//-------------------------------------------------------------------
//	mywebsvr.cpp
//
//	This is a minimal webserver application which will allow web
//	browsers (e.g., Mozilla Firefox or Internet Explorer) to get
//	a listing of all the files in your present working directory 
//	or get a textfile that has HyperText Markup Language format.  
//
//		to compile:  $ g++ mywebsvr.cpp -o mywebsvr
//		to execute:  $ ./mywebsvr
//
//	programmer: ALLAN CRUSE
//	written on: 03 APR 2009
//-------------------------------------------------------------------

#include <netdb.h>	// for gethostbyname()
#include <stdio.h>	// for printf(), perror() 
#include <unistd.h>	// for fork(), dup2(), close() 
#include <string.h>	// for strcpy(), strrchr()
#include <stdlib.h>	// for exit() 
#include <sys/stat.h>	// for stat()
#include <sys/wait.h>	// for wait()
#include <arpa/inet.h>	// for inet_ntoa()

#define DEMO_PORT	54321	

int main( int argc, char **argv )
{
	// get this server's hostname and network address
	char	hostname[ 64 ] = { 0 };
	gethostname( hostname, 63 );
	char	hostaddr[ 16 ] = { 0 };
	struct hostent	*hp = gethostbyname( hostname );
	if ( !hp ) { herror( "gethostbyname" ); exit(1); }
	strcpy( hostaddr, inet_ntoa( *(in_addr*)hp->h_addr ) );
	printf( "\nmywebsvr: \'%s\' (%s) \n", hostname, hostaddr );

	// prepare this server's socket-address structure	
	struct sockaddr_in	saddr = { 0 };
	socklen_t		salen = sizeof( saddr );
	saddr.sin_family	= AF_INET;
	saddr.sin_port		= htons( DEMO_PORT );
	saddr.sin_addr.s_addr	= inet_addr( hostaddr );

	// create a reusable connection-oriented socket for listening
	int	sock = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP );
	if ( sock < 0 ) { perror( "socket" ); exit(1); }
	int	oval = 1;
	int	olen = sizeof( oval );
	if ( setsockopt( sock, SOL_SOCKET, SO_REUSEADDR, &oval, olen ) < 0 )
		{ perror( "setsockopt SO_REUSEADDR" ); exit(1); }
	
	// bind this server's address and port-number to our socket
	if ( bind( sock, (sockaddr*)&saddr, salen ) < 0 ) 
		{ perror( "bind" ); exit(1); }

	// convert our socket into a listening socket
	int	backlog = 5;
	if ( listen( sock, backlog ) < 0 ) { perror( "listen" ); exit(1); }

	// begin an infinite loop to accept and process client requests
	int	count = 0;
	for(;;)	{
		// accept the next connection-request from a client
		struct sockaddr_in	caddr = { 0 };
		socklen_t		calen = sizeof( caddr );
		int	conn = accept( sock, (sockaddr*)&caddr, &calen );
		if ( conn  < 0 ) { perror( "accept" ); break; }
		printf( "\naccepting request #%d ", ++count );
		printf( "from %s\n", inet_ntoa( *(in_addr*)&caddr.sin_addr ) );

		// convert the connection-socket into separate I/O streams
		FILE	*rx = fdopen( conn, "r" );
		FILE	*tx = fdopen( dup( conn ), "w" );
		if ( !rx || !tx ) { perror( "fdopen" ); close( conn ); break; }

		// get the HTTP request-line
		char	request[ BUFSIZ ] = { 0 };
		fgets( request, BUFSIZ, rx );		
		printf( "\n %s", request );

		// exhaust the HTTP request-headers
		char	header[ BUFSIZ ] = { 0 };
		while ( fgets( header, BUFSIZ, rx ) )
			{
			printf( " %s", header );
			if ( strcmp( header, "\r\n" ) == 0 ) break;
			}

		// figure out what the client wants
		char	cmd[ BUFSIZ ] = {0}, arg[ BUFSIZ ] = { 0 };
		strcpy( arg, "./" );
		if ( sscanf( request, "%s%s", cmd, arg+2 ) != 2 )
			{ perror( "sscanf" ); close( conn ); break; } 

		// we can't do any command except "GET"
		if ( strcmp( cmd, "GET" ) != 0 )
			{ 
			fprintf( stderr, "server cannot do that\n" );
			//
			fprintf( tx, "HTTP/1.0 501 Not Implemented\r\n" );
			fprintf( tx, "Content-type: text/plain\r\n" );
			fprintf( tx, "\r\n" );
			//
			fprintf( tx, "That one is not yet implemented\r\n" );
			fclose( rx );
			fclose( tx );
			continue;
			}

		// check for presence of the requested file-object	
		struct stat	info = { 0 };
		if ( stat( arg, &info ) < 0 )
			{
			fprintf( stderr, "target does not exist\n" );
			// 
			fprintf( tx, "HTTP/1.0 404 Not Found\r\n" );
			fprintf( tx, "Content-type: text/plain\r\n" );
			fprintf( tx, "\r\n" );
			//
			fprintf( tx, "Requested item not found\r\n" );
			fclose( rx );
			fclose( tx );
			continue;
			}

		// process a request for directory listing
		if ( S_ISDIR( info.st_mode ) )
			{ 
			fprintf( stderr, "target is a directory\n" );
			//
			fprintf( tx, "HTTP/1.0 200 OK\r\n" );
			fprintf( tx, "Content-type: text/plain\r\n" );
			fprintf( tx, "\r\n" );
			//
			fflush( tx );
			if ( fork() == 0 )
				{
				dup2( conn, 1 );
				dup2( conn, 2 );
				close( conn );
				execlp( "ls", "ls", "-l", arg, NULL );
				perror( arg );
				exit(1);
				}
			wait( NULL );
			fclose( rx );
			fclose( tx );
			continue;
			}

		// process a request for an HTML textfile			
		if ( strcmp( strrchr( arg, '.' )+1, "html" ) == 0 )
			{
			fprintf( stderr, "target is an html file\n" );
			//
			fprintf( tx, "HTTP/1.0 200 OK\r\n" );
			fprintf( tx, "Content-type: text/html\r\n" );
			fprintf( tx, "\r\n" );
			//		
			fflush( tx );
			if ( fork() == 0 )
				{
				dup2( conn, 1 );
				dup2( conn, 2 );
				close( conn );
				execlp( "cat", "cat", arg, NULL );
				perror( arg );
				exit(1);
				}
			wait( NULL );
			fclose( rx );
			fclose( tx );
			continue;
			}

		// otherwise report that the object will not be served
		fprintf( stderr, "target is not an html file\n" );
		//
		fprintf( tx, "HTTP/1.0 406 Not acceptable\r\n" );
		fprintf( tx, "Content-type: text/plain\r\n" );
		fprintf( tx, "Connection: close\r\n" );
		fprintf( tx, "\r\n" );
		//
		fprintf( tx, "The format requested is not acceptable\r\n" );
		fflush( tx );
		fclose( rx );
		fclose( tx );
		continue;
		}

	close( sock );
	printf( "\nthis server has been terminated \n" );	
}