#include <cstring>
#include <iostream>

#include <SDL2/SDL.h>
#include <glm/gtc/matrix_transform.hpp>

#include "asset.h"
#include "dumbLog.h"
#include "GLDebug.h"
#include "shader.h"
#include "types.h"


struct SDLHandles
{
	SDL_Window* window;
	SDL_GLContext sdl_gl_ctx;
	SDL_DisplayMode display_mode;
};

struct RenderState
{
	memory_arena* arena;
	// FIXME: revert back to num_/max_(models|textures)
	model_assets* assets;
	texture_assets* textures;

	transforms* xforms; // NOTE: would be part of camera in libTangerine
	SDLHandles* handles;
	GLContext* gl_ctx;

	u32 num_gl_meshes;
	u32 max_gl_meshes;
	GLmesh* gl_meshes;

	u32 num_lights;
	u32 max_lights;
	PointLight* lights;
};

mesh
initCubeMesh()
{
	mesh m = {0};
	m.num_vertices = 8;
	m.vertices = (glm::vec3*) std::calloc(m.num_vertices, sizeof(glm::vec3));
	m.vertices[0] = { -1,  1, -1 };
	m.vertices[1] = { -1, -1, -1 };
	m.vertices[2] = {  1, -1, -1 };
	m.vertices[3] = {  1,  1, -1 };
	m.vertices[4] = { -1,  1,  1 };
	m.vertices[5] = { -1, -1,  1 };
	m.vertices[6] = {  1, -1,  1 };
	m.vertices[7] = {  1,  1,  1 };

	m.num_indices = 36; // 6 sides, 2 tris per side, 3 verts per tri
	m.indices = (u16*) std::calloc(m.num_indices, sizeof(u16));
	u16 indices[36] = {
		0, 1, 2, 0, 2, 3,
		3, 2, 6, 3, 6, 7,
		7, 6, 5, 7, 5, 4,
		4, 5, 0, 4, 1, 0,
		0, 3, 4, 0, 3, 7,
		1, 2, 5, 2, 6, 5
	};
	std::memcpy(m.indices, indices, m.num_indices * sizeof(u16));

	return m;
}

shader_program*
getShaderByName(const char* name, GLContext* gl_ctx)
{
	u64 hash = utilFNV64a_str(name);

	for (u32 i = 0; i < gl_ctx->num_shaders; i++) {
		if (utilFNV64a_str(gl_ctx->shaders[i].name) == hash)
			return &gl_ctx->shaders[i];
	}

	printf("%s(), shader not found, %s\n", __FUNCTION__, name);
	return nullptr;
}

shader_program*
getShaderByID(GLContext* gl_ctx, GLuint prog_id)
{
	for (u32 i = 0; i < gl_ctx->num_shaders; i++) {
		if (gl_ctx->shaders[i].prog_id)
			return &gl_ctx->shaders[i];
	}

	printf("%s(), shader not found, %d\n", __FUNCTION__, prog_id);
	return nullptr;
}

// NOTE: equivalent to rgAppend() in libTangerine
model*
getModel(RenderState* rs, const char* filepath)
{
	model* mdl = assetGetCached(rs->assets, utilFNV64a_str(filepath));

	if (!mdl)
		mdl = assetLoadFromFile(rs->assets, rs->textures, rs->arena, filepath);

	return mdl;
}

GLmesh*
getFreeGLMesh(RenderState* rs)
{
	if (rs->num_gl_meshes < rs->max_gl_meshes)
		return &rs->gl_meshes[rs->num_gl_meshes++];

	printf("%s(), Error, rs->gl_meshes is full\n", __FUNCTION__);
	return nullptr;
}

#define DEFAULT_SHADER_COUNT 64
#define DEFAULT_UBO_COUNT 32
GLContext*
initGLContext(memory_arena* arena)
{
	GLContext* gl_ctx =
		(GLContext*) arenaAllocateBlock(arena, sizeof(GLContext));
	gl_ctx->max_shaders = DEFAULT_SHADER_COUNT;
	gl_ctx->num_shaders = 0;
	gl_ctx->shaders = (shader_program*) arenaAllocateBlock(
		arena, DEFAULT_SHADER_COUNT * sizeof(shader_program));
	gl_ctx->max_ubos = DEFAULT_UBO_COUNT;
	gl_ctx->num_ubos = 0;
	gl_ctx->uniform_buffers = (gl_buffer*) arenaAllocateBlock(arena,
		gl_ctx->max_ubos * sizeof(gl_buffer));
	gl_ctx->binding_count = 0;

	return gl_ctx;
}

RenderState*
initRenderState(memory_arena* arena)
{
	RenderState* rs =
		(RenderState*) arenaAllocateBlock(arena, sizeof(RenderState));

	if (rs) {
		rs->arena = arena;
		rs->assets = assetInitModelBlock(arena, 256);
		rs->textures = assetInitTextureBlock(arena, 256);
		rs->gl_ctx = initGLContext(arena);
		rs->xforms =
			(transforms*) arenaAllocateBlock(arena, sizeof(transforms));
		rs->handles =
			(SDLHandles*) arenaAllocateBlock(arena, sizeof(SDLHandles));
		rs->max_gl_meshes = 256;
		rs->gl_meshes = (GLmesh*) arenaAllocateBlock(
			arena, rs->max_gl_meshes * sizeof(GLmesh));
	}

	return rs;
}

bool
initGraphics(SDLHandles* handles)
{
	handles->window = SDL_CreateWindow(
		"shader_testing",
		SDL_WINDOWPOS_CENTERED_DISPLAY(0),
		SDL_WINDOWPOS_CENTERED_DISPLAY(0),
		1280,
		720,
		SDL_WINDOW_OPENGL|SDL_WINDOW_RESIZABLE);

	if (SDL_Init(SDL_INIT_VIDEO) != 0) {
		std::cout << "error, sdl init: " << SDL_GetError() << "\n";
		return false;
	}

	SDL_GL_SetSwapInterval(1);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS,
		SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK,
		SDL_GL_CONTEXT_PROFILE_CORE);
	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
	SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
	SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
	SDL_GetCurrentDisplayMode(0, &handles->display_mode);

	handles->sdl_gl_ctx = SDL_GL_CreateContext(handles->window);

	if (!handles->sdl_gl_ctx) {
		std::cout << "error creating context\n";
		return false;
	}

	if (glewInit()) {
		std::cout << "error initializing opengl\n";
		return false;
	}

	std::cout << "opengl vendor: " << glGetString(GL_VENDOR) << "\n";
	std::cout << "opengl renderer: " << glGetString(GL_RENDERER) << "\n";
	std::cout << "opengl version: " << glGetString(GL_VERSION) << "\n";

	glEnable(GL_DEPTH_TEST);
	glEnable(GL_LINE_SMOOTH);
	glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);

	glEnable (GL_DEBUG_OUTPUT);
	glDebugMessageCallback((GLDEBUGPROC) openglDebugCallback, 0);

	return handles->window != nullptr;
}

bool
loadScene(RenderState* rs)
{
	mesh cube = initCubeMesh();
	const u32 NUM_CUBES = 4;
	glm::vec3 cube_locs[NUM_CUBES] = {
		glm::vec3(-10,  10,  0),
		glm::vec3(-10, -10,  0),
		glm::vec3( 10,  10,  0),
		glm::vec3( 10, -10,  0),
	};

	// TODO: full lighting model
	//model* tex_cube = getModel(rs, "data/textured_cube.gltf");

	// TODO: load debug shader from libTangerine for textured_cube
	shader_program* s = getShaderByName("default", rs->gl_ctx);

	if (!s)
		return false;

	for (u32 i = 0; i < NUM_CUBES; i++) {
		GLmesh* gmesh = getFreeGLMesh(rs);

		if (!gmesh)
			return false;

		*gmesh = loadGLMesh(s, cube, GL_TRIANGLES, cube_locs[i]);

		if (gmesh->vao_id == 0)
			return false;
	}

	return true;
}

void
loop(RenderState* rs)
{
	u32 delay = 60;
	u32 frame_start, frame_time;
	bool running = true;
	SDL_Event e;

	while (running) {
		frame_start = SDL_GetTicks();

		while (SDL_PollEvent(&e)) {
			if (e.type == SDL_QUIT ||
				(e.type == SDL_KEYDOWN && e.key.keysym.sym == SDLK_ESCAPE))
			{
				running = false;
				break;
			}
		}

		glClearColor(0.2, 0.2, 0.2, 1);
		glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

		for (u32 i = 0; i < rs->num_gl_meshes; i++) {
			GLmesh& glm = rs->gl_meshes[i];
			*glm.model_xform = glm::rotate(
				*glm.model_xform, (float) M_PI / 60, glm::vec3(0, 1, 0));
			renderVAO(&glm);
		}

		SDL_GL_SwapWindow(rs->handles->window);
		glUseProgram(0);
		frame_time = SDL_GetTicks() - frame_start;

		if (delay > frame_time)
			SDL_Delay(delay - frame_time);
	}
}

void
quit(RenderState* rs)
{
	SDL_GL_DeleteContext(rs->handles->sdl_gl_ctx);
	SDL_DestroyWindow(rs->handles->window);
	SDL_Quit();
	std::free(rs->arena);
}

int
main()
{
	memory_arena* arena = arenaInit(DEFAULT_ARENA_SIZE);
	RenderState* rs = initRenderState(arena);

	if (!initGraphics(rs->handles))
		return 1;

	if (rs) {

		// FIXME: need to test this with another shader that has another UBO
		gl_buffer& ubo = rs->gl_ctx->uniform_buffers[rs->gl_ctx->num_ubos++];
		initTransforms(arena, rs->xforms, &ubo, rs->gl_ctx);

		if (!addShaderProgram(arena,
				rs->gl_ctx,
				"../data/shader.vert",
				"../data/shader.frag",
				"default"))
		{
			LOG(Error) << "error loading shaders\n";
			return 1;
		}

		if (!addShaderProgram(arena,
				rs->gl_ctx,
				"../data/colored_vertices.vert",
				"../data/colored_vertices.frag",
				"colored_vertices"))
		{
			LOG(Error) << "error loading shaders\n";
			return 1;
		}

		if (!loadScene(rs)) {
			LOG(Error) << "error loading scene\n";
			return 1;
		}

		loop(rs);
		quit(rs);
		return 0;
	}

	std::cout << "error loading scene\n";
	return 1;
}