident, $a: tt, $b: tt, $swap: tt) => {
        impl Into<$type> for $end<$type> {
            fn into(self) -> $type {
                #[cfg(target_endian = $a)]
                return self.data;
                #[cfg(target_endian = $b)]
                return unsafe { transmute(self.data.$swap()) };
            }
        }

        impl From<$type> for $end<$type> {
            fn from(value: $type) -> Self {
                #[cfg(target_endian = $a)]
                return Self { data: value };
                #[cfg(target_endian = $b)]
                return Self {
                    data: unsafe { transmute(value.$swap()) },
                };
            }
        }
    };
}

macro_rules! le_into_from {
    ($type: ident) => {
        into_from! {$type, LittleEndian, "little", "big", to_le_bytes}
    };
}

macro_rules! be_into_from {
    ($type: ident) => {
        into_from! {$type, BigEndian, "big", "little", to_be_bytes}
    };
}

le_into_from! {u16}
le_into_from! {u32}
le_into_from! {u64}
le_into_from! {u128}
le_into_from! {usize}

le_into_from! {i16}
le_into_from! {i32}
le_into_from! {i64}
le_into_from! {i128}
le_into_from! {isize}

le_into_from! {f32}
le_into_from! {f64}

be_into_from! {u16}
be_into_from! {u32}
be_into_from! {u64}
be_into_from! {u128}
be_into_from! {usize}

be_into_from! {i16}
be_into_from! {i32}
be_into_from! {i64}
be_into_from! {i128}
be_into_from! {isize}

be_into_from! {f32}
be_into_from! {f64}

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

    macro_rules! test_type {
        ($fun: ident, $type: ident, $val: expr, $rev: expr) => {
            #[test]
            fn $fun() {
                let l: LittleEndian<$type> = $val.into();
                #[cfg(target_endian = "little")]
                assert_eq!(l.data, $val);
                #[cfg(target_endian = "big")]
                assert_eq!(l.data, $rev);

                let b: BigEndian<$type> = $val.into();
                #[cfg(target_endian = "little")]
                assert_eq!(b.data, $rev);
                #[cfg(target_endian = "big")]
                assert_eq!(b.data, $val);
            }
        };
    }

    test_type! {test_u128, u128, 0xaa000000000000000000000000000000, 0x000000000000000000000000000000aa}
    test_type! {test_u64, u64, 0xaa00000000000000, 0x00000000000000aa}
    test_type! {test_u32, u32, 0xaa000000, 0x000000aa}
    test_type! {test_u16, u16, 0xaa00, 0x00aa}

    #[cfg(target_pointer_width = "32")]
    test_type! {test_usize, usize, 0xaa000000, 0x000000aa}
    #[cfg(target_pointer_width = "64")]
    test_type! {test_usize, usize, 0xaa00000000000000, 0x00000000000000aa}

    #[cfg(target_pointer_width = "32")]
    test_type! {test_isize, isize, -2isize, -16777217isize}
    #[cfg(target_pointer_width = "64")]
    test_type! {test_isize, isize, -2isize, -72057594037927937isize}

    test_type! {test_i16, i16, -2i16, -257i16}
    test_type! {test_i32, i32, -2i32, -16777217i32}
    test_type! {test_i64, i64, -2i64, -72057594037927937i64}
    test_type! {test_i128, i128, -2i128, -1329227995784915872903807060280344577i128}

    #[test]
    fn test_floats() {
        const F32_VAL: f32 = 1.3_f32;
        const F32_REV: f32 = 272302750000000000000000_f32;
        const F64_VAL: f64 = 1.3_f64;
        const F64_REV: f64 = -6065988000116450000000000000000000000000000000000000000000000000000_f64;

        let l: LittleEndian<f32> = F32_VAL.into();
        #[cfg(target_endian = "little")]
        assert_eq!(l.data, F32_VAL);
        #[cfg(target_endian = "big")]
        assert_eq!(l.data, F32_REV);

        let b: BigEndian<f32> = F32_VAL.into();
        #[cfg(target_endian = "little")]
        assert_eq!(b.data, F32_REV);
        #[cfg(target_endian = "big")]
        assert_eq!(b.data, F32_VAL);

        let l: LittleEndian<f64> = F64_VAL.into();
        #[cfg(target_endian = "little")]
        assert_eq!(l.data, F64_VAL);
        #[cfg(target_endian = "big")]
        assert_eq!(l.data, F64_REV);

        let b: BigEndian<f64> = F64_VAL.into();
        #[cfg(target_endian = "little")]
        assert_eq!(b.data, F64_REV);
        #[cfg(target_endian = "big")]
        assert_eq!(b.data, F64_VAL);
    }
}