#define GLAD_GL_IMPLEMENTATION
#include"gl.h"

#include<assert.h>
#include<GLFW/glfw3.h>

void debug_callback(GLenum src, GLenum type, GLuint id, GLenum severity, GLsizei length, const GLchar *msg, const void *ud) {
	puts(msg);
}

int main() {
	assert(glfwInit() && "Failed to initialize glfw");
	
	glfwWindowHint(GLFW_CLIENT_API, GLFW_OPENGL_API);
	
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 6);
	
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_COMPAT_PROFILE);
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_FALSE);
	
	glfwWindowHint(GLFW_CONTEXT_DEBUG, GLFW_TRUE);
	
	GLFWwindow *window = glfwCreateWindow(512, 512, "OpenGL Test", NULL, NULL);
	
	assert(window && "Failed to create window");
	
	glfwMakeContextCurrent(window);
	
	assert(gladLoadGL(glfwGetProcAddress) && "Failed to load GL");
	
	glDebugMessageCallback(debug_callback, NULL);
	glEnable(GL_DEBUG_OUTPUT);
	
#if TEST == 0
	
	// Fixed-function lighting cannot be enabled without crashing
	glEnable(GL_LIGHTING);
	
#elif TEST == 1
	
	// Fixed-function lighting cannot be disabled without crashing
	// even though it's already disabled by default
	glDisable(GL_LIGHTING);
	
#elif TEST == 2 || TEST == 3 || TEST == 4
	
	// Expected result: draw a white triangle
	
	// (TEST == 2)
	// dFdx in a shader works
	
	// (TEST == 3)
	// dFdy in a shader will cause a crash in its draw call, even if
	// the return value is unused
	
	// (TEST == 4)
	// Any GLSL image function will also cause a crash in its draw call,
	// even if the return value is unused. Here I try imageLoad.
	
	int status;
	
	GLuint vs = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vs, 1, &(const char*) {
		"#version 430\n"
		"\n"
		"const vec4 positions[3] = vec4[3] (vec4(-1, -1, 0, 1), vec4(3, -1, 0, 1), vec4(-1, 3, 0, 1));\n"
		"\n"
		"out vec4 v_pos;\n"
		"\n"
		"void main() {\n"
		"	v_pos = positions[gl_VertexID];\n"
		"	gl_Position = v_pos;\n"
		"}\n"
	}, (GLuint[]) {-1});
	glCompileShader(vs);
	
	glGetShaderiv(vs, GL_COMPILE_STATUS, &status);
	assert(status == GL_TRUE);
	
	GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fs, 1, (const char*[]) {
		"#version 430\n"
		"\n"
		"in vec4 v_pos;\n"
		"\n"
		"layout(r32ui, binding = 0) uniform uimage2D imgtest;\n"
		"\n"
		"void main() {\n"
#if TEST == 2
		"	dFdx(v_pos);\n"
#elif TEST == 3
		"	dFdy(v_pos);\n"
#elif TEST == 4
		"	imageLoad(imgtest, ivec2(0, 0));\n"
#endif
		"	\n"
		"	gl_FragColor = vec4(1, 1, 1, 1);\n"
		"}\n"
	}, (GLuint[]) {-1});
	glCompileShader(fs);
	
	glGetShaderiv(fs, GL_COMPILE_STATUS, &status);
	assert(status == GL_TRUE);
	
	GLuint program = glCreateProgram();
	glAttachShader(program, vs);
	glAttachShader(program, fs);
	
	glLinkProgram(program);
	
	glGetProgramiv(program, GL_LINK_STATUS, &status);
	assert(status == GL_TRUE);
	
	GLuint vao;
	glGenVertexArrays(1, &vao);
	glBindVertexArray(vao);
	
	glUseProgram(program);
	
#if TEST == 4
	GLuint texture;
	glGenTextures(1, &texture);
	glBindTexture(GL_TEXTURE_2D, texture);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_R32UI, 128, 128, 0, GL_RED_INTEGER, GL_UNSIGNED_INT, NULL);
	
	glBindImageTexture(0, texture, 0, GL_FALSE, 0, GL_READ_WRITE, GL_R32UI);
#endif
	
	// Here is where each crash happens (except for TEST == 2, because
	// dFdx works just fine).
	glDrawArrays(GL_TRIANGLES, 0, 3);
#else
#error No such test.
#endif
	
	glfwSwapBuffers(window);
	
	while(!glfwWindowShouldClose(window)) {
		glfwPollEvents();
	}
}