# filelog.py - file history class for mercurial

#

# 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 re

import struct

from . import (

    error,

    mdiff,

    revlog,

)

_mdre = re.compile('\1\n')

def parsemeta(text):

    """return (metadatadict, metadatasize)"""

    # text can be buffer, so we can't use .startswith or .index

    if text[:2] != '\1\n':

        return None, None

    s = _mdre.search(text, 2).start()

    mtext = text[2:s]

    meta = {}

    for l in mtext.splitlines():

        k, v = l.split(": ", 1)

        meta[k] = v

    return meta, (s + 2)

def packmeta(meta, text):

    keys = sorted(meta)

    metatext = "".join("%s: %s\n" % (k, meta[k]) for k in keys)

    return "\1\n%s\1\n%s" % (metatext, text)

def _censoredtext(text):

    m, offs = parsemeta(text)

    return m and "censored" in m

class filelog(revlog.revlog):

    def __init__(self, opener, path):

        super(filelog, self).__init__(opener,

                        "/".join(("data", path + ".i")))

        # full name of the user visible file, relative to the repository root

        self.filename = path

    def read(self, node):

        t = self.revision(node)

        if not t.startswith('\1\n'):

            return t

        s = t.index('\1\n', 2)

        return t[s + 2:]

    def add(self, text, meta, transaction, link, p1=None, p2=None):

        if meta or text.startswith('\1\n'):

            text = packmeta(meta, text)

        return self.addrevision(text, transaction, link, p1, p2)

    def renamed(self, node):

        if self.parents(node)[0] != revlog.nullid:

            return False

        t = self.revision(node)

        m = parsemeta(t)[0]

        if m and "copy" in m:

            return (m["copy"], revlog.bin(m["copyrev"]))

        return False

    def size(self, rev):

        """return the size of a given revision"""

        # for revisions with renames, we have to go the slow way

        node = self.node(rev)

        if self.renamed(node):

            return len(self.read(node))

        if self.iscensored(rev):

            return 0

        # XXX if self.read(node).startswith("\1\n"), this returns (size+4)

        return super(filelog, self).size(rev)

    def cmp(self, node, text):

        """compare text with a given file revision

        returns True if text is different than what is stored.

        """

        t = text

        if text.startswith('\1\n'):

            t = '\1\n\1\n' + text

        samehashes = not super(filelog, self).cmp(node, t)

        if samehashes:

            return False

        # censored files compare against the empty file

        if self.iscensored(self.rev(node)):

            return text != ''

        # renaming a file produces a different hash, even if the data

        # remains unchanged. Check if it's the case (slow):

        if self.renamed(node):

            t2 = self.read(node)

            return t2 != text

        return True

    def checkhash(self, text, node, p1=None, p2=None, rev=None):

        try:

            super(filelog, self).checkhash(text, node, p1=p1, p2=p2, rev=rev)

        except error.RevlogError:

            if _censoredtext(text):

                raise error.CensoredNodeError(self.indexfile, node, text)

            raise

    def iscensored(self, rev):

        """Check if a file revision is censored."""

        return self.flags(rev) & revlog.REVIDX_ISCENSORED

    def _peek_iscensored(self, baserev, delta, flush):

        """Quickly check if a delta produces a censored revision."""

        # Fragile heuristic: unless new file meta keys are added alphabetically

        # preceding "censored", all censored revisions are prefixed by

        # "\1\ncensored:". A delta producing such a censored revision must be a

        # full-replacement delta, so we inspect the first and only patch in the

        # delta for this prefix.

        hlen = struct.calcsize(">lll")

        if len(delta) <= hlen:

            return False

        oldlen = self.rawsize(baserev)

        newlen = len(delta) - hlen

        if delta[:hlen] != mdiff.replacediffheader(oldlen, newlen):

            return False

        add = "\1\ncensored:"

        addlen = len(add)

        return newlen >= addlen and delta[hlen:hlen + addlen] == add