Anki/pylib/anki/template.py

# Copyright: Ankitects Pty Ltd and contributors
# License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html

"""
This file contains the Python portion of the template rendering code.

Templates can have filters applied to field replacements. The Rust template
rendering code will apply any built in filters, and stop at the first
unrecognized filter. The remaining filters are returned to Python,
and applied using the hook system. For example,
{{myfilter:hint:text:Field}} will apply the built in text and hint filters,
and then attempt to apply myfilter. If no add-ons have provided the filter,
the filter is skipped.

Add-ons can register a filter with the following code:

from anki import hooks
hooks.field_filter.append(myfunc)

This will call myfunc, passing the field text in as the first argument.
Your function should decide if it wants to modify the text by checking
the filter_name argument, and then return the text whether it has been
modified or not.

A Python implementation of the standard filters is currently available in the
template_legacy.py file, using the legacy addHook() system.
"""

from __future__ import annotations

import re
from typing import Any, Dict, List, Optional, Tuple

import anki
from anki import hooks
from anki.models import NoteType
from anki.rsbackend import TemplateReplacementList

QAData = Tuple[
    # Card ID this QA comes from. Corresponds to 'cid' column.
    int,
    # Note ID this QA comes from. Corresponds to 'nid' column.
    int,
    # ID of the model (i.e., NoteType) for this QA's note. Corresponds to 'mid' column.
    int,
    # Deck ID. Corresponds to 'did' column.
    int,
    # Index of the card template (within the NoteType) this QA was built
    # from. Corresponds to 'ord' column.
    int,
    # Tags, separated by space. Corresponds to 'tags' column.
    str,
    # Corresponds to 'flds' column. TODO: document.
    str,
    # Corresponds to 'cardFlags' column. TODO: document
    int,
]


class TemplateRenderContext:
    """Holds information for the duration of one card render.

    This may fetch information lazily in the future, so please avoid
    using the _private fields directly."""

    def __init__(
        self, col: anki.storage._Collection, qadata: QAData, fields: Dict[str, str]
    ) -> None:
        self._col = col
        self._qadata = qadata
        self._fields = fields

        self._note_type: Optional[NoteType] = None
        self._card: Optional[anki.cards.Card] = None
        self._note: Optional[anki.notes.Note] = None

        # if you need to store extra state to share amongst rendering
        # hooks, you can insert it into this dictionary
        self.extra_state: Dict[str, Any] = {}

    def col(self) -> anki.storage._Collection:
        return self._col

    def fields(self) -> Dict[str, str]:
        return self._fields

    def card_id(self) -> int:
        return self._qadata[0]

    def note_id(self) -> int:
        return self._qadata[1]

    def deck_id(self) -> int:
        return self._qadata[3]

    def card_ord(self) -> int:
        return self._qadata[4]

    def card(self) -> Optional[anki.cards.Card]:
        """Returns the card being rendered. Will return None in the add screen.

        Be careful not to call .q() or .a() on the card, or you'll create an
        infinite loop."""
        if not self._card:
            try:
                self._card = self.col().getCard(self.card_id())
            except:
                return None

        return self._card

    def note(self) -> anki.notes.Note:
        if not self._note:
            self._note = self.col().getNote(self.note_id())

        return self._note

    def note_type(self) -> NoteType:
        if not self._note_type:
            self._note_type = self.col().models.get(self._qadata[2])

        return self._note_type


def render_card(
    col: anki.storage._Collection, qfmt: str, afmt: str, ctx: TemplateRenderContext
) -> Tuple[str, str]:
    """Renders the provided templates, returning rendered q & a text.

    Will raise if the template is invalid."""
    (qnodes, anodes) = col.backend.render_card(qfmt, afmt, ctx.fields(), ctx.card_ord())

    qtext = apply_custom_filters(qnodes, ctx, front_side=None)
    atext = apply_custom_filters(anodes, ctx, front_side=qtext)

    return qtext, atext


def apply_custom_filters(
    rendered: TemplateReplacementList,
    ctx: TemplateRenderContext,
    front_side: Optional[str],
) -> str:
    "Complete rendering by applying any pending custom filters."
    # template already fully rendered?
    if len(rendered) == 1 and isinstance(rendered[0], str):
        return rendered[0]

    res = ""
    for node in rendered:
        if isinstance(node, str):
            res += node
        else:
            # do we need to inject in FrontSide?
            if node.field_name == "FrontSide" and front_side is not None:
                node.current_text = ctx.col().backend.strip_av_tags(front_side)

            field_text = node.current_text
            for filter_name in node.filters:
                field_text = hooks.field_filter(
                    field_text, node.field_name, filter_name, ctx
                )
                # legacy hook - the second and fifth argument are no longer used.
                field_text = anki.hooks.runFilter(
                    "fmod_" + filter_name,
                    field_text,
                    "",
                    ctx.fields(),
                    node.field_name,
                    "",
                )

            res += field_text
    return res


# Cloze handling
##########################################################################

# Matches a {{c123::clozed-out text::hint}} Cloze deletion, case-insensitively.
# The regex should be interpolated with a regex number and creates the following
# named groups:
#   - tag: The lowercase or uppercase 'c' letter opening the Cloze.
#          The c/C difference is only relevant to the legacy code.
#   - content: Clozed-out content.
#   - hint: Cloze hint, if provided.
clozeReg = r"(?si)\{\{(?P<tag>c)%s::(?P<content>.*?)(::(?P<hint>.*?))?\}\}"

# Constants referring to group names within clozeReg.
CLOZE_REGEX_MATCH_GROUP_TAG = "tag"
CLOZE_REGEX_MATCH_GROUP_CONTENT = "content"
CLOZE_REGEX_MATCH_GROUP_HINT = "hint"

# used by the media check functionality
def expand_clozes(string: str) -> List[str]:
    "Render all clozes in string."
    ords = set(re.findall(r"{{c(\d+)::.+?}}", string))
    strings = []

    def qrepl(m):
        if m.group(CLOZE_REGEX_MATCH_GROUP_HINT):
            return "[%s]" % m.group(CLOZE_REGEX_MATCH_GROUP_HINT)
        else:
            return "[...]"

    def arepl(m):
        return m.group(CLOZE_REGEX_MATCH_GROUP_CONTENT)

    for ord in ords:
        s = re.sub(clozeReg % ord, qrepl, string)
        s = re.sub(clozeReg % ".+?", arepl, s)
        strings.append(s)
    strings.append(re.sub(clozeReg % ".+?", arepl, string))

    return strings