use std::{

    slice::{

        from_raw_parts,

        from_raw_parts_mut

    },

    io,

    io::BufReader,

    fs::{File, read_dir},

    path::Path

};

use png::{

    ColorType,

    Decoder,

    DecodingError

};

use integral_geometry::Size;

use vec2d::Vec2D;

pub struct ThemeSprite {

    pixels: Vec2D<u32>

}

impl ThemeSprite {

    #[inline]

    pub fn size(&self) -> Size {

        self.pixels.size()

    }

    #[inline]

    pub fn width(&self) -> usize {

        self.size().width

    }

    #[inline]

    pub fn height(&self) -> usize {

        self.size().height

    }

    #[inline]

    pub fn rows(&self) -> impl DoubleEndedIterator<Item = &[u32]> {

        self.pixels.rows()

    }

    #[inline]

    pub fn get_row(&self, index: usize) -> &[u32] {

        &self.pixels[index]

    }

    #[inline]

    pub fn get_pixel(&self, x: usize, y: usize) -> u32 {

        self.pixels[y][x]

    }

    pub fn to_transposed(&self) -> ThemeSprite {

        let size = self.size().transpose();

        let mut pixels = Vec2D::new(size, 0u32);

        for (y, row) in self.pixels.rows().enumerate() {

            for (x, v) in row.iter().enumerate() {

                pixels[x][y] = *v;

            }

        }

        ThemeSprite { pixels }

    }

    pub fn to_tiled(&self) -> TiledSprite {

        let size = self.size();

        assert!(size.is_power_of_two());

        let tile_width_shift = size.width.trailing_zeros() as usize + 2;

        let mut pixels = vec![0u32; size.area()];

        for (y, row) in self.pixels.rows().enumerate() {

            for (x, v) in row.iter().enumerate() {

                pixels[get_tiled_index(x, y, tile_width_shift)] = *v;

            }

        }

        TiledSprite { tile_width_shift, size, pixels }

    }

}

#[inline]

fn get_tiled_index(x: usize, y: usize, tile_width_shift: usize) -> usize {

    (((y >> 2) << tile_width_shift) + ((x >> 2) << 4)) + ((y & 0b11) << 2) + (x & 0b11)

}

pub struct TiledSprite {

    tile_width_shift: usize,

    size: Size,

    pixels: Vec<u32>

}

impl TiledSprite {

    #[inline]

    pub fn size(&self) -> Size {

        self.size

    }

    #[inline]

    pub fn width(&self) -> usize {

        self.size().width

    }

    #[inline]

    pub fn height(&self) -> usize {

        self.size().height

    }

    #[inline]

    pub fn get_pixel(&self, x: usize, y: usize) -> u32 {

        self.pixels[get_tiled_index(x, y, self.tile_width_shift)]

    }

}

pub struct Theme {

    land_texture: Option<ThemeSprite>,

    border_texture: Option<ThemeSprite>

}

impl Theme {

    pub fn land_texture(&self) -> Option<&ThemeSprite> {

        self.land_texture.as_ref()

    }

    pub fn border_texture(&self) -> Option<&ThemeSprite> {

        self.border_texture.as_ref()

    }

}

#[derive(Debug)]

pub enum ThemeLoadError {

    File(io::Error),

    Decoding(DecodingError),

    Format(String)

}

impl From<io::Error> for ThemeLoadError {

    fn from(e: io::Error) -> Self {

        ThemeLoadError::File(e)

    }

}

impl From<DecodingError> for ThemeLoadError {

    fn from(e: DecodingError) -> Self {

        ThemeLoadError::Decoding(e)

    }

}

impl Theme {

    pub fn new() -> Self {

        Theme {

            land_texture: None,

            border_texture: None,

        }

    }

    pub fn load(path: &Path) -> Result<Theme, ThemeLoadError> {

        let mut theme = Self::new();

        for entry in read_dir(path)? {

            let file = entry?;

            if file.file_name() == "LandTex.png" {

                theme.land_texture = Some(load_sprite(&file.path())?)

            } else if file.file_name() == "Border.png" {

                theme.border_texture = Some(load_sprite(&file.path())?)

            }

        }

        Ok(theme)

    }

}

fn load_sprite(path: &Path) -> Result<ThemeSprite, ThemeLoadError> {

    let decoder = Decoder::new(

        BufReader::new(File::open(path)?));

    let (info, mut reader) = decoder.read_info()?;

    if info.color_type != ColorType::RGBA {

        return Err(ThemeLoadError::Format(

            format!("Unexpected format: {:?}", info.color_type)));

    }

    let size = Size::new(info.width as usize, info.height as usize);

    let mut pixels: Vec2D<u32> = Vec2D::new(size, 0);

    reader.next_frame(slice_u32_to_u8_mut(pixels.as_mut_slice()))?;

    Ok(ThemeSprite { pixels })

}

pub fn slice_u32_to_u8(slice_u32: &[u32]) -> &[u8] {

    unsafe {

        from_raw_parts::<u8>(

            slice_u32.as_ptr() as *const u8,

            slice_u32.len() * 4

        )

    }

}

pub fn slice_u32_to_u8_mut(slice_u32: &mut [u32]) -> &mut [u8] {

    unsafe {

        from_raw_parts_mut::<u8>(

            slice_u32.as_mut_ptr() as *mut u8,

            slice_u32.len() * 4

        )

    }

}