use crate::render::{

    atlas::{AtlasCollection, SpriteIndex},

    camera::Camera,

    gl::{

        Buffer, BufferType, BufferUsage, InputElement, InputFormat, InputLayout, PipelineState,

        Shader, Texture2D, TextureDataType, TextureFilter, TextureFormat, TextureInternalFormat,

        VariableBinding,

    },

};

use integral_geometry::{Rect, Size};

use png::{ColorType, Decoder, DecodingError};

use std::{

    collections::HashMap,

    ffi::OsString,

    fs::{read_dir, File},

    io,

    io::BufReader,

    mem::size_of,

    path::{Path, PathBuf},

};

const VERTEX_SHADER: &'static str = r#"

#version 330 core

uniform mat4 projection;

layout(location = 0) in vec2 position;

layout(location = 1) in vec2 texCoords;

out vec2 varTexCoords;

void main() {

    varTexCoords = texCoords;

	gl_Position = projection * vec4(position, 0.0, 1.0);

}

"#;

const PIXEL_SHADER: &'static str = r#"

#version 330 core

uniform sampler2D texture;

in vec2 varTexCoords;

out vec4 outColor;

void main() {

	 outColor = texture2D(texture, varTexCoords);

}

"#;

#[repr(C)]

#[derive(Copy, Clone)]

struct Vertex {

    position: [f32; 2],

    tex_coords: [f32; 2],

}

#[derive(PartialEq, Debug, Clone, Copy)]

#[repr(u32)]

pub enum SpriteId {

    Mine = 0,

    Grenade,

    Cheese,

    Cleaver,

    MaxSprite,

}

const SPRITE_LOAD_LIST: &[(SpriteId, &str)] = &[

];

const MAX_SPRITES: usize = SpriteId::MaxSprite as usize + 1;

type SpriteTexCoords = (u32, [[f32; 2]; 4]);

pub struct GearEntry {

    position: [f32; 2],

    size: Size,

}

impl GearEntry {

    pub fn new(x: f32, y: f32, size: Size) -> Self {

        Self {

            position: [x, y],

            size,

        }

    }

}

pub struct GearRenderer {

    atlas: AtlasCollection,

    texture: Texture2D,

    allocation: Box<[SpriteTexCoords; MAX_SPRITES]>,

    shader: Shader,

    layout: InputLayout,

    vertex_buffer: Buffer,

}

struct SpriteData {

    size: Size,

    filename: PathBuf,

}

const ATLAS_SIZE: Size = Size::square(2048);

impl GearRenderer {

    pub fn new(data_path: &Path) -> Self {

        let mut atlas = AtlasCollection::new(ATLAS_SIZE);

        let texture = Texture2D::new(

            ATLAS_SIZE,

            TextureInternalFormat::Rgba8,

            TextureFilter::Linear,

        );

        let mut allocation = Box::new([Default::default(); MAX_SPRITES]);

        for (sprite, file) in SPRITE_LOAD_LIST {

            let path = data_path.join(Path::new(file));

            let size = load_sprite_size(path.as_path()).expect(&format!("Unable to open {}", file));

            let index = atlas

                .insert_sprite(size)

                .expect(&format!("Could not store sprite {:?}", sprite));

            let (texture_index, rect) = atlas.get_rect(index).unwrap();

            let mut pixels = vec![255u8; size.area() * 4].into_boxed_slice();

            load_sprite_pixels(path.as_path(), &mut pixels).expect("Unable to load Graphics");

            texture.update(

                rect,

                &pixels,

                None,

                TextureFormat::Rgba,

                TextureDataType::UnsignedByte,

            );

            let mut tex_coords = [

                [rect.left() as f32, rect.bottom() as f32 + 1.0],

                [rect.right() as f32 + 1.0, rect.bottom() as f32 + 1.0],

                [rect.left() as f32, rect.top() as f32],

                [rect.right() as f32 + 1.0, rect.top() as f32],

            ]; //.map(|n| n as f32 / ATLAS_SIZE as f32);

            for coords in &mut tex_coords {

                coords[0] /= ATLAS_SIZE.width as f32;

                coords[1] /= ATLAS_SIZE.height as f32;

            }

            allocation[*sprite as usize] = (texture_index, tex_coords);

        }

        let shader = Shader::new(

            VERTEX_SHADER,

            Some(PIXEL_SHADER),

            &[VariableBinding::Sampler("texture", 0)],

        )

        .unwrap();

        let layout = InputLayout::new(vec![

            InputElement {

                shader_slot: 0,

                buffer_slot: 0,

                format: InputFormat::Float(gl::FLOAT, false),

                components: 2,

                stride: size_of::<Vertex>() as u32,

                offset: 0,

            },

            InputElement {

                shader_slot: 1,

                buffer_slot: 0,

                format: InputFormat::Float(gl::FLOAT, false),

                components: 2,

                stride: size_of::<Vertex>() as u32,

                offset: size_of::<[f32; 2]>() as u32,

            },

        ]);

        let vertex_buffer = Buffer::empty(BufferType::Array, BufferUsage::DynamicDraw);

        Self {

            atlas,

            texture,

            allocation,

            shader,

            layout,

            vertex_buffer,

        }

    }

    pub fn render(&mut self, camera: &Camera, entries: &[GearEntry]) {

        let mut data = Vec::with_capacity(entries.len() * 6);

        for (index, entry) in entries.iter().enumerate() {

            let sprite_id = match index & 0b11 {

                0 => SpriteId::Mine,

                1 => SpriteId::Grenade,

                2 => SpriteId::Cheese,

                _ => SpriteId::Cleaver,

            };

            let sprite_coords = &self.allocation[sprite_id as usize].1;

            let v = [

                Vertex {

                    position: [

                        entry.position[0] - entry.size.width as f32 / 2.0,

                        entry.position[1] + entry.size.height as f32 / 2.0,

                    ],

                    tex_coords: sprite_coords[0],

                },

                Vertex {

                    position: [

                        entry.position[0] + entry.size.width as f32 / 2.0,

                        entry.position[1] + entry.size.height as f32 / 2.0,

                    ],

                    tex_coords: sprite_coords[1],

                },

                Vertex {

                    position: [

                        entry.position[0] - entry.size.width as f32 / 2.0,

                        entry.position[1] - entry.size.height as f32 / 2.0,

                    ],

                    tex_coords: sprite_coords[2],

                },

                Vertex {

                    position: [

                        entry.position[0] + entry.size.width as f32 / 2.0,

                        entry.position[1] - entry.size.height as f32 / 2.0,

                    ],

                    tex_coords: sprite_coords[3],

                },

            ];

            data.extend_from_slice(&[v[0], v[1], v[2], v[1], v[3], v[2]]);

        }

        let projection = camera.projection();

        self.shader.bind();

        self.shader.set_matrix("projection", projection.as_ptr());

        self.shader.bind_texture_2d(0, &self.texture);

        self.vertex_buffer.write_typed(&data);

        let _buffer_bind = self.layout.bind(&[(0, &self.vertex_buffer)], None);

        let _state = PipelineState::new().with_blend();

        unsafe {

            gl::DrawArrays(gl::TRIANGLES, 0, entries.len() as i32 * 6);

        }

    }

}

fn load_sprite_pixels(path: &Path, buffer: &mut [u8]) -> io::Result<Size> {

    let decoder = Decoder::new(BufReader::new(File::open(path)?));

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

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

    reader.next_frame(buffer)?;

    Ok(size)

}

fn load_sprite_size(path: &Path) -> io::Result<Size> {

    let decoder = Decoder::new(BufReader::new(File::open(path)?));

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

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

    Ok(size)

}

fn load_sprites(path: &Path) -> io::Result<Vec<SpriteData>> {

    let mut result = vec![];

    for file in read_dir(path)? {

        let file = file?;

        if let Some(extension) = file.path().extension() {

            if extension == "png" {

                let path = file.path();

                let sprite = load_sprite_size(&path)?;

                result.push(SpriteData {

                    size: sprite,

                    filename: path,

                });

            }

        }

    }

    Ok(result)

}