# similar.py - mechanisms for finding similar files

#

# Copyright 2005-2007 Matt Mackall <mpm@selenic.com>

#

# 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 _

import util

import mdiff

import bdiff

def _findexactmatches(repo, added, removed):

    '''find renamed files that have no changes

    Takes a list of new filectxs and a list of removed filectxs, and yields

    (before, after) tuples of exact matches.

    '''

    numfiles = len(added) + len(removed)

    # Get hashes of removed files.

    hashes = {}

    for i, fctx in enumerate(removed):

        repo.ui.progress(_('searching for exact renames'), i, total=numfiles)

        h = util.sha1(fctx.data()).digest()

        hashes[h] = fctx

    # For each added file, see if it corresponds to a removed file.

    for i, fctx in enumerate(added):

        repo.ui.progress(_('searching for exact renames'), i + len(removed),

                total=numfiles)

        h = util.sha1(fctx.data()).digest()

        if h in hashes:

            yield (hashes[h], fctx)

    # Done

    repo.ui.progress(_('searching for exact renames'), None)

def _findsimilarmatches(repo, added, removed, threshold):

    '''find potentially renamed files based on similar file content

    Takes a list of new filectxs and a list of removed filectxs, and yields

    (before, after, score) tuples of partial matches.

    '''

    copies = {}

    for i, r in enumerate(removed):

        repo.ui.progress(_('searching for similar files'), i,

                         total=len(removed))

        # lazily load text

        @util.cachefunc

        def data():

            orig = r.data()

            return orig, mdiff.splitnewlines(orig)

        def score(text):

            orig, lines = data()

            # bdiff.blocks() returns blocks of matching lines

            # count the number of bytes in each

            equal = 0

            matches = bdiff.blocks(text, orig)

            for x1, x2, y1, y2 in matches:

                for line in lines[y1:y2]:

                    equal += len(line)

            lengths = len(text) + len(orig)

            return equal * 2.0 / lengths

        for a in added:

            bestscore = copies.get(a, (None, threshold))[1]

            myscore = score(a.data())

            if myscore >= bestscore:

                copies[a] = (r, myscore)

    repo.ui.progress(_('searching'), None)

    for dest, v in copies.iteritems():

        source, score = v

        yield source, dest, score

def findrenames(repo, added, removed, threshold):

    '''find renamed files -- yields (before, after, score) tuples'''

    parentctx = repo['.']

    workingctx = repo[None]

    # Zero length files will be frequently unrelated to each other, and

    # tracking the deletion/addition of such a file will probably cause more

    # harm than good. We strip them out here to avoid matching them later on.

    addedfiles = set([workingctx[fp] for fp in added

            if workingctx[fp].size() > 0])

    removedfiles = set([parentctx[fp] for fp in removed

            if fp in parentctx and parentctx[fp].size() > 0])

    # Find exact matches.

    for (a, b) in _findexactmatches(repo,

            sorted(addedfiles), sorted(removedfiles)):

        addedfiles.remove(b)

        yield (a.path(), b.path(), 1.0)

    # If the user requested similar files to be matched, search for them also.

    if threshold < 1.0:

        for (a, b, score) in _findsimilarmatches(repo,

                sorted(addedfiles), sorted(removedfiles), threshold):

            yield (a.path(), b.path(), score)