# Copyright 2008 The Tor Project, Inc.  See LICENSE for licensing information.

import os.path
import time
import threading

import thandy.master_keys

no_bt = None
try:
    import BitTorrent.bencode
    import BitTorrent.btformats
    import BitTorrent.download
except ImportError:
    no_bt = True
from sha import sha # XXX Use PyCrypto here?


class BtCompat:
    """Interface for different bittorrent implementations"""

    usingBt = False

    def __init__(self):
        self.tUrl = thandy.master_keys.DEFAULT_TRACKER
        if not no_bt:
            assert(self.tUrl is not None and self.tUrl != "")
        self.pieceLength = 2 ** 18 # Piece length of 262144 bytes

    # XXX Do we need to be thread-safe here and below?
    @staticmethod
    def shouldUseBt():
        return BtCompat.usingBt

    @staticmethod
    def setUseBt(useBt):
        if no_bt:
            return
        BtCompat.usingBt = useBt

    @staticmethod
    def getBtMetadataLocation(packagepath, filepath, pathprefix=""):
        """Given a path for the package, the path for a file of that
           package, and an optional prefix, return the path for the
           .torrent metadata file. Always return Unix-like paths, to
           ensure compatibility with fetching the path from a
           webserver.
        """
        return (os.path.join(pathprefix, os.path.dirname(packagepath),
                             os.path.basename(filepath)) + ".torrent"
               ).replace("\\", "/")

    def makeMetaFile(self, file):
        """Given a path to a file, create the contents of a .torrent
           metadata file and return them.
        """
        size = os.path.getsize(file)
        filename = os.path.basename(file)
        pieces = []
        p = 0
        h = open(file, 'rb')
        while p < size:
            x = h.read(min(self.pieceLength, size - p))
            pieces.append(sha(x).digest())
            p += self.pieceLength
            if p > size:
                p = size
        h.close()
        info = {'pieces': ''.join(pieces),
            'piece length': self.pieceLength, 'length': size,
            'name': filename}
        # Check we didn't screw up with the info
        BitTorrent.btformats.check_info(info)
        data = {'info': info, 'announce': self.tUrl,
                'creation date': long(time.time())}
        return BitTorrent.bencode.bencode(data)

    def getFileLength(self, file):
        """Parse the .torrent metainfo file and return the length of the
           file it refers to.
        """
        f = open(file, 'rb')
        metainfo = BitTorrent.bencode.bdecode(f.read())['info']
        f.close()
        assert(metainfo['length'])
        return metainfo['length']

    def getFileHash(self, file):
        """Parse the .torrent metainfo file and return the hash of the
           file it refers to.
        """
        f = open(file, 'rb')
        metainfo = BitTorrent.bencode.bdecode(f.read())['info']
        f.close()
        return sha(BitTorrent.bencode.bencode(metainfo)).hexdigest()

    def download(self, metaFile, saveTo ):
        """Initiate a download via bittorrent."""

        event = threading.Event()

        params = ['--responsefile', metaFile, '--saveas', saveTo]

        def filefunc(default, size, saveas, dir):
            return saveas

        def statusfunc(dict):
            # XXX we should see how fast we upload/download here.
            # If we don't get a connection for quite a while, or we are
            # _very_ slow, we should cancel bt, disable it, and start fetching
            # via http.
            pass

        def finfunc():
            # XXX here we can set a timer for how long to seed, or
            # wait for statusfunc to have shared some data, or something.
            # Not the real solution, though, because installation will be
            # delayed by the time we sleep...
            # time.sleep(60)
            event.set()
            pass

        def errorfunc(msg):
            # XXX Not really sure how to encounter an error here. Our best bet
            # is to cancel the download, stop bittorrent, and move on.
            BtCompat.setUseBt(False)
            event.set()


        BitTorrent.download.download(params, filefunc, statusfunc, finfunc,
                                     errorfunc, event, 80)