use std::collections::HashMap;
use std::ffi::c_void;
use std::process::abort;

use cstr::cstr;
use ecs::component::local::Local;
use ecs::sole::Single;
use ecs::system::{Into as _, System};
use ecs::{Component, Query};

use crate::camera::Camera;
use crate::color::Color;
use crate::data_types::dimens::Dimens;
use crate::event::{Present as PresentEvent, Start as StartEvent};
use crate::lighting::{GlobalLight, LightSource};
use crate::material::{Flags as MaterialFlags, Material};
use crate::matrix::Matrix;
use crate::mesh::Mesh;
use crate::opengl::buffer::{Buffer, Usage as BufferUsage};
#[cfg(feature = "debug")]
use crate::opengl::debug::{MessageSeverity, MessageSource, MessageType};
use crate::opengl::shader::{
    Error as GlShaderError,
    Program as GlShaderProgram,
    Shader as GlShader,
};
use crate::opengl::texture::{
    set_active_texture_unit,
    Texture as GlTexture,
    TextureUnit,
};
use crate::opengl::vertex_array::{
    DataType as VertexArrayDataType,
    PrimitiveKind,
    VertexArray,
};
use crate::opengl::{clear_buffers, enable, BufferClearMask, Capability};
use crate::projection::{new_perspective_matrix, Projection};
use crate::shader::Program as ShaderProgram;
use crate::texture::{Id as TextureId, Texture};
use crate::transform::Transform;
use crate::vector::{Vec2, Vec3};
use crate::vertex::{AttributeComponentType, Vertex};
use crate::window::Window;

#[derive(Debug, Default)]
pub struct Extension {}

impl ecs::extension::Extension for Extension
{
    fn collect(self, mut collector: ecs::extension::Collector<'_>)
    {
        collector.add_system(StartEvent, initialize);

        collector.add_system(
            PresentEvent,
            render.into_system().initialize((GlObjects::default(),)),
        );
    }
}

fn initialize(window: Single<Window>)
{
    window
        .make_context_current()
        .expect("Failed to make window context current");

    gl::load_with(|symbol| match window.get_proc_address(symbol) {
        Ok(addr) => addr as *const c_void,
        Err(err) => {
            println!(
                "FATAL ERROR: Failed to get adress of OpenGL function {symbol}: {err}",
            );

            abort();
        }
    });

    #[cfg(feature = "debug")]
    initialize_debug();

    let window_size = window.size().expect("Failed to get window size");

    set_viewport(Vec2 { x: 0, y: 0 }, window_size);

    window.set_framebuffer_size_callback(|new_window_size| {
        set_viewport(Vec2::ZERO, new_window_size);
    });

    enable(Capability::DepthTest);
}

fn render(
    query: Query<(
        Mesh,
        ShaderProgram,
        Material,
        Option<MaterialFlags>,
        Transform,
    )>,
    light_source_query: Query<(LightSource, Transform)>,
    camera_query: Query<(Camera,)>,
    window: Single<Window>,
    global_light: Single<GlobalLight>,
    mut gl_objects: Local<GlObjects>,
)
{
    let Some(camera) = camera_query.iter().find_map(|(camera,)| {
        if !camera.current {
            return None;
        }

        Some(camera)
    }) else {
        #[cfg(feature = "debug")]
        tracing::warn!("No current camera. Nothing will be rendered");
        return;
    };

    // TODO: Maybe find a way to not clone here? Cloning here is needed since a light
    // source transform can be in both the object query and the light source query
    let light_source = light_source_query
        .iter()
        .next()
        .map(|(light_source, transform)| (light_source.clone(), transform.clone()));

    let GlObjects {
        shader_programs: gl_shader_programs,
        textures: gl_textures,
    } = &mut *gl_objects;

    clear_buffers(BufferClearMask::COLOR | BufferClearMask::DEPTH);

    for (mesh, shader_program, material, material_flags, transform) in &query {
        let material_flags = material_flags
            .map(|material_flags| material_flags.clone())
            .unwrap_or_default();

        let shader_program = gl_shader_programs
            .entry(shader_program.u64_hash())
            .or_insert_with(|| create_gl_shader_program(&shader_program).unwrap());

        apply_transformation_matrices(
            &transform,
            shader_program,
            &camera,
            window.size().expect("Failed to get window size"),
        );

        apply_light(
            &material,
            &material_flags,
            &global_light,
            shader_program,
            light_source
                .as_ref()
                .map(|(light_source, light_source_transform)| {
                    (light_source, light_source_transform)
                }),
            &camera,
        );

        for texture in &material.textures {
            let gl_texture = gl_textures
                .entry(texture.id())
                .or_insert_with(|| create_gl_texture(texture));

            let texture_unit =
                TextureUnit::from_texture_id(texture.id()).unwrap_or_else(|| {
                    panic!("Texture id {} is a invalid texture unit", texture.id());
                });

            set_active_texture_unit(texture_unit);

            gl_texture.bind();
        }

        shader_program.activate();

        draw_mesh(&mesh);
    }
}

#[derive(Debug, Default, Component)]
struct GlObjects
{
    shader_programs: HashMap<u64, GlShaderProgram>,
    textures: HashMap<TextureId, GlTexture>,
}

fn set_viewport(position: Vec2<u32>, size: Dimens<u32>)
{
    crate::opengl::set_viewport(position, size);
}

#[cfg(feature = "debug")]
fn initialize_debug()
{
    use crate::opengl::debug::{
        enable_debug_output,
        set_debug_message_callback,
        set_debug_message_control,
        MessageIdsAction,
    };

    enable_debug_output();

    set_debug_message_callback(opengl_debug_message_cb);

    set_debug_message_control(None, None, None, &[], MessageIdsAction::Disable);
}

fn draw_mesh(mesh: &Mesh)
{
    // TODO: Creating a new vertex buffer each draw is really dumb and slow this
    // should be rethinked
    let renderable = Renderable::new(mesh.vertices(), mesh.indices());

    renderable.vertex_arr.bind();

    if let Some(index_info) = &renderable.index_info {
        VertexArray::draw_elements(PrimitiveKind::Triangles, 0, index_info.cnt);
    } else {
        VertexArray::draw_arrays(PrimitiveKind::Triangles, 0, 3);
    }
}

fn create_gl_texture(texture: &Texture) -> GlTexture
{
    let mut gl_texture = GlTexture::new();

    gl_texture.generate(
        *texture.dimensions(),
        texture.image().as_bytes(),
        texture.pixel_data_format(),
    );

    gl_texture.apply_properties(texture.properties());

    gl_texture
}

fn create_gl_shader_program(
    shader_program: &ShaderProgram,
) -> Result<GlShaderProgram, GlShaderError>
{
    let gl_shaders = shader_program
        .shaders()
        .iter()
        .map(|shader| {
            let gl_shader = GlShader::new(shader.kind());

            gl_shader.set_source(shader.source())?;
            gl_shader.compile()?;

            Ok(gl_shader)
        })
        .collect::<Result<Vec<_>, _>>()?;

    let gl_shader_program = GlShaderProgram::new();

    for gl_shader in &gl_shaders {
        gl_shader_program.attach(gl_shader);
    }

    gl_shader_program.link()?;

    Ok(gl_shader_program)
}

#[derive(Debug)]
struct Renderable
{
    vertex_arr: VertexArray,

    /// Vertex and index buffer has to live as long as the vertex array
    _vertex_buffer: Buffer<Vertex>,
    index_info: Option<IndexInfo>,
}

impl Renderable
{
    fn new(vertices: &[Vertex], indices: Option<&[u32]>) -> Self
    {
        let mut vertex_arr = VertexArray::new();
        let mut vertex_buffer = Buffer::new();

        let mut index_info = None;

        vertex_buffer.store(vertices, BufferUsage::Static);

        vertex_arr.bind_vertex_buffer(0, &vertex_buffer, 0);

        let mut offset = 0u32;

        for attrib in Vertex::attrs() {
            vertex_arr.enable_attrib(attrib.index);

            vertex_arr.set_attrib_format(
                attrib.index,
                match attrib.component_type {
                    AttributeComponentType::Float => VertexArrayDataType::Float,
                },
                false,
                offset,
            );

            vertex_arr.set_attrib_vertex_buf_binding(attrib.index, 0);

            offset += attrib.component_size * attrib.component_cnt as u32;
        }

        if let Some(indices) = indices {
            let mut index_buffer = Buffer::new();

            index_buffer.store(indices, BufferUsage::Static);

            vertex_arr.bind_element_buffer(&index_buffer);

            index_info = Some(IndexInfo {
                _buffer: index_buffer,
                cnt: indices.len().try_into().unwrap(),
            });
        }

        Self {
            vertex_arr,
            _vertex_buffer: vertex_buffer,
            index_info,
        }
    }
}

fn apply_transformation_matrices(
    transform: &Transform,
    gl_shader_program: &mut GlShaderProgram,
    camera: &Camera,
    window_size: Dimens<u32>,
)
{
    gl_shader_program.set_uniform_matrix_4fv(cstr!("model"), &transform.as_matrix());

    let view = create_view(camera);

    gl_shader_program.set_uniform_matrix_4fv(cstr!("view"), &view);

    #[allow(clippy::cast_precision_loss)]
    let projection = match &camera.projection {
        Projection::Perspective(perspective) => new_perspective_matrix(
            perspective,
            window_size.width as f32 / window_size.height as f32,
        ),
    };

    gl_shader_program.set_uniform_matrix_4fv(cstr!("projection"), &projection);
}

fn apply_light(
    material: &Material,
    material_flags: &MaterialFlags,
    global_light: &GlobalLight,
    gl_shader_program: &mut GlShaderProgram,
    light_source: Option<(&LightSource, &Transform)>,
    camera: &Camera,
)
{
    gl_shader_program.set_uniform_vec_3fv(
        cstr!("light.position"),
        &light_source.map_or_else(Vec3::default, |(_, light_source_transform)| {
            light_source_transform.position
        }),
    );

    gl_shader_program.set_uniform_vec_3fv(
        cstr!("light.ambient"),
        // There cannot be both a material ambient color and a global ambient color
        &if material_flags.use_ambient_color {
            Color::WHITE_F32.into()
        } else {
            global_light.ambient.clone().into()
        },
    );

    gl_shader_program.set_uniform_vec_3fv(
        cstr!("light.diffuse"),
        &light_source
            .map_or(Color::WHITE_F32, |(light_source, _)| {
                light_source.diffuse.clone()
            })
            .into(),
    );

    gl_shader_program.set_uniform_vec_3fv(
        cstr!("light.specular"),
        &light_source
            .map_or(Color::WHITE_F32, |(light_source, _)| {
                light_source.specular.clone()
            })
            .into(),
    );

    gl_shader_program.set_uniform_vec_3fv(
        cstr!("material.ambient"),
        // When using the material ambient color is disabled, the ambient color has to be
        // white and not black since the material's ambient color is multiplied
        // with the global ambient light in the shader
        &if material_flags.use_ambient_color {
            material.ambient.clone()
        } else {
            Color::WHITE_F32
        }
        .into(),
    );

    gl_shader_program
        .set_uniform_vec_3fv(cstr!("material.diffuse"), &material.diffuse.clone().into());

    #[allow(clippy::cast_possible_wrap)]
    gl_shader_program.set_uniform_vec_3fv(
        cstr!("material.specular"),
        &material.specular.clone().into(),
    );

    #[allow(clippy::cast_possible_wrap)]
    gl_shader_program.set_uniform_1i(
        cstr!("material.ambient_map"),
        material.ambient_map.into_inner() as i32,
    );

    #[allow(clippy::cast_possible_wrap)]
    gl_shader_program.set_uniform_1i(
        cstr!("material.diffuse_map"),
        material.diffuse_map.into_inner() as i32,
    );

    #[allow(clippy::cast_possible_wrap)]
    gl_shader_program.set_uniform_1i(
        cstr!("material.specular_map"),
        material.specular_map.into_inner() as i32,
    );

    gl_shader_program.set_uniform_1fv(cstr!("material.shininess"), material.shininess);

    gl_shader_program.set_uniform_vec_3fv(cstr!("view_pos"), &camera.position);
}

fn create_view(camera: &Camera) -> Matrix<f32, 4, 4>
{
    let mut view = Matrix::new();

    view.look_at(&camera.position, &camera.target, &camera.global_up);

    view
}

#[cfg(feature = "debug")]
#[tracing::instrument(skip_all)]
fn opengl_debug_message_cb(
    source: MessageSource,
    ty: MessageType,
    id: u32,
    severity: MessageSeverity,
    message: &str,
)
{
    use std::backtrace::{Backtrace, BacktraceStatus};

    use tracing::{event, Level};

    macro_rules! create_event {
        ($level: expr) => {
            event!($level, ?source, ?ty, id, ?severity, message);
        };
    }

    if matches!(severity, MessageSeverity::Notification) {
        return;
    }

    match ty {
        MessageType::Error => {
            create_event!(Level::ERROR);

            let backtrace = Backtrace::capture();

            if matches!(backtrace.status(), BacktraceStatus::Captured) {
                event!(Level::TRACE, "{backtrace}");
            }
        }
        MessageType::Other => {
            create_event!(Level::INFO);
        }
        _ => {
            create_event!(Level::WARN);
        }
    };
}

#[derive(Debug)]
struct IndexInfo
{
    _buffer: Buffer<u32>,
    cnt: u32,
}