# Maildir folder support
# Copyright (C) 2002-2015 John Goerzen & contributors
#
#    This program is free software; you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation; either version 2 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program; if not, write to the Free Software
#    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA

import socket
import time
import re
import os
from .Base import BaseFolder
from threading import Lock
try:
    from hashlib import md5
except ImportError:
    from md5 import md5
try: # python 2.6 has set() built in
    set
except NameError:
    from sets import Set as set

from offlineimap import OfflineImapError

# Find the UID in a message filename
re_uidmatch = re.compile(',U=(\d+)')
# Find a numeric timestamp in a string (filename prefix)
re_timestampmatch = re.compile('(\d+)');

timeseq = 0
lasttime = 0
timelock = Lock()

def _gettimeseq():
    global lasttime, timeseq, timelock
    timelock.acquire()
    try:
        thistime = long(time.time())
        if thistime == lasttime:
            timeseq += 1
            return (thistime, timeseq)
        else:
            lasttime = thistime
            timeseq = 0
            return (thistime, timeseq)
    finally:
        timelock.release()

class MaildirFolder(BaseFolder):
    def __init__(self, root, name, sep, repository):
        self.sep = sep # needs to be set before super().__init__
        super(MaildirFolder, self).__init__(name, repository)
        self.dofsync = self.config.getdefaultboolean("general", "fsync", True)
        self.root = root
        self.messagelist = None
        # check if we should use a different infosep to support Win file systems
        self.wincompatible = self.config.getdefaultboolean(
            "Account "+self.accountname, "maildir-windows-compatible", False)
        self.infosep = '!' if self.wincompatible else ':'
        """infosep is the separator between maildir name and flag appendix"""
        self.re_flagmatch = re.compile('%s2,(\w*)' % self.infosep)
        #self.ui is set in BaseFolder.init()
        # Everything up to the first comma or colon (or ! if Windows):
        self.re_prefixmatch = re.compile('([^'+ self.infosep + ',]*)')
        #folder's md, so we can match with recorded file md5 for validity
        self._foldermd5 = md5(self.getvisiblename()).hexdigest()
        # Cache the full folder path, as we use getfullname() very often
        self._fullname = os.path.join(self.getroot(), self.getname())

    # Interface from BaseFolder
    def getfullname(self):
        """Return the absolute file path to the Maildir folder (sans cur|new)"""
        return self._fullname

    # Interface from BaseFolder
    def get_uidvalidity(self):
        """Retrieve the current connections UIDVALIDITY value

        Maildirs have no notion of uidvalidity, so we just return a magic
        token."""
        return 42

    #Checks to see if the given message is within the maximum age according
    #to the maildir name which should begin with a timestamp
    def _iswithinmaxage(self, messagename, maxage):
        #In order to have the same behaviour as SINCE in an IMAP search
        #we must convert this to the oldest time and then strip off hrs/mins
        #from that day
        oldest_time_utc = time.time() - (60*60*24*maxage)
        oldest_time_struct = time.gmtime(oldest_time_utc)
        oldest_time_today_seconds = ((oldest_time_struct[3] * 3600) \
            + (oldest_time_struct[4] * 60) \
            + oldest_time_struct[5])
        oldest_time_utc -= oldest_time_today_seconds

        timestampmatch = re_timestampmatch.search(messagename)
        if not timestampmatch:
            return True
        timestampstr = timestampmatch.group()
        timestamplong = long(timestampstr)
        if(timestamplong < oldest_time_utc):
            return False
        else:
            return True

    def _parse_filename(self, filename):
        """Returns a messages file name components

        Receives the file name (without path) of a msg.  Usual format is
        '<%d_%d.%d.%s>,U=<%d>,FMD5=<%s>:2,<FLAGS>' (pointy brackets
        denoting the various components).

        If FMD5 does not correspond with the current folder MD5, we will
        return None for the UID & FMD5 (as it is not valid in this
        folder).  If UID or FMD5 can not be detected, we return `None`
        for the respective element.  If flags are empty or cannot be
        detected, we return an empty flags list.

        :returns: (prefix, UID, FMD5, flags). UID is a numeric "long"
            type. flags is a set() of Maildir flags"""

        prefix, uid, fmd5, flags = None, None, None, set()
        prefixmatch = self.re_prefixmatch.match(filename)
        if prefixmatch:
            prefix = prefixmatch.group(1)
        folderstr = ',FMD5=%s' % self._foldermd5
        foldermatch = folderstr in filename
        # If there was no folder MD5 specified, or if it mismatches,
        # assume it is a foreign (new) message and ret: uid, fmd5 = None, None
        if foldermatch:
            uidmatch = re_uidmatch.search(filename)
            if uidmatch:
                uid = long(uidmatch.group(1))
        flagmatch = self.re_flagmatch.search(filename)
        if flagmatch:
            # Filter out all lowercase (custom maildir) flags. We don't
            # handle them yet.
            flags = set((c for c in flagmatch.group(1) if not c.islower()))
        return prefix, uid, fmd5, flags

    def _scanfolder(self):
        """Cache the message list from a Maildir.

        Maildir flags are: R (replied) S (seen) T (trashed) D (draft) F
        (flagged).
        :returns: dict that can be used as self.messagelist"""
        maxage = self.config.getdefaultint("Account " + self.accountname,
                                           "maxage", None)
        maxsize = self.config.getdefaultint("Account " + self.accountname,
                                            "maxsize", None)
        retval = {}
        files = []
        nouidcounter = -1          # Messages without UIDs get negative UIDs.
        for dirannex in ['new', 'cur']:
            fulldirname = os.path.join(self.getfullname(), dirannex)
            files.extend((dirannex, filename) for
                         filename in os.listdir(fulldirname))

        for dirannex, filename in files:
            # We store just dirannex and filename, ie 'cur/123...'
            filepath = os.path.join(dirannex, filename)
            # check maxage/maxsize if this message should be considered
            if maxage and not self._iswithinmaxage(filename, maxage):
                continue
            if maxsize and (os.path.getsize(os.path.join(
                        self.getfullname(), filepath)) > maxsize):
                continue

            (prefix, uid, fmd5, flags) = self._parse_filename(filename)
            if uid is None: # assign negative uid to upload it.
                uid = nouidcounter
                nouidcounter -= 1
            else:                       # It comes from our folder.
                uidmatch = re_uidmatch.search(filename)
                uid = None
                if not uidmatch:
                    uid = nouidcounter
                    nouidcounter -= 1
                else:
                    uid = long(uidmatch.group(1))
            # 'filename' is 'dirannex/filename', e.g. cur/123,U=1,FMD5=1:2,S
            retval[uid] = self.msglist_item_initializer(uid)
            retval[uid]['flags'] = flags
            retval[uid]['filename'] = filepath
        return retval

    # Interface from BaseFolder
    def quickchanged(self, statusfolder):
        """Returns True if the Maildir has changed"""
        self.cachemessagelist()
        # Folder has different uids than statusfolder => TRUE
        if sorted(self.getmessageuidlist()) != \
                sorted(statusfolder.getmessageuidlist()):
            return True
        # Also check for flag changes, it's quick on a Maildir
        for (uid, message) in self.getmessagelist().iteritems():
            if message['flags'] != statusfolder.getmessageflags(uid):
                return True
        return False  #Nope, nothing changed


    # Interface from BaseFolder
    def msglist_item_initializer(self, uid):
        return {'flags': set(), 'filename': '/no-dir/no-such-file/'}


    # Interface from BaseFolder
    def cachemessagelist(self):
        if self.messagelist is None:
            self.messagelist = self._scanfolder()

    # Interface from BaseFolder
    def getmessagelist(self):
        return self.messagelist

    # Interface from BaseFolder
    def getmessage(self, uid):
        """Return the content of the message."""

        filename = self.messagelist[uid]['filename']
        filepath = os.path.join(self.getfullname(), filename)
        file = open(filepath, 'rt')
        retval = file.read()
        file.close()
        #TODO: WHY are we replacing \r\n with \n here? And why do we
        #      read it as text?
        return retval.replace("\r\n", "\n")

    # Interface from BaseFolder
    def getmessagetime(self, uid):
        filename = self.messagelist[uid]['filename']
        filepath = os.path.join(self.getfullname(), filename)
        return os.path.getmtime(filepath)

    def new_message_filename(self, uid, flags=set()):
        """Creates a new unique Maildir filename

        :param uid: The UID`None`, or a set of maildir flags
        :param flags: A set of maildir flags
        :returns: String containing unique message filename"""

        timeval, timeseq = _gettimeseq()
        return '%d_%d.%d.%s,U=%d,FMD5=%s%s2,%s' % \
            (timeval, timeseq, os.getpid(), socket.gethostname(),
             uid, self._foldermd5, self.infosep, ''.join(sorted(flags)))


    def save_to_tmp_file(self, filename, content):
        """Saves given content to the named temporary file in the
        'tmp' subdirectory of $CWD.

        Arguments:
        - filename: name of the temporary file;
        - content: data to be saved.

        Returns: relative path to the temporary file
        that was created."""

        tmpname = os.path.join('tmp', filename)
        # open file and write it out
        tries = 7
        while tries:
            tries = tries - 1
            try:
                fd = os.open(os.path.join(self.getfullname(), tmpname),
                             os.O_EXCL|os.O_CREAT|os.O_WRONLY, 0o666)
                break
            except OSError as e:
                if e.errno == e.EEXIST:
                    if tries:
                        time.sleep(0.23)
                        continue
                    severity = OfflineImapError.ERROR.MESSAGE
                    raise OfflineImapError("Unique filename %s already exists." % \
                      filename, severity)
                else:
                    raise

        fd = os.fdopen(fd, 'wt')
        fd.write(content)
        # Make sure the data hits the disk
        fd.flush()
        if self.dofsync:
            os.fsync(fd)
        fd.close()

        return tmpname


    # Interface from BaseFolder
    def savemessage(self, uid, content, flags, rtime):
        """Writes a new message, with the specified uid.

        See folder/Base for detail. Note that savemessage() does not
        check against dryrun settings, so you need to ensure that
        savemessage is never called in a dryrun mode."""
        # This function only ever saves to tmp/,
        # but it calls savemessageflags() to actually save to cur/ or new/.
        self.ui.savemessage('maildir', uid, flags, self)
        if uid < 0:
            # We cannot assign a new uid.
            return uid

        if uid in self.messagelist:
            # We already have it, just update flags.
            self.savemessageflags(uid, flags)
            return uid

        # Otherwise, save the message in tmp/ and then call savemessageflags()
        # to give it a permanent home.
        tmpdir = os.path.join(self.getfullname(), 'tmp')
        messagename = self.new_message_filename(uid, flags)
        tmpname = self.save_to_tmp_file(messagename, content)
        if rtime != None:
            os.utime(os.path.join(self.getfullname(), tmpname), (rtime, rtime))

        self.messagelist[uid] = self.msglist_item_initializer(uid)
        self.messagelist[uid]['flags'] = flags
        self.messagelist[uid]['filename'] = tmpname
        # savemessageflags moves msg to 'cur' or 'new' as appropriate
        self.savemessageflags(uid, flags)
        self.ui.debug('maildir', 'savemessage: returning uid %d' % uid)
        return uid

    # Interface from BaseFolder
    def getmessageflags(self, uid):
        return self.messagelist[uid]['flags']

    # Interface from BaseFolder
    def savemessageflags(self, uid, flags):
        """Sets the specified message's flags to the given set.

        This function moves the message to the cur or new subdir,
        depending on the 'S'een flag.

        Note that this function does not check against dryrun settings,
        so you need to ensure that it is never called in a
        dryrun mode."""

        assert uid in self.messagelist

        oldfilename = self.messagelist[uid]['filename']
        dir_prefix, filename = os.path.split(oldfilename)
        # If a message has been seen, it goes into 'cur'
        dir_prefix = 'cur' if 'S' in flags else 'new'

        if flags != self.messagelist[uid]['flags']:
            # Flags have actually changed, construct new filename Strip
            # off existing infostring (possibly discarding small letter
            # flags that dovecot uses TODO)
            infomatch = self.re_flagmatch.search(filename)
            if infomatch:
                filename = filename[:-len(infomatch.group())] #strip off
            infostr = '%s2,%s'% (self.infosep, ''.join(sorted(flags)))
            filename += infostr

        newfilename = os.path.join(dir_prefix, filename)
        if (newfilename != oldfilename):
            try:
                os.rename(os.path.join(self.getfullname(), oldfilename),
                          os.path.join(self.getfullname(), newfilename))
            except OSError as e:
                raise OfflineImapError("Can't rename file '%s' to '%s': %s" % (
                                       oldfilename, newfilename, e[1]),
                                       OfflineImapError.ERROR.FOLDER)

            self.messagelist[uid]['flags'] = flags
            self.messagelist[uid]['filename'] = newfilename

    # Interface from BaseFolder
    def change_message_uid(self, uid, new_uid):
        """Change the message from existing uid to new_uid

        This will not update the statusfolder UID, you need to do that yourself.
        :param new_uid: (optional) If given, the old UID will be changed
                        to a new UID. The Maildir backend can implement this as
                        an efficient rename.
        """

        if not uid in self.messagelist:
            raise OfflineImapError("Cannot change unknown Maildir UID %s" % uid)
        if uid == new_uid: return

        oldfilename = self.messagelist[uid]['filename']
        dir_prefix, filename = os.path.split(oldfilename)
        flags = self.getmessageflags(uid)
        newfilename = os.path.join(dir_prefix,
          self.new_message_filename(new_uid, flags))
        os.rename(os.path.join(self.getfullname(), oldfilename),
                  os.path.join(self.getfullname(), newfilename))
        self.messagelist[new_uid] = self.messagelist[uid]
        self.messagelist[new_uid]['filename'] = newfilename
        del self.messagelist[uid]

    # Interface from BaseFolder
    def deletemessage(self, uid):
        """Unlinks a message file from the Maildir.

        :param uid: UID of a mail message
        :type uid: String
        :return: Nothing, or an Exception if UID but no corresponding file
                 found.
        """
        if not self.uidexists(uid):
            return

        filename = self.messagelist[uid]['filename']
        filepath = os.path.join(self.getfullname(), filename)
        try:
            os.unlink(filepath)
        except OSError:
            # Can't find the file -- maybe already deleted?
            newmsglist = self._scanfolder()
            if uid in newmsglist:       # Nope, try new filename.
                filename = newmsglist[uid]['filename']
                filepath = os.path.join(self.getfullname(), filename)
                os.unlink(filepath)
            # Yep -- return.
        del(self.messagelist[uid])