/**  --------------------------------------------------------------------
 *  @file maildir-scan.cc
 *  @brief  Implementation of the Maildir class.
 *  @author Andreas Aardal Hanssen
 *  @date 2002-2005
 *  -----------------------------------------------------------------  **/
#include <fcntl.h>
#include <dirent.h>
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>

#include "iodevice.h"
#include "iofactory.h"
#include "maildir.h"

using namespace Binc;
using namespace ::std;

Lock::Lock(const string &path)
{
  lock = (path == "" ? "." : path) + "/bincimap-scan-lock";

  int lockfd = -1;
  while ((lockfd = ::open(lock.c_str(),
          O_CREAT | O_WRONLY | O_EXCL, 0666)) == -1) {
    if (errno != EEXIST) {
      bincWarning << "unable to lock mailbox: " << lock
      << ", " << string(strerror(errno)) << endl;
      return;
    }

    struct stat mystat;
    bincWarning << "waiting for mailbox lock " << lock << "." << endl;
    if (lstat(lock.c_str(), &mystat) == 0) {
      if ((time(0) - mystat.st_ctime) > 300) {
        if (unlink(lock.c_str()) == 0) continue;
        else bincWarning << "failed to force mailbox lock: " << lock
                         << ", " << string(strerror(errno)) << endl;
      }
    } else {
      if (errno != ENOENT) {
        string err = "invalid lock " + lock + ": "
                      + strerror(errno);
        bincWarning << err << endl;
        return;
      }
    }

    // sleep one second.
    sleep(1);
  }

  close(lockfd);
}

Lock::~Lock()
{
  // remove the lock
  if (unlink(lock.c_str()) != 0)
    bincWarning << "failed to unlock mailbox: " << lock << ", "
      << strerror(errno) << endl;
}

//------------------------------------------------------------------------
// scan the maildir. update flags, find messages in new/ and move them
// to cur, setting the recent flag in memory only. check for expunged
// messages. give newly arrived messages uids.
//------------------------------------------------------------------------
Maildir::ScanResult Maildir::scan(bool forceScan)
{
  const string newpath = path + "/new/";
  const string curpath = path + "/cur/";
  const string cachepath = path + "/bincimap-cache";

  // check wether or not we need to bother scanning the folder.
  if (firstscan || forceScan) {
    struct stat oldstat;
    if (stat(newpath.c_str(), &oldstat) != 0) {
      setLastError("Invalid Mailbox, " + newpath + ": "
       + string(strerror(errno)));
      return PermanentError;
    }

    old_new_st_mtime = oldstat.st_mtime;
    old_new_st_ctime = oldstat.st_ctime;

    if (stat(curpath.c_str(), &oldstat) != 0) {
      setLastError("Invalid Mailbox, " + curpath + ": "
       + string(strerror(errno)));
      return PermanentError;
    }

    old_cur_st_mtime = oldstat.st_mtime;
    old_cur_st_ctime = oldstat.st_ctime;

    if (stat(cachepath.c_str(), &oldstat) == 0) {
      old_bincimap_cache_st_mtime = oldstat.st_mtime;
      old_bincimap_cache_st_ctime = oldstat.st_ctime;
    } else {
      old_bincimap_cache_st_mtime = 0;
      old_bincimap_cache_st_ctime = 0;
    }
  } else {
    struct stat oldcurstat;
    struct stat oldnewstat;
    struct stat oldbincimapcachestat;
    if (stat(newpath.c_str(), &oldnewstat) != 0) {
      setLastError("Invalid Mailbox, " + newpath + ": "
                    + string(strerror(errno)));
      return PermanentError;
    }

    if (stat(curpath.c_str(), &oldcurstat) != 0) {
      setLastError("Invalid Mailbox, " + curpath + ": "
                    + string(strerror(errno)));
      return PermanentError;
    }

    if (stat(cachepath.c_str(), &oldbincimapcachestat) != 0) {
      oldbincimapcachestat.st_ctime = 0;
      oldbincimapcachestat.st_mtime = 0;
    }

    if (oldnewstat.st_mtime == old_new_st_mtime
        && oldnewstat.st_ctime == old_new_st_ctime
        && oldcurstat.st_mtime == old_cur_st_mtime
        && oldcurstat.st_ctime == old_cur_st_ctime
        && oldbincimapcachestat.st_mtime == old_bincimap_cache_st_mtime
        && oldbincimapcachestat.st_ctime == old_bincimap_cache_st_ctime) {
      return Success;
    }

    old_bincimap_cache_st_mtime = oldbincimapcachestat.st_mtime;
    old_bincimap_cache_st_ctime = oldbincimapcachestat.st_ctime;
    old_cur_st_mtime = oldcurstat.st_mtime;
    old_cur_st_ctime = oldcurstat.st_ctime;
    old_new_st_mtime = oldnewstat.st_mtime;
    old_new_st_ctime = oldnewstat.st_ctime;
  }

  // lock the directory as we are scanning. this prevents race
  // conditions with uid delegation
  Lock lock(path);

  // Read the cache file if it's there. It holds important information
  // about the state of the depository, and serves to communicate
  // changes to the depot across Binc IMAP instances that can not be
  // communicated via the depot itself.
  switch (readCache()) {
    case NoCache:
    case Error:
    // An error with reading the cache files when it's not the first
    // time we scan the depot is treated as an error.
      if (!firstscan && !readOnly) {
        old_cur_st_mtime = (time_t) 0;
        old_cur_st_ctime = (time_t) 0;
        old_new_st_mtime = (time_t) 0;
        old_new_st_ctime = (time_t) 0;
        return TemporaryError;
      }
       mailboxchanged = true;
      break;
    default:
      break;
  }

  // open new/ directory
  DIR *pdir = opendir(newpath.c_str());
  if (pdir == 0) {
    string reason = "failed to open \"" + newpath + "\" (";
    reason += strerror(errno);
    reason += ")";
    setLastError(reason);

    return PermanentError;
  }

  // scan all entries
  struct dirent *pdirent;
  while ((pdirent = readdir(pdir)) != 0) {
    // "Unless you're writing messages to a maildir, the format of a
    // unique name is none of your business. A unique name can be
    // anything that doesn't contain a colon (or slash) and doesn't
    // start with a dot. Do not try to extract information from unique
    // names." - The Maildir spec from cr.yp.to
    string filename = pdirent->d_name;
    if (filename[0] == '.'
        || filename.find(':') != string::npos
        || filename.find('/') != string::npos)
      continue;

    string fullfilename = newpath + filename;

    // We need to find the timestamp of the message in order to
    // determine whether or not it's safe to move the message in from
    // new/. qmail's default message file naming algorithm forces us
    // to never move messages out of new/ that are less than one
    // second old.
    struct stat mystat;
    if (stat(fullfilename.c_str(), &mystat) != 0) {
      if (errno == ENOENT) {
        // prevent looping due to stale symlinks
        if (lstat(fullfilename.c_str(), &mystat) == 0) { 
          bincWarning << "dangling symlink: " << fullfilename << endl; 
          continue;
        }

  // a rare race between readdir and stat force us to restart the scan.
        closedir(pdir);

        if ((pdir = opendir(newpath.c_str())) == 0) {
          string reason = "Warning: opendir(\"" + newpath + "\") == 0 (";
                           reason += strerror(errno);
                           reason += ")";
          setLastError(reason);
          return PermanentError;
        }
      } else
        bincWarning << "junk in Maildir: \"" << fullfilename << "\": "
                    << strerror(errno);

      continue;
    }

    // this is important. do not move messages from new/ that are not
    // at least one second old or messages may disappear. this
    // introduces a special case: we can not cache the old st_ctime
    // and st_mtime. the next time the mailbox is scanned, it must not
    // simply be skipped. :-)

    vector<MaildirMessage>::const_iterator newIt = newMessages.begin();
    bool ours = false;
    for (; newIt != newMessages.end(); ++newIt) {
      if ((filename == (*newIt).getUnique())
           && ((*newIt).getInternalFlags() & MaildirMessage::Committed)) {
        ours = true;
        break;
      }
    }

    if (!ours && ::time(0) <= mystat.st_mtime) {
      old_cur_st_mtime = (time_t) 0;
      old_cur_st_ctime = (time_t) 0;
      old_new_st_mtime = (time_t) 0;
      old_new_st_ctime = (time_t) 0;
      continue;
    }

    // move files from new/ to cur/
    string newName = curpath + pdirent->d_name;
    if (rename((newpath + pdirent->d_name).c_str(), 
         (newName + ":2,").c_str()) != 0) {
      bincWarning << "error moving messages from new to cur: skipping "
                  << newpath 
                  << pdirent->d_name << ": " << strerror(errno) << endl;
      continue;
    }
  }

  closedir(pdir);

  // Now, assume all known messages were expunged and have them prove
  // otherwise.
  {
    Mailbox::iterator i = begin(SequenceSet::all(),
      INCLUDE_EXPUNGED | SQNR_MODE);
    for (; i != end(); ++i)
      (*i).setExpunged();
  }

  // Then, scan cur
  // open directory

  if ((pdir = opendir(curpath.c_str())) == 0) {
    string reason = "Maildir::scan::opendir(\"" + curpath + "\") == 0 (";
                     reason += strerror(errno);
                     reason += ")";

    setLastError(reason);
    return PermanentError;
  }

  // erase all old maps between fixed filenames and actual file names.
  // we'll get a new list now, which will be more up to date.
  index.clearFileNames();

  // this is to sort recent messages by internaldate
  multimap<unsigned int, MaildirMessage> tempMessageMap;

  // scan all entries
  while ((pdirent = readdir(pdir)) != 0) {
    string filename = pdirent->d_name;
    if (filename[0] == '.') continue;

    string uniquename;
    string standard;
    string::size_type pos;
    if ((pos = filename.find(':')) != string::npos) {
      uniquename = filename.substr(0, pos);
      string tmp = filename.substr(pos);
      if ((pos = tmp.find("2,")) != string::npos)
        standard = tmp.substr(pos + 2);
    } else
      uniquename = filename;

    unsigned char mflags = Message::F_NONE;
    for (string::const_iterator i = standard.begin();
         i != standard.end(); ++i) {
      switch (*i) {
        case 'R': mflags |= Message::F_ANSWERED; break;
        case 'S': mflags |= Message::F_SEEN; break;
        case 'T': mflags |= Message::F_DELETED; break;
        case 'D': mflags |= Message::F_DRAFT; break;
        case 'F': mflags |= Message::F_FLAGGED; break;
        case 'P': mflags |= Message::F_PASSED; break;
        default: break;
      }
    }

    struct stat mystat;
    MaildirMessage *message = get(uniquename);
    if (!message || message->getInternalDate() == 0) {
      string fullfilename = curpath + filename;
      if (stat(fullfilename.c_str(), &mystat) != 0) {
        if (errno == ENOENT) {
          // prevent looping due to stale symlinks
          if (lstat(fullfilename.c_str(), &mystat) == 0) { 
            bincWarning << "dangling symlink: " << fullfilename << endl; 
            continue;
          }
    // a rare race between readdir and stat force us to restart
    // the scan.
          index.clearFileNames();

          closedir(pdir);

          if ((pdir = opendir(newpath.c_str())) == 0) {
            string reason = "Warning: opendir(\"" + newpath + "\") == 0 (";
                            reason += strerror(errno);
                            reason += ")";
            setLastError(reason);
            return PermanentError;
          }
        }
  
        continue;
      }

      mailboxchanged = true;
    }
    
    index.insert(uniquename, 0, filename);

    // If we have this message in memory already..
    if (message) {
      if (message->getInternalDate() == 0) {
        mailboxchanged = true;
        message->setInternalDate(mystat.st_mtime);
      }

      // then confirm that this message was not expunged
      message->setUnExpunged();

      // update the flags with what new flags we found in the filename,
      // but keep the \Recent flag regardless.
      if (mflags != (message->getStdFlags() & ~Message::F_RECENT)) {
        int oldflags = message->getStdFlags();
        message->resetStdFlags();
        message->setStdFlag(mflags | (oldflags & Message::F_RECENT));
      }

      continue;
    }

    // Wait with delegating UIDs until all entries have been
    // read. Only then can we sort by internaldate and delegate new
    // UIDs.
    MaildirMessage m(*this);
    m.setUID(0);
    m.setSize(0);
    m.setInternalDate(mystat.st_mtime);
    m.setStdFlag((mflags | Message::F_RECENT) & ~Message::F_EXPUNGED);
    m.setUnique(uniquename);
    tempMessageMap.insert(make_pair((unsigned int) mystat.st_mtime, m));

    mailboxchanged = true;
  }

  closedir(pdir);

  // Recent messages are added, ordered by internaldate.
  {
    int readonlyuidnext = uidnext;
    multimap<unsigned int, MaildirMessage>::iterator i = tempMessageMap.begin();
    while (i != tempMessageMap.end()) {
      i->second.setUID(readOnly ? readonlyuidnext++ : uidnext++);
      multimap<unsigned int, MaildirMessage>::iterator itmp = i;
      ++itmp;
      add(i->second);
      tempMessageMap.erase(i);
      i = itmp;
      mailboxchanged = true;
    }
  }

  tempMessageMap.clear();

  // Messages that existed in the cache that we read, but did not
  // exist in the Maildir, are removed from the messages list.
  Mailbox::iterator jj = begin(SequenceSet::all(), INCLUDE_EXPUNGED | SQNR_MODE);
  while (jj != end()) {
    MaildirMessage &message = (MaildirMessage &)*jj;

    if (message.isExpunged()) {
      mailboxchanged = true;
      if (message.getInternalFlags() & MaildirMessage::JustArrived) {
        jj.erase();
        continue;
      }
    } else if (message.getInternalFlags() & MaildirMessage::JustArrived) {
      message.clearInternalFlag(MaildirMessage::JustArrived);
    }

    ++jj;
  }

  // Special case: The first time we scan is in SELECT. All flags
  // changes for new messages will then appear to be recent, and
  // to avoid this to be sent to the client as a pending update,
  // we explicitly unset the "flagsChanged" flag in all messages.
  if (firstscan) {
    unsigned int lastuid = 0;

    Mailbox::iterator ii
      = begin(SequenceSet::all(), INCLUDE_EXPUNGED | SQNR_MODE);
    for (; ii != end(); ++ii) {
      MaildirMessage &message = (MaildirMessage &)*ii;
      message.clearInternalFlag(MaildirMessage::JustArrived);

      if (lastuid < message.getUID())
        lastuid = message.getUID();
      else {
        bincWarning << "UID values are not strictly ascending in this"
                       " mailbox: " << path << ". This is usually caused by "
                    << "access from a broken accessor. Bumping UIDVALIDITY." 
                    << endl;

        setLastError("An error occurred while scanning the mailbox. "
                     "Please contact your system administrator.");

        if (!readOnly) {
          bumpUidValidity(path);
          old_cur_st_mtime = (time_t) 0;
          old_cur_st_ctime = (time_t) 0;
          old_new_st_mtime = (time_t) 0;
          old_new_st_ctime = (time_t) 0;
          return TemporaryError;
        } else {
          return PermanentError;
        }
      }

      message.setFlagsUnchanged();
    }
  }

  if (mailboxchanged && !readOnly) {
    if (!writeCache()) return PermanentError;
    mailboxchanged = false;
  }

  firstscan = false;
  newMessages.clear();
  return Success;
}