#
# Secret Labs' Regular Expression Engine
#
# Copyright (c) 1998-2001 by Secret Labs AB.  All rights reserved.
#
# This version of the SRE library can be redistributed under CNRI's
# Python 1.6 license.  For any other use, please contact Secret Labs
# AB (info@pythonware.com).
#
# Portions of this engine have been developed in cooperation with
# CNRI.  Hewlett-Packard provided funding for 1.6 integration and
# other compatibility work.
#
# 2010-01-16 mrab Python front-end re-written and extended

r"""Support for regular expressions (RE).

This module provides regular expression matching operations similar to those
found in Perl. It supports both 8-bit and Unicode strings; both the pattern and
the strings being processed can contain null bytes and characters outside the
US ASCII range.

Regular expressions can contain both special and ordinary characters. Most
ordinary characters, like "A", "a", or "0", are the simplest regular
expressions; they simply match themselves. You can concatenate ordinary
characters, so last matches the string 'last'.

There are a few differences between the old (legacy) behaviour and the new
(enhanced) behaviour, which are indicated by VERSION0 or VERSION1.

The special characters are:
    "."                 Matches any character except a newline.
    "^"                 Matches the start of the string.
    "$"                 Matches the end of the string or just before the
                        newline at the end of the string.
    "*"                 Matches 0 or more (greedy) repetitions of the preceding
                        RE. Greedy means that it will match as many repetitions
                        as possible.
    "+"                 Matches 1 or more (greedy) repetitions of the preceding
                        RE.
    "?"                 Matches 0 or 1 (greedy) of the preceding RE.
    *?,+?,??            Non-greedy versions of the previous three special
                        characters.
    *+,++,?+            Possessive versions of the previous three special
                        characters.
    {m,n}               Matches from m to n repetitions of the preceding RE.
    {m,n}?              Non-greedy version of the above.
    {m,n}+              Possessive version of the above.
    {...}               Fuzzy matching constraints.
    "\\"                Either escapes special characters or signals a special
                        sequence.
    [...]               Indicates a set of characters. A "^" as the first
                        character indicates a complementing set.
    "|"                 A|B, creates an RE that will match either A or B.
    (...)               Matches the RE inside the parentheses. The contents are
                        captured and can be retrieved or matched later in the
                        string.
    (?flags-flags)      VERSION1: Sets/clears the flags for the remainder of
                        the group or pattern; VERSION0: Sets the flags for the
                        entire pattern.
    (?:...)             Non-capturing version of regular parentheses.
    (?>...)             Atomic non-capturing version of regular parentheses.
    (?flags-flags:...)  Non-capturing version of regular parentheses with local
                        flags.
    (?P<name>...)       The substring matched by the group is accessible by
                        name.
    (?<name>...)        The substring matched by the group is accessible by
                        name.
    (?P=name)           Matches the text matched earlier by the group named
                        name.
    (?#...)             A comment; ignored.
    (?=...)             Matches if ... matches next, but doesn't consume the
                        string.
    (?!...)             Matches if ... doesn't match next.
    (?<=...)            Matches if preceded by ....
    (?<!...)            Matches if not preceded by ....
    (?(id)yes|no)       Matches yes pattern if group id matched, the (optional)
                        no pattern otherwise.
    (?|...|...)         (?|A|B), creates an RE that will match either A or B,
                        but reuses capture group numbers across the
                        alternatives.

The fuzzy matching constraints are: "i" to permit insertions, "d" to permit
deletions, "s" to permit substitutions, "e" to permit any of these. Limits are
optional with "<=" and "<". If any type of error is provided then any type not
provided is not permitted.

A cost equation may be provided.

Examples:
    (?:fuzzy){i<=2}
    (?:fuzzy){i<=1,s<=2,d<=1,1i+1s+1d<3}

VERSION1: Set operators are supported, and a set can include nested sets. The
set operators, in order of increasing precedence, are:
    ||  Set union ("x||y" means "x or y").
    ~~  (double tilde) Symmetric set difference ("x~~y" means "x or y, but not
        both").
    &&  Set intersection ("x&&y" means "x and y").
    --  (double dash) Set difference ("x--y" means "x but not y").

Implicit union, ie, simple juxtaposition like in [ab], has the highest
precedence.

VERSION0 and VERSION1:
The special sequences consist of "\\" and a character from the list below. If
the ordinary character is not on the list, then the resulting RE will match the
second character.
    \number         Matches the contents of the group of the same number if
                    number is no more than 2 digits, otherwise the character
                    with the 3-digit octal code.
    \a              Matches the bell character.
    \A              Matches only at the start of the string.
    \b              Matches the empty string, but only at the start or end of a
                    word.
    \B              Matches the empty string, but not at the start or end of a
                    word.
    \d              Matches any decimal digit; equivalent to the set [0-9] when
                    matching a bytestring or a Unicode string with the ASCII
                    flag, or the whole range of Unicode digits when matching a
                    Unicode string.
    \D              Matches any non-digit character; equivalent to [^\d].
    \f              Matches the formfeed character.
    \g<name>        Matches the text matched by the group named name.
    \G              Matches the empty string, but only at the position where
                    the search started.
    \L<name>        Named list. The list is provided as a keyword argument.
    \m              Matches the empty string, but only at the start of a word.
    \M              Matches the empty string, but only at the end of a word.
    \n              Matches the newline character.
    \N{name}        Matches the named character.
    \p{name=value}  Matches the character if its property has the specified
                    value.
    \P{name=value}  Matches the character if its property hasn't the specified
                    value.
    \r              Matches the carriage-return character.
    \s              Matches any whitespace character; equivalent to
                    [ \t\n\r\f\v].
    \S              Matches any non-whitespace character; equivalent to [^\s].
    \t              Matches the tab character.
    \uXXXX          Matches the Unicode codepoint with 4-digit hex code XXXX.
    \UXXXXXXXX      Matches the Unicode codepoint with 8-digit hex code
                    XXXXXXXX.
    \v              Matches the vertical tab character.
    \w              Matches any alphanumeric character; equivalent to
                    [a-zA-Z0-9_] when matching a bytestring or a Unicode string
                    with the ASCII flag, or the whole range of Unicode
                    alphanumeric characters (letters plus digits plus
                    underscore) when matching a Unicode string. With LOCALE, it
                    will match the set [0-9_] plus characters defined as
                    letters for the current locale.
    \W              Matches the complement of \w; equivalent to [^\w].
    \xXX            Matches the character with 2-digit hex code XX.
    \X              Matches a grapheme.
    \Z              Matches only at the end of the string.
    \\              Matches a literal backslash.

This module exports the following functions:
    match      Match a regular expression pattern at the beginning of a string.
    search     Search a string for the presence of a pattern.
    sub        Substitute occurrences of a pattern found in a string.
    subn       Same as sub, but also return the number of substitutions made.
    split      Split a string by the occurrences of a pattern. VERSION1: will
               split at zero-width match; VERSION0: won't split at zero-width
               match.
    splititer  Return an iterator yielding the parts of a split string.
    findall    Find all occurrences of a pattern in a string.
    finditer   Return an iterator yielding a match object for each match.
    compile    Compile a pattern into a Pattern object.
    purge      Clear the regular expression cache.
    escape     Backslash all non-alphanumerics or special characters in a
               string.

Most of the functions support a concurrent parameter: if True, the GIL will be
released during matching, allowing other Python threads to run concurrently. If
the string changes during matching, the behaviour is undefined. This parameter
is not needed when working on the builtin (immutable) string classes.

Some of the functions in this module take flags as optional parameters. Most of
these flags can also be set within an RE:
    A   a   ASCII         Make \w, \W, \b, \B, \d, and \D match the
                          corresponding ASCII character categories. Default
                          when matching a bytestring.
    B   b   BESTMATCH     Find the best fuzzy match (default is first).
    D       DEBUG         Print the parsed pattern.
    F   f   FULLCASE      Use full case-folding when performing
                          case-insensitive matching in Unicode.
    I   i   IGNORECASE    Perform case-insensitive matching.
    L   L   LOCALE        Make \w, \W, \b, \B, \d, and \D dependent on the
                          current locale. (One byte per character only.)
    M   m   MULTILINE     "^" matches the beginning of lines (after a newline)
                          as well as the string. "$" matches the end of lines
                          (before a newline) as well as the end of the string.
    E   e   ENHANCEMATCH  Attempt to improve the fit after finding the first
                          fuzzy match.
    R   r   REVERSE       Searches backwards.
    S   s   DOTALL        "." matches any character at all, including the
                          newline.
    U   u   UNICODE       Make \w, \W, \b, \B, \d, and \D dependent on the
                          Unicode locale. Default when matching a Unicode
                          string.
    V0  V0  VERSION0      Turn on the old legacy behaviour.
    V1  V1  VERSION1      Turn on the new enhanced behaviour. This flag
                          includes the FULLCASE flag.
    W   w   WORD          Make \b and \B work with default Unicode word breaks
                          and make ".", "^" and "$" work with Unicode line
                          breaks.
    X   x   VERBOSE       Ignore whitespace and comments for nicer looking REs.

This module also defines an exception 'error'.

"""

# Public symbols.
__all__ = ["compile", "escape", "findall", "finditer", "match", "purge",
  "search", "split", "splititer", "sub", "subn", "template", "A", "ASCII", "B",
  "BESTMATCH", "D", "DEBUG", "E", "ENHANCEMATCH", "S", "DOTALL", "F",
  "FULLCASE", "I", "IGNORECASE", "L", "LOCALE", "M", "MULTILINE", "R",
  "REVERSE", "T", "TEMPLATE", "U", "UNICODE", "V0", "VERSION0", "V1",
  "VERSION1", "X", "VERBOSE", "W", "WORD", "error"]

__version__ = "2.4.1"

# --------------------------------------------------------------------
# Public interface.

def match(pattern, string, flags=0, pos=None, endpos=None, concurrent=None,
  **kwargs):
    """Try to apply the pattern at the start of the string, returning a match
    object, or None if no match was found."""
    return _compile(pattern, flags, kwargs).match(string, pos, endpos,
      concurrent)

def search(pattern, string, flags=0, pos=None, endpos=None, concurrent=None,
  **kwargs):
    """Search through string looking for a match to the pattern, returning a
    match object, or None if no match was found."""
    return _compile(pattern, flags, kwargs).search(string, pos, endpos,
      concurrent)

def sub(pattern, repl, string, count=0, flags=0, pos=None, endpos=None,
  concurrent=None, **kwargs):
    """Return the string obtained by replacing the leftmost (or rightmost with a
    reverse pattern) non-overlapping occurrences of the pattern in string by the
    replacement repl. repl can be either a string or a callable; if a string,
    backslash escapes in it are processed; if a callable, it's passed the match
    object and must return a replacement string to be used."""
    return _compile(pattern, flags, kwargs).sub(repl, string, count, pos,
      endpos, concurrent)

def subn(pattern, repl, string, count=0, flags=0, pos=None, endpos=None,
  concurrent=None, **kwargs):
    """Return a 2-tuple containing (new_string, number). new_string is the string
    obtained by replacing the leftmost (or rightmost with a reverse pattern)
    non-overlapping occurrences of the pattern in the source string by the
    replacement repl. number is the number of substitutions that were made. repl
    can be either a string or a callable; if a string, backslash escapes in it
    are processed; if a callable, it's passed the match object and must return a
    replacement string to be used."""
    return _compile(pattern, flags, kwargs).subn(repl, string, count, pos,
      endpos, concurrent)

def split(pattern, string, maxsplit=0, flags=0, concurrent=None, **kwargs):
    """Split the source string by the occurrences of the pattern, returning a
    list containing the resulting substrings.  If capturing parentheses are used
    in pattern, then the text of all groups in the pattern are also returned as
    part of the resulting list.  If maxsplit is nonzero, at most maxsplit splits
    occur, and the remainder of the string is returned as the final element of
    the list."""
    return _compile(pattern, flags, kwargs).split(string, maxsplit, concurrent)

def splititer(pattern, string, maxsplit=0, flags=0, concurrent=None, **kwargs):
    "Return an iterator yielding the parts of a split string."
    return _compile(pattern, flags, kwargs).splititer(string, maxsplit,
      concurrent)

def findall(pattern, string, flags=0, pos=None, endpos=None, overlapped=False,
  concurrent=None, **kwargs):
    """Return a list of all matches in the string. The matches may be overlapped
    if overlapped is True. If one or more groups are present in the pattern,
    return a list of groups; this will be a list of tuples if the pattern has
    more than one group. Empty matches are included in the result."""
    return _compile(pattern, flags, kwargs).findall(string, pos, endpos,
      overlapped, concurrent)

def finditer(pattern, string, flags=0, pos=None, endpos=None, overlapped=False,
  concurrent=None, **kwargs):
    """Return an iterator over all matches in the string. The matches may be
    overlapped if overlapped is True. For each match, the iterator returns a
    match object. Empty matches are included in the result."""
    return _compile(pattern, flags, kwargs).finditer(string, pos, endpos,
      overlapped, concurrent)

def compile(pattern, flags=0, **kwargs):
    "Compile a regular expression pattern, returning a pattern object."
    return _compile(pattern, flags, kwargs)

def purge():
    "Clear the regular expression cache"
    _cache.clear()

def template(pattern, flags=0):
    "Compile a template pattern, returning a pattern object."
    return _compile(pattern, flags | TEMPLATE)

def escape(pattern, special_only=False):
    "Escape all non-alphanumeric characters or special characters in pattern."
    if isinstance(pattern, str):
        s = []
        if special_only:
            for c in pattern:
                if c in NONLITERAL:
                    s.append("\\")
                    s.append(c)
                elif c == "\x00":
                    s.append("\\000")
                else:
                    s.append(c)
        else:
            for c in pattern:
                if c in ALNUM:
                    s.append(c)
                elif c == "\x00":
                    s.append("\\000")
                else:
                    s.append("\\")
                    s.append(c)

        return "".join(s)
    else:
        s = []
        if special_only:
            for c in pattern:
                if chr(c) in NONLITERAL:
                    s.extend(b"\\")
                    s.append(c)
                elif c == 0:
                    s.extend(b"\\000")
                else:
                    s.append(c)
        else:
            for c in pattern:
                if chr(c) in ALNUM:
                    s.append(c)
                elif c == 0:
                    s.extend(b"\\000")
                else:
                    s.extend(b"\\")
                    s.append(c)

        return bytes(s)

# --------------------------------------------------------------------
# Internals.

import _regex_core
import _regex
from _regex_core import *

# Version 0 is the old behaviour, compatible with the original 're' module.
# Version 1 is the new behaviour, which differs slightly.

DEFAULT_VERSION = VERSION0

ALL_VERSIONS = VERSION0 | VERSION1
ALL_ENCODINGS = ASCII | LOCALE | UNICODE

_regex_core.DEFAULT_VERSION = DEFAULT_VERSION

# Caches for the patterns and replacements.
_cache = {}
_named_args = {}

# Maximum size of the cache.
_MAXCACHE = 500

def _compile(pattern, flags=0, kwargs=None):
    "Compiles a regular expression to a PatternObject."
    # We're checking in this order because pattern_type isn't defined when
    # _compile() is first called, with a string pattern, but only after the
    # support objects are defined.
    if isinstance(pattern, (str, bytes)):
        pass
    elif isinstance(pattern, pattern_type):
        if flags:
            raise ValueError("can't process flags argument with a compiled pattern")
        return pattern
    else:
        raise TypeError("first argument must be a string or compiled pattern")

    if kwargs is None:
        kwargs = {}

    # Set the default version in the core code in case it has been changed.
    _regex_core.DEFAULT_VERSION = DEFAULT_VERSION

    # Do we know what keyword arguments are needed?
    args_key = pattern, type(pattern), flags
    args_needed = _named_args.get(args_key)
    if args_needed is not None:
        # Are we being provided with those keyword arguments?
        args_supplied = set()
        for k, v in args_needed:
            if k not in kwargs:
                raise error("missing named list")
            args_supplied.add((k, frozenset(kwargs[k])))

        # Have we already seen this regular expression and named list?
        pattern_key = (pattern, type(pattern), flags, frozenset(args_supplied),
          DEFAULT_VERSION)
        compiled_pattern = _cache.get(pattern_key)
        if compiled_pattern:
            return compiled_pattern

    # It's a new pattern (or new named list for a known pattern).

    # Guess the encoding from the class of the pattern string.
    if isinstance(pattern, bytes):
        guess_encoding = ASCII
    else:
        guess_encoding = UNICODE

    # Parse the pattern. In the old behaviour the inline flags are global and
    # the pattern will need to be reparsed if a flag becomes turned on.
    version = (flags & ALL_VERSIONS) or DEFAULT_VERSION
    global_flags = flags | _regex_core.DEFAULT_FLAGS.get(version, 0)

    while True:
        try:
            source = Source(pattern)
            info = Info(global_flags, source.char_type, kwargs)
            info.guess_encoding = guess_encoding
            source.ignore_space = bool(info.flags & VERBOSE)
            parsed = parse_pattern(source, info)
            break
        except UnscopedFlagSet as e:
            # Remember the global flags for the next attempt.
            global_flags = e.global_flags | flags

    if not source.at_end():
        raise error("trailing characters in pattern")

    # Check the global flags for conflicts.
    version = (info.flags & ALL_VERSIONS) or DEFAULT_VERSION
    if version not in (0, VERSION0, VERSION1):
        raise ValueError("VERSION0 and VERSION1 flags are mutually incompatible")

    if (info.flags & ALL_ENCODINGS) not in (0, ASCII, LOCALE, UNICODE):
        raise ValueError("ASCII, LOCALE and UNICODE flags are mutually incompatible")

    if isinstance(pattern, bytes) and (info.flags & UNICODE):
        raise ValueError("can't use UNICODE flag with a bytes pattern")
    if not (info.flags & ALL_ENCODINGS):
        if isinstance(pattern, str):
            info.flags |= UNICODE
        else:
            info.flags |= ASCII

    reverse = bool(info.flags & REVERSE)
    fuzzy = isinstance(parsed, Fuzzy)

    # Fix the group references.
    parsed.fix_groups(reverse, False)

    # Optimise the parsed pattern.
    parsed = parsed.optimise(info)
    parsed = parsed.pack_characters(info)

    # Get the required string.
    req_offset, req_chars, req_flags = get_required_string(parsed, info.flags)

    # Build the named lists.
    named_lists = {}
    named_list_indexes = [None] * len(info.named_lists_used)
    args_needed = set()
    for key, index in info.named_lists_used.items():
        name, case_flags = key
        values = frozenset(kwargs[name])
        if case_flags:
            items = frozenset(fold_case(info, v) for v in values)
        else:
            items = values
        named_lists[name] = values
        named_list_indexes[index] = items
        args_needed.add((name, values))

    # Should we print the parsed pattern?
    if flags & DEBUG:
        parsed.dump(indent=0, reverse=reverse)

    # Check the features of the groups.
    check_group_features(info, parsed)

    # Compile the parsed pattern. The result is a list of tuples.
    code = parsed.compile(reverse)

    # Is there a group call to the pattern as a whole?
    key = (0, reverse, fuzzy)
    ref = info.call_refs.get(key)
    if ref is not None:
        code = [(OP.CALL_REF, ref)] + code + [(OP.END, )]

    # Add the final 'success' opcode.
    code += [(OP.SUCCESS, )]

    # Compile the additional copies of the groups that we need.
    for group, rev, fuz in info.additional_groups:
        code += group.compile(rev, fuz)

    # Flatten the code into a list of ints.
    code = flatten_code(code)

    if not parsed.has_simple_start():
        # Get the first set, if possible.
        try:
            fs_code = compile_firstset(info, parsed.get_firstset(reverse))
            fs_code = flatten_code(fs_code)
            code = fs_code + code
        except FirstSetError:
            pass

    # The named capture groups.
    index_group = dict((v, n) for n, v in info.group_index.items())

    # Create the PatternObject.
    #
    # Local flags like IGNORECASE affect the code generation, but aren't needed
    # by the PatternObject itself. Conversely, global flags like LOCALE _don't_
    # affect the code generation but _are_ needed by the PatternObject.
    compiled_pattern = _regex.compile(pattern, info.flags | version, code,
      info.group_index, index_group, named_lists, named_list_indexes,
      req_offset, req_chars, req_flags)

    # Do we need to reduce the size of the cache?
    if len(_cache) >= _MAXCACHE:
        shrink_cache(_cache, _named_args, _MAXCACHE)

    args_needed = frozenset(args_needed)

    # Store this regular expression and named list.
    pattern_key = (pattern, type(pattern), flags, args_needed, DEFAULT_VERSION)
    _cache[pattern_key] = compiled_pattern

    # Store what keyword arguments are needed.
    _named_args[args_key] = args_needed

    return compiled_pattern

def compile_replacement(pattern, template):
    "Compiles a replacement template."
    # This function is called by the _regex module.
    is_unicode = isinstance(template, str)
    source = Source(template)
    if is_unicode:
        def make_string(char_codes):
            return "".join(chr(c) for c in char_codes)
    else:
        def make_string(char_codes):
            return bytes(char_codes)

    compiled = []
    literal = []
    while True:
        ch = source.get()
        if not ch:
            break
        if ch == "\\":
            # 'compile_repl_escape' will return either an int group reference
            # or a string literal. It returns items (plural) in order to handle
            # a 2-character literal (an invalid escape sequence).
            is_group, items = compile_repl_escape(source, pattern, is_unicode)
            if is_group:
                # It's a group, so first flush the literal.
                if literal:
                    compiled.append(make_string(literal))
                    literal = []
                compiled.extend(items)
            else:
                literal.extend(items)
        else:
            literal.append(ord(ch))

    # Flush the literal.
    if literal:
        compiled.append(make_string(literal))
    return compiled

# We define pattern_type here after all the support objects have been defined.
pattern_type = type(_compile("", 0, {}))

# We'll define an alias for the 'compile' function so that the repr of a
# pattern object is eval-able.
Regex = compile

# Register myself for pickling.
import copyreg

def pickle(p):
    return _compile, (p.pattern, p.flags)

copyreg.pickle(pattern_type, pickle, _compile)