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/*
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Limited support for some latex environments, only for rendering (not editing).
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*/
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export default function latexEnvs(value: string): string {
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  value = transformFigures(value);
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  value = transformItemEnvironments(value);
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  return value;
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}
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/*
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transformFigures -- dumb parser to turn this:
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---
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...
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\begin{figure}
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\centering
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\centerline{\includegraphics[width=WIDTH]{URL}}
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\caption{\label{foo}CAPTION}
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\end{figure}
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...
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---
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into this:
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---
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...
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<div style="text-align:center"><img src="URL" style="width:WIDTH"/><br/><br/>\figlabel{foo}CAPTION</div>
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...
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---
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There can be lots of figures.
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*/
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function transformFigures(content: string): string {
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  while (true) {
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    const i = content.indexOf("\\begin{figure}");
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    if (i == -1) {
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      return content;
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    }
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    const j = content.indexOf("\\end{figure}");
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    if (j == -1) {
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      return content;
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    }
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    const k = content.indexOf("\\includegraphics");
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    if (k == -1) {
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      return content;
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    }
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    const c = content.indexOf("\\caption{");
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    if (c == -1) {
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      return content;
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    }
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    const c2 = content.lastIndexOf("}", j);
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    if (c2 == -1) {
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      return content;
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    }
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    const w = content.indexOf("width=");
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    const w2 = content.indexOf("{", k);
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    const w3 = content.indexOf("}", k);
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    if (w2 == -1 || w3 == -1) {
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      return content;
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    }
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    let style = "";
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    if (w != -1) {
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      style = `width:${content.slice(w + "width=".length, w2 - 1)}`;
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    }
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    const url = content.slice(w2 + 1, w3);
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    let caption = content.slice(c + "\\caption{".length, c2);
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    const x = caption.indexOf("\\label{");
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    let figlabel;
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    if (x != -1) {
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      const y = caption.indexOf("}", x);
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      figlabel = `\\figlabel{${caption.slice(x + "\\label{".length, y)}}`;
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      caption = caption.slice(0, x) + caption.slice(y + 1);
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    } else {
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      figlabel = "";
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    }
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    const md = `\n\n<div style="text-align:center;margin:20px auto;max-width:750px"><img src="${url}" style="${style}"/><br/><br/><b>Figure${figlabel}:</b> ${caption}</div>\n\n`;
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    content =
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      content.slice(0, i) + md + content.slice(j + "\\end{figure}".length);
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  }
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}
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/*
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transformEnumerate -- dumb parser to turn this:
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---
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...
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\begin{enumerate}
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\item ITEM1
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\item ITEM2
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...
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\end{enumerate}
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...
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---
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into this:
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---
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...
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1. ITEM1
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1. ITEM2
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...
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---
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and
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---
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\begin{itemize}
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\item ITEM1
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\item ITEM2
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...
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\end{itemize}
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into
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- ITEM1
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- ITEM2
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*/
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function transformItemEnvironments(content: string) {
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  for (const type of ["itemize", "enumerate"]) {
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    content = transformItemsType(content, type as "itemize" | "enumerate");
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  }
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  return content;
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}
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function transformItemsType(
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  content: string,
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  type: "itemize" | "enumerate",
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): string {
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  while (true) {
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    const BEGIN = `\\begin{${type}}`;
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    const i = content.indexOf(BEGIN);
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    if (i == -1) {
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      return content;
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    }
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    const END = `\\end{${type}}`;
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    const j = content.indexOf(END);
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    if (j == -1) {
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      return content;
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    }
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    const body = content.slice(i + BEGIN.length + 1, j);
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    const items = body
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      .split("\\item")
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      .filter((x) => x.trim())
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      .map((x) => (type == "itemize" ? "- " : "1. ") + x)
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      .join("\n\n");
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    content =
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      content.slice(0, i) +
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      "\n\n" +
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      items +
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      "\n\n" +
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      content.slice(j + END.length + 1);
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  }
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  return content;
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}
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