#foreign_system_library "opengl32" when ODIN_OS == "windows";
#import win32 "sys/windows.odin" when ODIN_OS == "windows";
#include "opengl_constants.odin";

proc Clear         (mask u32)                                #foreign "glClear"
proc ClearColor    (r, g, b, a f32)                          #foreign "glClearColor"
proc Begin         (mode i32)                                #foreign "glBegin"
proc End           ()                                        #foreign "glEnd"
proc Finish        ()                                        #foreign "glFinish"
proc BlendFunc     (sfactor, dfactor i32)                    #foreign "glBlendFunc"
proc Enable        (cap i32)                                 #foreign "glEnable"
proc Disable       (cap i32)                                 #foreign "glDisable"
proc GenTextures   (count i32, result ^u32)                  #foreign "glGenTextures"
proc DeleteTextures(count i32, result ^u32)                  #foreign "glDeleteTextures"
proc TexParameteri (target, pname, param i32)                #foreign "glTexParameteri"
proc TexParameterf (target i32, pname i32, param f32)        #foreign "glTexParameterf"
proc BindTexture   (target i32, texture u32)                 #foreign "glBindTexture"
proc LoadIdentity  ()                                        #foreign "glLoadIdentity"
proc Viewport      (x, y, width, height i32)                 #foreign "glViewport"
proc Ortho         (left, right, bottom, top, near, far f64) #foreign "glOrtho"
proc Color3f       (r, g, b f32)                             #foreign "glColor3f"
proc Vertex3f      (x, y, z f32)                             #foreign "glVertex3f"
proc TexImage2D    (target, level, internal_format,
                    width, height, border,
                    format, _type i32, pixels rawptr) #foreign "glTexImage2D"

proc GetError   () -> i32            #foreign "glGetError"
proc GetString  (name i32) -> ^byte #foreign "glGetString"
proc GetIntegerv(name i32, v ^i32) #foreign "glGetIntegerv"



var _libgl = win32.LoadLibraryA(("opengl32.dll\x00" as string).data);

proc GetProcAddress(name string) -> proc() {
	assert(name[name.count-1] == 0);
	var res = win32.wglGetProcAddress(name.data);
	if res == nil {
		res = win32.GetProcAddress(_libgl, name.data);
	}
	return res;
}

var (
	GenBuffers      proc(count i32, buffers ^u32);
	GenVertexArrays proc(count i32, buffers ^u32);
	GenSamplers     proc(count i32, buffers ^u32);
	BindBuffer      proc(target i32, buffer u32);
	BindVertexArray proc(buffer u32);
	BindSampler     proc(position i32, sampler u32);
	BufferData      proc(target i32, size int, data rawptr, usage i32);
	BufferSubData   proc(target i32, offset, size int, data rawptr);

	DrawArrays      proc(mode, first i32, count u32);
	DrawElements    proc(mode i32, count u32, type_ i32, indices rawptr);

	MapBuffer       proc(target, access i32) -> rawptr;
	UnmapBuffer     proc(target i32);

	VertexAttribPointer proc(index u32, size, type_ i32, normalized i32, stride u32, pointer rawptr);
	EnableVertexAttribArray proc(index u32);

	CreateShader  proc(shader_type i32) -> u32;
	ShaderSource  proc(shader u32, count u32, str ^^byte, length ^i32);
	CompileShader proc(shader u32);
	CreateProgram proc() -> u32;
	AttachShader  proc(program, shader u32);
	DetachShader  proc(program, shader u32);
	DeleteShader  proc(shader u32);
	LinkProgram   proc(program u32);
	UseProgram    proc(program u32);
	DeleteProgram proc(program u32);


	GetShaderiv       proc(shader  u32, pname i32, params ^i32);
	GetProgramiv      proc(program u32, pname i32, params ^i32);
	GetShaderInfoLog  proc(shader  u32, max_length u32, length ^u32, info_long ^byte);
	GetProgramInfoLog proc(program u32, max_length u32, length ^u32, info_long ^byte);

	ActiveTexture  proc(texture i32);
	GenerateMipmap proc(target i32);

	SamplerParameteri    proc(sampler u32, pname i32, param i32);
	SamplerParameterf    proc(sampler u32, pname i32, param f32);
	SamplerParameteriv   proc(sampler u32, pname i32, params ^i32);
	SamplerParameterfv   proc(sampler u32, pname i32, params ^f32);
	SamplerParameterIiv  proc(sampler u32, pname i32, params ^i32);
	SamplerParameterIuiv proc(sampler u32, pname i32, params ^u32);


	Uniform1i        proc(loc i32, v0 i32);
	Uniform2i        proc(loc i32, v0, v1 i32);
	Uniform3i        proc(loc i32, v0, v1, v2 i32);
	Uniform4i        proc(loc i32, v0, v1, v2, v3 i32);
	Uniform1f        proc(loc i32, v0 f32);
	Uniform2f        proc(loc i32, v0, v1 f32);
	Uniform3f        proc(loc i32, v0, v1, v2 f32);
	Uniform4f        proc(loc i32, v0, v1, v2, v3 f32);
	UniformMatrix4fv proc(loc i32, count u32, transpose i32, value ^f32);

	GetUniformLocation proc(program u32, name ^byte) -> i32;
);

proc init() {
	proc set_proc_address(p rawptr, name string) #inline { (p as ^proc())^ = GetProcAddress(name); }

	set_proc_address(^GenBuffers,      "glGenBuffers\x00");
	set_proc_address(^GenVertexArrays, "glGenVertexArrays\x00");
	set_proc_address(^GenSamplers,     "glGenSamplers\x00");
	set_proc_address(^BindBuffer,      "glBindBuffer\x00");
	set_proc_address(^BindSampler,     "glBindSampler\x00");
	set_proc_address(^BindVertexArray, "glBindVertexArray\x00");
	set_proc_address(^BufferData,      "glBufferData\x00");
	set_proc_address(^BufferSubData,   "glBufferSubData\x00");

	set_proc_address(^DrawArrays,      "glDrawArrays\x00");
	set_proc_address(^DrawElements,    "glDrawElements\x00");

	set_proc_address(^MapBuffer,   "glMapBuffer\x00");
	set_proc_address(^UnmapBuffer, "glUnmapBuffer\x00");

	set_proc_address(^VertexAttribPointer,     "glVertexAttribPointer\x00");
	set_proc_address(^EnableVertexAttribArray, "glEnableVertexAttribArray\x00");

	set_proc_address(^CreateShader,  "glCreateShader\x00");
	set_proc_address(^ShaderSource,  "glShaderSource\x00");
	set_proc_address(^CompileShader, "glCompileShader\x00");
	set_proc_address(^CreateProgram, "glCreateProgram\x00");
	set_proc_address(^AttachShader,  "glAttachShader\x00");
	set_proc_address(^DetachShader,  "glDetachShader\x00");
	set_proc_address(^DeleteShader,  "glDeleteShader\x00");
	set_proc_address(^LinkProgram,   "glLinkProgram\x00");
	set_proc_address(^UseProgram,    "glUseProgram\x00");
	set_proc_address(^DeleteProgram, "glDeleteProgram\x00");

	set_proc_address(^GetShaderiv,       "glGetShaderiv\x00");
	set_proc_address(^GetProgramiv,      "glGetProgramiv\x00");
	set_proc_address(^GetShaderInfoLog,  "glGetShaderInfoLog\x00");
	set_proc_address(^GetProgramInfoLog, "glGetProgramInfoLog\x00");

	set_proc_address(^ActiveTexture,  "glActiveTexture\x00");
	set_proc_address(^GenerateMipmap, "glGenerateMipmap\x00");

	set_proc_address(^Uniform1i,        "glUniform1i\x00");
	set_proc_address(^UniformMatrix4fv, "glUniformMatrix4fv\x00");

	set_proc_address(^GetUniformLocation, "glGetUniformLocation\x00");

	set_proc_address(^SamplerParameteri,    "glSamplerParameteri\x00");
	set_proc_address(^SamplerParameterf,    "glSamplerParameterf\x00");
	set_proc_address(^SamplerParameteriv,   "glSamplerParameteriv\x00");
	set_proc_address(^SamplerParameterfv,   "glSamplerParameterfv\x00");
	set_proc_address(^SamplerParameterIiv,  "glSamplerParameterIiv\x00");
	set_proc_address(^SamplerParameterIuiv, "glSamplerParameterIuiv\x00");
}