/*
 * tiny.c - A simple, iterative HTTP/1.0 Web server that uses the 
 *     GET method to serve static and dynamic content.
 *
 * Updated 11/2019 droh 
 *   - Fixed sprintf() aliasing issue in serve_static(), and clienterror().
 */
#include "csapp.h"

void doit(int fd);
void read_requesthdrs(rio_t *rp);
int parse_uri(char *uri, char *filename, char *cgiargs);
void serve_static(int fd, char *filename, int filesize);
void get_filetype(char *filename, char *filetype);
void serve_dynamic(int fd, char *filename, char *cgiargs);
void clienterror(int fd, char *cause, char *errnum, 
		 char *shortmsg, char *longmsg);

int main(int argc, char **argv){
    int listenfd, connfd;
    char hostname[MAXLINE], port[MAXLINE];
    socklen_t clientlen;
    struct sockaddr_storage clientaddr;

    /* Check command line args */
    if (argc != 2) {
	fprintf(stderr, "usage: %s <port>\n", argv[0]);
	exit(1);
    }

    listenfd = Open_listenfd(argv[1]);
    while (1) {
	clientlen = sizeof(clientaddr);
	connfd = Accept(listenfd, (SA *)&clientaddr, &clientlen); 
        Getnameinfo((SA *) &clientaddr, clientlen, hostname, MAXLINE, 
                    port, MAXLINE, 0);
        printf("Accepted connection from (%s, %s)\n", hostname, port);
	doit(connfd);                                             
	Close(connfd);                                            
    }
}

/*
 * doit - handle one HTTP request/response transaction
 */
void doit(int fd){
    int is_static;
    struct stat sbuf;
    char buf[MAXLINE], method[MAXLINE], uri[MAXLINE], version[MAXLINE];
    char filename[MAXLINE], cgiargs[MAXLINE];
    rio_t rio;

    /* Read request line and headers */
    Rio_readinitb(&rio, fd);
    if (!Rio_readlineb(&rio, buf, MAXLINE))  
        return;
    printf("%s", buf);
    sscanf(buf, "%s %s %s", method, uri, version);
    if (strcasecmp(method, "GET")) {              
        clienterror(fd, method, "501", "Not Implemented",
                    "Tiny does not implement this method");
        return;
    }                                             
    read_requesthdrs(&rio);                       

    /* Parse URI from GET request */
    is_static = parse_uri(uri, filename, cgiargs); 
    if (stat(filename, &sbuf) < 0) {               
	clienterror(fd, filename, "404", "Not found",
		    "Tiny couldn't find this file");
	return;
    }              

    if (is_static) { /* Serve static content */          
	if (!(S_ISREG(sbuf.st_mode)) || !(S_IRUSR & sbuf.st_mode)) {
	    clienterror(fd, filename, "403", "Forbidden",
			"Tiny couldn't read the file");
	    return;
	}
	serve_static(fd, filename, sbuf.st_size);      
    }
    else { /* Serve dynamic content */
	if (!(S_ISREG(sbuf.st_mode)) || !(S_IXUSR & sbuf.st_mode)) { 
	    clienterror(fd, filename, "403", "Forbidden",
			"Tiny couldn't run the CGI program");
	    return;
	}
	serve_dynamic(fd, filename, cgiargs);        
    }
}

/*
 * read_requesthdrs - read HTTP request headers
 */
void read_requesthdrs(rio_t *rp){
    char buf[MAXLINE];

    Rio_readlineb(rp, buf, MAXLINE);
    printf("%s", buf);
    while(strcmp(buf, "\r\n")) {         
	Rio_readlineb(rp, buf, MAXLINE);
	printf("%s", buf);
    }
    return;
}

/*
 * parse_uri - parse URI into filename and CGI args
 *             return 0 if dynamic content, 1 if static
 */

int parse_uri(char *uri, char *filename, char *cgiargs){
    char *ptr;

    if (!strstr(uri, "cgi-bin")) {  /* Static content */ 
	strcpy(cgiargs, "");                             
	strcpy(filename, ".");                           
	strcat(filename, uri);                           
	if (uri[strlen(uri)-1] == '/')                   
	    strcat(filename, "home.html");               
	return 1;
    }
    else {  /* Dynamic content */                        
	ptr = index(uri, '?');                           
	if (ptr) {
	    strcpy(cgiargs, ptr+1);
	    *ptr = '\0';
	}
	else 
	    strcpy(cgiargs, "");                         
	strcpy(filename, ".");                           
	strcat(filename, uri);                           
	return 0;
    }
}

/*
 * serve_static - copy a file back to the client 
 */
void serve_static(int fd, char *filename, int filesize){
    int srcfd;
    char *srcp, filetype[MAXLINE], buf[MAXBUF];

    /* Send response headers to client */
    get_filetype(filename, filetype);    
    sprintf(buf, "HTTP/1.0 200 OK\r\n"); 
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "Server: Tiny Web Server\r\n");
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "Content-length: %d\r\n", filesize);
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "Content-type: %s\r\n\r\n", filetype);
    Rio_writen(fd, buf, strlen(buf));    

    /* Send response body to client */
    srcfd = Open(filename, O_RDONLY, 0); 
    srcp = Mmap(0, filesize, PROT_READ, MAP_PRIVATE, srcfd, 0); 
    Close(srcfd);                       
    Rio_writen(fd, srcp, filesize);     
    Munmap(srcp, filesize);             
}

/*
 * get_filetype - derive file type from file name
 */
void get_filetype(char *filename, char *filetype) {
    if (strstr(filename, ".html"))
	strcpy(filetype, "text/html");
    else if (strstr(filename, ".gif"))
	strcpy(filetype, "image/gif");
    else if (strstr(filename, ".png"))
	strcpy(filetype, "image/png");
    else if (strstr(filename, ".jpg"))
	strcpy(filetype, "image/jpeg");
    else
	strcpy(filetype, "text/plain");
}  

/*
 * serve_dynamic - run a CGI program on behalf of the client
 */
void serve_dynamic(int fd, char *filename, char *cgiargs){
    char buf[MAXLINE], *emptylist[] = { NULL };

    /* Return first part of HTTP response */
    sprintf(buf, "HTTP/1.0 200 OK\r\n"); 
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "Server: Tiny Web Server\r\n");
    Rio_writen(fd, buf, strlen(buf));
  
    if (Fork() == 0) { /* Child */ 
	/* Real server would set all CGI vars here */
	setenv("QUERY_STRING", cgiargs, 1); 
	Dup2(fd, STDOUT_FILENO);         /* Redirect stdout to client */ 
	Execve(filename, emptylist, environ); /* Run CGI program */ 
    }
    Wait(NULL); /* Parent waits for and reaps child */ 
}

/*
 * clienterror - returns an error message to the client
 */
void clienterror(int fd, char *cause, char *errnum, 
		 char *shortmsg, char *longmsg){
    char buf[MAXLINE];

    /* Print the HTTP response headers */
    sprintf(buf, "HTTP/1.0 %s %s\r\n", errnum, shortmsg);
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "Content-type: text/html\r\n\r\n");
    Rio_writen(fd, buf, strlen(buf));

    /* Print the HTTP response body */
    sprintf(buf, "<html><title>Tiny Error</title>");
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "<body bgcolor=""ffffff"">\r\n");
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "%s: %s\r\n", errnum, shortmsg);
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "<p>%s: %s\r\n", longmsg, cause);
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "<hr><em>The Tiny Web server</em>\r\n");
    Rio_writen(fd, buf, strlen(buf));
}