/* **************************************
 * proxy.c
 * Xiaoyin Li
 * xiaoyinl@andrew
 * 
 * Only part 1 is worked on - manually tested, everything works out
 * but I can't figure out for the life of me why this doesn't work
 * out when I'm running the tests. :'(
 *
 * ************************************** */

#define _GNU_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include "csapp.h"

#define DEFAULT_PORT 80

/* Contains the parsed HTTP request line */
typedef struct http_request_type {
    char* host;
    char* path;
    char* url;
    int port;
    int version;  
} http_request;  


/* Function prototypes */
int parse_request(char * req_str, http_request * req);
void free_http_request(http_request* req);

/* Main routine */
int main(int arc, char *argv[]) 
{
  int port=0, listenfd, connfd, serverfd, n;
  struct sockaddr_in serveraddr;
  struct http_request_type httpreq; 
  int serverln=sizeof(serveraddr);
  rio_t rio, rio_server;
  char buf[MAXLINE];

  port=atoi(argv[1]);

  listenfd = open_listenfd(port);
  while (1){
    /* connect */
    connfd = Accept(listenfd, (SA*)&serveraddr, &serverln);
    
    rio_readinitb(&rio, connfd);
    rio_readlineb(&rio, buf, MAXLINE);
    
    n=parse_request(buf, &httpreq);
    if (n<0){
      printf("Error on parse.\n");
      exit(0);
    }

    serverfd = open_clientfd(httpreq.host, 80);

    rio_readinitb(&rio_server, serverfd);

    sprintf(buf,"GET %s HTTP/1.0\r\n\r\n", httpreq.url);
    rio_writen(serverfd, buf, MAXLINE);
    while ( (n=rio_readnb(&rio_server, buf, MAXLINE))>0){
      rio_writen(connfd, buf, n);
    } 
    Close(connfd);
    Close(serverfd);
  }
  printf("Byebye from proxy.\n");
  exit(0);
}

/* 
 * free_http_request - Frees the http_request structure  
 */
void free_http_request(http_request* req)
{
    free(req->host);
    req->host = NULL;
    free(req->path);
    req->path = NULL;
    free(req->url);
    req->url = NULL;
}

/* 
 * parse_request - Parses the first line of a browser-formatted HTTP request
 * 
 * req_str - a NULL terminated string containing the HTTP request
 * req - the http request structure to store the parsed information
 *
 * Returns 0 on success and -1 on failure
 */
int parse_request(char * req_str, http_request * req)
{
    char * url_begin, * url_end, * host_begin, * host_end, * path;

    printf("%s\n", req_str);

    /* check for valid request method*/
    if (strncmp( req_str, "GET ", strlen("GET ") )) {
	printf("process_request: client issued an invalid request.\n");
	return -1;
    }

    /* parse out url from request */
    if((url_begin = strchr(req_str, ' ')) == NULL)
	return -1;
    url_begin++;

    if((url_end = strchr(url_begin, ' ')) == NULL)
	return -1;
  
    /* check for valid request version */
    if (!strncmp(url_end + 1, "HTTP/1.0\r\n", strlen("HTTP/1.0\r\n"))) {
	req->version = 0;
    }
    else if (!strncmp(url_end + 1, "HTTP/1.1\r\n", strlen("HTTP/1.1\r\n"))) {  
	req->version = 1;
    }
    else {
	printf("process_request: client issued an invalid request.\n");
	return -1;
    } 
  
    /* mallocs occur beyond this point - beware memory leaks */
    /* copy request url */
    req->url = strndup(url_begin, (int)(url_end - url_begin));

    /* parse out host server string from original request string */
    if((host_begin = strstr(req_str, "//")) == NULL)
	host_begin = url_begin;
    else
	host_begin += 2;

    host_end = strpbrk(host_begin , ":/ ");
    req->host = strndup(host_begin, (int)(host_end - host_begin));

    /* parse out optional port */
    req->port = DEFAULT_PORT;

    if(*host_end == ':') {
	req->port = atoi(host_end + 1);
    }
  
    /* parse out optional uri path */
    if((path = strchr(host_end, '/')) != NULL && path < url_end) {
	req->path = strndup(path, (int)(url_end - path));
    }
    else {
	req->path = strdup("/\0");
    }

    /* check all strndup and strdup's allocated memory successfully */
    if(req->url == NULL || req->host == NULL || 
       req->port == 0 || req->path == NULL) {

	free_http_request(req);
	return -1;
    }

    return 0;
}