package renderer

import "core:fmt"
import os "core:os/os2"

Shader :: struct {
    path: string,
    type: Shader_Type,
    backend: Shader_Backend,
}

Shader_Program :: struct {
    vertex_shader, fragment_shader: ^Shader,
    backend: Shader_Program_Backend,
}

Shader_Type :: enum {
    Vertex,
    Fragment,
    // ..
}

create_shader :: proc(renderer: ^Renderer, type: Shader_Type, path: string) -> (Shader, bool) {
    fmt.printfln("Creating shader")
    bytes, error := os.read_entire_file_from_path(path, context.allocator)
    if error != nil {
        return {}, false
    }
    defer delete(bytes)

    s: Shader
    s.type = type
    s.path = path
    
    when RENDER_BACKEND_OPENGL {
        shader_opengl, ok := opengl_create_shader(renderer, type, bytes)
        if !ok {
            return {}, false
        }
        s.backend = shader_opengl
        fmt.printfln("Backend id: %v", s.backend)
    }
    else {
        #assert(false)
    }

    return s, true
}

delete_shader :: proc(renderer: ^Renderer, shader: ^Shader) {
    assert(shader != nil)

    when RENDER_BACKEND_OPENGL {
        opengl_delete_shader(renderer, shader)
    }
}

create_shader_program :: proc(renderer: ^Renderer, vertex_shader, fragment_shader: ^Shader) -> (Shader_Program, bool) {
    assert(vertex_shader != nil)
    assert(fragment_shader != nil)

    p: Shader_Program
    p.vertex_shader = vertex_shader
    p.fragment_shader = fragment_shader

    when RENDER_BACKEND_OPENGL {
        program_opengl, ok := opengl_create_shader_program(renderer, vertex_shader, fragment_shader)
        if !ok {
            return {}, false
        }
        p.backend = program_opengl
    }
    else {
        #assert(false)
    }
    
    return p, true
}

delete_shader_program :: proc(renderer: ^Renderer, shader_program: ^Shader_Program) {
    assert(shader_program != nil)

    when RENDER_BACKEND_OPENGL {
        opengl_delete_shader_program(renderer, shader_program)
    }
}

reload_shader_program :: proc(renderer: ^Renderer, p: ^Shader_Program) -> bool {
    assert(renderer != nil)
    assert(p != nil)
    assert(p.vertex_shader != nil)
    assert(p.fragment_shader != nil)

    new_vs, vs_ok := create_shader(renderer, p.vertex_shader.type, p.vertex_shader.path)
    if !vs_ok {
        fmt.printfln("Failed to reload vertex shader")
        return false
    }

    new_fs, fs_ok := create_shader(renderer, p.fragment_shader.type, p.fragment_shader.path)
    if !fs_ok {
        fmt.printfln("Failed to reload fragment shader")
        delete_shader(renderer, &new_vs)
        return false
    }

    new_program, program_ok := create_shader_program(renderer, &new_vs, &new_fs)
    if !program_ok {
        fmt.printfln("Failed to relink shader program")
        delete_shader(renderer, &new_vs)
        delete_shader(renderer, &new_fs)
        return false
    }

    delete_shader_program(renderer, p)
    delete_shader(renderer, p.vertex_shader)
    delete_shader(renderer, p.fragment_shader)

    p.backend         = new_program.backend
    p.vertex_shader^  = new_vs
    p.fragment_shader^ = new_fs

    return true
}