markup.py

# -*- coding: utf-8 -*-

# Copyright (C) 2005-2009 Osmo Salomaa
#
# This file is part of Gaupol.
#
# Gaupol is free software: you can redistribute it and/or modify it under the
# terms of the GNU General Public License as published by the Free Software
# Foundation, either version 3 of the License, or (at your option) any later
# version.
#
# Gaupol 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
# Gaupol. If not, see <http://www.gnu.org/licenses/>.

"""Base class for text markup."""

import aeidon
import re

__all__ = ("Markup",)


class Markup(aeidon.Singleton, metaclass=aeidon.Contractual):

    """
    Base class for text markup.

    Markup conversions between different formats are done via an internal
    format, which has the following BBcode-style tags with angle brackets.
    Conversions are best done via the ``_decode_*`` and ``_encode_*`` methods
    rather than hard-coding the internal tags in regular expression
    substitutions.

     * ``<b>...................</b>``
     * ``<i>...................</i>``
     * ``<u>...................</u>``
     * ``<color=#RRGGBB>...</color>``
     * ``<font=NAME>........</font>``
     * ``<size=POINTS>......</size>``

    :class:`Markup` is effectively equivalent to a format with no markup and
    can therefore be merely subclassed with a ``pass``-statement by formats
    that do not implement any markup. The caller of any tagging methods, e.g.
    :meth:`bolden`, must be prepared to handle :exc:`NotImplementedError`.
    """

    _flags = re.DOTALL | re.MULTILINE
    format = aeidon.formats.NONE

    def _decode_apply_require(self, text, regex, replacement, groups):
        assert replacement.count("{}") == len(groups)

    def _decode_apply(self, text, regex, replacement, groups):
        """
        Return `text` with all matches of `regex` replaced.

        `replacement` may contain one or more of ``{}``, which are replaced
        with parts of the match as defined by `groups`, a ``tuple`` of numbers.
        """
        orig_text = text
        match = regex.search(text)
        if match is None: return text
        a, z = match.span()
        new = replacement.format(*tuple(map(match.group, groups)))
        text = "".join((text[:a], new, text[z:]))
        if text == orig_text: return text
        return self._decode_apply(text, regex, replacement, groups)

    def _decode_b(self, text, pattern, target, flags=0):
        """Return `text` with bold markup converted to internal format."""
        regex = self._get_regex(pattern, flags)
        return self._decode_apply(text, regex, "<b>{}</b>", (target,))

    def _decode_c(self, text, pattern, value, target, flags=0):
        """Return `text` with color markup converted to internal format."""
        regex = self._get_regex(pattern, flags)
        replacement = "<color=#{}>{}</color>"
        return self._decode_apply(text, regex, replacement, (value, target))

    def _decode_f(self, text, pattern, value, target, flags=0):
        """Return `text` with font markup converted to internal format."""
        regex = self._get_regex(pattern, flags)
        replacement = "<font={}>{}</font>"
        return self._decode_apply(text, regex, replacement, (value, target))

    def _decode_i(self, text, pattern, target, flags=0):
        """Return `text` with italic markup converted to internal format."""
        regex = self._get_regex(pattern, flags)
        return self._decode_apply(text, regex, "<i>{}</i>", (target,))

    def _decode_s(self, text, pattern, value, target, flags=0):
        """Return `text` with size markup converted to internal format."""
        regex = self._get_regex(pattern, flags)
        replacement = "<size={}>{}</size>"
        return self._decode_apply(text, regex, replacement, (value, target))

    def _decode_u(self, text, pattern, target, flags=0):
        """Return `text` with underline markup converted to internal format."""
        regex = self._get_regex(pattern, flags)
        return self._decode_apply(text, regex, "<u>{}</u>", (target,))

    def _encode_apply(self, text, regex, method, target, value=None):
        """
        Return `text` with internal tags removed and `method` applied.

        `method` should be one the tagging methods, e.g. meth:`bolden`.
        `target` and `value` should be group numbers in `regex`.
        """
        orig_text = text
        match = regex.search(text)
        if match is None: return text
        text = regex.sub(r"\{}".format(target), text, 1)
        a = match.start()
        z = a + len(match.group(target))
        args = (text, (a, z))
        if value is not None:
            args = (text, match.group(value), (a, z))
        try: text = method(*args)
        except NotImplementedError: pass
        if text == orig_text: return text
        return self._encode_apply(text, regex, method, target, value)

    def _encode_b(self, text):
        """Return `text` with bold markup converted to this format."""
        regex = self._get_regex(r"<b>(.*?)</b>")
        return self._encode_apply(text, regex, self.bolden, 1)

    def _encode_c(self, text):
        """Return `text` with color markup converted to this format."""
        regex = self._get_regex(r"<color=#([a-fA-F0-9]{6})>(.*?)</color>")
        return self._encode_apply(text, regex, self.colorize, 2, 1)

    def _encode_f(self, text):
        """Return `text` with font markup converted to this format."""
        regex = self._get_regex(r"<font=(.+?)>(.*?)</font>")
        return self._encode_apply(text, regex, self.fontify, 2, 1)

    def _encode_i(self, text):
        """Return `text` with italic markup converted to this format."""
        regex = self._get_regex(r"<i>(.*?)</i>")
        return self._encode_apply(text, regex, self.italicize, 1)

    def _encode_s(self, text):
        """Return `text` with size markup converted to this format."""
        regex = self._get_regex(r"<size=(\d+)>(.*?)</size>")
        return self._encode_apply(text, regex, self.scale, 2, 1)

    def _encode_u(self, text):
        """Return `text` with underline markup converted to this format."""
        regex = self._get_regex(r"<u>(.*?)</u>")
        return self._encode_apply(text, regex, self.underline, 1)

    @aeidon.deco.memoize(100)
    def _get_regex(self, pattern, flags=0):
        """Return compiled regular expression from cache."""
        flags = self._flags | flags
        return re.compile(pattern, flags)

    def _main_decode(self, text):
        """Return `text` with decodable markup decoded."""
        return text

    def _post_decode(self, text):
        """Return `text` with markup finalized after decoding."""
        return text

    def _pre_decode(self, text):
        """Return `text` with markup prepared for decoding."""
        return text

    def _substitute(self, text, pattern, replacement, flags=0):
        """Return `text` with matches of `pattern` replaced."""
        regex = self._get_regex(pattern, flags)
        return regex.sub(replacement, text)

    def bolden_require(self, text, bounds=None):
        if bounds is not None:
            assert 0 <= bounds[0] <= bounds[1] <= len(text)

    def bolden(self, text, bounds=None):
        """Return bolded `text`."""
        raise NotImplementedError

    def clean(self, text):
        """
        Return `text` with less ugly markup.

        Subclasses can implement this to, for example, remove redundant markup,
        finetune tag positioning or to join or split tags, in general, whatever
        that changes the style of the markup but not that of the text.
        """
        return text

    def colorize_require(self, text, color, bounds=None):
        regex = self._get_regex(r"[0-9a-fA-F]{6}")
        assert regex.match(color) is not None
        if bounds is not None:
            assert 0 <= bounds[0] <= bounds[1] <= len(text)

    def colorize(self, text, color, bounds=None):
        """Return `text` colorized to hexadecimal value."""
        raise NotImplementedError

    def decode(self, text):
        """Return `text` with markup converted from this to internal format."""
        text = self._pre_decode(text)
        text = self._main_decode(text)
        return self._post_decode(text)

    def encode(self, text):
        """Return `text` with markup converted from internal to this format."""
        text = self._encode_b(text)
        text = self._encode_c(text)
        text = self._encode_f(text)
        text = self._encode_i(text)
        text = self._encode_s(text)
        return self._encode_u(text)

    def fontify_require(self, text, font, bounds=None):
        if bounds is not None:
            assert 0 <= bounds[0] <= bounds[1] <= len(text)

    def fontify(self, text, font, bounds=None):
        """Return `text` changed to `font`."""
        raise NotImplementedError

    @property
    def italic_tag(self):
        """Regular expression for an italic markup tag or ``None``."""
        return None

    def italicize_require(self, text, bounds=None):
        if bounds is not None:
            assert 0 <= bounds[0] <= bounds[1] <= len(text)

    def italicize(self, text, bounds=None):
        """Return italicized `text`."""
        raise NotImplementedError

    def scale_require(self, text, size, bounds=None):
        assert isinstance(size, int) or size.isdigit()
        if bounds is not None:
            assert 0 <= bounds[0] <= bounds[1] <= len(text)

    def scale(self, text, size, bounds=None):
        """Return `text` scaled to `size`."""
        raise NotImplementedError

    @property
    def tag(self):
        """Regular expression for any markup tag or ``None``."""
        return None

    def underline_require(self, text, bounds=None):
        if bounds is not None:
            assert 0 <= bounds[0] <= bounds[1] <= len(text)

    def underline(self, text, bounds=None):
        """Return underlined `text`."""
        raise NotImplementedError