TexTeller/texteller/api/katex.py

import re

from ..utils.latex import change_all
from .format import format_latex


def _rm_dollar_surr(content):
    pattern = re.compile(r'\\[a-zA-Z]+\$.*?\$|\$.*?\$')
    matches = pattern.findall(content)

    for match in matches:
        if not re.match(r'\\[a-zA-Z]+', match):
            new_match = match.strip('$')
            content = content.replace(match, ' ' + new_match + ' ')

    return content


def to_katex(formula: str) -> str:
    """
    Convert LaTeX formula to KaTeX-compatible format.

    This function processes a LaTeX formula string and converts it to a format
    that is compatible with KaTeX rendering. It removes unsupported commands
    and structures, simplifies LaTeX environments, and optimizes the formula
    for web display.

    Args:
        formula: LaTeX formula string to convert

    Returns:
        KaTeX-compatible formula string
    """
    res = formula
    # remove mbox surrounding
    res = change_all(res, r'\mbox ', r' ', r'{', r'}', r'', r'')
    res = change_all(res, r'\mbox', r' ', r'{', r'}', r'', r'')
    # remove hbox surrounding
    res = re.sub(r'\\hbox to ?-? ?\d+\.\d+(pt)?\{', r'\\hbox{', res)
    res = change_all(res, r'\hbox', r' ', r'{', r'}', r'', r' ')
    # remove raise surrounding
    res = re.sub(r'\\raise ?-? ?\d+\.\d+(pt)?', r' ', res)
    # remove makebox
    res = re.sub(r'\\makebox ?\[\d+\.\d+(pt)?\]\{', r'\\makebox{', res)
    res = change_all(res, r'\makebox', r' ', r'{', r'}', r'', r' ')
    # remove vbox surrounding, scalebox surrounding
    res = re.sub(r'\\raisebox\{-? ?\d+\.\d+(pt)?\}\{', r'\\raisebox{', res)
    res = re.sub(r'\\scalebox\{-? ?\d+\.\d+(pt)?\}\{', r'\\scalebox{', res)
    res = change_all(res, r'\scalebox', r' ', r'{', r'}', r'', r' ')
    res = change_all(res, r'\raisebox', r' ', r'{', r'}', r'', r' ')
    res = change_all(res, r'\vbox', r' ', r'{', r'}', r'', r' ')

    origin_instructions = [
        r'\Huge',
        r'\huge',
        r'\LARGE',
        r'\Large',
        r'\large',
        r'\normalsize',
        r'\small',
        r'\footnotesize',
        r'\tiny',
    ]
    for old_ins, new_ins in zip(origin_instructions, origin_instructions):
        res = change_all(res, old_ins, new_ins, r'$', r'$', '{', '}')
    res = change_all(res, r'\mathbf', r'\bm', r'{', r'}', r'{', r'}')
    res = change_all(res, r'\boldmath ', r'\bm', r'{', r'}', r'{', r'}')
    res = change_all(res, r'\boldmath', r'\bm', r'{', r'}', r'{', r'}')
    res = change_all(res, r'\boldmath ', r'\bm', r'$', r'$', r'{', r'}')
    res = change_all(res, r'\boldmath', r'\bm', r'$', r'$', r'{', r'}')
    res = change_all(res, r'\scriptsize', r'\scriptsize', r'$', r'$', r'{', r'}')
    res = change_all(res, r'\emph', r'\textit', r'{', r'}', r'{', r'}')
    res = change_all(res, r'\emph ', r'\textit', r'{', r'}', r'{', r'}')

    # remove bold command
    res = change_all(res, r'\bm', r' ', r'{', r'}', r'', r'')

    origin_instructions = [
        r'\left',
        r'\middle',
        r'\right',
        r'\big',
        r'\Big',
        r'\bigg',
        r'\Bigg',
        r'\bigl',
        r'\Bigl',
        r'\biggl',
        r'\Biggl',
        r'\bigm',
        r'\Bigm',
        r'\biggm',
        r'\Biggm',
        r'\bigr',
        r'\Bigr',
        r'\biggr',
        r'\Biggr',
    ]
    for origin_ins in origin_instructions:
        res = change_all(res, origin_ins, origin_ins, r'{', r'}', r'', r'')

    res = re.sub(r'\\\[(.*?)\\\]', r'\1\\newline', res)

    if res.endswith(r'\newline'):
        res = res[:-8]

    # remove multiple spaces
    res = re.sub(r'(\\,){1,}', ' ', res)
    res = re.sub(r'(\\!){1,}', ' ', res)
    res = re.sub(r'(\\;){1,}', ' ', res)
    res = re.sub(r'(\\:){1,}', ' ', res)
    res = re.sub(r'\\vspace\{.*?}', '', res)

    # merge consecutive text
    def merge_texts(match):
        texts = match.group(0)
        merged_content = ''.join(re.findall(r'\\text\{([^}]*)\}', texts))
        return f'\\text{{{merged_content}}}'

    res = re.sub(r'(\\text\{[^}]*\}\s*){2,}', merge_texts, res)

    res = res.replace(r'\bf ', '')
    res = _rm_dollar_surr(res)

    # remove extra spaces (keeping only one)
    res = re.sub(r' +', ' ', res)

    # format latex
    res = res.strip()
    res = format_latex(res)

    return res