#include <sstream> // TODO: remove this and make something in util.h
#include <cassert>

#include <glm/glm.hpp>
#include <glm/geometric.hpp>
#include <glm/gtc/matrix_transform.hpp>

#include "aixlog.hpp"

#include "render_group.h"
#include "util.h"

#define INFO_LOG_MAX_LENGTH 312


// forward declarations

void freeRenderObject(render_object* ro);
void rgInitGLIndexBuffer(gl_index_buffer* index_buffer, GLenum usage, GLenum target);


// interface

render_object *
rgAllocateRenderObject(uint buffer_len, uint index_len)
{
	render_object* ro = UTIL_ALLOC(1, render_object);

	if (ro == nullptr)
		return nullptr;

	ro->vertex_buffer.buffer = UTIL_ALLOC(buffer_len, GLfloat);
	ro->vertex_buffer.count = ro->vertex_buffer.max_count = buffer_len;
	ro->normal_buffer.buffer = UTIL_ALLOC(buffer_len, GLfloat);
	ro->normal_buffer.count = ro->normal_buffer.max_count = buffer_len;
	ro->uv_buffer.buffer = UTIL_ALLOC(buffer_len, GLfloat);
	ro->uv_buffer.count = ro->uv_buffer.max_count = buffer_len;

	if (index_len > 0) {
		ro->index_buffer.buffer = UTIL_ALLOC(index_len, uint);
		ro->index_buffer.count = index_len;
	}

	if (ro->vertex_buffer.buffer == nullptr ||
		ro->normal_buffer.buffer == nullptr ||
		((index_len > 0) && (ro->vertex_buffer.buffer == nullptr)))
	{
		freeRenderObject(ro);
		return nullptr;
	}

	return ro;
}

render_group*
rgInitSingle(rg_shader_program& sp, uint vertex_buffer_len,
			bool use_normals, uint index_buffer_len,
			GLenum draw_mode)
{
	render_group* rg = UTIL_ALLOC(1, render_group);
	rg->shader = sp;
	rg->use_normals = use_normals;
	rg->draw_indexed = (index_buffer_len > 0);
	rg->draw_mode = draw_mode;

	rg->render_objects = UTIL_ALLOC(1, render_object*);
	rg->render_objects[0] = rgAllocateRenderObject(vertex_buffer_len, index_buffer_len);
	rg->num_objects = 1;

	if (rg->render_objects[0] == nullptr) {
		LOG(ERROR) << "Allocation Error\n";
		rgFree(rg);
	}

	return rg;
}

bool
rgInitShaderProgram(rg_shader_program& sp, const char * vertex_code, const char * frag_code)
{
	glGenVertexArrays(1, &sp.vertex_array_id);
	glBindVertexArray(sp.vertex_array_id);
	GLuint vertex_shader_id = glCreateShader(GL_VERTEX_SHADER);
	GLuint fragment_shader_id = glCreateShader(GL_FRAGMENT_SHADER);

	glShaderSource(vertex_shader_id, 1, &vertex_code, NULL);
	glShaderSource(fragment_shader_id, 1, &frag_code, NULL);
	glCompileShader(vertex_shader_id);
	glCompileShader(fragment_shader_id);

	sp.program_id = glCreateProgram();
	glAttachShader(sp.program_id, vertex_shader_id);
	glAttachShader(sp.program_id, fragment_shader_id);
	glLinkProgram(sp.program_id);

	sp.model_matrix_id = glGetUniformLocation(sp.program_id, "model");
	sp.view_matrix_id = glGetUniformLocation(sp.program_id, "view");
	sp.projection_matrix_id = glGetUniformLocation(sp.program_id, "projection");
	sp.normal_matrix_id = glGetUniformLocation(sp.program_id, "normal_matrix");
	sp.num_lights_id = glGetUniformLocation(sp.program_id, "num_lights");
	sp.sampler_id = glGetUniformLocation(sp.program_id, "sampler");

	glDetachShader(sp.program_id, vertex_shader_id);
	glDetachShader(sp.program_id, fragment_shader_id);
	glDeleteShader(vertex_shader_id);
	glDeleteShader(fragment_shader_id);

	// TODO: quick hack to allow 'dynamic' stack allocation for msvc
	// 	also remove INFO_LOG_MAX_LENGTH define
	GLint isLinked = 0;
	glGetProgramiv(sp.program_id, GL_LINK_STATUS, &isLinked);
	if (isLinked == GL_FALSE) {
		GLint maxLength = INFO_LOG_MAX_LENGTH;
		glGetProgramiv(sp.program_id, GL_INFO_LOG_LENGTH, &maxLength);
#ifdef _WIN32
		GLchar infoLog[312] = { 0 };
#else
		GLchar infoLog[maxLength] = { 0 };
#endif
		glGetProgramInfoLog(sp.program_id, maxLength, &maxLength, &infoLog[0]);
		LOG(ERROR) << infoLog << "\n";
		glDeleteProgram(sp.program_id);

		return false;
	}

	return true;
}

bool
rgInitGLTexture(GLuint& tex_id, util_image image)
{
	glGenTextures(1, &tex_id);
	glBindTexture(GL_TEXTURE_2D, tex_id);
	glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
	GLenum pixel_format = (image.num_channels == 3) ? GL_RGB : GL_RGBA;
	glTexImage2D(GL_TEXTURE_2D, 0, pixel_format, image.w, image.h, 0,
			pixel_format, GL_UNSIGNED_BYTE, image.pixels);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

	return (glGetError() == GL_NO_ERROR);
}

void
rgInitGLFloatBuffer(gl_buffer* buffer, GLenum usage, GLenum target)
{
	glGenBuffers(1, &buffer->buffer_id);
	glBindBuffer(target, buffer->buffer_id);
	glBufferData(target, buffer->max_count * sizeof(GLfloat), buffer->buffer, usage);
}

void
rgInitGLIndexBuffer(gl_index_buffer* index_buffer, GLenum usage, GLenum target)
{
	glGenBuffers(1, &index_buffer->buffer_id);
	glBindBuffer(target, index_buffer->buffer_id);
	glBufferData(target, index_buffer->count * sizeof(uint), index_buffer->buffer, usage);
}

void
rgDraw(render_group* rg, glm::mat4 model_matrix,
	glm::mat4 view_matrix, glm::mat4 projection_matrix,
	rg_point_light* lights, uint num_lights, bool update_vertex_data)
{
	for (uint i = 0; i < rg->num_objects; i++) {
		render_object* ro = rg->render_objects[i];

		glUseProgram(rg->shader.program_id);
		glUniformMatrix4fv(rg->shader.model_matrix_id, 1, GL_FALSE, &model_matrix[0][0]);
		glUniformMatrix4fv(rg->shader.view_matrix_id, 1, GL_FALSE, &view_matrix[0][0]);
		glUniformMatrix4fv(rg->shader.projection_matrix_id, 1, GL_FALSE, &projection_matrix[0][0]);

		// 1st attribute buffer : vertices
		glEnableVertexAttribArray(0);
		glBindBuffer(GL_ARRAY_BUFFER, ro->vertex_buffer.buffer_id);
		glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*) 0);

		if (update_vertex_data)
		{
			glBufferSubData(GL_ARRAY_BUFFER, 0, ro->vertex_buffer.count * sizeof(GLfloat),
				ro->vertex_buffer.buffer);
		}

		// 2rd attribute buffer: normals
		if (rg->use_normals) {
			glEnableVertexAttribArray(1);
			glBindBuffer(GL_ARRAY_BUFFER, ro->normal_buffer.buffer_id);
			glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, (void*) 0);

			glm::mat3 normal_matrix = glm::transpose(glm::inverse(glm::mat3(model_matrix)));
			glUniformMatrix3fv(rg->shader.normal_matrix_id, 1, GL_FALSE, &normal_matrix[0][0]);

			// TODO: use Uniform Buffer Objects to update light data
			// 	https://www.khronos.org/registry/OpenGL/extensions/ARB/ARB_uniform_buffer_object.txt
			// 	https://www.khronos.org/opengl/wiki/Uniform_Buffer_Objects

			glUniform1ui(rg->shader.num_lights_id, num_lights);

			for (uint i = 0; i < num_lights; i++) {
				// TODO: don't do this every frame * every render_group
				std::stringstream ss;
				ss << "lights[" << i << "].position";
				int light_pos_loc = glGetUniformLocation(rg->shader.program_id, ss.str().c_str());
				glUniform3fv(light_pos_loc, 1, &lights[i].position[0]);
			}
		}

		// 3rd attribute buffer: UV coordinates
		if (ro->use_texture) {
			glEnableVertexAttribArray(2);
			glBindBuffer(GL_ARRAY_BUFFER, ro->uv_buffer.buffer_id);
			glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, 0, (void*) 0);
			glBindTexture(GL_TEXTURE_2D, ro->tex_id);
			glUniform1i(rg->shader.sampler_id, 0);
		}

		// draw
		if (rg->draw_indexed) {
			glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ro->index_buffer.buffer_id);
			glDrawElements(rg->draw_mode, ro->index_buffer.count, GL_UNSIGNED_INT, 0);
		} else {
			glDrawArrays(rg->draw_mode, 0, ro->vertex_buffer.count / 3);
		}

		// cleanup
		glDisableVertexAttribArray(0);
		if (rg->use_normals)
			glDisableVertexAttribArray(1);
		if (ro->use_texture)
			glDisableVertexAttribArray(2);

		glUseProgram(0);
	}
}

void
rgFree(render_group* rg)
{
	if (rg == nullptr) {
		LOG(ERROR) << "tried to free nullptr\n";
		return;
	}

	for (uint i = 0; i < rg->num_objects; i++)
		freeRenderObject(rg->render_objects[i]);

	utilSafeFree(rg->render_objects);
	utilSafeFree(rg);
}


// internal

void
freeRenderObject(render_object* ro)
{
	if (ro == nullptr) {
		LOG(ERROR) << "Tried to free nullptr\n";
		return;
	}

	glDeleteTextures(1, &ro->tex_id);
	utilSafeFree(ro->vertex_buffer.buffer);
	utilSafeFree(ro->normal_buffer.buffer);
	utilSafeFree(ro->uv_buffer.buffer);
	utilSafeFree(ro->index_buffer.buffer);
	utilSafeFree(ro);
}