markdown-it-katex.js

// markdown-it-katex moved here to use a newer version of katex
// https://github.com/waylonflinn/markdown-it-katex

"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
}