text: #pragma once
  // Std. Includes
  #include <string>
  #include <fstream>
  #include <sstream>
  #include <iostream>
  #include <map>
  #include <vector>
  using namespace std;
  // GL Includes
  #include <GL/glew.h> // Contains all the necessery OpenGL includes
  #include "Antons_maths_funcs.h"
  #include "stb_image.h"
  //#include <SOIL.h>
  #include <assimp/Importer.hpp>
  #include <assimp/scene.h>
  #include <assimp/postprocess.h>
  
  #include "Mesh.h"
  
  GLint TextureFromFile(const char* path, string directory);
  
  class Model
  {
  public:
  	/*  Functions   */
  	// Constructor, expects a filepath to a 3D 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  */
  	vector<Mesh> meshes;
  	string directory;
  	vector<Texture> textures_loaded;	// Stores all the textures loaded so far, optimization to make sure textures aren't loaded more than once.
  
  										/*  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());
  		}
  
  		// 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;
  	}
  };