mwparserfromhell/src/mwparserfromhell/parser/contexts.py

# Copyright (C) 2012-2019 Ben Kurtovic <ben.kurtovic@gmail.com>
#
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"""
This module contains various "context" definitions, which are essentially flags
set during the tokenization process, either on the current parse stack (local
contexts) or affecting all stacks (global contexts). They represent the context
the tokenizer is in, such as inside a template's name definition, or inside a
level-two heading. This is used to determine what tokens are valid at the
current point and also if the current parsing route is invalid.

The tokenizer stores context as an integer, with these definitions bitwise OR'd
to set them, AND'd to check if they're set, and XOR'd to unset them. The
advantage of this is that contexts can have sub-contexts (as ``FOO == 0b11``
will cover ``BAR == 0b10`` and ``BAZ == 0b01``).

Local (stack-specific) contexts:

* :const:`TEMPLATE`

    * :const:`TEMPLATE_NAME`
    * :const:`TEMPLATE_PARAM_KEY`
    * :const:`TEMPLATE_PARAM_VALUE`

* :const:`ARGUMENT`

    * :const:`ARGUMENT_NAME`
    * :const:`ARGUMENT_DEFAULT`

* :const:`WIKILINK`

    * :const:`WIKILINK_TITLE`
    * :const:`WIKILINK_TEXT`

* :const:`EXT_LINK`

    * :const:`EXT_LINK_URI`
    * :const:`EXT_LINK_TITLE`

* :const:`HEADING`

    * :const:`HEADING_LEVEL_1`
    * :const:`HEADING_LEVEL_2`
    * :const:`HEADING_LEVEL_3`
    * :const:`HEADING_LEVEL_4`
    * :const:`HEADING_LEVEL_5`
    * :const:`HEADING_LEVEL_6`

* :const:`TAG`

    * :const:`TAG_OPEN`
    * :const:`TAG_ATTR`
    * :const:`TAG_BODY`
    * :const:`TAG_CLOSE`

* :const:`STYLE`

    * :const:`STYLE_ITALICS`
    * :const:`STYLE_BOLD`
    * :const:`STYLE_PASS_AGAIN`
    * :const:`STYLE_SECOND_PASS`

* :const:`DL_TERM`

* :const:`SAFETY_CHECK`

    * :const:`HAS_TEXT`
    * :const:`FAIL_ON_TEXT`
    * :const:`FAIL_NEXT`
    * :const:`FAIL_ON_LBRACE`
    * :const:`FAIL_ON_RBRACE`
    * :const:`FAIL_ON_EQUALS`
    * :const:`HAS_TEMPLATE`

* :const:`TABLE`

    * :const:`TABLE_OPEN`
    * :const:`TABLE_CELL_OPEN`
    * :const:`TABLE_CELL_STYLE`
    * :const:`TABLE_TD_LINE`
    * :const:`TABLE_TH_LINE`
    * :const:`TABLE_CELL_LINE_CONTEXTS`

* :const:`HTML_ENTITY`

Global contexts:

* :const:`GL_HEADING`

Aggregate contexts:

* :const:`FAIL`
* :const:`UNSAFE`
* :const:`DOUBLE`
* :const:`NO_WIKILINKS`
* :const:`NO_EXT_LINKS`

"""

# Local contexts:

TEMPLATE_NAME = 1 << 0
TEMPLATE_PARAM_KEY = 1 << 1
TEMPLATE_PARAM_VALUE = 1 << 2
TEMPLATE = TEMPLATE_NAME + TEMPLATE_PARAM_KEY + TEMPLATE_PARAM_VALUE

ARGUMENT_NAME = 1 << 3
ARGUMENT_DEFAULT = 1 << 4
ARGUMENT = ARGUMENT_NAME + ARGUMENT_DEFAULT

WIKILINK_TITLE = 1 << 5
WIKILINK_TEXT = 1 << 6
WIKILINK = WIKILINK_TITLE + WIKILINK_TEXT

EXT_LINK_URI = 1 << 7
EXT_LINK_TITLE = 1 << 8
EXT_LINK = EXT_LINK_URI + EXT_LINK_TITLE

HEADING_LEVEL_1 = 1 << 9
HEADING_LEVEL_2 = 1 << 10
HEADING_LEVEL_3 = 1 << 11
HEADING_LEVEL_4 = 1 << 12
HEADING_LEVEL_5 = 1 << 13
HEADING_LEVEL_6 = 1 << 14
HEADING = (
    HEADING_LEVEL_1
    + HEADING_LEVEL_2
    + HEADING_LEVEL_3
    + HEADING_LEVEL_4
    + HEADING_LEVEL_5
    + HEADING_LEVEL_6
)

TAG_OPEN = 1 << 15
TAG_ATTR = 1 << 16
TAG_BODY = 1 << 17
TAG_CLOSE = 1 << 18
TAG = TAG_OPEN + TAG_ATTR + TAG_BODY + TAG_CLOSE

STYLE_ITALICS = 1 << 19
STYLE_BOLD = 1 << 20
STYLE_PASS_AGAIN = 1 << 21
STYLE_SECOND_PASS = 1 << 22
STYLE = STYLE_ITALICS + STYLE_BOLD + STYLE_PASS_AGAIN + STYLE_SECOND_PASS

DL_TERM = 1 << 23

HAS_TEXT = 1 << 24
FAIL_ON_TEXT = 1 << 25
FAIL_NEXT = 1 << 26
FAIL_ON_LBRACE = 1 << 27
FAIL_ON_RBRACE = 1 << 28
FAIL_ON_EQUALS = 1 << 29
HAS_TEMPLATE = 1 << 30
SAFETY_CHECK = (
    HAS_TEXT
    + FAIL_ON_TEXT
    + FAIL_NEXT
    + FAIL_ON_LBRACE
    + FAIL_ON_RBRACE
    + FAIL_ON_EQUALS
    + HAS_TEMPLATE
)

TABLE_OPEN = 1 << 31
TABLE_CELL_OPEN = 1 << 32
TABLE_CELL_STYLE = 1 << 33
TABLE_ROW_OPEN = 1 << 34
TABLE_TD_LINE = 1 << 35
TABLE_TH_LINE = 1 << 36
TABLE_CELL_LINE_CONTEXTS = TABLE_TD_LINE + TABLE_TH_LINE + TABLE_CELL_STYLE
TABLE = (
    TABLE_OPEN
    + TABLE_CELL_OPEN
    + TABLE_CELL_STYLE
    + TABLE_ROW_OPEN
    + TABLE_TD_LINE
    + TABLE_TH_LINE
)

HTML_ENTITY = 1 << 37

# Global contexts:

GL_HEADING = 1 << 0

# Aggregate contexts:

FAIL = TEMPLATE + ARGUMENT + WIKILINK + EXT_LINK_TITLE + HEADING + TAG + STYLE + TABLE
UNSAFE = (
    TEMPLATE_NAME
    + WIKILINK_TITLE
    + EXT_LINK_TITLE
    + TEMPLATE_PARAM_KEY
    + ARGUMENT_NAME
    + TAG_CLOSE
)
DOUBLE = TEMPLATE_PARAM_KEY + TAG_CLOSE + TABLE_ROW_OPEN
NO_WIKILINKS = TEMPLATE_NAME + ARGUMENT_NAME + WIKILINK_TITLE + EXT_LINK_URI
NO_EXT_LINKS = TEMPLATE_NAME + ARGUMENT_NAME + WIKILINK_TITLE + EXT_LINK


def describe(context):
    """Return a string describing the given context value, for debugging."""
    flags = []
    for name, value in globals().items():
        if not isinstance(value, int) or name.startswith("GL_"):
            continue
        if bin(value).count("1") != 1:
            continue  # Hacky way to skip aggregate contexts
        if context & value:
            flags.append((name, value))
    flags.sort(key=lambda it: it[1])
    return "|".join(it[0] for it in flags)