# Module dedicated to host utility code dedicated to changeset rewrite
#
# 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.

# Status: Stabilization of the API in progress
#
#   The content of this module should move into core incrementally once we are
#   happy one piece of it (and hopefully, able to reuse it in other core
#   commands).

import functools

from mercurial import (
    cmdutil,
    commands,
    context,
    copies,
    error,
    lock as lockmod,
    mergeutil,
    node,
    obsolete,
    obsutil,
    pycompat,
    revset,
    rewriteutil as corerewriteutil,
    scmutil,
    util,
)

from mercurial.i18n import _

from . import (
    compat,
)

def _formatrevs(repo, revs, maxrevs=4):
    """return a string summarising revision in a descent size

    If there is few enough revision, we list them otherwise we display a
    summary in the form:

        1ea73414a91b and 5 others
    """
    tonode = repo.changelog.node
    numrevs = len(revs)
    if numrevs < maxrevs:
        shorts = [node.short(tonode(r)) for r in revs]
        summary = b', '.join(shorts)
    else:
        first = revs.first()
        summary = _(b'%s and %d others')
        summary %= (node.short(tonode(first)), numrevs - 1)
    return summary

def precheck(repo, revs, action=b'rewrite', check_divergence=True):
    """check if <revs> can be rewritten

    <action> can be used to control the commit message.
    """
    if not pycompat.ispy3 and isinstance(corerewriteutil.precheck, functools.partial):
        # inspect.getargspec() on py2 cannot inspect functools.partial objects
        # directly, so we need to provide it with the underlying function
        args = pycompat.getargspec(corerewriteutil.precheck.func).args
    else:
        args = pycompat.getargspec(corerewriteutil.precheck).args
    # hg <= 6.1 (d4752aeb20f1)
    if r'check_divergence' in args:
        return corerewriteutil.precheck(repo, revs, action,
                                        check_divergence=check_divergence)

    if node.nullrev in revs:
        msg = _(b"cannot %s the null revision") % (action)
        hint = _(b"no changeset checked out")
        raise compat.InputError(msg, hint=hint)
    if any(util.safehasattr(r, 'rev') for r in revs):
        msg = b"rewriteutil.precheck called with ctx not revs"
        repo.ui.develwarn(msg)
        revs = (r.rev() for r in revs)
    if len(repo[None].parents()) > 1:
        raise compat.StateError(_(b"cannot %s changesets while merging")
                                % action)
    publicrevs = repo.revs(b'%ld and public()', revs)
    if publicrevs:
        summary = _formatrevs(repo, publicrevs)
        msg = _(b"cannot %s public changesets: %s") % (action, summary)
        hint = _(b"see 'hg help phases' for details")
        raise compat.InputError(msg, hint=hint)
    newunstable = disallowednewunstable(repo, revs)
    if newunstable:
        msg = _(b"cannot %s changeset, as that will orphan %i descendants")
        msg %= (action, len(newunstable))
        hint = _(b"see 'hg help evolution.instability'")
        raise compat.InputError(msg, hint=hint)
    if not check_divergence:
        return
    allowdivergence = compat.isenabled(repo, compat.allowdivergenceopt)
    if allowdivergence:
        return
    divergence = new_divergence(repo, revs)
    if divergence:
        local, other, common_prec = divergence
        localdiv = repo[local]
        otherdiv, base = repo[other], repo[common_prec]
        msg = _(b"cannot %s %s, as that creates content-divergence "
                b"with %s") % (action, localdiv, otherdiv)
        if localdiv.rev() != base.rev():
            msg += _(b', from %s') % base
        hint = _(b"add --verbose for details or see "
                 b"'hg help evolution.instability'")
        if repo.ui.verbose:
            if localdiv.rev() != base.rev():
                msg += _(b'\n    changeset %s is a successor of '
                         b'changeset %s') % (localdiv, base)
            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, otherdiv, localdiv)
            hint = _(b"see 'hg help evolution.instability' for details "
                     b"on content-divergence")
        raise compat.InputError(msg, hint=hint)

def bookmarksupdater(repo, oldid, tr):
    """Return a callable update(newid) updating the current bookmark
    and bookmarks bound to oldid to newid.
    """
    def updatebookmarks(newid):
        oldbookmarks = repo.nodebookmarks(oldid)
        bmchanges = [(b, newid) for b in oldbookmarks]
        if bmchanges:
            repo._bookmarks.applychanges(repo, tr, bmchanges)
    return updatebookmarks

def new_divergence(repo, revs):
    """Return a tuple (rev, divergent, common_precursor) if rewriting one of
    the revs will create content-divergence.
    """
    obsrevs = repo.revs(b'%ld and obsolete()', revs)
    for r in obsrevs:
        div_prec = precheck_contentdiv(repo, repo[r])
        if div_prec:
            divergent, common_prec = div_prec
            return (r, divergent, common_prec)

def disallowednewunstable(repo, revs):
    """Check that editing <revs> will not create disallowed unstable

    (unstable creation is controled by some special config).
    """
    allowunstable = obsolete.isenabled(repo, obsolete.allowunstableopt)
    if allowunstable:
        return revset.baseset()
    return repo.revs(b"(%ld::) - %ld", revs, revs)

def foldcheck(repo, revs):
    """check that <revs> can be folded"""
    precheck(repo, revs, action=b'fold')
    roots = repo.revs(b'roots(%ld)', revs)
    if len(roots) > 1:
        raise error.Abort(_(b"cannot fold non-linear revisions "
                            b"(multiple roots given)"))
    heads = repo.revs(b'heads(%ld)', revs)
    if len(heads) > 1:
        raise error.Abort(_(b"cannot fold non-linear revisions "
                            b"(multiple heads given)"))
    head = repo[heads.first()]
    baseparents = repo.revs(b'parents(%ld) - %ld', revs, revs)
    if len(baseparents) > 2:
        raise error.Abort(_(b"cannot fold revisions that merge with more than "
                            b"one external changeset (not in revisions)"))
    if not compat.isenabled(repo, compat.allowdivergenceopt):
        obsoleterevs = repo.revs(b'%ld and obsolete()', revs)
        if obsoleterevs:
            msg = _(b'folding obsolete revisions may cause divergence')
            hint = _(b'set experimental.evolution.allowdivergence=yes'
                     b' to allow folding them')
            raise error.Abort(msg, hint=hint)
    root = repo[roots.first()]
    # root's p1 is already used as the target ctx p1
    baseparents -= {root.p1().rev()}
    p2 = repo[baseparents.first()]
    return root, head, p2

def deletebookmark(repo, repomarks, bookmarks):
    wlock = lock = tr = None
    try:
        wlock = repo.wlock()
        lock = repo.lock()
        tr = repo.transaction(b'prune')
        bmchanges = []
        for bookmark in bookmarks:
            bmchanges.append((bookmark, None))
        repo._bookmarks.applychanges(repo, tr, bmchanges)
        tr.close()
        for bookmark in sorted(bookmarks):
            b = repo.ui.label(bookmark, b'bookmarks')
            repo.ui.write(_(b"bookmark '%s' deleted\n") % b)
    finally:
        lockmod.release(tr, lock, wlock)

def presplitupdate(repo, ui, prev, ctx):
    """prepare the working directory for a split (for topic hooking)
    """
    compat.hg_update(repo, prev)
    commands.revert(ui, repo, rev=ctx.hex(), all=True)

def reachablefrombookmark(repo, revs, bookmarks):
    """filter revisions and bookmarks reachable from the given bookmark
    yoinked from mq.py
    """
    repomarks = repo._bookmarks
    if not bookmarks.issubset(repomarks):
        raise error.Abort(_(b"bookmark '%s' not found") %
                          b','.join(sorted(bookmarks - set(repomarks.keys()))))

    # If the requested bookmark is not the only one pointing to a
    # a revision we have to only delete the bookmark and not strip
    # anything. revsets cannot detect that case.
    nodetobookmarks = {}
    for mark, bnode in repomarks.items():
        nodetobookmarks.setdefault(bnode, []).append(mark)
    for marks in nodetobookmarks.values():
        if bookmarks.issuperset(marks):
            rsrevs = scmutil.bookmarkrevs(repo, marks[0])
            revs = set(revs)
            revs.update(set(rsrevs))
            revs = sorted(revs)
    return repomarks, revs

def rewrite(repo, old, head, newbases, commitopts):
    """Return (nodeid, created) where nodeid is the identifier of the
    changeset generated by the rewrite process, and created is True if
    nodeid was actually created. If created is False, nodeid
    references a changeset existing before the rewrite call.
    """
    # Until there was memmergestate, in-memory would clear the on-disk
    # mergestate and use that. We don't want that to happen, so we'll require
    # users of old Mercurial versions to run `hg touch` etc without
    # mergestate.
    if not compat.hasmemmergestate:
        ms = compat.mergestate.read(repo)
        mergeutil.checkunresolved(ms)

    wlock = lock = tr = None
    try:
        wlock = repo.wlock()
        lock = repo.lock()
        tr = repo.transaction(b'rewrite')
        base = old.p1()
        updatebookmarks = bookmarksupdater(repo, old.node(), tr)

        message = cmdutil.logmessage(repo.ui, commitopts)
        if not message:
            message = old.description()

        user = commitopts.get(b'user') or old.user()
        # TODO: In case not date is given, we should take the old commit date
        # if we are working one one changeset or mimic the fold behavior about
        # date
        date = commitopts.get(b'date') or None
        extra = dict(commitopts.get(b'extra', old.extra()))
        extra[b'branch'] = head.branch()

        wctx = context.overlayworkingctx(repo)
        wctx.setbase(base)
        compat._update(repo,
                       head.node(),
                       branchmerge=False,
                       force=True,
                       wc=wctx)
        for pctx in head.parents():
            for dst, src in copies.pathcopies(pctx, head).items():
                wctx[dst].markcopied(src)
        editor = None
        if commitopts.get(b'edit'):
            editor = cmdutil.commitforceeditor
        new = wctx.tomemctx(text=message,
                            branch=extra[b'branch'],
                            parents=newbases,
                            date=date,
                            extra=extra,
                            user=user,
                            editor=editor)
        revcount = len(repo)
        newid = repo.commitctx(new)
        created = len(repo) != revcount
        updatebookmarks(newid)

        tr.close()
        return newid, created
    finally:
        lockmod.release(tr, lock, wlock)

def precheck_contentdiv(repo, ctx):
    """return divergent revision if rewriting an obsolete cset (ctx) will
    create divergence"""
    # 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)
    divergent = [] # contains [divergent_cset, common_precursor]
    sset = obsutil.successorssets(repo, ctx.node())
    nodivergencerisk = (len(sset) == 0
                        or (len(sset) == 1
                            and len(sset[0]) == 1
                            and repo[sset[0][0]].rev() == ctx.rev()
                        ))
    if nodivergencerisk:
        # case 2: one of the precursors of the rev being revived has a
        #     non-obsolete successor (we need divergentsets for this)
        from . import evolvecmd
        divsets = evolvecmd.divergentsets(repo, ctx)
        if divsets:
            nsuccset = divsets[0][b'divergentnodes']
            divergent.append(nsuccset[0])
            prec = divsets[0][b'commonprecursor']
            divergent.append(prec)
    else:
        divergent.append(sset[0][0])
        divergent.append(ctx.node())
    return divergent
