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"""An extension to capture amsmath latex environments."""
from __future__ import annotations
from collections.abc import Callable, Sequence
import re
from typing import TYPE_CHECKING
from markdown_it import MarkdownIt
from markdown_it.common.utils import escapeHtml
from markdown_it.rules_block import StateBlock
from mdit_py_plugins.utils import is_code_block
if TYPE_CHECKING:
from markdown_it.renderer import RendererProtocol
from markdown_it.token import Token
from markdown_it.utils import EnvType, OptionsDict
# Taken from amsmath version 2.1
# http://anorien.csc.warwick.ac.uk/mirrors/CTAN/macros/latex/required/amsmath/amsldoc.pdf
ENVIRONMENTS = [
# 3.2 single equation with an automatically gen-erated number
"equation",
# 3.3 variation equation, used for equations that dont fit on a single line
"multline",
# 3.5 a group of consecutive equations when there is no alignment desired among them
"gather",
# 3.6 Used for two or more equations when vertical alignment is desired
"align",
# allows the horizontal space between equationsto be explicitly specified.
"alignat",
# stretches the space betweenthe equation columns to the maximum possible width
"flalign",
# 4.1 The pmatrix, bmatrix, Bmatrix, vmatrix and Vmatrix have (respectively)
# (),[],{},||,and ‖‖ delimiters built in.
"matrix",
"pmatrix",
"bmatrix",
"Bmatrix",
"vmatrix",
"Vmatrix",
# eqnarray is another math environment, it is not part of amsmath,
# and note that it is better to use align or equation+split instead
"eqnarray",
]
# other "non-top-level" environments:
# 3.4 the split environment is for single equations that are too long to fit on one line
# and hence must be split into multiple lines,
# it is intended for use only inside some other displayed equation structure,
# usually an equation, align, or gather environment
# 3.7 variants gathered, aligned,and alignedat are provided
# whose total width is the actual width of the contents;
# thus they can be used as a component in a containing expression
RE_OPEN = r"\\begin\{(" + "|".join(ENVIRONMENTS) + r")([\*]?)\}"
def amsmath_plugin(
md: MarkdownIt, *, renderer: Callable[[str], str] | None = None
) -> None:
"""Parses TeX math equations, without any surrounding delimiters,
only for top-level `amsmath <https://ctan.org/pkg/amsmath>`__ environments:
.. code-block:: latex
\\begin{gather*}
a_1=b_1+c_1\\\\
a_2=b_2+c_2-d_2+e_2
\\end{gather*}
:param renderer: Function to render content, by default escapes HTML
"""
md.block.ruler.before(
"blockquote",
"amsmath",
amsmath_block,
{"alt": ["paragraph", "reference", "blockquote", "list", "footnote_def"]},
)
_renderer = (lambda content: escapeHtml(content)) if renderer is None else renderer
def render_amsmath_block(
self: RendererProtocol,
tokens: Sequence[Token],
idx: int,
options: OptionsDict,
env: EnvType,
) -> str:
content = _renderer(str(tokens[idx].content))
return f'<div class="math amsmath">\n{content}\n</div>\n'
md.add_render_rule("amsmath", render_amsmath_block)
def amsmath_block(
state: StateBlock, startLine: int, endLine: int, silent: bool
) -> bool:
# note the code principally follows the logic in markdown_it/rules_block/fence.py,
# except that:
# (a) it allows for closing tag on same line as opening tag
# (b) it does not allow for opening tag without closing tag (i.e. no auto-closing)
if is_code_block(state, startLine):
return False
# does the first line contain the beginning of an amsmath environment
first_start = state.bMarks[startLine] + state.tShift[startLine]
first_end = state.eMarks[startLine]
first_text = state.src[first_start:first_end]
if not (match_open := re.match(RE_OPEN, first_text)):
return False
# construct the closing tag
environment = match_open.group(1)
numbered = match_open.group(2)
closing = rf"\end{{{match_open.group(1)}{match_open.group(2)}}}"
# start looking for the closing tag, including the current line
nextLine = startLine - 1
while True:
nextLine += 1
if nextLine >= endLine:
# reached the end of the block without finding the closing tag
return False
next_start = state.bMarks[nextLine] + state.tShift[nextLine]
next_end = state.eMarks[nextLine]
if next_start < first_end and state.sCount[nextLine] < state.blkIndent:
# non-empty line with negative indent should stop the list:
# - \begin{align}
# test
return False
if state.src[next_start:next_end].rstrip().endswith(closing):
# found the closing tag
break
state.line = nextLine + 1
if not silent:
token = state.push("amsmath", "math", 0)
token.block = True
token.content = state.getLines(
startLine, state.line, state.sCount[startLine], False
)
token.meta = {"environment": environment, "numbered": numbered}
token.map = [startLine, nextLine]
return True
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