markdown-it-anchor.js

// markdown it anchor module
// it's necessary to have it as a source file because of compatibility problems with electron and react packaging
// https://github.com/valeriangalliat/markdown-it-anchor

const string = require("string")

const slugify = s =>
    string(s)
        .slugify()
        .toString()

const position = {
    false: "push",
    true: "unshift",
}

const hasProp = {}.hasOwnProperty

const permalinkHref = slug => `#${slug}`

const renderPermalink = (slug, opts, state, idx) => {
    const space = () => Object.assign(new state.Token("text", "", 0), {content: " "})

    const linkTokens = [
        Object.assign(new state.Token("link_open", "a", 1), {
            attrs: [
                ["class", opts.permalinkClass],
                ["href", opts.permalinkHref(slug, state)],
                ["aria-hidden", "true"],
            ],
        }),
        Object.assign(new state.Token("html_block", "", 0), {
            content: opts.permalinkSymbol,
        }),
        new state.Token("link_close", "a", -1),
    ]

    // `push` or `unshift` according to position option.
    // Space is at the opposite side.
    linkTokens[position[!opts.permalinkBefore]](space())
    state.tokens[idx + 1].children[position[opts.permalinkBefore]](...linkTokens)
}

const uniqueSlug = (slug, slugs) => {
    // Mark this slug as used in the environment.
    slugs[slug] = (hasProp.call(slugs, slug) ? slugs[slug] : 0) + 1

    // First slug, return as is.
    if (slugs[slug] === 1) {
        return slug
    }

    // Duplicate slug, add a `-2`, `-3`, etc. to keep ID unique.
    return slug + "-" + slugs[slug]
}

const isLevelSelectedNumber = selection => level => level >= selection
const isLevelSelectedArray = selection => level => selection.includes(level)

const anchor = (md, opts) => {
    opts = Object.assign({}, anchor.defaults, opts)

    md.core.ruler.push("anchor", state => {
        const slugs = {}
        const tokens = state.tokens

        const isLevelSelected = Array.isArray(opts.level)
            ? isLevelSelectedArray(opts.level)
            : isLevelSelectedNumber(opts.level)

        tokens
            .filter(token => token.type === "heading_open")
            .filter(token => isLevelSelected(Number(token.tag.substr(1))))
            .forEach(token => {
                // Aggregate the next token children text.
                const title = tokens[tokens.indexOf(token) + 1].children
                    .filter(token => token.type === "text" || token.type === "code_inline")
                    .reduce((acc, t) => acc + t.content, "")

                let slug = token.attrGet("id")

                if (slug == null) {
                    slug = uniqueSlug(opts.slugify(title), slugs)
                    token.attrPush(["id", slug])
                }

                if (opts.permalink) {
                    opts.renderPermalink(slug, opts, state, tokens.indexOf(token))
                }

                if (opts.callback) {
                    opts.callback(token, {slug, title})
                }
            })
    })
}

anchor.defaults = {
    level: 1,
    slugify,
    permalink: false,
    renderPermalink,
    permalinkClass: "header-anchor",
    permalinkSymbol: "¶",
    permalinkBefore: false,
    permalinkHref,
}

module.exports = anchor