# 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 __future__ import absolute_import

import hashlib

from .i18n import _

from . import (

    bdiff,

    mdiff,

)

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,

                         unit=_('files'))

        h = hashlib.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, unit=_('files'))

        adata = fctx.data()

        h = hashlib.sha1(adata).digest()

        if h in hashes:

            rfctx = hashes[h]

            # compare between actual file contents for exact identity

            if adata == rfctx.data():

                yield (rfctx, fctx)

    # Done

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

def _ctxdata(fctx):

    # lazily load text

    orig = fctx.data()

    return orig, mdiff.splitnewlines(orig)

def _score(fctx, otherdata):

    orig, lines = otherdata

    text = fctx.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

def score(fctx1, fctx2):

    return _score(fctx1, _ctxdata(fctx2))

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), unit=_('files'))

        data = None

        for a in added:

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

            if data is None:

                data = _ctxdata(r)

            myscore = _score(a, data)

            if myscore >= bestscore:

                copies[a] = (r, myscore)

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

    for dest, v in copies.iteritems():

        source, bscore = v

        yield source, dest, bscore

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

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

    wctx = repo[None]

    pctx = wctx.p1()

    # 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.

    # Find exact matches.

    matchedfiles = set()

    for (a, b) in _findexactmatches(repo, addedfiles, removedfiles):

        matchedfiles.add(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:

        addedfiles = [x for x in addedfiles if x not in matchedfiles]

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

                                                 removedfiles, threshold):

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