Gophermaps generation code for Hexo

0-hexo-gopher.txt

Here's my code to generate Gophermaps for posts on a Hexo site.

I cannot guarantee this will work on your Hexo site. I had custom multilingual support on my site,
and manually removed all language related stuff from this code snippet. I did not test that the 
code still functions after this modification.

Usage:

Put gopher.js into "scripts" folder of your theme, e.g. "themes/lantian/scripts/gopher.js".

Run "hexo clean" followed by "hexo generate".

gopher.js

var unified = require('unified');
var remark_parse = require('remark-parse');
var remark_stringify = require('remark-stringify');
var remark_gfm = require('remark-gfm');
var remark_frontmatter = require('remark-frontmatter');
var remark_inline_links = require('remark-inline-links');
var prettier = require('prettier');
var fs = require('hexo-fs');
var path = require('path');
const isFullwidthCodePoint = require('is-fullwidth-code-point');

const crlf = '\r\n';
const gopherBefore = 'i';
const gopherBeforeLink = '1';
const gopherBeforeImage = 'I';
const gopherAfter = '\t\t{{server_addr}}\t{{server_port}}' + crlf;
const gopherEOF = '.' + crlf;

function slice_width(str, start, length) {
    var idx_first = 0;
    while (true) {
        var w = isFullwidthCodePoint(str.codePointAt(idx_first)) ? 2 : 1;
        if (start < w) break;
        idx_first++;
        start -= w;
    }

    var idx_last = idx_first;
    while (true) {
        var w = isFullwidthCodePoint(str.codePointAt(idx_last)) ? 2 : 1;
        if (length < w) break;
        idx_last++;
        length -= w;
    }
    return str.slice(idx_first, idx_last);
}

function markdown_formatter(rel_path, md) {
    const markdownRegex = /([^!]?)(!?)\[([^\]]+)\]\(([^)]+)\)(.?)/g;

    var rows = md.split('\n');
    for (var i = 0; i < rows.length; i++) {
        // Link regex can also match images
        if (rows[i].match(markdownRegex)) {
            var replace_at_beginning = false,
                replace_at_end = false;

            var replace_fn = (
                match,
                prefix,
                img_marker,
                label,
                href,
                suffix,
            ) => {
                // Don't touch external links
                if (href.match("://")) {
                    return match;
                }

                if (prefix !== null) {
                    replace_at_beginning = true;
                }
                if (suffix !== null) {
                    replace_at_end = true;
                }

                href = path.join('/', rel_path, href);

                return (
                    (prefix ? prefix + gopherAfter : '') +
                    (img_marker === '!'
                        ? gopherBeforeImage
                        : gopherBeforeLink) +
                    label +
                    '\t' +
                    href +
                    '\t{{server_addr}}\t{{server_port}}' +
                    crlf +
                    (suffix ? gopherBefore + suffix : '')
                );
            };

            rows[i] = rows[i].replaceAll(markdownRegex, replace_fn);
            rows[i] =
                (replace_at_beginning ? '' : gopherBefore) +
                rows[i] +
                (replace_at_end ? '' : gopherAfter);
        } else {
            rows[i] = gopherBefore + rows[i] + gopherAfter;
        }
    }

    return rows.join('') + gopherEOF;
}

var markdown_to_gopher = (result, data) => {
    if (data.page.raw) {
        unified()
            .use(remark_parse)
            .use(remark_frontmatter)
            .use(remark_gfm)
            .use(remark_inline_links)
            .use(remark_stringify, {
                bullet: '-',
                fences: true,
                listItemIndent: 'one',
                resourceLink: false,
            })
            .process(data.page.raw)
            .then((file) => {
                var md = String(file);
                if (!md) return;

                md = prettier.format(md, {
                    parser: 'markdown',
                    printWidth: 70,
                    tabWidth: 2,
                    proseWrap: 'always',
                    endOfLine: 'lf',
                });
                if (!md) return;

                md = markdown_formatter(path.dirname(data.path), md);

                var target_path = data.path;
                target_path = target_path.replace(/index\.html$/, 'gophermap');
                target_path = target_path.replace(/.html$/, '.gopher');

                var promise = fs.writeFile(
                    path.join(hexo.public_dir, target_path),
                    md,
                );

                hexo.log.info('[LT Gopher] Generated: ' + target_path);
                return promise;
            });
    }
    return result;
};

var gophermap_index_generator = (locals) => {
    var data = '';
    data += gopherBefore + '#' + gopherAfter;
    data += gopherBefore + '# ' + hexo.config.title + gopherAfter;
    data += gopherBefore + '#' + gopherAfter;
    data += gopherBefore + gopherAfter;

    data += gopherBefore + 'Posts:' + gopherAfter;
    locals.posts.sort('date', 'desc').each((post) => {
        data +=
            gopherBeforeLink +
            '- ' +
            slice_width(post.title, 0, 56) +
            ' (' +
            new Date(post.date).toISOString().replace('T', ' ').substr(0, 19) +
            ')' +
            '\t/' +
            post.path.replace(/index\.html$/g, '') +
            '\t{{server_addr}}\t{{server_port}}' +
            crlf;

        var summary = post.content.trim().replace(EXCERPT_REGEX, '');
        data +=
            gopherBefore +
            '  ' +
            slice_width(summary, 0, 68) +
            gopherAfter;
        data +=
            gopherBefore +
            '  ' +
            slice_width(summary, 68, 68) +
            gopherAfter;
        data +=
            gopherBefore +
            '  ' +
            slice_width(summary, 136, 68) +
            gopherAfter;
        data += gopherBefore + gopherAfter;
    });
    data += gopherEOF;

    var path = '/gophermap';
    hexo.log.info('[LT Gopher] Generated: ' + path);
    return {
        path: path,

        data: data,
    };
};

hexo.extend.filter.register('after_render:html', markdown_to_gopher, 1);
hexo.extend.generator.register(
    'gophermap_index_generator',
    gophermap_index_generator,
);