# flagutils.py - code to deal with revlog flags and their processors

#

# Copyright 2016 Remi Chaintron <remi@fb.com>

# Copyright 2016-2019 Pierre-Yves David <pierre-yves.david@ens-lyon.org>

#

# 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 _

from .constants import (

    REVIDX_DEFAULT_FLAGS,

    REVIDX_ELLIPSIS,

    REVIDX_EXTSTORED,

    REVIDX_FLAGS_ORDER,

    REVIDX_HASCOPIESINFO,

    REVIDX_ISCENSORED,

    REVIDX_RAWTEXT_CHANGING_FLAGS,

)

from .. import error, util

# blanked usage of all the name to prevent pyflakes constraints

# We need these name available in the module for extensions.

REVIDX_ISCENSORED

REVIDX_ELLIPSIS

REVIDX_EXTSTORED

REVIDX_HASCOPIESINFO,

REVIDX_DEFAULT_FLAGS

REVIDX_FLAGS_ORDER

REVIDX_RAWTEXT_CHANGING_FLAGS

# Keep this in sync with REVIDX_KNOWN_FLAGS in rust/hg-core/src/revlog/revlog.rs

REVIDX_KNOWN_FLAGS = util.bitsfrom(REVIDX_FLAGS_ORDER)

# Store flag processors (cf. 'addflagprocessor()' to register)

flagprocessors = {

    REVIDX_ISCENSORED: None,

    REVIDX_HASCOPIESINFO: None,

}

def addflagprocessor(flag, processor):

    """Register a flag processor on a revision data flag.

    Invariant:

    - Flags need to be defined in REVIDX_KNOWN_FLAGS and REVIDX_FLAGS_ORDER,

      and REVIDX_RAWTEXT_CHANGING_FLAGS if they can alter rawtext.

    - Only one flag processor can be registered on a specific flag.

    - flagprocessors must be 3-tuples of functions (read, write, raw) with the

      following signatures:

          - (read)  f(self, rawtext) -> text, bool

          - (write) f(self, text) -> rawtext, bool

          - (raw)   f(self, rawtext) -> bool

      "text" is presented to the user. "rawtext" is stored in revlog data, not

      directly visible to the user.

      The boolean returned by these transforms is used to determine whether

      the returned text can be used for hash integrity checking. For example,

      if "write" returns False, then "text" is used to generate hash. If

      "write" returns True, that basically means "rawtext" returned by "write"

      should be used to generate hash. Usually, "write" and "read" return

      different booleans. And "raw" returns a same boolean as "write".

      Note: The 'raw' transform is used for changegroup generation and in some

      debug commands. In this case the transform only indicates whether the

      contents can be used for hash integrity checks.

    """

    insertflagprocessor(flag, processor, flagprocessors)

def insertflagprocessor(flag, processor, flagprocessors):

    if not flag & REVIDX_KNOWN_FLAGS:

        msg = _(b"cannot register processor on unknown flag '%#x'.") % flag

        raise error.ProgrammingError(msg)

    if flag not in REVIDX_FLAGS_ORDER:

        msg = _(b"flag '%#x' undefined in REVIDX_FLAGS_ORDER.") % flag

        raise error.ProgrammingError(msg)

    if flag in flagprocessors:

        msg = _(b"cannot register multiple processors on flag '%#x'.") % flag

        raise error.Abort(msg)

    flagprocessors[flag] = processor

def processflagswrite(revlog, text, flags):

    """Inspect revision data flags and applies write transformations defined

    by registered flag processors.

    ``text`` - the revision data to process

    ``flags`` - the revision flags

    This method processes the flags in the order (or reverse order if

    ``operation`` is 'write') defined by REVIDX_FLAGS_ORDER, applying the

    flag processors registered for present flags. The order of flags defined

    in REVIDX_FLAGS_ORDER needs to be stable to allow non-commutativity.

    Returns a 2-tuple of ``(text, validatehash)`` where ``text`` is the

    processed text and ``validatehash`` is a bool indicating whether the

    returned text should be checked for hash integrity.

    """

    return _processflagsfunc(

        revlog,

        text,

        flags,

        b'write',

    )[:2]

def processflagsread(revlog, text, flags):

    """Inspect revision data flags and applies read transformations defined

    by registered flag processors.

    ``text`` - the revision data to process

    ``flags`` - the revision flags

    ``raw`` - an optional argument describing if the raw transform should be

    applied.

    This method processes the flags in the order (or reverse order if

    ``operation`` is 'write') defined by REVIDX_FLAGS_ORDER, applying the

    flag processors registered for present flags. The order of flags defined

    in REVIDX_FLAGS_ORDER needs to be stable to allow non-commutativity.

    Returns a 2-tuple of ``(text, validatehash)`` where ``text`` is the

    processed text and ``validatehash`` is a bool indicating whether the

    returned text should be checked for hash integrity.

    """

    return _processflagsfunc(revlog, text, flags, b'read')

def processflagsraw(revlog, text, flags):

    """Inspect revision data flags to check is the content hash should be

    validated.

    ``text`` - the revision data to process

    ``flags`` - the revision flags

    This method processes the flags in the order (or reverse order if

    ``operation`` is 'write') defined by REVIDX_FLAGS_ORDER, applying the

    flag processors registered for present flags. The order of flags defined

    in REVIDX_FLAGS_ORDER needs to be stable to allow non-commutativity.

    Returns a 2-tuple of ``(text, validatehash)`` where ``text`` is the

    processed text and ``validatehash`` is a bool indicating whether the

    returned text should be checked for hash integrity.

    """

    return _processflagsfunc(revlog, text, flags, b'raw')[1]

def _processflagsfunc(revlog, text, flags, operation):

    """internal function to process flag on a revlog

    This function is private to this module, code should never needs to call it

    directly."""

    # fast path: no flag processors will run

    if flags == 0:

        return text, True

    if operation not in (b'read', b'write', b'raw'):

        raise error.ProgrammingError(_(b"invalid '%s' operation") % operation)

    # Check all flags are known.

    if flags & ~REVIDX_KNOWN_FLAGS:

        raise revlog._flagserrorclass(

            _(b"incompatible revision flag '%#x'")

            % (flags & ~REVIDX_KNOWN_FLAGS)

        )

    validatehash = True

    # Depending on the operation (read or write), the order might be

    # reversed due to non-commutative transforms.

    orderedflags = REVIDX_FLAGS_ORDER

    if operation == b'write':

        orderedflags = reversed(orderedflags)

    for flag in orderedflags:

        # If a flagprocessor has been registered for a known flag, apply the

        # related operation transform and update result tuple.

        if flag & flags:

            vhash = True

            if flag not in revlog._flagprocessors:

                message = _(b"missing processor for flag '%#x'") % flag

                raise revlog._flagserrorclass(message)

            processor = revlog._flagprocessors[flag]

            if processor is not None:

                readtransform, writetransform, rawtransform = processor

                if operation == b'raw':

                    vhash = rawtransform(revlog, text)

                elif operation == b'read':

                    text, vhash = readtransform(revlog, text)

                else:  # write operation

                    text, vhash = writetransform(revlog, text)

            validatehash = validatehash and vhash

    return text, validatehash