# encoding.py - character transcoding support for Mercurial

#

#  Copyright 2005-2009 Matt Mackall <mpm@selenic.com> and others

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

import error

import unicodedata, locale, os

def _getpreferredencoding():

    '''

    On darwin, getpreferredencoding ignores the locale environment and

    always returns mac-roman. http://bugs.python.org/issue6202 fixes this

    for Python 2.7 and up. This is the same corrected code for earlier

    Python versions.

    However, we can't use a version check for this method, as some distributions

    patch Python to fix this. Instead, we use it as a 'fixer' for the mac-roman

    encoding, as it is unlikely that this encoding is the actually expected.

    '''

    try:

        locale.CODESET

    except AttributeError:

        # Fall back to parsing environment variables :-(

        return locale.getdefaultlocale()[1]

    oldloc = locale.setlocale(locale.LC_CTYPE)

    locale.setlocale(locale.LC_CTYPE, "")

    result = locale.nl_langinfo(locale.CODESET)

    locale.setlocale(locale.LC_CTYPE, oldloc)

    return result

_encodingfixers = {

    '646': lambda: 'ascii',

    'ANSI_X3.4-1968': lambda: 'ascii',

    'mac-roman': _getpreferredencoding

}

try:

    encoding = os.environ.get("HGENCODING")

    if not encoding:

        encoding = locale.getpreferredencoding() or 'ascii'

        encoding = _encodingfixers.get(encoding, lambda: encoding)()

except locale.Error:

    encoding = 'ascii'

encodingmode = os.environ.get("HGENCODINGMODE", "strict")

fallbackencoding = 'ISO-8859-1'

class localstr(str):

    '''This class allows strings that are unmodified to be

    round-tripped to the local encoding and back'''

    def __new__(cls, u, l):

        s = str.__new__(cls, l)

        s._utf8 = u

        return s

    def __hash__(self):

        return hash(self._utf8) # avoid collisions in local string space

def tolocal(s):

    """

    Convert a string from internal UTF-8 to local encoding

    All internal strings should be UTF-8 but some repos before the

    implementation of locale support may contain latin1 or possibly

    other character sets. We attempt to decode everything strictly

    using UTF-8, then Latin-1, and failing that, we use UTF-8 and

    replace unknown characters.

    The localstr class is used to cache the known UTF-8 encoding of

    strings next to their local representation to allow lossless

    round-trip conversion back to UTF-8.

    >>> u = 'foo: \\xc3\\xa4' # utf-8

    >>> l = tolocal(u)

    >>> l

    'foo: ?'

    >>> fromlocal(l)

    'foo: \\xc3\\xa4'

    >>> u2 = 'foo: \\xc3\\xa1'

    >>> d = { l: 1, tolocal(u2): 2 }

    >>> len(d) # no collision

    2

    >>> 'foo: ?' in d

    False

    >>> l1 = 'foo: \\xe4' # historical latin1 fallback

    >>> l = tolocal(l1)

    >>> l

    'foo: ?'

    >>> fromlocal(l) # magically in utf-8

    'foo: \\xc3\\xa4'

    """

    try:

        try:

            # make sure string is actually stored in UTF-8

            u = s.decode('UTF-8')

            if encoding == 'UTF-8':

                # fast path

                return s

            r = u.encode(encoding, "replace")

            if u == r.decode(encoding):

                # r is a safe, non-lossy encoding of s

                return r

            return localstr(s, r)

        except UnicodeDecodeError:

            # we should only get here if we're looking at an ancient changeset

            try:

                u = s.decode(fallbackencoding)

                r = u.encode(encoding, "replace")

                if u == r.decode(encoding):

                    # r is a safe, non-lossy encoding of s

                    return r

                return localstr(u.encode('UTF-8'), r)

            except UnicodeDecodeError:

                u = s.decode("utf-8", "replace") # last ditch

                return u.encode(encoding, "replace") # can't round-trip

    except LookupError, k:

        raise error.Abort(k, hint="please check your locale settings")

def fromlocal(s):

    """

    Convert a string from the local character encoding to UTF-8

    We attempt to decode strings using the encoding mode set by

    HGENCODINGMODE, which defaults to 'strict'. In this mode, unknown

    characters will cause an error message. Other modes include

    'replace', which replaces unknown characters with a special

    Unicode character, and 'ignore', which drops the character.

    """

    # can we do a lossless round-trip?

    if isinstance(s, localstr):

        return s._utf8

    try:

        return s.decode(encoding, encodingmode).encode("utf-8")

    except UnicodeDecodeError, inst:

        sub = s[max(0, inst.start - 10):inst.start + 10]

        raise error.Abort("decoding near '%s': %s!" % (sub, inst))

    except LookupError, k:

        raise error.Abort(k, hint="please check your locale settings")

# How to treat ambiguous-width characters. Set to 'wide' to treat as wide.

wide = (os.environ.get("HGENCODINGAMBIGUOUS", "narrow") == "wide"

        and "WFA" or "WF")

def colwidth(s):

    "Find the column width of a string for display in the local encoding"

    return ucolwidth(s.decode(encoding, 'replace'))

def ucolwidth(d):

    "Find the column width of a Unicode string for display"

    eaw = getattr(unicodedata, 'east_asian_width', None)

    if eaw is not None:

        return sum([eaw(c) in wide and 2 or 1 for c in d])

    return len(d)

def getcols(s, start, c):

    '''Use colwidth to find a c-column substring of s starting at byte

    index start'''

    for x in xrange(start + c, len(s)):

        t = s[start:x]

        if colwidth(t) == c:

            return t

def lower(s):

    "best-effort encoding-aware case-folding of local string s"

    try:

        s.decode('ascii') # throw exception for non-ASCII character

        return s.lower()

    except UnicodeDecodeError:

        pass

    try:

        if isinstance(s, localstr):

            u = s._utf8.decode("utf-8")

        else:

            u = s.decode(encoding, encodingmode)

        lu = u.lower()

        if u == lu:

            return s # preserve localstring

        return lu.encode(encoding)

    except UnicodeError:

        return s.lower() # we don't know how to fold this except in ASCII

    except LookupError, k:

        raise error.Abort(k, hint="please check your locale settings")

def upper(s):

    "best-effort encoding-aware case-folding of local string s"

    try:

        s.decode('ascii') # throw exception for non-ASCII character

        return s.upper()

    except UnicodeDecodeError:

        pass

    try:

        if isinstance(s, localstr):

            u = s._utf8.decode("utf-8")

        else:

            u = s.decode(encoding, encodingmode)

        uu = u.upper()

        if u == uu:

            return s # preserve localstring

        return uu.encode(encoding)

    except UnicodeError:

        return s.upper() # we don't know how to fold this except in ASCII

    except LookupError, k:

        raise error.Abort(k, hint="please check your locale settings")

def toutf8b(s):

    '''convert a local, possibly-binary string into UTF-8b

    This is intended as a generic method to preserve data when working

    with schemes like JSON and XML that have no provision for

    arbitrary byte strings. As Mercurial often doesn't know

    what encoding data is in, we use so-called UTF-8b.

    If a string is already valid UTF-8 (or ASCII), it passes unmodified.

    Otherwise, unsupported bytes are mapped to UTF-16 surrogate range,

    uDC00-uDCFF.

    Principles of operation:

    - ASCII and UTF-8 data successfully round-trips and is understood

      by Unicode-oriented clients

    - filenames and file contents in arbitrary other encodings can have

      be round-tripped or recovered by clueful clients

    - local strings that have a cached known UTF-8 encoding (aka

      localstr) get sent as UTF-8 so Unicode-oriented clients get the

      Unicode data they want

    - because we must preserve UTF-8 bytestring in places such as

      filenames, metadata can't be roundtripped without help

    (Note: "UTF-8b" often refers to decoding a mix of valid UTF-8 and

    arbitrary bytes into an internal Unicode format that can be

    re-encoded back into the original. Here we are exposing the

    internal surrogate encoding as a UTF-8 string.)

    '''

    if isinstance(s, localstr):

        return s._utf8

    try:

        if s.decode('utf-8'):

            return s

    except UnicodeDecodeError:

        # surrogate-encode any characters that don't round-trip

        s2 = s.decode('utf-8', 'ignore').encode('utf-8')

        r = ""

        pos = 0

        for c in s:

            if s2[pos:pos + 1] == c:

                r += c

                pos += 1

            else:

                r += unichr(0xdc00 + ord(c)).encode('utf-8')

        return r

def fromutf8b(s):

    '''Given a UTF-8b string, return a local, possibly-binary string.

    return the original binary string. This

    is a round-trip process for strings like filenames, but metadata

    that's was passed through tolocal will remain in UTF-8.

    >>> m = "\\xc3\\xa9\\x99abcd"

    >>> n = toutf8b(m)

    >>> n

    '\\xc3\\xa9\\xed\\xb2\\x99abcd'

    >>> fromutf8b(n) == m

    True

    '''

    # fast path - look for uDxxx prefixes in s

    if "\xed" not in s:

        return s

    u = s.decode("utf-8")

    r = ""

    for c in u:

        if ord(c) & 0xff00 == 0xdc00:

            r += chr(ord(c) & 0xff)

        else:

            r += c.encode("utf-8")

    return r