#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define 	VERSION 	23
#define 	BUFSIZE 	8096
//#define 	BUFSIZE 	1024
#define 	ERROR      	42
#define 	LOG        	44
#define 	FORBIDDEN 	403
#define 	NOTFOUND  	404

void filter_tag(char *);
char httpbuffer[BUFSIZE+1];
long httplen = 0;

#ifndef SIGCLD
#   define SIGCLD SIGCHLD
#endif

struct {
	char *ext;
	char *filetype;
} extensions [] = {
	{"gif", "image/gif" },  
	{"jpg", "image/jpg" }, 
	{"jpeg","image/jpeg"},
	{"png", "image/png" },  
	{"ico", "image/ico" },  
	{"zip", "image/zip" },  
	{"gz",  "image/gz"  },  
	{"tar", "image/tar" },  
	{"htm", "text/html" },  
	{"html","text/html" },  
	{0,0} };


//by jatin mehta & aditya chaturvedi
struct tm *current_date, *catched_date;

int dateisexpired(struct tm *t) {
        if(current_date -> tm_year < t -> tm_year)
            return 0;
        if(current_date -> tm_year > t -> tm_year)
            return 1;
        if(current_date -> tm_mon < t -> tm_mon)
            return 0;
        if(current_date -> tm_mon > t -> tm_mon)
            return 1;
        if(current_date -> tm_mday < t -> tm_mday)
            return 0;
        if(current_date -> tm_mday > t -> tm_mday)
            return 1;
        return 0;
}

int start_tag(int x) {
        while(x >= 0 && httpbuffer[x] != '<'){
                //printf("%c",httpbuffer[x--]);
                x--;
        }
        return x;
}

int end_tag(int x) {        
	int open = 1;        
	int close = 0;        
	while(x < httplen) {                
		if(httpbuffer[x] == '<') {                        
			int check = 0;                        
			while(x < httplen && httpbuffer[x] != '>') {                                
				if(httpbuffer[x] == '<' && httpbuffer[x+1] == '/') {                                        		check = 1;                                
				}                                
				x++;                        
			}                        
			if(check) {                                
				close++;                        
			}else{                                
				open++;                        
			}                        
			if(open == close) {                                
				return (x);                        
			}                
		}                
		x++;        
	}        
	//printf("someting worng happend :( \n");        
	while(1);
}

void del_tag(int x, int y) {        
	//printf("removed tag : ");        
	for(; x <= y; x++) {                
		//printf("%c",httpbuffer[x]);                
		httpbuffer[x] = ' ';        
	}        
	//printf("\n");
}

void filter_tag(char str[]) {        
	int i = 0;        
	while(i < httplen) {                
		//printf("%d \n",i);                
		if(httpbuffer[i] == str[0]) {                        
			int j = i;                        
			int k = 0;                        
			int check = 0;                        
			while(j < httplen && str[k] != '\0') {                                
				if(str[k] != httpbuffer[j]) {
					check = 1;
					break;                                
				}                                
				j++;                                
				k++;                        
			}                        
                        if(!check) {
                                int ax;
                                int date[8];

                                ax = j + 2;

                                //Assuming date format as exp="dd/mm/yyyy"
                                date[0] = (int)httpbuffer[ax] - 48;
                                date[1] = (int)httpbuffer[ax+1] - 48;
                                date[2] = (int)httpbuffer[ax+3] - 48;
                                date[3] = (int)httpbuffer[ax+4] - 48;
                                date[4] = (int)httpbuffer[ax+6] - 48;
                                date[5] = (int)httpbuffer[ax+7] - 48;
                                date[6] = (int)httpbuffer[ax+8] - 48;
                                date[7] = (int)httpbuffer[ax+9] - 48;

                                //Catched_date contains the date extracted from the HTML.
                                catched_date = (struct tm *)malloc(sizeof(struct tm));
                                catched_date -> tm_mday = (date[0] * 10) + date[1];
                                catched_date -> tm_mon = (date[2] * 10) + date[3];
                                catched_date -> tm_year = (date[4] * 1000) + (date[5] * 100) + (date[6] * 10) + date[7];

                                if(dateisexpired(catched_date)) {
                                    int start = start_tag(i);
                                    int end = end_tag(j);
                                    del_tag(start,end);
                                }
                        }
		}                
		i++;        
	}
}

void logger(int type, char *s1, char *s2, int socket_fd) {
	int fd ;
	char logbuffer[BUFSIZE*2];

	switch (type) {
	case ERROR: 
		(void)sprintf(logbuffer,"ERROR: %s:%s Errno=%d exiting pid=%d",s1, s2, errno,getpid()); 
		break;
	case FORBIDDEN: 
		(void)write(socket_fd, "HTTP/1.1 403 Forbidden\nContent-Length: 185\nConnection: close\nContent-Type: text/html\n\n<html><head>\n<title>403 Forbidden</title>\n</head><body>\n<h1>Forbidden</h1>\nThe requested URL, file type or operation is not allowed on this simple static file webserver.\n</body></html>\n",271);
		(void)sprintf(logbuffer,"FORBIDDEN: %s:%s",s1, s2); 
		break;
	case NOTFOUND: 
		(void)write(socket_fd, "HTTP/1.1 404 Not Found\nContent-Length: 136\nConnection: close\nContent-Type: text/html\n\n<html><head>\n<title>404 Not Found</title>\n</head><body>\n<h1>Not Found</h1>\nThe requested URL was not found on this server.\n</body></html>\n",224);
		(void)sprintf(logbuffer,"NOT FOUND: %s:%s",s1, s2); 
		break;
	case LOG: 
		(void)sprintf(logbuffer," INFO: %s:%s:%d",s1, s2,socket_fd); 
		break;
	}	
	/* No checks here, nothing can be done with a failure anyway */
	if((fd = open("nweb.log", O_CREAT| O_WRONLY | O_APPEND,0644)) >= 0) {
		(void)write(fd,logbuffer,strlen(logbuffer)); 
		(void)write(fd,"\n",1);      
		(void)close(fd);
	}
	if(type == ERROR || type == NOTFOUND || type == FORBIDDEN) exit(3);
}

/* this is a child web server process, so we can exit on errors */
void web(int fd, int hit) {
	int j, file_fd, buflen;
	long i, ret, len;
	char * fstr;
	static char buffer[BUFSIZE+1]; /* static so zero filled */

	ret = read(fd,buffer,BUFSIZE); 	/* read Web request in one go */
	if(ret == 0 || ret == -1) {	/* read failure stop now */
		logger(FORBIDDEN,"failed to read browser request","",fd);
	}
	if(ret > 0 && ret < BUFSIZE)	/* return code is valid chars */
		buffer[ret]=0;		/* terminate the buffer */
	else buffer[0]=0;
	for(i=0;i<ret;i++)	/* remove CF and LF characters */
		if(buffer[i] == '\r' || buffer[i] == '\n')
			buffer[i]='*';
	logger(LOG,"request",buffer,hit);
	if( strncmp(buffer,"GET ",4) && strncmp(buffer,"get ",4) ) {
		logger(FORBIDDEN,"Only simple GET operation supported",buffer,fd);
	}
	for(i=4;i<BUFSIZE;i++) { /* null terminate after the second space to ignore extra stuff */
		if(buffer[i] == ' ') { /* string is "GET URL " +lots of other stuff */
			buffer[i] = 0;
			break;
		}
	}
	for(j=0;j<i-1;j++) 	/* check for illegal parent directory use .. */
		if(buffer[j] == '.' && buffer[j+1] == '.') {
			logger(FORBIDDEN,"Parent directory (..) path names not supported",buffer,fd);
		}
	if( !strncmp(&buffer[0],"GET /\0",6) || !strncmp(&buffer[0],"get /\0",6) ) /* convert no filename to index file */
		(void)strcpy(buffer,"GET /index.html");

	/* work out the file type and check we support it */
	buflen=strlen(buffer);
	fstr = (char *)0;
	for(i=0;extensions[i].ext != 0;i++) {
		len = strlen(extensions[i].ext);
		if( !strncmp(&buffer[buflen-len], extensions[i].ext, len)) {
			fstr =extensions[i].filetype;
			break;
		}
	}
	if(fstr == 0) logger(FORBIDDEN,"file extension type not supported",buffer,fd);

	if(( file_fd = open(&buffer[5],O_RDONLY)) == -1) {  /* open the file for reading */
		logger(NOTFOUND, "failed to open file",&buffer[5],fd);
	}
	logger(LOG,"SEND",&buffer[5],hit);
        
	/* lseek to the file end to find the length */
	len = (long)lseek(file_fd, (off_t)0, SEEK_END);
	/* lseek back to the file start ready for reading */
	(void)lseek(file_fd, (off_t)0, SEEK_SET); 
         
	(void)sprintf(buffer,"HTTP/1.1 200 OK\nServer: nweb/%d.0\nContent-Length: %ld\nConnection: close\nContent-Type: %s\n\n", VERSION, len, fstr); /* Header + a blank line */
	logger(LOG,"Header",buffer,hit);
	(void)write(fd,buffer,strlen(buffer));

	/* send file in 1KB block - last block may be smaller */
	while (	(ret = read(file_fd, buffer, BUFSIZE)) > 0 ) {
		for (i=0; i<ret; i++) {
			httpbuffer[i] = buffer[i];
		}
        	httplen = ret;
		filter_tag("expDate");
		httplen = strlen(httpbuffer);
		(void)write(fd,httpbuffer,httplen);
		logger(LOG,"Body",httpbuffer,httplen);
	}
	sleep(1);	/* allow socket to drain before signalling the socket is closed */
	close(fd);
	exit(1);
}

int main(int argc, char **argv) {
	int i, port, pid, listenfd, socketfd, hit;
	socklen_t length;
	static struct sockaddr_in cli_addr; /* static = initialised to zeros */
	static struct sockaddr_in serv_addr; /* static = initialised to zeros */

        //Finding current time. Declared Global. Required <time.h> header file.
        time_t now = time(NULL);
        current_date = localtime(&now);
        current_date -> tm_mon = current_date -> tm_mon+1 ;
        current_date -> tm_year = current_date -> tm_year+1900;


	if( argc < 3  || argc > 3 || !strcmp(argv[1], "-?") ) {
		(void)printf("hint: nweb Port-Number Top-Directory\t\tversion %d\n\n"
	"\tnweb is a small and very safe mini web server\n"
	"\tnweb only servers out file/web pages with extensions named below\n"
	"\t and only from the named directory or its sub-directories.\n"
	"\tThere is no fancy features = safe and secure.\n\n"
	"\tExample: nweb 8181 /home/nwebdir &\n\n"
	"\tOnly Supports:", VERSION);
		for(i=0;extensions[i].ext != 0;i++)
			(void)printf(" %s",extensions[i].ext);

		(void)printf("\n\tNot Supported: URLs including \"..\", Java, Javascript, CGI\n"
	"\tNot Supported: directories / /etc /bin /lib /tmp /usr /dev /sbin \n"
	"\tNo warranty given or implied\n\tNigel Griffiths nag@uk.ibm.com\n"  );
		exit(0);
	}
	if( !strncmp(argv[2],"/"   ,2 ) || !strncmp(argv[2],"/etc", 5 ) ||
	    !strncmp(argv[2],"/bin",5 ) || !strncmp(argv[2],"/lib", 5 ) ||
	    !strncmp(argv[2],"/tmp",5 ) || !strncmp(argv[2],"/usr", 5 ) ||
	    !strncmp(argv[2],"/dev",5 ) || !strncmp(argv[2],"/sbin",6) ){
		(void)printf("ERROR: Bad top directory %s, see nweb -?\n",argv[2]);
		exit(3);
	}
	if(chdir(argv[2]) == -1){ 
		(void)printf("ERROR: Can't Change to directory %s\n",argv[2]);
		exit(4);
	}
	/* Become deamon + unstopable and no zombies children (= no wait()) */
	if(fork() != 0)
		return 0; /* parent returns OK to shell */
	(void)signal(SIGCLD, SIG_IGN); /* ignore child death */
	(void)signal(SIGHUP, SIG_IGN); /* ignore terminal hangups */
	for(i=0;i<32;i++)
		(void)close(i);		/* close open files */
	(void)setpgrp();		/* break away from process group */
	logger(LOG,"nweb starting",argv[1],getpid());
	/* setup the network socket */
	if((listenfd = socket(AF_INET, SOCK_STREAM,0)) <0)
		logger(ERROR, "system call","socket",0);
	port = atoi(argv[1]);
	if(port < 1024 || port >60000)
		logger(ERROR,"Invalid port number (try 1->60000)",argv[1],0);
	serv_addr.sin_family = AF_INET;
	serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
	serv_addr.sin_port = htons(port);
	if(bind(listenfd, (struct sockaddr *)&serv_addr,sizeof(serv_addr)) <0)
		logger(ERROR,"system call","bind",0);
	if( listen(listenfd,64) <0)
		logger(ERROR,"system call","listen",0);
	for(hit=1; ;hit++) {
		length = sizeof(cli_addr);
		if((socketfd = accept(listenfd, (struct sockaddr *)&cli_addr, &length)) < 0)
			logger(ERROR,"system call","accept",0);
		if((pid = fork()) < 0) {
			logger(ERROR,"system call","fork",0);
		}
		else {
			if(pid == 0) { 	/* child */
				(void)close(listenfd);
				web(socketfd,hit); /* never returns */
			} else { 	/* parent */
				(void)close(socketfd);
			}
		}
	}
}