#[macro_use]
extern crate glium;
extern crate imgui;

use glium::{DrawError, GlObject, IndexBuffer, Program, Surface, Texture2d, VertexBuffer};
use glium::backend::{Context, Facade};
use glium::program;
use glium::index::{self, PrimitiveType};
use glium::texture;
use glium::vertex;
use imgui::{DrawList, ImDrawIdx, ImDrawVert, ImGui, Ui};
use std::borrow::Cow;
use std::fmt;
use std::rc::Rc;

pub type RendererResult<T> = Result<T, RendererError>;

#[derive(Clone, Debug)]
pub enum RendererError {
    Vertex(vertex::BufferCreationError),
    Index(index::BufferCreationError),
    Program(program::ProgramChooserCreationError),
    Texture(texture::TextureCreationError),
    Draw(DrawError),
}

impl fmt::Display for RendererError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        use self::RendererError::*;
        match *self {
            Vertex(_) => write!(f, "Vertex buffer creation failed"),
            Index(_) => write!(f, "Index buffer creation failed"),
            Program(ref e) => write!(f, "Program creation failed: {}", e),
            Texture(_) => write!(f, "Texture creation failed"),
            Draw(ref e) => write!(f, "Drawing failed: {}", e),
        }
    }
}

impl From<vertex::BufferCreationError> for RendererError {
    fn from(e: vertex::BufferCreationError) -> RendererError { RendererError::Vertex(e) }
}

impl From<index::BufferCreationError> for RendererError {
    fn from(e: index::BufferCreationError) -> RendererError { RendererError::Index(e) }
}

impl From<program::ProgramChooserCreationError> for RendererError {
    fn from(e: program::ProgramChooserCreationError) -> RendererError { RendererError::Program(e) }
}

impl From<texture::TextureCreationError> for RendererError {
    fn from(e: texture::TextureCreationError) -> RendererError { RendererError::Texture(e) }
}

impl From<DrawError> for RendererError {
    fn from(e: DrawError) -> RendererError { RendererError::Draw(e) }
}

pub struct Renderer {
    ctx: Rc<Context>,
    device_objects: DeviceObjects,
}

impl Renderer {
    pub fn init<F: Facade>(imgui: &mut ImGui, ctx: &F) -> RendererResult<Renderer> {
        let device_objects = try!(DeviceObjects::init(imgui, ctx));
        Ok(Renderer {
            ctx: Rc::clone(ctx.get_context()),
            device_objects: device_objects,
        })
    }

    pub fn render<'a, S: Surface>(&mut self, surface: &mut S, ui: Ui<'a>) -> RendererResult<()> {
        let _ = self.ctx.insert_debug_marker("imgui-rs: starting rendering");
        let result = ui.render(|ui, draw_list| {
            self.render_draw_list(surface, ui, &draw_list)
        });
        let _ = self.ctx.insert_debug_marker("imgui-rs: rendering finished");
        result
    }

    fn render_draw_list<'a, S: Surface>(
        &mut self,
        surface: &mut S,
        ui: &'a Ui<'a>,
        draw_list: &DrawList<'a>,
    ) -> RendererResult<()> {
        use glium::{Blend, DrawParameters, Rect};
        use glium::uniforms::{MinifySamplerFilter, MagnifySamplerFilter};

        try!(self.device_objects.upload_vertex_buffer(
            &self.ctx,
            draw_list.vtx_buffer,
        ));
        try!(self.device_objects.upload_index_buffer(
            &self.ctx,
            draw_list.idx_buffer,
        ));

        let (width, height) = ui.imgui().display_size();
        let (scale_width, scale_height) = ui.imgui().display_framebuffer_scale();

        if width == 0.0 || height == 0.0 {
            return Ok(());
        }

        let matrix = [
            [2.0 / width as f32, 0.0, 0.0, 0.0],
            [0.0, 2.0 / -(height as f32), 0.0, 0.0],
            [0.0, 0.0, -1.0, 0.0],
            [-1.0, 1.0, 0.0, 1.0],
        ];
        let font_texture_id = self.device_objects.texture.get_id() as usize;

        let mut idx_start = 0;
        for cmd in draw_list.cmd_buffer {
            // We don't support custom textures...yet!
            assert!(cmd.texture_id as usize == font_texture_id);

            let idx_end = idx_start + cmd.elem_count as usize;

            try!(
                surface.draw(
                    &self.device_objects.vertex_buffer,
                    &self.device_objects
                        .index_buffer
                        .slice(idx_start..idx_end)
                        .expect("Invalid index buffer range"),
                    &self.device_objects.program,
                    &uniform! {
                          matrix: matrix,
                          tex: self.device_objects.texture.sampled()
                              .magnify_filter(MagnifySamplerFilter::Nearest)
                              .minify_filter(MinifySamplerFilter::Nearest),
                      },
                    &DrawParameters {
                        blend: Blend::alpha_blending(),
                        scissor: Some(Rect {
                            left: (cmd.clip_rect.x * scale_width) as u32,
                            bottom: ((height - cmd.clip_rect.w) * scale_height) as u32,
                            width: ((cmd.clip_rect.z - cmd.clip_rect.x) * scale_width) as u32,
                            height: ((cmd.clip_rect.w - cmd.clip_rect.y) * scale_height) as u32,
                        }),
                        ..DrawParameters::default()
                    },
                )
            );

            idx_start = idx_end;
        }

        Ok(())
    }
}

pub struct DeviceObjects {
    vertex_buffer: VertexBuffer<ImDrawVert>,
    index_buffer: IndexBuffer<ImDrawIdx>,
    program: Program,
    texture: Texture2d,
}

fn compile_default_program<F: Facade>(
    ctx: &F,
) -> Result<Program, program::ProgramChooserCreationError> {
    program!(
        ctx,
        400 => {
            vertex: include_str!("shader/glsl_400.vert"),
            fragment: include_str!("shader/glsl_400.frag"),
            outputs_srgb: true,
        },
        130 => {
            vertex: include_str!("shader/glsl_130.vert"),
            fragment: include_str!("shader/glsl_130.frag"),
            outputs_srgb: true,
        },
        110 => {
            vertex: include_str!("shader/glsl_110.vert"),
            fragment: include_str!("shader/glsl_110.frag"),
            outputs_srgb: true,
        },
        300 es => {
            vertex: include_str!("shader/glsles_300.vert"),
            fragment: include_str!("shader/glsles_300.frag"),
            outputs_srgb: true,
        },
        100 es => {
            vertex: include_str!("shader/glsles_100.vert"),
            fragment: include_str!("shader/glsles_100.frag"),
            outputs_srgb: true,
        },
    )
}

impl DeviceObjects {
    pub fn init<F: Facade>(im_gui: &mut ImGui, ctx: &F) -> RendererResult<DeviceObjects> {
        use glium::texture::{ClientFormat, RawImage2d};

        let vertex_buffer = try!(VertexBuffer::empty_dynamic(ctx, 0));
        let index_buffer = try!(IndexBuffer::empty_dynamic(
            ctx,
            PrimitiveType::TrianglesList,
            0,
        ));

        let program = try!(compile_default_program(ctx));
        let texture = try!(im_gui.prepare_texture(|handle| {
            let data = RawImage2d {
                data: Cow::Borrowed(handle.pixels),
                width: handle.width,
                height: handle.height,
                format: ClientFormat::U8U8U8U8,
            };
            Texture2d::new(ctx, data)
        }));
        im_gui.set_texture_id(texture.get_id() as usize);

        Ok(DeviceObjects {
            vertex_buffer: vertex_buffer,
            index_buffer: index_buffer,
            program: program,
            texture: texture,
        })
    }
    pub fn upload_vertex_buffer<F: Facade>(
        &mut self,
        ctx: &F,
        vtx_buffer: &[ImDrawVert],
    ) -> RendererResult<()> {
        self.vertex_buffer.invalidate();
        if let Some(slice) = self.vertex_buffer.slice_mut(0..vtx_buffer.len()) {
            slice.write(vtx_buffer);
            return Ok(());
        }
        self.vertex_buffer = try!(VertexBuffer::dynamic(ctx, vtx_buffer));
        let _ = ctx.get_context().insert_debug_marker(&format!(
            "imgui-rs: resized vertex buffer to {} bytes",
            self.vertex_buffer.get_size()
        ));
        Ok(())
    }
    pub fn upload_index_buffer<F: Facade>(
        &mut self,
        ctx: &F,
        idx_buffer: &[ImDrawIdx],
    ) -> RendererResult<()> {
        self.index_buffer.invalidate();
        if let Some(slice) = self.index_buffer.slice_mut(0..idx_buffer.len()) {
            slice.write(idx_buffer);
            return Ok(());
        }
        self.index_buffer = try!(IndexBuffer::dynamic(
            ctx,
            PrimitiveType::TrianglesList,
            idx_buffer,
        ));
        let _ = ctx.get_context().insert_debug_marker(&format!(
            "imgui-rs: resized index buffer to {} bytes",
            self.index_buffer.get_size()
        ));
        Ok(())
    }
}