/**************************************************************************
 *
 *  Currency Converter
 *
 *  program       : multi_convert
 *  dependencies  : wget
 *  author        : yetimach
 *  date          : 4 July 2022
 *
 *
 *  usage: multi_convert FROM TO AMOUNT
 *
 *  Also works without arguments.
 *
 ***************************************************************************/


#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <math.h>

#define USD 1
#define EUR 2
#define GBP 3
#define CAD 4
#define AUD 5
#define JPY 6
#define INR 7
#define PLN 8
#define PEN 9

#define MAX_CH 4
#define MAX_NL 20 //max number of chars per number 
#define MAX_URL 200
#define MAX_CMD 220
#define MAX_PAT 100

#define TEMP_FILE "convert123456temp.txt"
char g_curr_str[MAX_CH]; //global currency string

FILE *convert_file;


int s_curr, d_curr; // source currency, destination currency (from to)
char s_curr_str[MAX_CH], d_curr_str[MAX_CH];  // strings to print 
long int s_curr_amt, d_curr_amt;  // amounts for calculation

// check for valid currency code and return its number code
int valid_curr(char *curr_str){
	//Here list all valid currency names
	if (strcmp(curr_str, "usd") == 0)
		return USD;
	if (strcmp(curr_str, "eur") == 0)
		return EUR;
	if (strcmp(curr_str, "gbp") == 0)
		return GBP;
	if (strcmp(curr_str, "cad") == 0)
		return CAD;
	if (strcmp(curr_str, "aud") == 0)
		return AUD;
	if (strcmp(curr_str, "jpy") == 0)
		return JPY;
	if (strcmp(curr_str, "inr") == 0)
		return INR;
	if (strcmp(curr_str, "pln") == 0)
		return PLN;
	if (strcmp(curr_str, "pen") == 0)
		return PEN;
	return 0;
}

int currency_selector(){
	int success = 0;
	int ch, i = 0;
	while ((ch = getchar()) != '\n'){
		if (isalpha(ch)){
			success = 1;
			ch = tolower(ch);
			g_curr_str[i++] = ch;
		}
		if (i > MAX_CH - 1)
			break;
	}
	if (ch != '\n')
		while (getchar() != '\n')
			; //read to newline
	g_curr_str[i] = '\0';
	if (!success)
		return 0;
	return valid_curr(g_curr_str);
	
}

void id_curr(int curr, char *curr_str, int argc){
	switch (curr) {
		case USD: 
			strcpy(curr_str, "USD");
			break;
		case EUR:
			strcpy(curr_str, "EUR");
			break;
		case GBP:
			strcpy(curr_str, "GBP");
			break;
		case CAD:
			strcpy(curr_str, "CAD");
			break;
		case AUD:
			strcpy(curr_str, "AUD");
			break;
		case JPY:
			strcpy(curr_str, "JPY");
			break;
		case INR:
			strcpy(curr_str, "INR");
			break;
		case PLN:
			strcpy(curr_str, "PLN");
			break;
		case PEN:
			strcpy(curr_str, "PEN");
			break;
	}
	if (argc != 4)
		printf("\n\tYou have selected %s ", curr_str);
}

int long convert_str_to_int(char *string){
	char units_str[MAX_NL];
	char cents_str[4];
	int long amount;
	int i = 0, i2 = 0, ch;
	while ((units_str[i] = string[i]) != '\0' && string[i] != '.')
		++i;
	units_str[i] = '\0';
	amount = (atoi(units_str) * 100);
	if (string[i] == '.'){
		++i;
		while ((ch = string[i++]) != '\0')
			if (isdigit(ch))
				cents_str[i2++] = ch;
		if (i2 == 1){
			cents_str[i2++] = '0';
			cents_str[i2] = '\0';
		}else
			cents_str[i2] = '\0';
		amount += atoi(cents_str);

	}
	return amount;	
}

long int read_amount(){
	char amount_str[MAX_NL];
	int i = 0, cents = 0, count_cents = 0, ch;
	while ((ch = getchar()) != '\n'){
		if (isdigit(ch) || ch == '.'){
			if (ch == '.')
				count_cents = 1;
			if ((i < MAX_NL - 2) && (cents < 3)){
				amount_str[i++] = ch;
			}else{
				; // do nothing
			}
			if (count_cents)
				++cents;
		}
	}
	if (cents == 2){
		amount_str[i++] = '0';
		amount_str[i] = '\0';
	}else
		amount_str[i] = '\0';
	return convert_str_to_int(amount_str);
}

double get_con_amount(){
	char convert_url[MAX_URL] = "\"www.xe.com/currencyconverter/convert/?From=";     
	strcat(convert_url, s_curr_str); 
	strcat(convert_url, "&To=");
	strcat(convert_url, d_curr_str);
	strcat(convert_url, "\" ");
	char wget_cmd[MAX_CMD] = "wget ";
	strcat(wget_cmd, convert_url);
	strcat(wget_cmd, " -q -O ");
	strcat(wget_cmd, TEMP_FILE);
	system(wget_cmd);

	int pattern_len = 0;
	int ch;
	char num_str[MAX_NL];
	char pattern[MAX_PAT] = "1<!-- --> <!-- -->";
	strcat( pattern, s_curr_str);
	strcat( pattern, "</a></td><td>");
	convert_file = fopen(TEMP_FILE, "r");

	while ((ch = pattern[pattern_len++]) != '\0')
		;
	--pattern_len;
	int matches = 0;
	int sp = 0;
	while ((ch = getc(convert_file)) != EOF){
		if (ch != pattern[matches])
			matches = 0;
		else
			++matches;
		if (matches == pattern_len)
			break;
	}
		if (ch == EOF)
			return -1;
	    int i = 0;
		while ((ch = getc(convert_file)) != '<'){
			i++;
			if (isdigit(ch) || ch == '.')
				num_str[sp++] = ch;
			if (i > MAX_NL)
				break;
		}
	num_str[sp] = '\0';
	fclose(convert_file);
	system("rm "TEMP_FILE);
	return atof(num_str);
}

void print_valid_options(){
	printf("\n\tUSD - US Dollar, EUR - Euro, GBP - British Pound,"
		   "\n\tCAD - Canadian Dollar, AUD - Australian Dollar,"
		   "\n\tJPY - Japanese Yen, INR - Indian Rupee,"
		   "\n\tPLN - Polish Zloty, PEN - Peruvian New Sol");
	return;
}

void print_usage(){
	printf("\n\n\tTo use with arguments,\n\n\tusage: multi_convert FROM TO AMOUNT"
		   "\n\n\twhere FROM and TO are the three-letter currency codes"
		   "\n\tfor the currencies you wish to convert from and to:");
	print_valid_options();
	printf("\n\n\tex: multi_convert USD EUR 130.40\n\n\tAlso works with no arguments.\n\n");
	return;
}
	
int main(int argc, char *argv[])
{
	if (argc != 1 && argc != 4){
		print_usage();
		return 0;
	}else if (argc == 4){
		int i = 0, ch;
		for (int ai = 1; ai < 3; ai++){
			i = 0;
			while (( ch = argv[ai][i]) != '\0'){
				argv[ai][i++] = tolower(ch);
			}
		}
		if ((s_curr = valid_curr(argv[1])) == 0){
			print_usage();
			return 0;
		}else{
			id_curr(s_curr, s_curr_str, argc);
		}
		if ((d_curr = valid_curr(argv[2])) == 0){
			print_usage();
			return 0;
		}else{
			id_curr(d_curr, d_curr_str, argc);
		}
		if ((s_curr_amt = convert_str_to_int(argv[3])) < 0){
			print_usage();
			return 0;
		}

		double con_amount = get_con_amount();
		d_curr_amt = lround(s_curr_amt * con_amount);
		printf("\n\tAt the current rate of %lf,\n\t%s %li.%02li is %s %li.%02li.\n\n", 
			con_amount, s_curr_str, s_curr_amt / 100, s_curr_amt % 100, d_curr_str, 
			d_curr_amt / 100, d_curr_amt % 100);
		return 0;
	}else if (argc == 1){

		double con_amount;
		printf("\n\t:::::::::::::Currency Converter:::::::::::::"
			   "\n\n\tChoose a currency to convert from");
			   print_valid_options();
			   printf("\n\tcurrency: ");
		while ((s_curr = currency_selector()) == 0)
			printf("\n\tInvalid input: try again: ");
		id_curr(s_curr, s_curr_str, argc);
		printf("as your source currency.\n");
	
		printf("\n\tChoose a currency to convert to"
			   "\n\tcurrency: ");
		while ((d_curr = currency_selector()) == 0 || d_curr == s_curr){
			if (d_curr == s_curr)
				printf("\n\tYou must select a different currency to convert to.\n\n\tTry again: ");
			else
				printf("\n\tInvalid input: try again: ");
		}
		id_curr(d_curr, d_curr_str, argc);
		printf("as your destinaton currency.\n\n\tEnter amount of %s you wish to convert to %s: ", 
				s_curr_str, d_curr_str);
		s_curr_amt = read_amount();
		con_amount = get_con_amount();
		d_curr_amt = lround(s_curr_amt * con_amount);
		printf("\n\tAt the current rate of %lf,\n\t%s %li.%02li is %s %li.%02li.\n\n", 
				con_amount, s_curr_str, s_curr_amt / 100, s_curr_amt % 100, d_curr_str, 
				d_curr_amt / 100, d_curr_amt % 100);
	}
	return 0;
}