package main

import gl "vendor:OpenGL"
import "vendor:glfw"
import "core:fmt"
import "core:os"
import "core:c"

framebuffer_cb :: proc "c" (window: glfw.WindowHandle, width: i32, height: i32) {
  gl.Viewport(0, 0, width, height)
}

vertexSrc: cstring =
`#version 330 core
layout (location = 0) in vec3 aPos;
void main() {
  gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
}`

fragSrc: cstring =
`#version 330 core
out vec4 FragColor;
void main() {
  FragColor = vec4(1.f, .5f, .2f, 1.f);
}`

WIDTH :: 500
HEIGHT :: 300

main ::proc() {
  glfw.Init()
  glfw.WindowHint(glfw.CONTEXT_VERSION_MAJOR, 3)
  glfw.WindowHint(glfw.CONTEXT_VERSION_MINOR, 3)
  glfw.WindowHint(glfw.OPENGL_PROFILE, glfw.OPENGL_CORE_PROFILE)

  window := glfw.CreateWindow(WIDTH, HEIGHT, "例え", nil, nil)
  defer glfw.Terminate()
  if window == nil {
    fmt.println("GLFWウィンドウを開くに失敗")
    os.exit(-1)
  }
  glfw.MakeContextCurrent(window)

  gl.load_up_to(3, 3, glfw.gl_set_proc_address)
  gl.Viewport(0, 0, WIDTH, HEIGHT)
  glfw.SetFramebufferSizeCallback(window, framebuffer_cb)

  success: i32
  infoLog: [512]c.char

  vertexShader := gl.CreateShader(gl.VERTEX_SHADER)
  gl.ShaderSource(vertexShader, 1, &vertexSrc, nil)
  gl.CompileShader(vertexShader)

  gl.GetShaderiv(vertexShader, gl.COMPILE_STATUS, &success)
  if success != 1 {
    gl.GetShaderInfoLog(vertexShader, 512, nil, raw_data(&infoLog))
    os.exit(-1)
  }

  fragShader := gl.CreateShader(gl.FRAGMENT_SHADER)
  gl.ShaderSource(fragShader, 1, &fragSrc, nil)
  gl.CompileShader(fragShader)

  gl.GetShaderiv(fragShader, gl.COMPILE_STATUS, &success)
  if success != 1 {
    gl.GetShaderInfoLog(fragShader, 512, nil, raw_data(&infoLog))
    os.exit(-1)
  }

  shaderProgram := gl.CreateProgram()
  defer gl.DeleteProgram(shaderProgram)
  gl.AttachShader(shaderProgram, vertexShader)
  gl.AttachShader(shaderProgram, fragShader)
  gl.LinkProgram(shaderProgram)

  gl.GetProgramiv(fragShader, gl.LINK_STATUS, &success)
  if success != 1 {
    gl.GetShaderInfoLog(fragShader, 512, nil, raw_data(&infoLog))
    os.exit(-1)
  }

  gl.DeleteShader(vertexShader)
  gl.DeleteShader(fragShader)

  vertices := [?]f32 {
     .5,  .5, .0,
     .5, -.5, .0,
    -.5, -.5, .0,
    -.5,  .5, .0,
  }

  indices := [?]u32 {
    0, 1, 3,
    1, 2, 3,
  }

  VBO, VAO, EBO: u32
  gl.GenVertexArrays(1, &VAO)
  defer gl.DeleteVertexArrays(1, &VAO)
  gl.GenBuffers(1, &VBO)
  defer gl.DeleteBuffers(1, &VBO)
  gl.GenBuffers(1, &EBO)
  defer gl.DeleteBuffers(1, &EBO)
  gl.BindVertexArray(VAO)

  gl.BindBuffer(gl.ARRAY_BUFFER, VBO)
  gl.BufferData(gl.ARRAY_BUFFER, size_of(vertices),
                raw_data(&vertices), gl.STATIC_DRAW)

  gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, EBO)
  gl.BufferData(gl.ELEMENT_ARRAY_BUFFER, size_of(indices),
                raw_data(&indices), gl.STATIC_DRAW)

  gl.VertexAttribPointer(0, 3, gl.FLOAT, gl.FALSE, 3 * size_of(f32), 0)
  gl.EnableVertexAttribArray(0)

  gl.BindBuffer(gl.ARRAY_BUFFER, 0)
  gl.BindVertexArray(0)

  for !glfw.WindowShouldClose(window) {
    if glfw.GetKey(window, glfw.KEY_Q) == glfw.PRESS {
      glfw.SetWindowShouldClose(window, true)
    }

    gl.ClearColor(.6, .1, .6, 1.)
    gl.Clear(gl.COLOR_BUFFER_BIT)
    gl.UseProgram(shaderProgram)
    gl.BindVertexArray(VAO)
    gl.DrawElements(gl.TRIANGLES, 6, gl.UNSIGNED_INT, nil)

    glfw.SwapBuffers(window)
    glfw.PollEvents()
  }
}