# remotefilectx.py - filectx/workingfilectx implementations for remotefilelog
#
# 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.

import collections, os
from mercurial.node import bin, hex, nullid, nullrev, short
from mercurial import revlog, mdiff, filelog, context, util, error, ancestor

propertycache = util.propertycache

class remotefilectx(context.filectx):
    def __init__(self, repo, path, changeid=None, fileid=None,
                 filelog=None, changectx=None, ancestormap=None):
        if fileid == nullrev:
            fileid = nullid
        if fileid and len(fileid) == 40:
            fileid = bin(fileid)
        super(remotefilectx, self).__init__(repo, path, changeid,
            fileid, filelog, changectx)
        self._ancestormap = ancestormap

    def size(self):
        return self._filelog.size(self._filenode)

    @propertycache
    def _changeid(self):
        if '_changeid' in self.__dict__:
            return self._changeid
        elif '_changectx' in self.__dict__:
            return self._changectx.rev()
        elif '_descendantrev' in self.__dict__:
            # this file context was created from a revision with a known
            # descendant, we can (lazily) correct for linkrev aliases
            linknode = self._adjustlinknode(self._path, self._filelog,
                                            self._filenode, self._descendantrev)
            return self._repo.changelog.rev(linknode)
        else:
            return self.linkrev()

    def filectx(self, fileid, changeid=None):
        '''opens an arbitrary revision of the file without
        opening a new filelog'''
        return remotefilectx(self._repo, self._path, fileid=fileid,
                             filelog=self._filelog, changeid=changeid)

    def linkrev(self):
        if self._fileid == nullid:
            return nullrev

        ancestormap = self.ancestormap()
        p1, p2, linknode, copyfrom = ancestormap[self._fileid]
        rev = self._repo.changelog.nodemap.get(linknode)
        if rev is not None:
            return rev

        # Search all commits for the appropriate linkrev (slow, but uncommon)
        path = self._path
        fileid = self._fileid
        cl = self._repo.unfiltered().changelog
        ma = self._repo.manifest

        for rev in range(len(cl) - 1, 0, -1):
            node = cl.node(rev)
            data = cl.read(node) # get changeset data (we avoid object creation)
            if path in data[3]: # checking the 'files' field.
                # The file has been touched, check if the hash is what we're
                # looking for.
                if fileid == ma.readfast(data[0]).get(path):
                    return rev

        # Couldn't find the linkrev. This should generally not happen, and will
        # likely cause a crash.
        return None

    def introrev(self):
        """return the rev of the changeset which introduced this file revision

        This method is different from linkrev because it take into account the
        changeset the filectx was created from. It ensures the returned
        revision is one of its ancestors. This prevents bugs from
        'linkrev-shadowing' when a file revision is used by multiple
        changesets.
        """
        lkr = self.linkrev()
        attrs = vars(self)
        noctx = not ('_changeid' in attrs or '_changectx' in attrs)
        if noctx or self.rev() == lkr:
            return lkr
        linknode = self._adjustlinknode(self._path, self._filelog,
                                        self._filenode, self.rev(),
                                        inclusive=True)
        return self._repo.changelog.rev(linknode)

    def renamed(self):
        """check if file was actually renamed in this changeset revision

        If rename logged in file revision, we report copy for changeset only
        if file revisions linkrev points back to the changeset in question
        or both changeset parents contain different file revisions.
        """
        ancestormap = self.ancestormap()

        p1, p2, linknode, copyfrom = ancestormap[self._filenode]
        if not copyfrom:
            return None

        renamed = (copyfrom, p1)
        if self.rev() == self.linkrev():
            return renamed

        name = self.path()
        fnode = self._filenode
        for p in self._changectx.parents():
            try:
                if fnode == p.filenode(name):
                    return None
            except error.LookupError:
                pass
        return renamed

    def ancestormap(self):
        if not self._ancestormap:
            self._ancestormap = self.filelog().ancestormap(self._filenode)

        return self._ancestormap

    def parents(self):
        repo = self._repo
        ancestormap = self.ancestormap()

        p1, p2, linknode, copyfrom = ancestormap[self._filenode]
        results = []
        if p1 != nullid:
            path = copyfrom or self._path
            flog = repo.file(path)
            p1ctx = remotefilectx(repo, path, fileid=p1, filelog=flog,
                                  ancestormap=ancestormap)
            p1ctx._descendantrev = self.rev()
            results.append(p1ctx)

        if p2 != nullid:
            path = self._path
            flog = repo.file(path)
            p2ctx = remotefilectx(repo, path, fileid=p2, filelog=flog,
                                  ancestormap=ancestormap)
            p2ctx._descendantrev = self.rev()
            results.append(p2ctx)

        return results

    def _adjustlinknode(self, path, filelog, fnode, srcrev, inclusive=False):
        """return the first ancestor of <srcrev> introducing <fnode>

        If the linkrev of the file revision does not point to an ancestor of
        srcrev, we'll walk down the ancestors until we find one introducing
        this file revision.

        :repo: a localrepository object (used to access changelog and manifest)
        :path: the file path
        :fnode: the nodeid of the file revision
        :filelog: the filelog of this path
        :srcrev: the changeset revision we search ancestors from
        :inclusive: if true, the src revision will also be checked

        Note: This is based on adjustlinkrev in core, but it's quite different.

        adjustlinkrev depends on the fact that the linkrev is the bottom most
        node, and uses that as a stopping point for the ancestor traversal. We
        can't do that here because the linknode is not guaranteed to be the
        bottom most one.

        In our code here, we actually know what a bunch of potential ancestor
        linknodes are, so instead of stopping the cheap-ancestor-traversal when
        we get to a linkrev, we stop when we see any of the known linknodes.
        """
        repo = self._repo
        cl = repo.unfiltered().changelog
        ma = repo.manifest
        ancestormap = self.ancestormap()
        p1, p2, linknode, copyfrom = ancestormap[fnode]

        if srcrev is None:
            # wctx case, used by workingfilectx during mergecopy
            revs = [p.rev() for p in self._repo[None].parents()]
            inclusive = True # we skipped the real (revless) source
        else:
            revs = [srcrev]

        # First use the C fastpath to check if the given linknode is correct.
        try:
            if revs:
                srcnode = cl.node(revs[0])
                if cl.isancestor(linknode, srcnode):
                    return linknode
        except error.LookupError:
            # The node read from the blob may be old and not present, thus not
            # existing in the changelog.
            pass

        # Build a list of linknodes that are known to be ancestors of fnode
        knownancestors = set()
        queue = collections.deque(p for p in (p1, p2) if p != nullid)
        while queue:
            current = queue.pop()
            p1, p2, anclinknode, copyfrom = ancestormap[current]
            queue.extend(p for p in (p1, p2) if p != nullid)
            knownancestors.add(anclinknode)

        iteranc = cl.ancestors(revs, inclusive=inclusive)
        for a in iteranc:
            ac = cl.read(a) # get changeset data (we avoid object creation)
            if path in ac[3]: # checking the 'files' field.
                # The file has been touched, check if the content is
                # similar to the one we search for.
                if fnode == ma.readfast(ac[0]).get(path):
                    return cl.node(a)

        return linknode

    def ancestors(self, followfirst=False):
        repo = self._repo
        clrev = repo.changelog.rev

        ancestors = []
        queue = collections.deque((self,))
        while queue:
            current = queue.pop()
            ancestors.append(current)

            parents = current.parents()
            first = True
            for p in parents:
                if first or not followfirst:
                    queue.append(p)
                first = False

        # Remove self
        ancestors.pop(0)

        # Sort by linkrev
        # The copy tracing algorithm depends on these coming out in order
        ancestors = sorted(ancestors, reverse=True, key=lambda x:x.linkrev())

        for ancestor in ancestors:
            yield ancestor

    def ancestor(self, fc2, actx):
        # the easy case: no (relevant) renames
        if fc2.path() == self.path() and self.path() in actx:
            return actx[self.path()]

        # the next easiest cases: unambiguous predecessor (name trumps
        # history)
        if self.path() in actx and fc2.path() not in actx:
            return actx[self.path()]
        if fc2.path() in actx and self.path() not in actx:
            return actx[fc2.path()]

        # do a full traversal
        amap = self.ancestormap()
        bmap = fc2.ancestormap()

        def parents(x):
            f, n = x
            p = amap.get(n) or bmap.get(n)
            if not p:
                return []

            return [(p[3] or f, p[0]), (f, p[1])]

        a = (self.path(), self.filenode())
        b = (fc2.path(), fc2.filenode())
        result = ancestor.genericancestor(a, b, parents)
        if result:
            f, n = result
            r = remotefilectx(self._repo, f, fileid=n,
                                 ancestormap=amap)
            return r

        return None

    def annotate(self, follow=False, linenumber=None, diffopts=None):
        # use linkrev to find the first changeset where self appeared
        fetch = []
        ancestors = self.ancestors()
        for ancestor in ancestors:
            fetch.append((ancestor.path(), hex(ancestor.filenode())))

        self._repo.fileservice.prefetch(fetch)

        return super(remotefilectx, self).annotate(follow, linenumber, diffopts)

    def cmp(self, fctx):
        """compare with other file context

        returns True if different than fctx.
        """
        if (self.size() == fctx.size() or
            self._repo._encodefilterpats):
            return self._filelog.cmp(self._filenode, fctx.data())

        return True

    # Return empty set so that the hg serve and thg don't stack trace
    def children(self):
        return []

class remoteworkingfilectx(context.workingfilectx, remotefilectx):
    def __init__(self, repo, path, filelog=None, workingctx=None):
        self._ancestormap = None
        return super(remoteworkingfilectx, self).__init__(repo, path,
            filelog, workingctx)

    def parents(self):
        return remotefilectx.parents(self)

    def ancestormap(self):
        if not self._ancestormap:
            path = self._path
            pcl = self._changectx._parents
            renamed = self.renamed()

            if renamed:
                p1 = renamed
            else:
                p1 = (path, pcl[0]._manifest.get(path, nullid))

            p2 = (path, nullid)
            if len(pcl) > 1:
                p2 = (path, pcl[1]._manifest.get(path, nullid))

            m = {}
            if p1[1] != nullid:
                p1ctx = self._repo.filectx(p1[0], fileid=p1[1])
                m.update(p1ctx.filelog().ancestormap(p1[1]))

            if p2[1] != nullid:
                p2ctx = self._repo.filectx(p2[0], fileid=p2[1])
                m.update(p2ctx.filelog().ancestormap(p2[1]))

            copyfrom = ''
            if renamed:
                copyfrom = renamed[0]
            m[None] = (p1[1], p2[1], nullid, copyfrom)
            self._ancestormap = m

        return self._ancestormap