#include <GL/glew.h>
#include <stdlib.h>
#include <string.h>

#include "voxel.h"
#include "utils.h"
#include "list.h"
#include "gl.h"

static void print_shader_log(const char *filename, u32 id)
{
	i32 log_len;
	char *log;
	glGetShaderiv(id, GL_INFO_LOG_LENGTH, &log_len);
	log = xalloc(log_len + 1);
	glGetShaderInfoLog(id, log_len, &log_len, log);
	log[log_len] = 0;
	ERROR("failed to compile shader: '%s'\n%s", filename, log);
	free(log);
}

static GL_RESULT compile_shader(u32 *out, const char *filename, const char *code, u32 type)
{
	u32 id;
	i32 status, code_len;

	id = glCreateShader(type);
	code_len = strlen(code);
	glShaderSource(id, 1, &code, &code_len);
	glCompileShader(id);
	glGetShaderiv(id, GL_COMPILE_STATUS, &status);
	if (status == GL_FALSE) {
		print_shader_log(filename, id);
		glDeleteShader(id);
		return GL_ERROR;
	}

	*out = id;
	return GL_OK;
}

static void locate_attributes(Shader *shader)
{
	i32 count, max_len;
	List names, locations;

	list_init_string(&names);
	list_init_i32(&locations);

	glGetProgramiv(shader->program_id, GL_ACTIVE_ATTRIBUTES, &count);
	glGetProgramiv(shader->program_id, GL_ACTIVE_ATTRIBUTE_MAX_LENGTH, &max_len);
	DEBUG("shader %d has %d attributes", shader->program_id, count);

	for (i32 i = 0; i < count; i++) {
		i32 size, location;
		u32 type;
		char *name;

		name = xalloc(max_len + 1);
		glGetActiveAttrib(shader->program_id, i, max_len, NULL, &size, &type, name);

		location = glGetAttribLocation(shader->program_id, name);
		DEBUG("shader %d located attribute %s at location %d", shader->program_id, name,
			  location);

		list_push_string(&names, name);
		list_push_i32(&locations, location);
	}

	shader->attribute_names = names;
	shader->attribute_locations = locations;
}

static void locate_uniforms(Shader *shader)
{
	i32 count, max_len;
	List names, locations;

	list_init_string(&names);
	list_init_i32(&locations);

	glGetProgramiv(shader->program_id, GL_ACTIVE_UNIFORMS, &count);
	glGetProgramiv(shader->program_id, GL_ACTIVE_UNIFORM_MAX_LENGTH, &max_len);
	DEBUG("shader %d has %d uniforms", shader->program_id, count);

	for (i32 i = 0; i < count; i++) {
		i32 size, location;
		u32 type;
		char *name;

		name = xalloc(max_len + 1);
		glGetActiveUniform(shader->program_id, i, max_len, NULL, &size, &type, name);

		location = glGetUniformLocation(shader->program_id, name);
		DEBUG("shader %d located uniform %s at location %d", shader->program_id, name,
			  location);

		list_push_string(&names, name);
		list_push_i32(&locations, location);
	}

	shader->uniform_names = names;
	shader->uniform_locations = locations;
}

static void locate_uniform_blocks(Shader *shader)
{
	i32 count;
	List names, indicies;

	list_init_string(&names);
	list_init_i32(&indicies);

	glGetProgramiv(shader->program_id, GL_ACTIVE_UNIFORM_BLOCKS, &count);
	DEBUG("shader %d has %d uniform blocks", shader->program_id, count);

	for (i32 i = 0; i < count; i++) {
		i32 index, name_len;
		char *name;

		glGetActiveUniformBlockiv(shader->program_id, i, GL_UNIFORM_BLOCK_NAME_LENGTH,
								  &name_len);
		name = xalloc(name_len + 1);
		glGetActiveUniformBlockName(shader->program_id, i, name_len, NULL, name);

		index = glGetUniformBlockIndex(shader->program_id, name);
		DEBUG("shader %d located uniform block %s at index %d", shader->program_id, name,
			  index);

		list_push_string(&names, name);
		list_push_i32(&indicies, index);
	}

	shader->uniform_block_names = names;
	shader->uniform_block_indicies = indicies;
}

GL_RESULT shader_init(Shader *shader, const char *vertex_file, const char *fragment_file)
{
	char *vertex, *fragment;

	// read shader code from file
	vertex = read_file(vertex_file);
	fragment = read_file(fragment_file);
	if (!vertex || !fragment)
		goto failure;

	// compile shaders
	if (compile_shader(&shader->vertex_id, vertex_file, vertex, GL_VERTEX_SHADER))
		goto failure;
	if (compile_shader(&shader->fragment_id, fragment_file, fragment, GL_FRAGMENT_SHADER))
		goto failure;

	shader->program_id = glCreateProgram();
	glAttachShader(shader->program_id, shader->vertex_id);
	glAttachShader(shader->program_id, shader->fragment_id);
	glLinkProgram(shader->program_id);
	glValidateProgram(shader->program_id);

	locate_attributes(shader);
	locate_uniforms(shader);
	locate_uniform_blocks(shader);

	if (vertex)
		free(vertex);
	if (fragment)
		free(fragment);

	return GL_OK;

failure:
	if (vertex)
		free(vertex);
	if (fragment)
		free(fragment);
	free(shader);
	return GL_ERROR;
}

void shader_bind(Shader *shader)
{
	glEnable(GL_DEPTH_TEST);
	glEnable(GL_CULL_FACE);
	glCullFace(GL_BACK);
	glFrontFace(GL_CW);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glUseProgram(shader->program_id);
}

void shader_unbind(void)
{
	glDisable(GL_CULL_FACE);
	glUseProgram(0);
}

void shader_free(Shader *shader)
{
	glDetachShader(shader->program_id, shader->vertex_id);
	glDetachShader(shader->program_id, shader->fragment_id);
	glDeleteShader(shader->vertex_id);
	glDeleteShader(shader->fragment_id);
	glDeleteProgram(shader->program_id);
	for (u32 i = 0; i < shader->attribute_names.len; i++)
		free(shader->attribute_names.strings[i]);
	list_free(&shader->attribute_names);
	list_free(&shader->attribute_locations);
	for (u32 i = 0; i < shader->uniform_names.len; i++)
		free(shader->uniform_names.strings[i]);
	list_free(&shader->uniform_names);
	list_free(&shader->uniform_locations);
	for (u32 i = 0; i < shader->uniform_block_names.len; i++)
		free(shader->uniform_block_names.strings[i]);
	list_free(&shader->uniform_block_names);
	list_free(&shader->uniform_block_indicies);
}

int shader_attribute_location(Shader *shader, const char *name)
{
	for (u32 i = 0; i < shader->attribute_names.len; i++) {
		const char *attribute = shader->attribute_names.strings[i];
		if (strcmp(attribute, name) == 0)
			return shader->attribute_locations.ints[i];
	}
	WARN("unknown attribute '%s'", name);
	return -1;
}

int shader_uniform_location(Shader *shader, const char *name)
{
	for (u32 i = 0; i < shader->uniform_names.len; i++) {
		const char *uniform = shader->uniform_names.strings[i];
		if (strcmp(uniform, name) == 0)
			return shader->uniform_locations.ints[i];
	}
	WARN("unknown uniform '%s'", name);
	return -1;
}

int shader_uniform_block_index(Shader *shader, const char *name)
{
	for (u32 i = 0; i < shader->uniform_block_names.len; i++) {
		const char *uniform_block = shader->uniform_block_names.strings[i];
		if (strcmp(uniform_block, name) == 0)
			return shader->uniform_block_indicies.ints[i];
	}
	WARN("unknown uniform block '%s'", name);
	return -1;
}

void shader_load_float(Shader *shader, const char *name, float value)
{
	int location = shader_uniform_location(shader, name);
	glUniform1f(location, value);
}

void shader_load_int(Shader *shader, const char *name, int value)
{
	int location = shader_uniform_location(shader, name);
	glUniform1i(location, value);
}

void shader_load_vec3(Shader *shader, const char *name, vec3 value)
{
	int location = shader_uniform_location(shader, name);
	glUniform3f(location, value[0], value[1], value[2]);
}

void shader_load_ivec3(Shader *shader, const char *name, ivec3 value)
{
	int location = shader_uniform_location(shader, name);
	glUniform3i(location, value[0], value[1], value[2]);
}

void shader_load_mat4(Shader *shader, const char *name, mat4 value)
{
	int location = shader_uniform_location(shader, name);
	glUniformMatrix4fv(location, 1, GL_FALSE, (float *)value);
}

void shader_load_ubo(Shader *shader, const char *name, u32 binding)
{
	int index = shader_uniform_block_index(shader, name);
	glUniformBlockBinding(shader->program_id, index, binding);
}