# changegroup.py - Mercurial changegroup manipulation functions

#

#  Copyright 2006 Matt Mackall <mpm@selenic.com>

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

from i18n import _

import util

import struct, os, bz2, zlib, tempfile

def readexactly(stream, n):

    '''read n bytes from stream.read and abort if less was available'''

    s = stream.read(n)

    if len(s) < n:

        raise util.Abort(_("stream ended unexpectedly"

                           " (got %d bytes, expected %d)")

                          % (len(s), n))

    return s

def getchunk(stream):

    """return the next chunk from stream as a string"""

    d = readexactly(stream, 4)

    l = struct.unpack(">l", d)[0]

    if l <= 4:

        if l:

            raise util.Abort(_("invalid chunk length %d") % l)

        return ""

    return readexactly(stream, l - 4)

def chunkheader(length):

    """return a changegroup chunk header (string)"""

    return struct.pack(">l", length + 4)

def closechunk():

    """return a changegroup chunk header (string) for a zero-length chunk"""

    return struct.pack(">l", 0)

class nocompress(object):

    def compress(self, x):

        return x

    def flush(self):

        return ""

bundletypes = {

    "": ("", nocompress),

    "HG10UN": ("HG10UN", nocompress),

    "HG10BZ": ("HG10", lambda: bz2.BZ2Compressor()),

    "HG10GZ": ("HG10GZ", lambda: zlib.compressobj()),

}

def collector(cl, mmfs, files):

    # Gather information about changeset nodes going out in a bundle.

    # We want to gather manifests needed and filelogs affected.

    def collect(node):

        c = cl.read(node)

        files.update(c[3])

        mmfs.setdefault(c[0], node)

    return collect

# hgweb uses this list to communicate its preferred type

bundlepriority = ['HG10GZ', 'HG10BZ', 'HG10UN']

def writebundle(cg, filename, bundletype):

    """Write a bundle file and return its filename.

    Existing files will not be overwritten.

    If no filename is specified, a temporary file is created.

    bz2 compression can be turned off.

    The bundle file will be deleted in case of errors.

    """

    fh = None

    cleanup = None

    try:

        if filename:

            fh = open(filename, "wb")

        else:

            fd, filename = tempfile.mkstemp(prefix="hg-bundle-", suffix=".hg")

            fh = os.fdopen(fd, "wb")

        cleanup = filename

        header, compressor = bundletypes[bundletype]

        fh.write(header)

        z = compressor()

        # parse the changegroup data, otherwise we will block

        # in case of sshrepo because we don't know the end of the stream

        # an empty chunkgroup is the end of the changegroup

        # a changegroup has at least 2 chunkgroups (changelog and manifest).

        # after that, an empty chunkgroup is the end of the changegroup

        empty = False

        count = 0

        while not empty or count <= 2:

            empty = True

            count += 1

            while 1:

                chunk = getchunk(cg)

                if not chunk:

                    break

                empty = False

                fh.write(z.compress(chunkheader(len(chunk))))

                pos = 0

                while pos < len(chunk):

                    next = pos + 2**20

                    fh.write(z.compress(chunk[pos:next]))

                    pos = next

            fh.write(z.compress(closechunk()))

        fh.write(z.flush())

        cleanup = None

        return filename

    finally:

        if fh is not None:

            fh.close()

        if cleanup is not None:

            os.unlink(cleanup)

def decompressor(fh, alg):

    if alg == 'UN':

        return fh

    elif alg == 'GZ':

        def generator(f):

            zd = zlib.decompressobj()

            for chunk in f:

                yield zd.decompress(chunk)

    elif alg == 'BZ':

        def generator(f):

            zd = bz2.BZ2Decompressor()

            zd.decompress("BZ")

            for chunk in util.filechunkiter(f, 4096):

                yield zd.decompress(chunk)

    else:

        raise util.Abort("unknown bundle compression '%s'" % alg)

    return util.chunkbuffer(generator(fh))

class unbundle10(object):

    def __init__(self, fh, alg):

        self._stream = decompressor(fh, alg)

        self._type = alg

        self.callback = None

    def compressed(self):

        return self._type != 'UN'

    def read(self, l):

        return self._stream.read(l)

    def seek(self, pos):

        return self._stream.seek(pos)

    def tell(self):

        return self._stream.tell()

    def close(self):

        return self._stream.close()

    def chunklength(self):

        d = readexactly(self._stream, 4)

        l = struct.unpack(">l", d)[0]

        if l <= 4:

            if l:

                raise util.Abort(_("invalid chunk length %d") % l)

            return 0

        if self.callback:

            self.callback()

        return l - 4

    def chunk(self):

        """return the next chunk from changegroup 'source' as a string"""

        l = self.chunklength()

        return readexactly(self._stream, l)

    def parsechunk(self):

        l = self.chunklength()

        if not l:

            return {}

        h = readexactly(self._stream, 80)

        node, p1, p2, cs = struct.unpack("20s20s20s20s", h)

        data = readexactly(self._stream, l - 80)

        return dict(node=node, p1=p1, p2=p2, cs=cs, data=data)

class headerlessfixup(object):

    def __init__(self, fh, h):

        self._h = h

        self._fh = fh

    def read(self, n):

        if self._h:

            d, self._h = self._h[:n], self._h[n:]

            if len(d) < n:

                d += readexactly(self._fh, n - len(d))

            return d

        return readexactly(self._fh, n)

def readbundle(fh, fname):

    header = readexactly(fh, 6)

    if not fname:

        fname = "stream"

        if not header.startswith('HG') and header.startswith('\0'):

            fh = headerlessfixup(fh, header)

            header = "HG10UN"

    magic, version, alg = header[0:2], header[2:4], header[4:6]

    if magic != 'HG':

        raise util.Abort(_('%s: not a Mercurial bundle') % fname)

    if version != '10':

        raise util.Abort(_('%s: unknown bundle version %s') % (fname, version))

    return unbundle10(fh, alg)