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1"""An extension to capture amsmath latex environments."""
3from __future__ import annotations
5import re
6from typing import TYPE_CHECKING, Callable, Sequence
8from markdown_it import MarkdownIt
9from markdown_it.common.utils import escapeHtml
10from markdown_it.rules_block import StateBlock
12from mdit_py_plugins.utils import is_code_block
14if TYPE_CHECKING:
15 from markdown_it.renderer import RendererProtocol
16 from markdown_it.token import Token
17 from markdown_it.utils import EnvType, OptionsDict
19# Taken from amsmath version 2.1
20# http://anorien.csc.warwick.ac.uk/mirrors/CTAN/macros/latex/required/amsmath/amsldoc.pdf
21ENVIRONMENTS = [
22 # 3.2 single equation with an automatically gen-erated number
23 "equation",
24 # 3.3 variation equation, used for equations that dont fit on a single line
25 "multline",
26 # 3.5 a group of consecutive equations when there is no alignment desired among them
27 "gather",
28 # 3.6 Used for two or more equations when vertical alignment is desired
29 "align",
30 # allows the horizontal space between equationsto be explicitly specified.
31 "alignat",
32 # stretches the space betweenthe equation columns to the maximum possible width
33 "flalign",
34 # 4.1 The pmatrix, bmatrix, Bmatrix, vmatrix and Vmatrix have (respectively)
35 # (),[],{},||,and ‖‖ delimiters built in.
36 "matrix",
37 "pmatrix",
38 "bmatrix",
39 "Bmatrix",
40 "vmatrix",
41 "Vmatrix",
42 # eqnarray is another math environment, it is not part of amsmath,
43 # and note that it is better to use align or equation+split instead
44 "eqnarray",
45]
46# other "non-top-level" environments:
48# 3.4 the split environment is for single equations that are too long to fit on one line
49# and hence must be split into multiple lines,
50# it is intended for use only inside some other displayed equation structure,
51# usually an equation, align, or gather environment
53# 3.7 variants gathered, aligned,and alignedat are provided
54# whose total width is the actual width of the contents;
55# thus they can be used as a component in a containing expression
57RE_OPEN = r"\\begin\{(" + "|".join(ENVIRONMENTS) + r")([\*]?)\}"
60def amsmath_plugin(
61 md: MarkdownIt, *, renderer: Callable[[str], str] | None = None
62) -> None:
63 """Parses TeX math equations, without any surrounding delimiters,
64 only for top-level `amsmath <https://ctan.org/pkg/amsmath>`__ environments:
66 .. code-block:: latex
68 \\begin{gather*}
69 a_1=b_1+c_1\\\\
70 a_2=b_2+c_2-d_2+e_2
71 \\end{gather*}
73 :param renderer: Function to render content, by default escapes HTML
75 """
76 md.block.ruler.before(
77 "blockquote",
78 "amsmath",
79 amsmath_block,
80 {"alt": ["paragraph", "reference", "blockquote", "list", "footnote_def"]},
81 )
83 _renderer = (lambda content: escapeHtml(content)) if renderer is None else renderer
85 def render_amsmath_block(
86 self: RendererProtocol,
87 tokens: Sequence[Token],
88 idx: int,
89 options: OptionsDict,
90 env: EnvType,
91 ) -> str:
92 content = _renderer(str(tokens[idx].content))
93 return f'<div class="math amsmath">\n{content}\n</div>\n'
95 md.add_render_rule("amsmath", render_amsmath_block)
98def amsmath_block(
99 state: StateBlock, startLine: int, endLine: int, silent: bool
100) -> bool:
101 # note the code principally follows the logic in markdown_it/rules_block/fence.py,
102 # except that:
103 # (a) it allows for closing tag on same line as opening tag
104 # (b) it does not allow for opening tag without closing tag (i.e. no auto-closing)
106 if is_code_block(state, startLine):
107 return False
109 # does the first line contain the beginning of an amsmath environment
110 first_start = state.bMarks[startLine] + state.tShift[startLine]
111 first_end = state.eMarks[startLine]
112 first_text = state.src[first_start:first_end]
114 if not (match_open := re.match(RE_OPEN, first_text)):
115 return False
117 # construct the closing tag
118 environment = match_open.group(1)
119 numbered = match_open.group(2)
120 closing = rf"\end{{{match_open.group(1)}{match_open.group(2)}}}"
122 # start looking for the closing tag, including the current line
123 nextLine = startLine - 1
125 while True:
126 nextLine += 1
127 if nextLine >= endLine:
128 # reached the end of the block without finding the closing tag
129 return False
131 next_start = state.bMarks[nextLine] + state.tShift[nextLine]
132 next_end = state.eMarks[nextLine]
133 if next_start < first_end and state.sCount[nextLine] < state.blkIndent:
134 # non-empty line with negative indent should stop the list:
135 # - \begin{align}
136 # test
137 return False
139 if state.src[next_start:next_end].rstrip().endswith(closing):
140 # found the closing tag
141 break
143 state.line = nextLine + 1
145 if not silent:
146 token = state.push("amsmath", "math", 0)
147 token.block = True
148 token.content = state.getLines(
149 startLine, state.line, state.sCount[startLine], False
150 )
151 token.meta = {"environment": environment, "numbered": numbered}
152 token.map = [startLine, nextLine]
154 return True