foreign_system_library (
	lib "opengl32.lib" when ODIN_OS == "windows";
	lib "gl" when ODIN_OS == "linux";
)
import (
	win32 "sys/windows.odin" when ODIN_OS == "windows";
	"sys/wgl.odin" when ODIN_OS == "windows";
)
import_load "opengl_constants.odin";

foreign lib {
	proc Clear         (mask: u32)                                #link_name "glClear";
	proc ClearColor    (r, g, b, a: f32)                          #link_name "glClearColor";
	proc Begin         (mode: i32)                                #link_name "glBegin";
	proc End           ()                                         #link_name "glEnd";
	proc Finish        ()                                         #link_name "glFinish";
	proc BlendFunc     (sfactor, dfactor: i32)                    #link_name "glBlendFunc";
	proc Enable        (cap: i32)                                 #link_name "glEnable";
	proc Disable       (cap: i32)                                 #link_name "glDisable";
	proc GenTextures   (count: i32, result: ^u32)                 #link_name "glGenTextures";
	proc DeleteTextures(count: i32, result: ^u32)                 #link_name "glDeleteTextures";
	proc TexParameteri (target, pname, param: i32)                #link_name "glTexParameteri";
	proc TexParameterf (target: i32, pname: i32, param: f32)      #link_name "glTexParameterf";
	proc BindTexture   (target: i32, texture: u32)                #link_name "glBindTexture";
	proc LoadIdentity  ()                                         #link_name "glLoadIdentity";
	proc Viewport      (x, y, width, height: i32)                 #link_name "glViewport";
	proc Ortho         (left, right, bottom, top, near, far: f64) #link_name "glOrtho";
	proc Color3f       (r, g, b: f32)                             #link_name "glColor3f";
	proc Vertex3f      (x, y, z: f32)                             #link_name "glVertex3f";
	proc GetError      () -> i32                                  #link_name "glGetError";
	proc GetString     (name: i32) -> ^u8                         #link_name "glGetString";
	proc GetIntegerv   (name: i32, v: ^i32)                       #link_name "glGetIntegerv";
	proc TexCoord2f    (x, y: f32)                                #link_name "glTexCoord2f";
	proc TexImage2D    (target, level, internal_format,
	                    width, height, border,
	                    format, type_: i32, pixels: rawptr)       #link_name "glTexImage2D";
}


proc _string_data(s: string) -> ^u8 #inline { return &s[0]; }

var _libgl = win32.load_library_a(_string_data("opengl32.dll\x00"));

proc get_proc_address(name: string) -> proc() #cc_c {
	if name[len(name)-1] == 0 {
		name = name[0..<len(name)-1];
	}
	// NOTE(bill): null terminated
	assert((&name[0] + len(name))^ == 0);
	var res = wgl.get_proc_address(&name[0]);
	if res == nil {
		res = win32.get_proc_address(_libgl, &name[0]);
	}
	return res;
}

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

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

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

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

	CreateShader:             proc(shader_type: i32) -> u32 #cc_c;
	ShaderSource:             proc(shader: u32, count: u32, str: ^^u8, length: ^i32) #cc_c;
	CompileShader:            proc(shader: u32) #cc_c;
	CreateProgram:            proc() -> u32 #cc_c;
	AttachShader:             proc(program, shader: u32) #cc_c;
	DetachShader:             proc(program, shader: u32) #cc_c;
	DeleteShader:             proc(shader:  u32) #cc_c;
	LinkProgram:              proc(program: u32) #cc_c;
	UseProgram:               proc(program: u32) #cc_c;
	DeleteProgram:            proc(program: u32) #cc_c;


	GetShaderiv:              proc(shader:  u32, pname: i32, params: ^i32) #cc_c;
	GetProgramiv:             proc(program: u32, pname: i32, params: ^i32) #cc_c;
	GetShaderInfoLog:         proc(shader:  u32, max_length: u32, length: ^u32, info_long: ^u8) #cc_c;
	GetProgramInfoLog:        proc(program: u32, max_length: u32, length: ^u32, info_long: ^u8) #cc_c;

	ActiveTexture:            proc(texture: i32) #cc_c;
	GenerateMipmap:           proc(target:  i32) #cc_c;

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


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

	GetUniformLocation:       proc(program: u32, name: ^u8) -> i32 #cc_c;
)

proc init() {
	proc set_proc_address(p: rawptr, name: string) #inline {
		var x = ^(proc() #cc_c)(p);
		x^ = get_proc_address(name);
	}

	set_proc_address(&GenBuffers,              "glGenBuffers\x00");
	set_proc_address(&GenVertexArrays,         "glGenVertexArrays\x00");
	set_proc_address(&GenSamplers,             "glGenSamplers\x00");
	set_proc_address(&DeleteBuffers,           "glDeleteBuffers\x00");
	set_proc_address(&BindBuffer,              "glBindBuffer\x00");
	set_proc_address(&BindSampler,             "glBindSampler\x00");
	set_proc_address(&BindVertexArray,         "glBindVertexArray\x00");
	set_proc_address(&DeleteVertexArrays,      "glDeleteVertexArrays\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");
}