match.py

# Copyright (C) 2007-2010 Samuel Abels.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2, as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
"""
Shorthands for regular expression matching.
"""
import re
from Exscript.protocols import Protocol

def _first_match(string, compiled):
    match = compiled.search(string)
    if match is None and compiled.groups <= 1:
        return None
    elif match is None:
        return (None,) * compiled.groups
    elif compiled.groups == 0:
        return string
    elif compiled.groups == 1:
        return match.groups(1)[0]
    else:
        return match.groups(0)

def first_match(string, regex, flags = re.M):
    """
    Matches the given string against the given regex.

      - If no match is found and the regular expression has zero or one
      groups, this function returns None.

      - If no match is found and the regular expression has more than one
      group, this function returns a tuple of None. The number of elements
      in the tuple equals the number of groups in the regular expression.

      - If a match is found and the regular expression has no groups,
      the entire string is returned.

      - If a match is found and the regular expression has one group,
      the matching string from the group is returned.

      - If a match is found and the regular expression has multiple groups,
      a tuple containing the matching strings from the groups is returned.

    This behavior ensures that the following assignments can never fail::

       foo   = 'my test'
       match = first_match(foo, r'aaa')         # Returns None
       match = first_match(foo, r'\S+')         # Returns 'my test'
       match = first_match(foo, r'(aaa)')       # Returns None
       match = first_match(foo, r'(\S+)')       # Returns 'my'
       match = first_match(foo, r'(aaa) (\S+)') # Returns (None, None)
       match = first_match(foo, r'(\S+) (\S+)') # Returns ('my', 'foo')

    @type  string: string|Exscript.protocols.Protocol
    @param string: The string that is matched, or a Protocol object.
    @type  regex: string
    @param regex: A regular expression.
    @type  flags: int
    @param flags: The flags for compiling the regex; e.g. re.I
    @rtype:  string|tuple
    @return: A match, or a tuple of matches.
    """
    if isinstance(string, Protocol):
        string = string.response
    return _first_match(string, re.compile(regex, flags))

def any_match(string, regex, flags = re.M):
    """
    Matches the given string against the given regex.

      - If no match is found, this function returns an empty list.

      - If a match is found and the regular expression has no groups,
      a list of matching lines returned.

      - If a match is found and the regular expression has one group,
      a list of matching strings is returned.

      - If a match is found and the regular expression has multiple groups,
      a list containing tuples of matching strings is returned.

    This behavior ensures that the following can never fail::

        foo = '1 uno\\n2 due'
        for m in any_match(foo, r'aaa'):         # Returns []
            print m

        for m in any_match(foo, r'\S+'):         # Returns ['1 uno', '2 due']
            print m

        for m in any_match(foo, r'(aaa)'):       # Returns []
            print m

        for m in any_match(foo, r'(\S+)'):       # Returns ['1', '2']
            print m

        for one, two in any_match(foo, r'(aaa) (\S+)'): # Returns []
            print m

        for one, two in any_match(foo, r'(\S+) (\S+)'): # Returns [('1', 'uno'), ('2', 'due')]
            print m

    @type  string: string|Exscript.protocols.Protocol
    @param string: The string that is matched, or a Protocol object.
    @type  regex: string
    @param regex: A regular expression.
    @type  flags: int
    @param flags: The flags for compiling the regex; e.g. re.I
    @rtype:  list[string|tuple]
    @return: A list of strings, or a list of tuples.
    """
    if isinstance(string, Protocol):
        string = string.response
    compiled = re.compile(regex, flags)
    results  = []
    if compiled.groups <= 1:
        for line in string.split('\n'):
            match = _first_match(line, compiled)
            if match is None:
                continue
            results.append(match)
    else:
        for line in string.split('\n'):
            match = _first_match(line, compiled)
            if match[0] is None:
                continue
            results.append(match)
    return results