#include <iostream.h>
#include <ctype.h>
#include <stdlib.h>
#include "fraction.h"

const int LINE_LENGTH = 81;

Fraction current_value;

bool eat( istream& is )
{
	char ch;

	while( is.get( ch ) ) {
		if( ch == '\n' ) {
			is.putback( ch );
			return false;
		} else if( !isspace( ch ) ) {
			is.putback( ch );
			return true;
		}
	}

	return false;
}

bool getNumber( istream& is, myInt& num )
{
	if( !eat( is ) ) {
		return false;
	}

	num = myInt( 0 );
	char ch;

	if( !isdigit( is.peek() ) ) {
		return false;
	}

	while( is.get( ch ) ) {
		if( isdigit( ch ) ) {
			num = myInt( 10 ) * num + myInt( (ch - '0') );
		} else {
			is.putback( ch );
			break;
		}
	}

	return true;
}

bool getFraction( istream& is, Fraction& frac )
{
	myInt num( 0 );
	myInt denom( 0 );

	if( !getNumber( is, num ) ) {
		return false;
	}

	if( !eat( is ) ) {
		// Nothing left on line.  That's okay - return a single int.
		frac = Fraction( num );
		return true;
	} 

	char ch;
	is.get( ch );
	if( ch != '/' ) {
		return false;
	}

	if( !getNumber( is, denom ) ) {
		return false;
	}

	frac = Fraction( num, denom );
	return true;
}

void ignoreLine( istream& is )
{
	cout << "incomprehensible line ignored" << endl;
	char ch;
	while( cin.get( ch ) && ch != '\n' );
}

bool readArgument( istream& is, Fraction& frac )
{
	if( getFraction( is, frac ) ) {
		if( eat( cin ) ) {
			ignoreLine( cin );
		} else {
			return true;
		}
	} else {
		ignoreLine( cin );
	}

	return false;
}

int main()
{
	char ch;
	Fraction arg;

	cout << "Current value is " << current_value << endl;
	while( true ) {
		while( !eat( cin ) ) {
			if( cin ) {
				cin.get();
			} else {
				return 0;
			}
		}
		
		cin.get( ch );
		switch( ch ) {
		case '+':
			if( readArgument( cin, arg ) ) {
				current_value = current_value + arg;
			}
			break;
		case '-':
			if( eat( cin ) ) {
				if( getFraction( cin, arg ) ) {
					if( eat( cin ) ) {
						ignoreLine( cin );
					} else {
						current_value = current_value - arg;
					}
				} else {
					ignoreLine( cin );
				}
			} else {
				current_value = -current_value;
				cin.get();
			}
			break;
		case '*':
			if( readArgument( cin, arg ) ) {
				current_value = current_value * arg;
			}
			break;
		case '/':
			if( readArgument( cin, arg ) ) {
				current_value = current_value / arg;
			}
			break;
		case 'd':
			if( eat( cin ) ) {
				ignoreLine( cin );
			} else {
				cout << current_value.toDouble() << endl;
			}
			break;
		case 'e':
			if( eat( cin ) ) {
				ignoreLine( cin );
			} else {
				char buf[ LINE_LENGTH ];
				current_value.expand( buf, LINE_LENGTH );
				cout << buf << endl;
			}
			break;
		default:
			if( isdigit( ch ) ) {
				cin.putback( ch );

				if( readArgument( cin, arg ) ) {
					current_value = arg;
				}
			} else {
				ignoreLine( cin );
			}
			break;
		}

		cout << "Current value is " << current_value << endl;
	}
}