use integral_geometry::{GridIndex, Point, Rect, Size};

use land2d::Land2D;

use vec2d::Vec2D;

use super::{

    camera::Camera,

    gl::{

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

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

        VariableBinding,

    },

};

use std::num::NonZeroU32;

const VERTEX_SHADER: &'static str = r#"

#version 150

in vec2 Position;

in vec3 Uv;

out vec3 a_Uv;

//uniform Common {

uniform mat4 Projection;

//};

void main()

{

	a_Uv = Uv;

	gl_Position = Projection * vec4(Position, 0.0, 1.0);

}

"#;

const PIXEL_SHADER: &'static str = r#"

#version 150

in vec3 a_Uv;

uniform sampler2D Texture;

out vec4 Target;

void main()

{

	 Target = texture2D(Texture, a_Uv.xy);

}

"#;

struct MapTile {

    // either index into GL texture array or emulated [Texture; N]

    texture_index: u32,

    width: u32,

    height: u32,

}

#[repr(C)]

#[derive(Copy, Clone)]

struct TileVertex {

    pos: [f32; 2],

    // doesn't hurt to include another float, just in case..

    uv: [f32; 3],

}

struct DrawTile {

    texture_index: u32,

    index_len: u32,

}

pub struct MapRenderer {

    tiles: Vec<MapTile>,

    textures: Vec<Texture2D>,

    tile_vertex_buffer: Buffer,

    tile_index_buffer: Buffer,

    tile_vertices: Vec<TileVertex>,

    tile_indices: Vec<u16>,

    tile_draw_calls: Vec<DrawTile>,

    index_offset: u16,

    tile_shader: Shader,

    tile_layout: InputLayout,

    tile_size: Size,

    num_tile_x: usize,

}

impl MapRenderer {

    pub fn new(tile_size: Size) -> Self {

        debug_assert!(tile_size.is_power_of_two());

        let tile_shader = Shader::new(

            VERTEX_SHADER,

            Some(PIXEL_SHADER),

            &[

                VariableBinding::Attribute("Position", 0),

                VariableBinding::Attribute("Uv", 1),

                VariableBinding::Sampler("Texture", 0),

            ],

        )

        .unwrap();

        let vertex_size = std::mem::size_of::<TileVertex>() as u32;

        let tile_layout = InputLayout::new(vec![

            // position

            InputElement {

                shader_slot: 0,

                buffer_slot: 0,

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

                components: 2,

                stride: vertex_size,

                offset: 0,

            },

            // uv

            InputElement {

                shader_slot: 1,

                buffer_slot: 0,

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

                components: 3,

                stride: vertex_size,

                offset: 8,

            },

        ]);

        MapRenderer {

            tiles: Vec::new(),

            textures: Vec::new(),

            tile_vertex_buffer: Buffer::empty(BufferType::Array, BufferUsage::DynamicDraw),

            tile_index_buffer: Buffer::empty(BufferType::ElementArray, BufferUsage::DynamicDraw),

            tile_vertices: Vec::new(),

            tile_indices: Vec::new(),

            index_offset: 0,

            tile_draw_calls: Vec::new(),

            tile_shader,

            tile_layout,

            tile_size,

            num_tile_x: 0,

        }

    }

    pub fn init(&mut self, land: &Vec2D<u32>) {

        // clear tiles, but keep our textures for potential re-use

        self.tiles.clear();

        let tw = self.tile_size.width;

        let th = self.tile_size.height;

        let lw = land.width();

        let lh = land.height();

        let num_tile_x = lw / tw;

        let num_tile_y = lh / th;

        self.num_tile_x = num_tile_x;

        for y in 0..num_tile_y {

            for x in 0..num_tile_x {

                let idx = x + y * num_tile_x;

                let (data, stride) = {

                    let bpp = 4;

                    let offset = x * tw * bpp + y * th * lw * bpp;

                    let data = unsafe { &land.as_bytes()[offset..] };

                    let stride = land.width();

                    (data, NonZeroU32::new(stride as u32))

                };

                let texture_index = if idx >= self.textures.len() {

                    let texture = Texture2D::with_data(

                        data,

                        stride,

                        self.tile_size,

                        TextureInternalFormat::Rgba8,

                        TextureFormat::Rgba,

                        TextureDataType::UnsignedByte,

                        TextureFilter::Nearest,

                    );

                    let texture_index = self.textures.len();

                    self.textures.push(texture);

                    texture_index

                } else {

                    let texture_region = Rect::at_origin(self.tile_size);

                    self.textures[idx].update(

                        texture_region,

                        data,

                        stride,

                        TextureFormat::Rgba,

                        TextureDataType::UnsignedByte,

                    );

                    idx

                };

                let tile = MapTile {

                    texture_index: texture_index as u32,

                    // TODO: are there ever non-power of two textures?

                    width: self.tile_size.width as u32,

                    height: self.tile_size.height as u32,

                };

                self.tiles.push(tile);

            }

        }

    }

    pub fn update(&mut self, land: &Land2D<u32>, region: Rect) {}

    pub fn render(&mut self, camera: &Camera) {

        let viewport = camera.viewport();

        self.tile_vertices.clear();

        self.tile_indices.clear();

        self.tile_draw_calls.clear();

        self.index_offset = 0;

        for (idx, tile) in self.tiles.iter().enumerate() {

            let tile_x = idx % self.num_tile_x;

            let tile_y = idx / self.num_tile_x;

            let tile_w = self.tile_size.width;

            let tile_h = self.tile_size.width;

            let origin = Point::new((tile_x * tile_w) as i32, (tile_y * tile_h) as i32);

            let tile_rect = Rect::from_size(origin, self.tile_size);

            if viewport.intersects(&tile_rect) {

                // lazy

                //dbg!(origin);

                let tile_x = origin.x as f32;

                let tile_y = origin.y as f32;

                let tile_w = tile_x + tile_w as f32;

                let tile_h = tile_y + tile_h as f32;

                let uv_depth = tile.texture_index as f32;

                //dbg!(tile_x);

                let tl = TileVertex {

                    pos: [tile_x, tile_y],

                    uv: [0f32, 0f32, uv_depth],

                };

                let bl = TileVertex {

                    pos: [tile_x, tile_h],

                    uv: [0f32, 1f32, uv_depth],

                };

                let br = TileVertex {

                    pos: [tile_w, tile_h],

                    uv: [1f32, 1f32, uv_depth],

                };

                let tr = TileVertex {

                    pos: [tile_w, tile_y],

                    uv: [1f32, 0f32, uv_depth],

                };

                self.tile_vertices.extend(&[tl, bl, br, tr]);

                let i = self.index_offset;

                self.tile_indices

                    .extend(&[i + 0, i + 1, i + 2, i + 2, i + 3, i + 0]);

                self.index_offset += 4;

                self.tile_draw_calls.push(DrawTile {

                    texture_index: tile.texture_index,

                    index_len: 6,

                });

            }

        }

        self.tile_vertex_buffer.write_typed(&self.tile_vertices);

        self.tile_index_buffer.write_typed(&self.tile_indices);

        let _g = self.tile_layout.bind(

            &[(0, &self.tile_vertex_buffer)],

            Some(&self.tile_index_buffer),

        );

        let projection = camera.projection();

        self.tile_shader.bind();

        self.tile_shader

            .set_matrix("Projection", projection.as_ptr());

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

        let mut draw_offset = 0;

        for draw_call in &self.tile_draw_calls {

            unsafe {

                self.tile_shader

                    .bind_texture_2d(0, &self.textures[draw_call.texture_index as usize]);

                gl::DrawElements(

                    gl::TRIANGLES,

                    draw_call.index_len as i32,

                    gl::UNSIGNED_SHORT,

                    draw_offset as *const _,

                );

            }

            draw_offset += draw_call.index_len * 2;

        }

    }

}