///////////////////////////////////////////////////////////////////
//
// polygon_input_stringstream.cpp
//
// Jeff Ondich, 5/30/03
//
// This shows one approach to taking input from a polygon
// file formatted as described in the polygon intersection
// assignment for CS257, Spring 2003.  The file format is:
//
//		[number of polygons]
//		[name of first polygon]
//		[number of vertices in first polygon]
//		[x space y coordinates for first vertex]
//		...
//		[x space y coordinates for last vertex]
//		[name of second polygon]
//		...
//
// For example:
//
//		1
//		My right triangle
//		3
//		100 100
//		200 200
//		100 200
//
// The format also allows comment lines, starting with #.
// This program adds a bit of robustness by also allowing blank
// lines and spaces preceding the #.
//
// This program doesn't do anything sensible other than complain
// when it encounters a violation of the format.
//
// The format is verified (as far as it goes) using the state
// of an istringstream object attached to the current line of
// text.  If an extraction operation fails, the state of the
// istringstream goes bad, and in a boolean context like this:
//
//		if( sin >> n )
//
// the extraction will evaluate to false.
//
// Unfortunately, the implementation of stringstreams on our
// Linux machines gives a segmentation fault when I call
// istringstream::str.  I've used test code from an authoritative
// web site, and it fails in the same way as mine does.  I have
// also used this code here on a FreeBSD system with g++, and
// everything worked fine.  I hope to figure out the problem
// soon, but since we are also seeing memory leaks with the
// string class, I just think our STL implementation is buggy.
//
///////////////////////////////////////////////////////////////////


#include <iostream>
#include <string>
#include <sstream>
#include <cctype>

void trim( string& s );
bool getnextline( istream& in, string& s );

void test_trim();

int main()
{
	string s;
	istringstream sin;
	int m, n, x, y;

	// Number of polygons.
	if( getnextline( cin, s ) )
	{
		sin.str( s );
		if( sin >> n )
			cout << "There are " << n << " polygons." << endl;
		else
			cout << "Trouble reading number of polygons." << endl;
	}

	// For each polygon...
	for( int j=0; j < n; j++ )
	{
		// Name.
		if( getnextline( cin, s ) )
			cout << "Polygon " << j << " is named: " << s << endl;
		else
			cout << "Trouble reading name of polygon " << j << endl;
			
		// Number of vertices.
		if( getnextline( cin, s ) )
		{
			sin.str( s );
			if( sin >> m )
				cout << "There are " << m << " vertices." << endl;
			else
				cout << "Trouble reading number of vertices." << endl;
		}

		// Vertices.
		cout << "Vertices:" << endl;
		for( int k=0; k < m; k++ )
		{
			if( getnextline( cin, s ) )
			{
				sin.str( s );
				if( sin >> x >> y )
					cout << "(" << x << "," << y << ")" << endl;
				else
					cout << "Trouble reading vertex." << endl;
			}
		}
	}

	return 0;
}


// Just a little test for my trim function.

void test_trim()
{
	string s;
	
	s = "  \t howdy\t\n\r  \t";
	trim( s );
	cout << "[" << s << "] should be [howdy]" << endl;

	s = "    ";
	trim( s );
	cout << "[" << s << "] should be []" << endl;

	s = "pig";
	trim( s );
	cout << "[" << s << "] should be [pig]" << endl;

	s = "";
	trim( s );
	cout << "[" << s << "] should be []" << endl;
}


// Removes all white space (as defined by isspace()) from the beginning
// and end of the string.

void trim( string& s )
{
	int j;
	for( j=s.length()-1; j >=0  &&  isspace(s[j]); j-- )
	{
	}
	s.erase( j + 1);

	int len = s.length();
	for( j=0; j < len  &&  isspace(s[j]); j++ )
	{
	}
	s.erase( 0, j );
}


// Skips over comment lines (including those that begin with white space
// followed by a #), blank lines, and all-white-space lines.  Returns in s
// the first line that is none of these.  Returns false if there is no
// such line remaining in the input, and true if there is.

bool getnextline( istream& in, string& s )
{
	while( getline( in, s ) )
	{
		trim( s );
		if( s.length() > 0  &&  s[0] != '#' )
			return true;
	}

	return false;
}