use std::{

    slice,

    io,

    io::BufReader,

    fs::{File, read_dir},

    path::Path

};

use png::{

    BitDepth,

    ColorType,

    Decoder,

    DecodingError

};

use integral_geometry::{

    Rect, Size

};

pub struct ThemeSprite {

    bounds: Size,

    pixels: Vec<u32>

}

pub struct Theme {

    land_texture: Option<ThemeSprite>

}

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

        }

    }

    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" {

                let buffer = BufReader::new(File::create(file.path())?);

                let decoder = Decoder::new(buffer);

                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 buffer: Vec<u32> = Vec::with_capacity(size.area());

                let mut slice_u32 = buffer.as_mut_slice();

                let mut slice_u8 = unsafe {

                    slice::from_raw_parts_mut::<u8>(

                        slice.as_mut_ptr() as *mut u8,

                        slice.len() / 4

                    )

                };

                reader.next_frame(slice_u8);

                let land_tex = ThemeSprite {

                    bounds: size,

                    pixels: buffer

                };

                theme.land_texture = Some(land_tex)

            }

        }

        Ok(theme)

    }

}