#include <cassert>
#include <cmath>

#include <glm/gtc/matrix_transform.hpp>

#include "tangerine.h"


bool
loadLights(RenderState* rs)
{
	LightsBuffer* lb = rs->lights_buf;
	u32 idx = 0;

#if 0
	// NOTE: add a directional light
	idx = (*lb->active_d_lights)++;
	lb->dl_directions[idx] = vec4(-2, 1, 3, 1);
	lb->dl_colors[idx] = vec4(0.5, 0.5, 0.3, 1);
	lb->dl_intensities[idx] = uvec4(1, 0, 0, 0);
#endif
	// NOTE: add a point light
	idx = (*lb->active_p_lights)++;
	lb->pl_positions[idx] = vec4(-10, 0, -10, 1);
	lb->pl_colors[idx] = vec4(1, 1, 0.8, 1);
	lb->pl_intensities[idx] = vec4(3, 0, 0, 0);

	GLBuffer* lights_ubo = getUBOByName(rs->gl_ctx, "lights");
	assert(lights_ubo != nullptr);
	updateGLBuffer(lights_ubo, lb->buffer);

	// NOTE: add a debug mesh to view the point light source
	RenderGroup* debug_group = getFreeRenderGroup(rs);
	assert(debug_group);
	ShaderProgram* s_debug = getShaderByName("debug", rs->gl_ctx);
	assert(s_debug);
	initRenderGroup(debug_group, rs->rg_arena, s_debug, 256, "debug_lights");
	Entity* e = getFreeEntity(debug_group);
	assert(e);
	if (!initEntity(e,
					rs->gl_ctx,
					rs->rg_arena,
					&rs->assets.models[0], // tex_cube from loadScene()
					s_debug->num_vertex_attribs,
					s_debug->attrib_mappings,
					"debug_light"))
	{
		LOGF(Error, "Error initializing debug entity for light\n");
		return false;
	}

	setEntityPosition(e, vec3(lb->pl_positions[idx]));

	return true;
}

bool
loadCubes(RenderState* rs)
{
	// NOTE: load model
	Model* tex_cube = getModelByPath(&rs->assets, "../data/textured_cube.gltf");
	if (!tex_cube) return false;

	// NOTE: load new shader, or get one of the defaults
	// NOTE: the default shaders already have their attribute mappings created
	// 	in initRenderState, but if you use a custom shader, you will need to
	// 	create a GLBufferToAttribMapping manually
	ShaderProgram* shader_lit = getShaderByName("full_lighting", rs->gl_ctx);
	if (!shader_lit) return false;

	// NOTE: init new render group
	RenderGroup* textured_cubes = getFreeRenderGroup(rs);
	assert(textured_cubes);
	initRenderGroup(textured_cubes, rs->rg_arena, shader_lit, 256,
			"textured_cubes");

	// NOTE: init entities
	const u32 NUM_CUBES = 5;
	vec3 cube_locs[NUM_CUBES] = {
		vec3(  0,   0,  0),
		vec3(-10,  10,  0),
		vec3(-10, -10,  0),
		vec3( 10,  10,  0),
		vec3( 10, -10,  0),
	};

	for (u32 i = 0; i < NUM_CUBES; i++) {
		Entity* e = getFreeEntity(textured_cubes);
		assert(e);
		char cube_name[256] = {0};
		snprintf(cube_name, 256, "textured_cube%d", i);

		if (!initEntity(e,
				rs->gl_ctx,
				rs->rg_arena,
				tex_cube,
				shader_lit->num_vertex_attribs,
				shader_lit->attrib_mappings,
				cube_name))
		{
			return false;
		}

		setEntityPosition(e, cube_locs[i]);
		scaleEntity(e, 3);
	}

	return true;
}

// NOTE: test an entity with multiple meshes
bool
loadSpaceShip(RenderState* rs)
{
	Model* ship = getModelByPath(&rs->assets, "../data/spaceship.gltf");
	if (!ship)
		return false;

	ShaderProgram* shader_lit = getShaderByName("full_lighting", rs->gl_ctx);
	if (!shader_lit)
		return false;

	// load model into gl
	RenderGroup* rg = getFreeRenderGroup(rs);
	assert(rg);
	initRenderGroup(rg, rs->rg_arena, shader_lit, 256, "ships");
	Entity* e = getFreeEntity(rg);
	assert(e);

	if (initEntity(e, rs->gl_ctx,
					rs->rg_arena,
					ship,
					shader_lit->num_vertex_attribs,
					shader_lit->attrib_mappings,
					"ship 01"))
	{
		setEntityPosition(e, vec3(0, -10, -15));
	} else {
		return false;
	}

	return true;
}

bool
testColoredVertices(RenderState* rs)
{
	Mesh m = {0};
	m.num_vertices = 5;
	m.num_indices = 12;

	vec3 vertices[m.num_vertices] = {
		{  0,  1,  0   },
		{ -1, -1, -1   },
		{ -1, -1,  1   },
		{  1, -1,  0.5 },
	};

	u16 indices[m.num_indices] = {
		0, 1, 2,
		0, 2, 3,
		0, 3, 1,
		1, 2, 3
	};

	vec3 colors[m.num_vertices] = {
		{ 1, 0, 0 },
		{ 0, 1, 0 },
		{ 0, 0, 1 },
		{ 1, 1, 0 }
	};

	m.vertices = vertices;
	m.colors = colors;
	m.indices = indices;
	mat4 xform = mat4(1);
	m.xform = &xform;
	Model mdl = {0};
	mdl.num_meshes = 1;
	mdl.meshes = &m;

	ShaderProgram* shader = getShaderByName("colored_vertices", rs->gl_ctx);
	RenderGroup* rg = getFreeRenderGroup(rs);
	assert(shader && rg);
	initRenderGroup(rg, rs->rg_arena, shader, 256, "colored_pyramids");
	Entity* e = getFreeEntity(rg);
	assert(e);

	if (initEntity(e, rs->gl_ctx,
					rs->rg_arena,
					&mdl,
					shader->num_vertex_attribs,
					shader->attrib_mappings,
					"colored pyramid 01"))
	{
		setEntityPosition(e, vec3(0, -10, 15));
	} else {
		return false;
	}

	return true;
}

bool
loadCamera(RenderState* rs)
{
	Camera* cam = rs->camera;
	vec3 cam_pos = { 0, 15, 40 };
	vec3 look_pos = { 0, 0, 0 };
	vec3 up = { 0, 1, 0 };
	cameraInitPerspective(cam, cam_pos, look_pos, up);
	GLBuffer* xforms_ubo = getUBOByName(rs->gl_ctx, "matrices");

	if (!xforms_ubo)
		return false;

	updateGLBuffer(xforms_ubo, &cam->xforms);

	return true;
}

bool
loadScene(RenderState* rs)
{
	if (!loadCubes(rs)) {
		LOGF(Error, "Error loading cubes\n");
		return false;
	}

	if (!testColoredVertices(rs)) {
		LOGF(Error, "Error loading colored vertices\n");
		return false;
	}

	if (!loadSpaceShip(rs)) {
		LOGF(Error, "Error loading ship modeln");
		return false;
	}

	if (!loadCamera(rs)) {
		LOGF(Error, "Error loading camera\n");
		return false;
	}

	return loadLights(rs);
}

void
orbitPositionZ0(vec4* pos, float angle)
{
	// get radius length
	float r = sqrt(pow(abs(pos->x), 2) + pow(abs(pos->z), 2));
	// get current angle about z axis
	float a = atan2f(pos->z, pos->x);
	// apply increment
	a += angle;
	// get new x/z components
	pos->x = r * cos(a);
	pos->z = r * sin(a);
}

void
render_cb_pre(RenderState* rs, void* user_data = nullptr)
{
	SDL_Event e;

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

	// NOTE: orbit point light
	LightsBuffer* lb = rs->lights_buf;
	orbitPositionZ0(&lb->pl_positions[0], 2 * M_PI / 180);
	RenderGroup* rg = getRenderGroupByName(rs, "debug_lights");
	Entity* ent = &rg->entities[0];
	setEntityPosition(ent, vec3(lb->pl_positions[0]));

	GLBuffer* lights_ubo = getUBOByName(rs->gl_ctx, "lights");
	assert(lights_ubo);
	updateGLBuffer(lights_ubo, lb->buffer);

	// NOTE: orbit camera
	static vec4 cam_pos;
	static vec3 look_pos;
	static vec3 up;
	static bool initialized = false;

	if (!initialized) {
		cam_pos = { 0, 15, 40, 1 };
		look_pos = { 0, 0, 0 };
		up = { 0, 1, 0 };
		initialized = true;
	}

	orbitPositionZ0(&cam_pos, 0.5 * M_PI / 180);
	rs->camera->xforms.view =
		glm::lookAt(vec3(cam_pos), vec3(0, 0, 0), vec3(0, 1, 0));

	static GLBuffer* xform_ubo = nullptr;

	if (!xform_ubo) {
		xform_ubo = getUBOByName(rs->gl_ctx, "matrices");
		assert(xform_ubo != nullptr);
	}

	updateGLBuffer(xform_ubo, &rs->camera->xforms);

	// NOTE: rotate cubes
	RenderGroup* rg2 = getRenderGroupByName(rs, "textured_cubes");

	for (u32 j = 0; j < rg2->num_entities; j++) {
		Entity& e = rg2->entities[j];
		float direction = (j % 2 == 0) ? 1 : -1;
		rotateEntity(&e, vec3(0, 1, 0), direction * (float) M_PI / (3 * 60));
	}
}

int
main()
{
	RenderState* rs = initRenderState("tangerine example", uvec2(1600, 900));

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

		doRenderLoop(rs, 60, render_cb_pre, nullptr, nullptr);

		freeRenderState(rs);
		return 0;
	}

	LOGF(Error, "error loading scene\n");
	return 1;
}