#include "shader.h"
#include "platform_gl.h"
#include "platform_log.h"
#include <assert.h>
#include <stdlib.h>
#include <string.h>

#define TAG "shaders"

static void log_v_fixed_length(const GLchar* source, const GLint length) {
	if (LOGGING_ON) {
		char log_buffer[length + 1];
		memcpy(log_buffer, source, length);
		log_buffer[length] = '\0';

		DEBUG_LOG_WRITE_V(TAG, log_buffer);
	}
}

static void log_shader_info_log(GLuint shader_object_id) {
	if (LOGGING_ON) {
		GLint log_length;
		glGetShaderiv(shader_object_id, GL_INFO_LOG_LENGTH, &log_length);
		GLchar log_buffer[log_length];
		glGetShaderInfoLog(shader_object_id, log_length, NULL, log_buffer);

		DEBUG_LOG_WRITE_V(TAG, log_buffer);
	}
}

static void log_program_info_log(GLuint program_object_id) {
	if (LOGGING_ON) {
		GLint log_length;
		glGetProgramiv(program_object_id, GL_INFO_LOG_LENGTH, &log_length);
		GLchar log_buffer[log_length];
		glGetProgramInfoLog(program_object_id, log_length, NULL, log_buffer);

		DEBUG_LOG_WRITE_V(TAG, log_buffer);
	}
}

GLuint compile_shader(const GLenum type, const GLchar* source, const GLint length) {
	assert(source != NULL);
	GLuint shader_object_id = glCreateShader(type);
	GLint compile_status;

	assert(shader_object_id != 0);

	glShaderSource(shader_object_id, 1, (const GLchar **)&source, &length);
	glCompileShader(shader_object_id);
	glGetShaderiv(shader_object_id, GL_COMPILE_STATUS, &compile_status);

	if (LOGGING_ON) {
		DEBUG_LOG_WRITE_D(TAG, "Results of compiling shader source:");
		log_v_fixed_length(source, length);
		log_shader_info_log(shader_object_id);
	}

	assert(compile_status != 0);

	return shader_object_id;
}

GLuint link_program(const GLuint vertex_shader, const GLuint fragment_shader) {
	GLuint program_object_id = glCreateProgram();
	GLint link_status;

	assert(program_object_id != 0);

	glAttachShader(program_object_id, vertex_shader);
	glAttachShader(program_object_id, fragment_shader);
	glLinkProgram(program_object_id);
	glGetProgramiv(program_object_id, GL_LINK_STATUS, &link_status);

	if (LOGGING_ON) {
		DEBUG_LOG_WRITE_D(TAG, "Results of linking program:");
		log_program_info_log(program_object_id);
	}

	assert(link_status != 0);

	return program_object_id;
}

GLuint build_program(
    const GLchar * vertex_shader_source, const GLint vertex_shader_source_length,
    const GLchar * fragment_shader_source, const GLint fragment_shader_source_length) {
	assert(vertex_shader_source != NULL);
	assert(fragment_shader_source != NULL);

	GLuint vertex_shader = compile_shader(
        GL_VERTEX_SHADER, vertex_shader_source, vertex_shader_source_length);
	GLuint fragment_shader = compile_shader(
        GL_FRAGMENT_SHADER, fragment_shader_source, fragment_shader_source_length);
	return link_program(vertex_shader, fragment_shader);
}

GLint validate_program(const GLuint program) {
	if (LOGGING_ON) {
		int validate_status;

		glValidateProgram(program);
		glGetProgramiv(program, GL_VALIDATE_STATUS, &validate_status);
		DEBUG_LOG_PRINT_D(TAG, "Results of validating program: %d", validate_status);
		log_program_info_log(program);
		return validate_status;
	}

	return 0;
}