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index.js
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/* Process inline math */
/*
Like markdown-it-simplemath, this is a stripped down, simplified version of:
https://github.com/runarberg/markdown-it-math
It differs in that it takes (a subset of) LaTeX as input and relies on KaTeX
for rendering output.
*/
/*jslint node: true */
'use strict';
var katex = require('katex');
// Test if potential opening or closing delimieter
// Assumes that there is a "$" at state.src[pos]
function isValidDelim(state, pos) {
var prevChar, nextChar,
max = state.posMax,
can_open = true,
can_close = true;
prevChar = pos > 0 ? state.src.charCodeAt(pos - 1) : -1;
nextChar = pos + 1 <= max ? state.src.charCodeAt(pos + 1) : -1;
// Check non-whitespace conditions for opening and closing, and
// check that closing delimeter isn't followed by a number
if (prevChar === 0x20/* " " */ || prevChar === 0x09/* \t */ ||
(nextChar >= 0x30/* "0" */ && nextChar <= 0x39/* "9" */)) {
can_close = false;
}
if (nextChar === 0x20/* " " */ || nextChar === 0x09/* \t */) {
can_open = false;
}
return {
can_open: can_open,
can_close: can_close
};
}
function math_inline(state, silent) {
var start, match, token, res, pos, esc_count;
if (state.src[state.pos] !== "$") { return false; }
res = isValidDelim(state, state.pos);
if (!res.can_open) {
if (!silent) { state.pending += "$"; }
state.pos += 1;
return true;
}
// First check for and bypass all properly escaped delimieters
// This loop will assume that the first leading backtick can not
// be the first character in state.src, which is known since
// we have found an opening delimieter already.
start = state.pos + 1;
match = start;
while ((match = state.src.indexOf("$", match)) !== -1) {
// Found potential $, look for escapes, pos will point to
// first non escape when complete
pos = match - 1;
while (state.src[pos] === "\\") { pos -= 1; }
// Even number of escapes, potential closing delimiter found
if (((match - pos) % 2) == 1) { break; }
match += 1;
}
// No closing delimter found. Consume $ and continue.
if (match === -1) {
if (!silent) { state.pending += "$"; }
state.pos = start;
return true;
}
// Check if we have empty content, ie: $$. Do not parse.
if (match - start === 0) {
if (!silent) { state.pending += "$$"; }
state.pos = start + 1;
return true;
}
// Check for valid closing delimiter
res = isValidDelim(state, match);
if (!res.can_close) {
if (!silent) { state.pending += "$"; }
state.pos = start;
return true;
}
if (!silent) {
token = state.push('math_inline', 'math', 0);
token.markup = "$";
token.content = state.src.slice(start, match);
}
state.pos = match + 1;
return true;
}
function math_block(state, start, end, silent) {
var firstLine, lastLine, next, lastPos, found = false, token,
pos = state.bMarks[start] + state.tShift[start],
max = state.eMarks[start]
if (pos + 2 > max) { return false; }
if (state.src.slice(pos, pos + 2) !== '$$') { return false; }
pos += 2;
firstLine = state.src.slice(pos, max);
if (silent) { return true; }
if (firstLine.trim().slice(-2) === '$$') {
// Single line expression
firstLine = firstLine.trim().slice(0, -2);
found = true;
}
for (next = start; !found;) {
next++;
if (next >= end) { break; }
pos = state.bMarks[next] + state.tShift[next];
max = state.eMarks[next];
if (pos < max && state.tShift[next] < state.blkIndent) {
// non-empty line with negative indent should stop the list:
break;
}
if (state.src.slice(pos, max).trim().slice(-2) === '$$') {
lastPos = state.src.slice(0, max).lastIndexOf('$$');
lastLine = state.src.slice(pos, lastPos);
found = true;
}
}
state.line = next + 1;
token = state.push('math_block', 'math', 0);
token.block = true;
token.content = (firstLine && firstLine.trim() ? firstLine + '\n' : '')
+ state.getLines(start + 1, next, state.tShift[start], true)
+ (lastLine && lastLine.trim() ? lastLine : '');
token.map = [start, state.line];
token.markup = '$$';
return true;
}
module.exports = function math_plugin(md, options) {
// Default options
options = options || {};
// set KaTeX as the renderer for markdown-it-simplemath
var katexInline = function (latex) {
options.displayMode = false;
try {
return katex.renderToString(latex, options);
}
catch (error) {
if (options.throwOnError) { console.log(error); }
return latex;
}
};
var inlineRenderer = function (tokens, idx) {
return katexInline(tokens[idx].content);
};
var katexBlock = function (latex) {
options.displayMode = true;
try {
return "<p>" + katex.renderToString(latex, options) + "</p>";
}
catch (error) {
if (options.throwOnError) { console.log(error); }
return latex;
}
}
var blockRenderer = function (tokens, idx) {
return katexBlock(tokens[idx].content) + '\n';
}
md.inline.ruler.after('escape', 'math_inline', math_inline);
md.block.ruler.after('blockquote', 'math_block', math_block, {
alt: ['paragraph', 'reference', 'blockquote', 'list']
});
md.renderer.rules.math_inline = inlineRenderer;
md.renderer.rules.math_block = blockRenderer;
};