text: #pragma once
  // Std. Includes
  #include <string>
  #include <fstream>
  #include <sstream>
  #include <iostream>
  #include <map>
  #include <vector>
  using namespace std;
  // GL Includes
  #define GLEW_STATIC
  #include <GL/glew.h> // Contains all the necessery OpenGL includes
  #include <glm/glm.hpp>
  #include <glm/gtc/matrix_transform.hpp>
  #include <SOIL.h>
  #include <assimp/Importer.hpp>
  #include <assimp/scene.h>
  #include <assimp/postprocess.h>
  
  #include "Shader.h"
  #include "Mesh.h"
  
  namespace genesis {
  
  	class Model
  	{
  	public:
  		/*  Model Data  */
  		vector<Mesh> meshes;
  		vector<Texture> textures_loaded;	// Stores all the textures loaded so far, optimization to make sure textures aren't loaded more than once.
  		/*  Functions   */
  		// Constructor, expects a filepath to a 3D model.
  		Model() { }
  
  		Model(GLchar* path)
  		{
  			this->loadModel(path);
  		}
  
  		// Draws the model, and thus all its meshes
  		void Draw(Shader shader)
  		{
  			for (GLuint i = 0; i < this->meshes.size(); i++)
  				this->meshes[i].Draw(shader);
  		}
  
  	private:
  		/*  Model Data  */
  		string directory;
  
  		GLint TextureFromFile(const char* path, string directory)
  		{
  			//Generate texture ID and load texture data 
  			string filename = string(path);
  			filename = directory + '/' + filename;
  			GLuint textureID;
  			glGenTextures(1, &textureID);
  			int width, height;
  			unsigned char* image = SOIL_load_image(filename.c_str(), &width, &height, 0, SOIL_LOAD_RGB);
  			// Assign texture to ID
  			glBindTexture(GL_TEXTURE_2D, textureID);
  			glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
  			glGenerateMipmap(GL_TEXTURE_2D);
  
  			// Parameters
  			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
  			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
  			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
  			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  			glBindTexture(GL_TEXTURE_2D, 0);
  			SOIL_free_image_data(image);
  			return textureID;
  		}
  
  		/*  Functions   */
  		// Loads a model with supported ASSIMP extensions from file and stores the resulting meshes in the meshes vector.
  		void loadModel(string path)
  		{
  			// Read file via ASSIMP
  			Assimp::Importer importer;
  			const aiScene* scene = importer.ReadFile(path, aiProcess_Triangulate | aiProcess_FlipUVs);
  			// Check for errors
  			if (!scene || scene->mFlags == AI_SCENE_FLAGS_INCOMPLETE || !scene->mRootNode) // if is Not Zero
  			{
  				cout << "ERROR::ASSIMP:: " << importer.GetErrorString() << endl;
  				return;
  			}
  			// Retrieve the directory path of the filepath
  			this->directory = path.substr(0, path.find_last_of('/'));
  
  			// Process ASSIMP's root node recursively
  			this->processNode(scene->mRootNode, scene);
  		}
  
  		// Processes a node in a recursive fashion. Processes each individual mesh located at the node and repeats this process on its children nodes (if any).
  		void processNode(aiNode* node, const aiScene* scene)
  		{
  			// Process each mesh located at the current node
  			for (GLuint i = 0; i < node->mNumMeshes; i++)
  			{
  				// The node object only contains indices to index the actual objects in the scene. 
  				// The scene contains all the data, node is just to keep stuff organized (like relations between nodes).
  				aiMesh* mesh = scene->mMeshes[node->mMeshes[i]];
  				this->meshes.push_back(this->processMesh(mesh, scene));
  			}
  			// After we've processed all of the meshes (if any) we then recursively process each of the children nodes
  			for (GLuint i = 0; i < node->mNumChildren; i++)
  			{
  				this->processNode(node->mChildren[i], scene);
  			}
  
  		}
  
  		Mesh processMesh(aiMesh* mesh, const aiScene* scene)
  		{
  			// Data to fill
  			vector<Vertex> vertices;
  			vector<GLuint> indices;
  			vector<Texture> textures;
  
  			// Walk through each of the mesh's vertices
  			for (GLuint i = 0; i < mesh->mNumVertices; i++)
  			{
  				Vertex vertex;
  				glm::vec3 vector; // We declare a placeholder vector since assimp uses its own vector class that doesn't directly convert to glm's vec3 class so we transfer the data to this placeholder glm::vec3 first.
  								  // Positions
  				vector.x = mesh->mVertices[i].x;
  				vector.y = mesh->mVertices[i].y;
  				vector.z = mesh->mVertices[i].z;
  				vertex.Position = vector;
  				// Normals
  				vector.x = mesh->mNormals[i].x;
  				vector.y = mesh->mNormals[i].y;
  				vector.z = mesh->mNormals[i].z;
  				vertex.Normal = vector;
  				// Texture Coordinates
  				if (mesh->mTextureCoords[0]) // Does the mesh contain texture coordinates?
  				{
  					glm::vec2 vec;
  					// A vertex can contain up to 8 different texture coordinates. We thus make the assumption that we won't 
  					// use models where a vertex can have multiple texture coordinates so we always take the first set (0).
  					vec.x = mesh->mTextureCoords[0][i].x;
  					vec.y = mesh->mTextureCoords[0][i].y;
  					vertex.TexCoords = vec;
  				}
  				else
  					vertex.TexCoords = glm::vec2(0.0f, 0.0f);
  				vertices.push_back(vertex);
  			}
  			// Now wak through each of the mesh's faces (a face is a mesh its triangle) and retrieve the corresponding vertex indices.
  			for (GLuint i = 0; i < mesh->mNumFaces; i++)
  			{
  				aiFace face = mesh->mFaces[i];
  				// Retrieve all indices of the face and store them in the indices vector
  				for (GLuint j = 0; j < face.mNumIndices; j++)
  					indices.push_back(face.mIndices[j]);
  			}
  			// Process materials
  			if (mesh->mMaterialIndex >= 0)
  			{
  				aiMaterial* material = scene->mMaterials[mesh->mMaterialIndex];
  				// We assume a convention for sampler names in the shaders. Each diffuse texture should be named
  				// as 'texture_diffuseN' where N is a sequential number ranging from 1 to MAX_SAMPLER_NUMBER. 
  				// Same applies to other texture as the following list summarizes:
  				// Diffuse: texture_diffuseN
  				// Specular: texture_specularN
  				// Normal: texture_normalN
  
  				// 1. Diffuse maps
  				vector<Texture> diffuseMaps = this->loadMaterialTextures(material, aiTextureType_DIFFUSE, "texture_diffuse");
  				textures.insert(textures.end(), diffuseMaps.begin(), diffuseMaps.end());
  				// 2. Specular maps
  				vector<Texture> specularMaps = this->loadMaterialTextures(material, aiTextureType_SPECULAR, "texture_specular");
  				textures.insert(textures.end(), specularMaps.begin(), specularMaps.end());
  				vector<Texture> ambientMaps = this->loadMaterialTextures(material, aiTextureType_AMBIENT, "texture_ambient");
  				textures.insert(textures.end(), ambientMaps.begin(), ambientMaps.end());
  				vector<Texture> normalMaps = this->loadMaterialTextures(material, aiTextureType_NORMALS, "texture_normal");
  				textures.insert(textures.end(), normalMaps.begin(), normalMaps.end());
  			}
  
  			// Return a mesh object created from the extracted mesh data
  			return Mesh(vertices, indices, textures);
  		}
  
  		// Checks all material textures of a given type and loads the textures if they're not loaded yet.
  		// The required info is returned as a Texture struct.
  		vector<Texture> loadMaterialTextures(aiMaterial* mat, aiTextureType type, string typeName)
  		{
  			vector<Texture> textures;
  			for (GLuint i = 0; i < mat->GetTextureCount(type); i++)
  			{
  				aiString str;
  				mat->GetTexture(type, i, &str);
  				// Check if texture was loaded before and if so, continue to next iteration: skip loading a new texture
  				GLboolean skip = false;
  				for (GLuint j = 0; j < textures_loaded.size(); j++)
  				{
  					if (textures_loaded[j].path == str)
  					{
  						textures.push_back(textures_loaded[j]);
  						skip = true; // A texture with the same filepath has already been loaded, continue to next one. (optimization)
  						break;
  					}
  				}
  				if (!skip)
  				{   // If texture hasn't been loaded already, load it
  					Texture texture;
  					texture.id = TextureFromFile(str.C_Str(), this->directory);
  					texture.type = typeName;
  					texture.path = str;
  					textures.push_back(texture);
  					this->textures_loaded.push_back(texture);  // Store it as texture loaded for entire model, to ensure we won't unnecesery load duplicate textures.
  				}
  			}
  			return textures;
  		}
  	};
  
  }