# bundle2.py - generic container format to transmit arbitrary data.

#

# Copyright 2013 Facebook, Inc.

#

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

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

"""Handling of the new bundle2 format

The goal of bundle2 is to act as an atomically packet to transmit a set of

payloads in an application agnostic way. It consist in a sequence of "parts"

that will be handed to and processed by the application layer.

General format architecture

===========================

The format is architectured as follow

 - magic string

 - stream level parameters

 - payload parts (any number)

 - end of stream marker.

the Binary format

============================

All numbers are unsigned and big endian.

stream level parameters

------------------------

Binary format is as follow

:params size: (16 bits integer)

  The total number of Bytes used by the parameters

:params value: arbitrary number of Bytes

  A blob of `params size` containing the serialized version of all stream level

  parameters.

  The blob contains a space separated list of parameters. parameter with value

  are stored in the form `<name>=<value>`. Both name and value are urlquoted.

  Empty name are obviously forbidden.

  Name MUST start with a letter. If this first letter is lower case, the

  parameter is advisory and can be safefly ignored. However when the first

  letter is capital, the parameter is mandatory and the bundling process MUST

  stop if he is not able to proceed it.

  Stream parameters use a simple textual format for two main reasons:

  - Stream level parameters should remains simple and we want to discourage any

    crazy usage.

  - Textual data allow easy human inspection of a the bundle2 header in case of

    troubles.

  Any Applicative level options MUST go into a bundle2 part instead.

Payload part

------------------------

Binary format is as follow

:header size: (16 bits inter)

  The total number of Bytes used by the part headers. When the header is empty

  (size = 0) this is interpreted as the end of stream marker.

:header:

    The header defines how to interpret the part. It contains two piece of

    data: the part type, and the part parameters.

    The part type is used to route an application level handler, that can

    interpret payload.

    Part parameters are passed to the application level handler.  They are

    meant to convey information that will help the application level object to

    interpret the part payload.

    The binary format of the header is has follow

    :typesize: (one byte)

    :typename: alphanumerical part name

    :partid: A 32bits integer (unique in the bundle) that can be used to refer

             to this part.

    :parameters:

        Part's parameter may have arbitraty content, the binary structure is::

            <mandatory-count><advisory-count><param-sizes><param-data>

        :mandatory-count: 1 byte, number of mandatory parameters

        :advisory-count:  1 byte, number of advisory parameters

        :param-sizes:

            N couple of bytes, where N is the total number of parameters. Each

            couple contains (<size-of-key>, <size-of-value) for one parameter.

        :param-data:

            A blob of bytes from which each parameter key and value can be

            retrieved using the list of size couples stored in the previous

            field.

            Mandatory parameters comes first, then the advisory ones.

:payload:

    payload is a series of `<chunksize><chunkdata>`.

    `chunksize` is a 32 bits integer, `chunkdata` are plain bytes (as much as

    `chunksize` says)` The payload part is concluded by a zero size chunk.

    The current implementation always produces either zero or one chunk.

    This is an implementation limitation that will ultimatly be lifted.

Bundle processing

============================

Each part is processed in order using a "part handler". Handler are registered

for a certain part type.

The matching of a part to its handler is case insensitive. The case of the

part type is used to know if a part is mandatory or advisory. If the Part type

contains any uppercase char it is considered mandatory. When no handler is

known for a Mandatory part, the process is aborted and an exception is raised.

If the part is advisory and no handler is known, the part is ignored. When the

process is aborted, the full bundle is still read from the stream to keep the

channel usable. But none of the part read from an abort are processed. In the

future, dropping the stream may become an option for channel we do not care to

preserve.

"""

import util

import struct

import urllib

import string

import StringIO

import changegroup

from i18n import _

_pack = struct.pack

_unpack = struct.unpack

_magicstring = 'HG20'

_fstreamparamsize = '>H'

_fpartheadersize = '>H'

_fparttypesize = '>B'

_fpartid = '>I'

_fpayloadsize = '>I'

_fpartparamcount = '>BB'

preferedchunksize = 4096

def _makefpartparamsizes(nbparams):

    """return a struct format to read part parameter sizes

    The number parameters is variable so we need to build that format

    dynamically.

    """

    return '>'+('BB'*nbparams)

parthandlermapping = {}

def parthandler(parttype):

    """decorator that register a function as a bundle2 part handler

    eg::

        @parthandler('myparttype')

        def myparttypehandler(...):

            '''process a part of type "my part".'''

            ...

    """

    def _decorator(func):

        lparttype = parttype.lower() # enforce lower case matching.

        assert lparttype not in parthandlermapping

        parthandlermapping[lparttype] = func

        return func

    return _decorator

class unbundlerecords(object):

    """keep record of what happens during and unbundle

    New records are added using `records.add('cat', obj)`. Where 'cat' is a

    category of record and obj is an arbitraty object.

    `records['cat']` will return all entries of this category 'cat'.

    Iterating on the object itself will yield `('category', obj)` tuples

    for all entries.

    All iterations happens in chronological order.

    """

    def __init__(self):

        self._categories = {}

        self._sequences = []

        self._replies = {}

    def add(self, category, entry, inreplyto=None):

        """add a new record of a given category.

        The entry can then be retrieved in the list returned by

        self['category']."""

        self._categories.setdefault(category, []).append(entry)

        self._sequences.append((category, entry))

        if inreplyto is not None:

            self.getreplies(inreplyto).add(category, entry)

    def getreplies(self, partid):

        """get the subrecords that replies to a specific part"""

        return self._replies.setdefault(partid, unbundlerecords())

    def __getitem__(self, cat):

        return tuple(self._categories.get(cat, ()))

    def __iter__(self):

        return iter(self._sequences)

    def __len__(self):

        return len(self._sequences)

    def __nonzero__(self):

        return bool(self._sequences)

class bundleoperation(object):

    """an object that represents a single bundling process

    Its purpose is to carry unbundle-related objects and states.

    A new object should be created at the beginning of each bundle processing.

    The object is to be returned by the processing function.

    The object has very little content now it will ultimately contain:

    * an access to the repo the bundle is applied to,

    * a ui object,

    * a way to retrieve a transaction to add changes to the repo,

    * a way to record the result of processing each part,

    * a way to construct a bundle response when applicable.

    """

    def __init__(self, repo, transactiongetter):

        self.repo = repo

        self.ui = repo.ui

        self.records = unbundlerecords()

        self.gettransaction = transactiongetter

        self.reply = None

class TransactionUnavailable(RuntimeError):

    pass

def _notransaction():

    """default method to get a transaction while processing a bundle

    Raise an exception to highlight the fact that no transaction was expected

    to be created"""

    raise TransactionUnavailable()

def processbundle(repo, unbundler, transactiongetter=_notransaction):

    """This function process a bundle, apply effect to/from a repo

    It iterates over each part then searches for and uses the proper handling

    code to process the part. Parts are processed in order.

    This is very early version of this function that will be strongly reworked

    before final usage.

    Unknown Mandatory part will abort the process.

    """

    op = bundleoperation(repo, transactiongetter)

    # todo:

    # - only create reply bundle if requested.

    op.reply = bundle20(op.ui)

    # todo:

    # - replace this is a init function soon.

    # - exception catching

    unbundler.params

    iterparts = iter(unbundler)

    try:

        for part in iterparts:

            parttype = part.type

            # part key are matched lower case

            key = parttype.lower()

            try:

                handler = parthandlermapping[key]

                op.ui.debug('found a handler for part %r\n' % parttype)

            except KeyError:

                if key != parttype: # mandatory parts

                    # todo:

                    # - use a more precise exception

                    raise

                op.ui.debug('ignoring unknown advisory part %r\n' % key)

                # todo:

                # - consume the part once we use streaming

                continue

            # handler is called outside the above try block so that we don't

            # risk catching KeyErrors from anything other than the

            # parthandlermapping lookup (any KeyError raised by handler()

            # itself represents a defect of a different variety).

            handler(op, part)

    except Exception:

        for part in iterparts:

            pass # consume the bundle content

        raise

    return op

class bundle20(object):

    """represent an outgoing bundle2 container

    Use the `addparam` method to add stream level parameter. and `addpart` to

    populate it. Then call `getchunks` to retrieve all the binary chunks of

    datathat compose the bundle2 container."""

    def __init__(self, ui):

        self.ui = ui

        self._params = []

        self._parts = []

    def addparam(self, name, value=None):

        """add a stream level parameter"""

        if not name:

            raise ValueError('empty parameter name')

        if name[0] not in string.letters:

            raise ValueError('non letter first character: %r' % name)

        self._params.append((name, value))

    def addpart(self, part):

        """add a new part to the bundle2 container

        Parts contains the actuall applicative payload."""

        assert part.id is None

        part.id = len(self._parts) # very cheap counter

        self._parts.append(part)

    def getchunks(self):

        self.ui.debug('start emission of %s stream\n' % _magicstring)

        yield _magicstring

        param = self._paramchunk()

        self.ui.debug('bundle parameter: %s\n' % param)

        yield _pack(_fstreamparamsize, len(param))

        if param:

            yield param

        self.ui.debug('start of parts\n')

        for part in self._parts:

            self.ui.debug('bundle part: "%s"\n' % part.type)

            for chunk in part.getchunks():

                yield chunk

        self.ui.debug('end of bundle\n')

        yield '\0\0'

    def _paramchunk(self):

        """return a encoded version of all stream parameters"""

        blocks = []

        for par, value in self._params:

            par = urllib.quote(par)

            if value is not None:

                value = urllib.quote(value)

                par = '%s=%s' % (par, value)

            blocks.append(par)

        return ' '.join(blocks)

class unpackermixin(object):

    """A mixin to extract bytes and struct data from a stream"""

    def __init__(self, fp):

        self._fp = fp

    def _unpack(self, format):

        """unpack this struct format from the stream"""

        data = self._readexact(struct.calcsize(format))

        return _unpack(format, data)

    def _readexact(self, size):

        """read exactly <size> bytes from the stream"""

        return changegroup.readexactly(self._fp, size)

class unbundle20(unpackermixin):

    """interpret a bundle2 stream

    (this will eventually yield parts)"""

    def __init__(self, ui, fp):

        self.ui = ui

        super(unbundle20, self).__init__(fp)

        header = self._readexact(4)

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

        if magic != 'HG':

            raise util.Abort(_('not a Mercurial bundle'))

        if version != '20':

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

        self.ui.debug('start processing of %s stream\n' % header)

    @util.propertycache

    def params(self):

        """dictionnary of stream level parameters"""

        self.ui.debug('reading bundle2 stream parameters\n')

        params = {}

        paramssize = self._unpack(_fstreamparamsize)[0]

        if paramssize:

            for p in self._readexact(paramssize).split(' '):

                p = p.split('=', 1)

                p = [urllib.unquote(i) for i in p]

                if len(p) < 2:

                    p.append(None)

                self._processparam(*p)

                params[p[0]] = p[1]