/*
 * vim: sw=2 ts=2 expandtab
 *
 * Copyright (c) 2013-2019 Thomas Kolb
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

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

#include <strings.h>
#include <errno.h>

#include <sys/stat.h>

#include <linux/limits.h>
#include <linux/unistd.h>
#include <dirent.h>

#include "logger.h"
#include "templates.h"
#include "util.h"

#define FLG_USED 1
#define FLG_ISDIR 2

struct Entry {
  char *name;
  off_t size;
  uint8_t flags;
};

const char* format_size(off_t s) {
  static char buf[32];
  const char *prefixes = " kMGTPEZY";
  float fs = s;

  int divisions = 0;

  while(fs > 1024) {
    fs /= 1024.0f;
    divisions++;
  }

  if(divisions == 0) {
    sprintf(buf, "%lli B", (long long)s);
  } else {
    sprintf(buf, "%.2f %ciB", fs, prefixes[divisions]);
  }

  return buf;
}

static int compare_entries(const void *sp1,const void *sp2 ) {
  const struct Entry *e1 = sp1;
  const struct Entry *e2 = sp2;

  return( strcasecmp(e1->name, e2->name) );
}

char* gen_html(const char *url, struct Entry *entries, size_t numentries, int uploadEnabled) {
  char *result;
  size_t allocated;
  size_t i;

  const size_t BUFSIZE = 5*PATH_MAX;
  char buf[BUFSIZE];
  char fullpath[PATH_MAX];
  char encName[3*PATH_MAX]; // urlencode grows string by factor 3 at most

  // allocate a buffer for the result string
  allocated = strlen(HEADER1 HEADER2 FOOTER) + 64 * numentries + 4096;
  LOG(LVL_DEBUG, "initially allocating result string - size: %lu bytes", allocated * sizeof(char));
  result = malloc(allocated * sizeof(char));
  result[0] = '\0';

  result = safe_append(result, &allocated, HEADER1);

  snprintf(buf, BUFSIZE, "<title>Directory listing for %s</title>", url);
  result = safe_append(result, &allocated, buf);

  result = safe_append(result, &allocated, HEADER2);

  snprintf(buf, BUFSIZE, "<h1>Directory listing for %s</h1>", url);
  result = safe_append(result, &allocated, buf);

  int isrootdir = strcmp(url, "/") == 0;

  // Begin Navigation
  result = safe_append(result, &allocated, "<p>Navigation: ");

  // tokenize the URL: init
  char *token, *urlclone;

  urlclone = strdup(url);
  token = strtok(urlclone, "/");
  strcpy(fullpath, "/");

  if(isrootdir) {
    result = safe_append(result, &allocated, "/");
  } else {
    result = safe_append(result, &allocated, "<a href=\"/\">/</a>");

    // create a link for each token in URL
    do {
      LOG(LVL_DUMP, "Found token of %s: %s", url, token);

      // TODO: check if this is safe
      strcat(fullpath, token);
      strcat(fullpath, "/");

      snprintf(buf, BUFSIZE, " <a href=\"%s\">%s</a> /", fullpath, token);
      result = safe_append(result, &allocated, buf);
    }
    while((token = strtok(NULL, "/")) != NULL);
  }

  free(urlclone);

  result = safe_append(result, &allocated, "</p>");

  // begin listing subdirs
  result = safe_append(result, &allocated, "<h2>Sub-directories</h2>");
  result = safe_append(result, &allocated, "<ul>");

  for(i = 0; i < numentries; i++) {
    // skip all non-directories
    if(!(entries[i].flags & FLG_ISDIR))
      continue;

    urlencode(entries[i].name, encName);

    if(isrootdir) {
      snprintf(buf, BUFSIZE, "<li><a href=\"/%s/\">%s/</a></li>\n",
          encName, entries[i].name);
    } else {
      snprintf(buf, BUFSIZE, "<li><a href=\"%s/%s/\">%s/</a></li>\n",
          url, encName, entries[i].name);
    }
    result = safe_append(result, &allocated, buf);
  }

  result = safe_append(result, &allocated, "</ul>");

  // begin listing files
  result = safe_append(result, &allocated, "<h2>Files</h2>");
  result = safe_append(result, &allocated, "<ul>");

  // here the listing entries are generated
  for(i = 0; i < numentries; i++) {
    // skip all directories
    if(entries[i].flags & FLG_ISDIR)
      continue;

    urlencode(entries[i].name, encName);

    if(isrootdir) {
      snprintf(buf, BUFSIZE, "<li><a href=\"/%s\">%s</a> [%s]</li>\n",
          encName, entries[i].name, format_size(entries[i].size));
    } else {
      snprintf(buf, BUFSIZE, "<li><a href=\"%s/%s\">%s</a> [%s]</li>\n",
          url, encName, entries[i].name, format_size(entries[i].size));
    }
    result = safe_append(result, &allocated, buf);
  }

  result = safe_append(result, &allocated, "</ul>");

  if(uploadEnabled) {
    result = safe_append(result, &allocated, "<h2>Upload</h2>");
    result = safe_append(result, &allocated, "<p>Upload a file to this directory:</p>");
    result = safe_append(result, &allocated,
        "<p>"
        "  <form method=\"POST\" action=\".\" enctype=\"multipart/form-data\">"
        "    <input name=\"data\" type=\"file\" size=\"30\">"
        "    <input type=\"submit\" value=\"Go!\">"
        "  </form>"
        "</p>"
        );
  }

  result = safe_append(result, &allocated, FOOTER);

  LOG(LVL_DEBUG, "result string (files) usage: %lu/%lu bytes", strlen(result), allocated);

  return result;
}

char* create_dirlisting(const char *url, const char *localpath, int uploadEnabled) {
  char *result;
  struct Entry *entries;

  size_t numentries, allocated;
  size_t i;

  DIR *dir;
  struct dirent *de;

  struct stat s;

  char fullpath[PATH_MAX];

  if((dir = opendir(localpath)) == NULL) {
    LOG(LVL_ERR, "Cannot opendir %s: %s", localpath, strerror(errno));
    return NULL;
  }

  // allocate some entry pointers
  allocated = 100;
  numentries = 0;

  entries = malloc(allocated * sizeof(struct Entry));
  if(!entries) {
    LOG(LVL_ERR, "malloc failed for directory entries: %s", strerror(errno));
    return NULL;
  }

  // initialize all entry strings with NULL
  for(i = 0; i < allocated; i++) {
    entries[i].flags = 0;
  }

  while((de = readdir(dir)) != NULL) {
    if(de->d_name[0] == '.') {
      continue;
    }

    // check if entries array is full
    if(numentries == allocated) {
      // double the size of the entries array
      LOG(LVL_DEBUG, "reallocating entry list - new size: %lu bytes", 2 * allocated * sizeof(struct Entry));
      struct Entry *tmpentries = realloc(entries, 2 * allocated * sizeof(struct Entry));
      if(!tmpentries) {
        LOG(LVL_ERR, "realloc failed for directory entries: %s", strerror(errno));
        free(entries);
        return NULL;
      }

      entries = tmpentries;

      // initialize the new entries
      for(i = allocated; i < 2*allocated; i++) {
        entries[i].flags = 0;
      }

      allocated *= 2;
    }

    snprintf(fullpath, PATH_MAX, "%s/%s", localpath, de->d_name);

    if(stat(fullpath, &s) == -1) {
      LOG(LVL_WARN, "Cannot stat %s while listing directories: %s",
          fullpath, strerror(errno));

      // stat failed -> ignore this entry
      continue;
    }

    entries[numentries].name = strdup(de->d_name);
    entries[numentries].flags |= FLG_USED;
    entries[numentries].size = s.st_size;

    if(S_ISDIR(s.st_mode)) {
      entries[numentries].flags |= FLG_ISDIR;
    }

    numentries++;
  }

  closedir(dir);

  qsort(entries, numentries, sizeof(struct Entry), compare_entries);

  result = gen_html(url, entries, numentries, uploadEnabled);

  for(i = 0; i < numentries; i++) {
    if(entries[i].flags & FLG_USED) free(entries[i].name);
  }
  free(entries);

  return result;
}