# rewriteutil.py - utility functions for rewriting changesets

#

# Copyright 2017 Octobus <contact@octobus.net>

#

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

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

from __future__ import absolute_import

import re

from .i18n import _

from .node import (

    hex,

    nullrev,

)

from . import (

    error,

    obsolete,

    obsutil,

    revset,

    scmutil,

    util,

)

NODE_RE = re.compile(br'\b[0-9a-f]{6,64}\b')

def precheck(repo, revs, action=b'rewrite'):

    """check if revs can be rewritten

    action is used to control the error message.

    Make sure this function is called after taking the lock.

    """

    if nullrev in revs:

        msg = _(b"cannot %s the null revision") % action

        hint = _(b"no changeset checked out")

        raise error.InputError(msg, hint=hint)

    if any(util.safehasattr(r, 'rev') for r in revs):

        repo.ui.develwarn(b"rewriteutil.precheck called with ctx not revs")

        revs = (r.rev() for r in revs)

    if len(repo[None].parents()) > 1:

        raise error.StateError(

            _(b"cannot %s changesets while merging") % action

        )

    publicrevs = repo.revs(b'%ld and public()', revs)

    if publicrevs:

        msg = _(b"cannot %s public changesets") % action

        hint = _(b"see 'hg help phases' for details")

        raise error.InputError(msg, hint=hint)

    newunstable = disallowednewunstable(repo, revs)

    if newunstable:

        hint = _(b"see 'hg help evolution.instability'")

        raise error.InputError(

            _(b"cannot %s changeset with children") % action, hint=hint

        )

    if not obsolete.isenabled(repo, obsolete.allowdivergenceopt):

        new_divergence = _find_new_divergence(repo, revs)

        if new_divergence:

            local_ctx, other_ctx, base_ctx = new_divergence

            msg = _(

                b'cannot %s %s, as that creates content-divergence with %s'

            ) % (

                action,

                local_ctx,

                other_ctx,

            )

            if local_ctx.rev() != base_ctx.rev():

                msg += _(b', from %s') % base_ctx

            if repo.ui.verbose:

                if local_ctx.rev() != base_ctx.rev():

                    msg += _(

                        b'\n    changeset %s is a successor of ' b'changeset %s'

                    ) % (local_ctx, base_ctx)

                msg += _(

                    b'\n    changeset %s already has a successor in '

                    b'changeset %s\n'

                    b'    rewriting changeset %s would create '

                    b'"content-divergence"\n'

                    b'    set experimental.evolution.allowdivergence=True to '

                    b'skip this check'

                ) % (base_ctx, other_ctx, local_ctx)

                raise error.InputError(msg)

            else:

                raise error.InputError(

                    msg, hint=_(b"add --verbose for details")

                )

def disallowednewunstable(repo, revs):

    """Checks whether editing the revs will create new unstable changesets and

    are we allowed to create them.

    To allow new unstable changesets, set the config:

        `experimental.evolution.allowunstable=True`

    """

    allowunstable = obsolete.isenabled(repo, obsolete.allowunstableopt)

    if allowunstable:

        return revset.baseset()

    return repo.revs(b"(%ld::) - %ld", revs, revs)

def _find_new_divergence(repo, revs):

    obsrevs = repo.revs(b'%ld and obsolete()', revs)

    for r in obsrevs:

        div = find_new_divergence_from(repo, repo[r])

        if div:

            return (repo[r], repo[div[0]], repo[div[1]])

    return None

def find_new_divergence_from(repo, ctx):

    """return divergent revision if rewriting an obsolete cset (ctx) will

    create divergence

    Returns (<other node>, <common ancestor node>) or None

    """

    if not ctx.obsolete():

        return None

    # We need to check two cases that can cause divergence:

    # case 1: the rev being rewritten has a non-obsolete successor (easily

    #     detected by successorssets)

    sset = obsutil.successorssets(repo, ctx.node())

    if sset:

        return (sset[0][0], ctx.node())

    else:

        # case 2: one of the precursors of the rev being revived has a

        #     non-obsolete successor (we need divergentsets for this)

        divsets = obsutil.divergentsets(repo, ctx)

        if divsets:

            nsuccset = divsets[0][b'divergentnodes']

            prec = divsets[0][b'commonpredecessor']

            return (nsuccset[0], prec)

        return None

def skip_empty_successor(ui, command):

    empty_successor = ui.config(b'rewrite', b'empty-successor')

    if empty_successor == b'skip':

        return True

    elif empty_successor == b'keep':

        return False

    else:

        raise error.ConfigError(

            _(

                b"%s doesn't know how to handle config "

                b"rewrite.empty-successor=%s (only 'skip' and 'keep' are "

                b"supported)"

            )

            % (command, empty_successor)

        )

def update_hash_refs(repo, commitmsg, pending=None):

    """Replace all obsolete commit hashes in the message with the current hash.

    If the obsolete commit was split or is divergent, the hash is not replaced

    as there's no way to know which successor to choose.

    For commands that update a series of commits in the current transaction, the

    new obsolete markers can be considered by setting ``pending`` to a mapping

    of ``pending[oldnode] = [successor_node1, successor_node2,..]``.

    """

    if not pending:

        pending = {}

    cache = {}

    hashes = re.findall(NODE_RE, commitmsg)

    unfi = repo.unfiltered()

    for h in hashes:

        fullnode = scmutil.resolvehexnodeidprefix(unfi, h)

        if fullnode is None:

            continue

        ctx = unfi[fullnode]

        if not ctx.obsolete():

            successors = pending.get(fullnode)

            if successors is None:

                continue

            # obsutil.successorssets() returns a list of list of nodes

            successors = [successors]

        else:

            successors = obsutil.successorssets(repo, ctx.node(), cache=cache)

        # We can't make any assumptions about how to update the hash if the

        # cset in question was split or diverged.

        if len(successors) == 1 and len(successors[0]) == 1:

            successor = successors[0][0]

            if successor is not None:

                newhash = hex(successor)

                commitmsg = commitmsg.replace(h, newhash[: len(h)])

            else:

                repo.ui.note(

                    _(

                        b'The stale commit message reference to %s could '

                        b'not be updated\n(The referenced commit was dropped)\n'

                    )

                    % h

                )

        else:

            repo.ui.note(

                _(

                    b'The stale commit message reference to %s could '

                    b'not be updated\n'

                )

                % h

            )

    return commitmsg