/*Copyright (C) 2022  Brian R. Smith
 * Contact: briansmith2865@gmail.com

**The source code in this file is free software: you can
**redistribute it and/or modify it under the terms of the GNU
**General Public License (GNU GPL) as published by the Free Software
**foundation, either version 3 of the License, or (at your option)
**any later version.  The code is distributed WITHOUT ANY WARRANTY;
**without even the implied warranty of MERCHANTABILITY or FITNESS
**FOR A PARTICULAR PURPOSE.  See the GNU GPL for more details.
**
**As additional permission under GNU GPL version 3 section 7, you
**may distribute non-source (e.g., minimized or compacted) forms of
**that code without the copy of the GNU GPL normally required by
**section 4, provided you include this license notice and a URL
**through which recipients can access the Corresponding Source.
**
** @licend  The above is the entire license notice
**for the source code in this file.
*/

#include<iostream>
#include<iomanip>
#include<stdlib.h>

#if defined(__WIN32__)
	#include<windows.h>
	#define CLS "cls"
	#define SLEEP Sleep(1000)
#elif defined(__linux__)
	#include<unistd.h>
	#define CLS  "clear"
	#define SLEEP sleep(1)
#else
	#error UNSUPPORTED PLATFORM
#endif


using namespace std;

static inline void displaytable(float debt, float amort, float interestrate);

string theCopywrite = "**This program (amort) is free software: you can\n"
	"**redistribute it and/or modify it under the terms of the GNU\n"
	"**General Public License (GNU GPL) as published by the Free Software\n"
	"**foundation, either version 3 of the License, or (at your option)\n"
	"**any later version.  This program is distributed WITHOUT ANY WARRANTY;\n"
	"**without even the implied warranty of MERCHANTABILITY or FITNESS\n"
	"**FOR A PARTICULAR PURPOSE.  See the GNU GPL for more details.\n"
	"**The source code as well as a copy of the GNU GPL can be obtained at\n"
	"**\tbriansmath.ddns.net/Code/amort/Contents.html\n";

string help = "\nEXAMPLE OF USE. Suppose you wish to get a table for the following situation:\n"
	"initial debt -- 125000;\n"  
	"payments each period towards the principal -- 12500.\n"
	"interest rate during each period -- 5\%\n\n" 
	"Then you should enter (order doesn't matter): \n\n"
	"debt 125000\nprpy 12500\nintr 5\n\n"
	"After the table has been displayed you can change any of your entries by entering\n"
	"single lines. For instance\n\n"
	"intr 6\n";

string info = "PROGRAM 'AMORT'. Enter 'copy' to see copywrite information. Enter 'help' for an example of use.";

int main () {

	float debt = 0;
	float amort = 0;
	float interestrate = 0;
	string buffer;
	string keyword;
	float value = 0;

	cout << info << "\n\n";

	bool firsttime = true;
	while(true) {
		cout << ">> ";
		getline(cin, buffer);
		istringstream is(buffer);
		is >> keyword; is >> value;

		if(keyword == "exit")
			break;
		else if(keyword == "copy") {
			cout << theCopywrite << "\n\n" << "Press enter to contiune.";
			getline(cin,buffer);
			system(CLS);
			cout << info << "\n\n";
		}
		else if(keyword == "help") {
			cout << help << "\n\n" << "Press enter to continue.";
			getline(cin, buffer);
			system(CLS);
			cout << info << "\n\n";
		}
		else if(keyword == "debt") {
			if (value <= 0) {
				cout << "Debt should be positive." << endl;
				if(!firsttime)
					SLEEP;
			}
			else 
				debt = value;
		}
		else if (keyword == "prpy") {
			if(value <= 0) {
				cout << "Payment towards principle should be positive." << endl;
				if(!firsttime)
					SLEEP;
			}
			else 
				amort = value;
		}
		else if (keyword == "intr")
			if(value <= 0) {
				cout << "Interest rate should be positive." << endl;
				if(!firsttime)
					SLEEP;
			}
			else
				interestrate = value;
		else {
			cout << "Invalid command" << endl;
			if(!firsttime)
				SLEEP;
		}
			
		if(debt > 0 && amort > 0 && interestrate > 0) {
			system(CLS);
			cout << info << "\n\n";
			displaytable(debt, amort, interestrate);
			firsttime = false;
		}
		value = 0;
	}	

	cout << "GOODBYE" << "\n\n";

	return 0;
}



static inline void displaytable(float debt, float amort, float interestrate){
	//VARIABLER
	int period = 1;
	float interest;
	float due;
	float tot_amort = 0;
	float tot_paym = 0;
	float tot_interest = 0;


	//SHOW CURRENT INTEREST RATE.
	cout << "INTEREST RATE: " << setprecision(2)
		<< fixed << interestrate << "%\n"
		<< "---------------------------------------------------------------"
		<< endl;

	//DISPLAY COLUMN TITLE. 
	cout << "PERIOD |"   
		<< left << setw(12)  << " DEBT" <<  '|'
		<<  left << setw(15)  << " PRINC. PAYMENT" << '|' 
		<< left << setw(12)  << " INTEREST " << '|'
		<< left << setw(12)   << "  AMOUNT DUE"  << endl;
	cout << setprecision(2) << fixed;


	//CALCULATE AND DISPLAY TABLE.
	do {
		if(debt < amort)
			amort = debt;
		interest = debt * interestrate/100;
		due = interest + amort;
		tot_amort += amort;
		tot_paym += due;
		tot_interest += interest;

		cout << right << setw(7) << period << '|' 
			<< right << setw(12) << debt << '|' 
			<< right << setw(15) << amort << '|' 
			<< right << setw(12) << interest << '|'
			<<  right << setw(12) << due << endl;

		debt -= amort;
		++period;
	} while(debt > 0);


	//SHOW TOTAL PAYMENTS TOWARDS PRINCIPAL, INTEREST AND ALLTOGETHER.  
	cout << "---------------------------------------------------------------\n"
		<< left << setw(21) << "TOTAL:" 
		<< right << setw(15)  << tot_amort << '|'
		<< right << setw(12)  << tot_interest << '|'
		<< right << setw(12) << tot_paym  << endl;

	cout << "\n \n";
}