/*
 * © Copyright 2014 – Urheberrechtshinweis
 * Alle Rechte vorbehalten / All Rights Reserved
 *
 * Programmcode ist urheberrechtlich geschuetzt.
 * Das Urheberrecht liegt, soweit nicht ausdruecklich anders gekennzeichnet, bei Frank Ebner.
 * Keine Verwendung ohne explizite Genehmigung.
 * (vgl. § 106 ff UrhG / § 97 UrhG)
 */

#ifndef OBJREADER_H
#define OBJREADER_H

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

/**
 * prase .obj files
 */
class OBJReader {

public:

	/** group vertex+normal+texture */
	struct VNT {
		int idxVertex;
		int idxNormal;
		int idxTexture;
		Point3 vertex;
		Point3 normal;
		Point2 texture;
	};

	/** one triangle */
	struct Face {
		VNT vnt[3];
		Face(VNT v1, VNT v2, VNT v3) : vnt{v1,v2,v3} {;}
	};

	/** one object within the file */
	struct Object {
		std::string material;
		std::string name;
		std::vector<Face> faces;
	};

	/** internal data */
	struct Data {
		std::vector<Point3> vertices;
		std::vector<Point2> texCoords;
		std::vector<Point3> normals;
		std::vector<std::string> materialFiles;
		std::vector<Object> objects;
		Object& curObj() {
			if (objects.empty()) {objects.push_back(Object());}
			return objects.back();
		}
	} data;

public:

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

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

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

	/** get the parsed data */
	const Data& getData() const {return data;}


private:

	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;
	}

	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;
		}
	}

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

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

		if ("mtllib" == token)	{data.materialFiles.push_back(tokens[1]);}
		if ("usemtl" == token)	{data.curObj().material = tokens[1];}
		if ("v"  == token)		{parseVertex(tokens);}
		if ("vt" == token)		{parseTexCoord(tokens);}
		if ("vn" == token)		{parseNormal(tokens);}
		if ("f"  == token)		{parseFace(tokens);}
		if ("g"  == token)		{newObject(tokens[1]);}
		if ("o"  == token)		{newObject(tokens[1]);}

	}

	/** allocate a new object */
	void newObject(const std::string& name) {
		Object o;
		o.name = name;
		data.objects.push_back(o);
	}

	/** parse one vertex from the tokenizer */
	void parseVertex(const std::vector<std::string>& t) {
		const float x = std::stof(t[1]);
		const float y = std::stof(t[2]);
		const float z = std::stof(t[3]);
		data.vertices.push_back(Point3(x,y,z));
	}

	/** parse one texture-coordinate from the tokenizer */
	void parseTexCoord(const std::vector<std::string>& t) {
		const float u = std::stof(t[1]);
		const float v = std::stof(t[2]);
		data.texCoords.push_back(Point2(u, -v));
	}

	/** parse one normal from the tokenizer */
	void parseNormal(const std::vector<std::string>& t) {
		const float x = std::stof(t[1]);
		const float y = std::stof(t[2]);
		const float z = std::stof(t[3]);
		data.normals.push_back(Point3(x,y,z));
	}

	/** parse one face from the tokenizer */
	void parseFace(const std::vector<std::string>& t) {

		std::vector<VNT> indices;

		int numVertices = 0;
		for (size_t i = 1; i < t.size(); ++i) {

			// one V/T/N
			const std::string entry = t[i];
			const std::vector<std::string> vtn = split(entry, '/');

			++numVertices;
			const std::string v = vtn[0];
			const std::string vt = (vtn.size() > 1) ? (vtn[1]) : ("");
			const std::string vn = (vtn.size() > 2) ? (vtn[2]) : ("");
			//const std::string vt = t2.getToken('/', false);
			//const std::string vn = t2.getToken('/', false);

			// create a new vertex/normal/texture combination
			VNT vnt;
			vnt.idxVertex =								(std::stoi(v)  - 1);
			vnt.idxNormal =		(vn.empty()) ? (-1) :	(std::stoi(vn) - 1);
			vnt.idxTexture =	(vt.empty()) ? (-1) :	(std::stoi(vt) - 1);

			if (vnt.idxVertex >= 0)		{vnt.vertex =	data.vertices[vnt.idxVertex];}
			if (vnt.idxNormal >= 0)		{vnt.normal =	data.normals[vnt.idxNormal];}
			if (vnt.idxTexture >= 0)	{vnt.texture =	data.texCoords[vnt.idxTexture];}

			indices.push_back(vnt);

		}

		// this will both, create normal triangles and triangulate polygons
		// see: http://www.mathopenref.com/polygontriangles.html
		for (int i = 1; i < (int) indices.size()-1; ++i) {
			Face face(indices[0], indices[1], indices[i+1]);
			data.curObj().faces.push_back(face);
		}

		// sanity check
//		if (numVertices != 3) {throw "this face is not a triangle!";}

	}

};

#endif // OBJREADER_H