#include <string.h>
#include <stdlib.h>

#define MAXSTRLEN 512


int findloc_r(char * str, char c, int start);
int findStrLoc(char * str, char* pattern, int i);

/*
 * Given a path (inPath) and current url, convert the path
 * to an absolute path.
 * The following are examples
 * 1. inPath = ./a/b/test.html currentUrl = http://x.y.z/m/n/
 *    the returned path shoul dbe /m/n/a/b/test.html
 * 2. inPath = ./a/b/c/.././test.html, currentUrl = http://x.y.z/m/
 *    the returned path should be /m/a/b/test.html
 */
char* convertRelPath(char * inPath, char * currentUrl) {

  char * workBuf = (char*)malloc(MAXSTRLEN);
  char * base = (char*)malloc(MAXSTRLEN);
  char * path = (char*)malloc(MAXSTRLEN);
  char * loc = strstr(currentUrl, "://"); /* locate host */

  loc = strstr(loc+3, "/");  /* then the path */
  strcpy(path, loc);       /* copy the path portion from the currentUrl */
  if (inPath == NULL) 
    return path;
  else if (inPath[0] == '/') /* root path */
    strcpy(path, inPath);
  else
    strcat(path, inPath);    /* attach the inPath to path */

  if (path == NULL) return currentUrl;

  /* collapse all "/./" */
  int changed = 0;
  int i = findStrLoc(path, "/./", 0);
  while (i >= 0) {
    changed = 1;
    strncpy(workBuf, path, i);  /* copy the first part */
    workBuf[i] = 0;
    strcat(workBuf, &(path[i+2]));  /* then the second part */
    strcpy(path, workBuf);
    i = findStrLoc(path, "/./", 0);
  }

  /* collapse all "/../" */
  i = findStrLoc(path, "/../", 0);
  while (i >= 0) {
    changed = 1;
    int i2 =findloc_r(path, '/', i-1);
    if (i2 < 0) i2 = i;
    strncpy(workBuf, path, i2);  /* copy the first part */
    workBuf[i2] = 0;
    strcat(workBuf, &(path[i+3]));  /* then the second part */
    strcpy(path, workBuf);
    i = findStrLoc(path, "/../", 0);
  }

  return path;
}

int findloc_r(char * str, char c, int i) {
  /* find and return the location of 'c' in 'str' in reverse direction */

  while (i >= 0 && str[i] != 0 && str[i] != c) {
    i --;
  }
  if (i >= 0 && str[i] == c)
    return i;
  else
    return -1;   /* not found */
}

int findStrLoc(char * str, char* pattern, int i) {
  /* find and return the location of 'pattern' in 'str' */

  int len = strlen(pattern);
  int found = -1;

  while (str[i] != 0 && found == -1) {
    if (str[i] == pattern[0] && strncmp(&(str[i]), pattern, len) == 0)
      found = i;
    i ++;
  }
  return found;
}