#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, "%lu B", 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) {
  char *result;
  size_t allocated;
  size_t i;
  char buf[256];
  char fullpath[PATH_MAX];
  char encName[2*PATH_MAX];

  // 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';

  // this is still safe
  strcat(result, HEADER1);

  sprintf(buf, "<title>Directory listing for %s</title>", url);
  strcat(result, buf);

  strcat(result, HEADER2);

  sprintf(buf, "<h1>Directory listing for %s</h1>", url);
  strcat(result, buf);

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

  // Begin Navigation
  strcat(result, "<p>Navigation: ");

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

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

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

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

      strcat(fullpath, token);
      strcat(fullpath, "/");

      sprintf(buf, " <a href=\"%s\">%s</a> /", fullpath, token);
      strcat(result, buf);
    }
    while((token = strtok(NULL, "/")) != NULL);
  }

  free(urlclone);

  strcat(result, "</p>");

  // begin listing subdirs
  strcat(result, "<h2>Sub-directories</h2>");
  strcat(result, "<ul>");

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

    size_t entrylen = 32 + 2 * strlen(entries[i].name);
    size_t resultlen = strlen(result);

    if(allocated < resultlen + entrylen) {
      allocated *= 2;
      LOG(LVL_DEBUG, "reallocating result string (subdirs) - new size: %lu bytes", allocated * sizeof(char));
      char *tmpresult = realloc(result, allocated * sizeof(char));
      if(!tmpresult) {
        LOG(LVL_ERR, "realloc failed for result string: %s", strerror(errno));
        break;
      }

      result = tmpresult;
    }

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

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

  strcat(result, "</ul>");

  // begin listing files
  strcat(result, "<h2>Files</h2>");
  strcat(result, "<ul>");

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

    size_t entrylen = 64 + 2 * strlen(entries[i].name);
    size_t resultlen = strlen(result);

    if(allocated < resultlen + entrylen) {
      allocated *= 2;
      LOG(LVL_DEBUG, "reallocating result string (files) - new size: %lu bytes", allocated * sizeof(char));
      char *tmpresult = realloc(result, allocated * sizeof(char));
      if(!tmpresult) {
        LOG(LVL_ERR, "realloc failed for result string: %s", strerror(errno));
        break;
      }

      result = tmpresult;
    }

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

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

  strcat(result, "</ul>");
  strcat(result, FOOTER);

  return result;
}

char* create_dirlisting(const char *url, const char *localpath) {
  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);

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

  return result;
}