#ifndef MTLREADER_H
#define MTLREADER_H

#include <vector>
#include <unordered_map>
#include <string>
#include <fstream>
#include "../../../geo/Point2.h"
#include "../../../geo/Point3.h"

/**
 * prase .mtl files
 */
class MTLReader {

public:

	struct Material {
		std::string textureFile = "";
		Point3 diffuse = Point3(1,1,1);
		float alpha = 1.0;
	};

	Material* cur = nullptr;
	std::unordered_map<std::string, Material> map;

	/** ctor. use readXYZ() */
	MTLReader() {
		;
	}

	/** read .mtl from the given file */
	void readFile(const std::string& file) {
		std::ifstream is(file);
		std::string line;
		while(getline(is, line)) {parseLine(line);}
		is.close();
	}

	/** read mtl from the given data string (.mtl file contents) */
	void readData(const char* data) {
		readData(std::string(data));
	}

	/** read mtl from the given data string (.mtl file contents) */
	void readData(const std::string& data) {
		std::stringstream is(data);
		std::string line;
		while(getline(is, line)) {parseLine(line);}
	}

	/** get the given material */
	const Material& getMaterial(const std::string& mat) const {
		const auto& it = map.find(mat);
		if (it == map.end()) {throw Exception("material not available");}
		return it->second;
	}


private:

	template<typename Out>
	void split(const std::string &s, char delim, Out result) {
		std::stringstream ss(s);
		std::string item;
		while (std::getline(ss, item, delim)) {
			*(result++) = item;
		}
	}

	void replaceAll(std::string& str, const std::string& from, const std::string& to) {
		size_t start_pos = 0;
		while((start_pos = str.find(from, start_pos)) != std::string::npos) {
			size_t end_pos = start_pos + from.length();
			str.replace(start_pos, end_pos, to);
			start_pos += to.length(); // In case 'to' contains 'from', like replacing 'x' with 'yx'
		}
	}

	/** remove empty strings from the vector */
	std::vector<std::string> nonEmpty(const std::vector<std::string>& src) {
		std::vector<std::string> res;
		for (const std::string& s : src) {
			if (!s.empty()) {res.push_back(s);}
		}
		return res;
	}

	std::vector<std::string> split(const std::string &s, char delim) {
		std::vector<std::string> elems;
		split(s, delim, std::back_inserter(elems));
		return elems;
	}

	/** parse one line of the .obj file */
	void parseLine(std::string line) {

		if (line.length() < 2) {return;}

		// remove leading "#"
		while (line[0] == ' ' || line[0] == '\t') {
			line.erase(line.begin());
		}

		// remove other linebreaks
		replaceAll(line, "\r", "");

		const std::vector<std::string> tokens = nonEmpty(split(line, ' '));
		const std::string token = tokens.front();

		if ("newmtl" == token) {
			const std::string id = tokens[1];
			map[id] = Material();
			cur = &map[id];
		} else if ("map_Ka" == token) {
			const std::string texFile = tokens[1];
			cur->textureFile = texFile;
		} else if ("map_Kd" == token) {
			const std::string texFile = tokens[1];
			cur->textureFile = texFile;
		} else if ("Kd" == token) {
			cur->diffuse.x = std::stof(tokens[1]);
			cur->diffuse.y = std::stof(tokens[2]);
			cur->diffuse.z = std::stof(tokens[3]);
		} else if ("d" == token) {
			cur->alpha = std::stof(tokens[1]);
		}

	}



};

#endif // MTLREADER_H