#include "Skybox.h"
#include <vector>
#include <iostream>
#include "glew.h"
#include "freeglut.h"
#include "glm.hpp"
#include "ext.hpp"
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

static GLuint skyboxVAO, skyboxVBO;
float skyboxVertices[] = {
	// positions          
	-10.0f,  10.0f, -10.0f,
	-10.0f, -10.0f, -10.0f,
	 10.0f, -10.0f, -10.0f,
	 10.0f, -10.0f, -10.0f,
	 10.0f,  10.0f, -10.0f,
	-10.0f,  10.0f, -10.0f,

	-10.0f, -10.0f,  10.0f,
	-10.0f, -10.0f, -10.0f,
	-10.0f,  10.0f, -10.0f,
	-10.0f,  10.0f, -10.0f,
	-10.0f,  10.0f,  10.0f,
	-10.0f, -10.0f,  10.0f,

	 10.0f, -10.0f, -10.0f,
	 10.0f, -10.0f,  10.0f,
	 10.0f,  10.0f,  10.0f,
	 10.0f,  10.0f,  10.0f,
	 10.0f,  10.0f, -10.0f,
	 10.0f, -10.0f, -10.0f,

	-10.0f, -10.0f,  10.0f,
	-10.0f,  10.0f,  10.0f,
	 10.0f,  10.0f,  10.0f,
	 10.0f,  10.0f,  10.0f,
	 10.0f, -10.0f,  10.0f,
	-10.0f, -10.0f,  10.0f,

	-10.0f,  10.0f, -10.0f,
	 10.0f,  10.0f, -10.0f,
	 10.0f,  10.0f,  10.0f,
	 10.0f,  10.0f,  10.0f,
	-10.0f,  10.0f,  10.0f,
	-10.0f,  10.0f, -10.0f,

	-10.0f, -10.0f, -10.0f,
	-10.0f, -10.0f,  10.0f,
	 10.0f, -10.0f, -10.0f,
	 10.0f, -10.0f, -10.0f,
	-10.0f, -10.0f,  10.0f,
	 10.0f, -10.0f,  10.0f
};

unsigned int Skybox::loadCubemap(std::vector<std::string> faces)
{
	unsigned int textureID;
	glGenTextures(1, &textureID);
	glBindTexture(GL_TEXTURE_CUBE_MAP, textureID);

	int width, height, nrChannels;
	for (unsigned int i = 0; i < faces.size(); i++)
	{
		unsigned char* data = stbi_load(faces[i].c_str(), &width , &height, &nrChannels, 0);
		if (data)
		{
			glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i,
				0, GL_RGB, width , height , 0, GL_RGB, GL_UNSIGNED_BYTE, data
			);
			stbi_image_free(data);
		}
		else
		{
			std::cout << "Cubemap tex failed to load at path: " << faces[i] << std::endl;
			stbi_image_free(data);
		}
	}
	glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
	glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
	glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);

	return textureID;
}

void Skybox::drawSkybox(GLuint program, glm::mat4 cameraMatrix, glm::mat4 perspectiveMatrix, GLuint texture)
{
	glUseProgram(program);
	glDepthFunc(GL_LEQUAL);
	glGenVertexArrays(1, &skyboxVAO);
	glGenBuffers(1, &skyboxVBO);
	glBindVertexArray(skyboxVAO);
	glBindBuffer(GL_ARRAY_BUFFER, skyboxVBO);
	glBufferData(GL_ARRAY_BUFFER, sizeof(skyboxVertices), &skyboxVertices, GL_STATIC_DRAW);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(0);
	glm::mat4 view = glm::mat4(glm::mat3(cameraMatrix));
	glUniformMatrix4fv(glGetUniformLocation(program, "projection"), 1, GL_FALSE, (float*)&perspectiveMatrix);
	glUniformMatrix4fv(glGetUniformLocation(program, "view"), 1, GL_FALSE, (float*)&view);
	glBindVertexArray(skyboxVAO);
	glActiveTexture(GL_TEXTURE0);
	glBindTexture(GL_TEXTURE_CUBE_MAP, texture);
	glDrawArrays(GL_TRIANGLES, 0, 36);
	glBindVertexArray(0);
	glBindBuffer(GL_ARRAY_BUFFER, 0);
	glDeleteBuffers(1, &skyboxVBO);
	glDeleteVertexArrays(1, &skyboxVAO);
	glDepthFunc(GL_LESS);
	glUseProgram(0);
}