koa-meta/index.js

SEO <title> and <meta name="description"> middleware for Koa and Lad

const process = require('node:process');
const isSANB = require('is-string-and-not-blank');
const sanitizeHtml = require('sanitize-html');

class Meta {
  constructor(
    config = {},
    logger = console,
    /* istanbul ignore next */
    levelForMissing = process.env.NODE_ENV === 'development' ? 'error' : 'debug'
  ) {
    this.config = { '/': ['', ''], ...config };
    this.logger = logger;
    this.levelForMissing = levelForMissing;
    // ensure all config keys are arrays with two keys
    for (const path of Object.keys(this.config)) {
      if (!Array.isArray(this.config[path]))
        throw new Error(`path "${path}" was not an array`);
      // slice only the first two keys (0 = title, 1 = description)
      this.config[path] = this.config[path].slice(0, 2);
      // ensure it has both keys
      if (this.config[path].length !== 2)
        throw new Error(`path "${path}" must have exactly two keys`);
      // ensure both keys are strings
      if (typeof this.config[path][0] !== 'string')
        throw new Error(`path "${path}" needs String for title`);
      if (typeof this.config[path][1] !== 'string')
        throw new Error(`path "${path}" needs String for description`);
    }

    this.getByPath = this.getByPath.bind(this);
    this.middleware = this.middleware.bind(this);
  }

  getByPath(path = '/', t, originalPath, ctx) {
    if (typeof path !== 'string')
      throw new Error('path is required and must be a String');

    if (originalPath === null || originalPath === undefined)
      originalPath = path;

    if (t !== null && t !== undefined && typeof t !== 'function')
      throw new Error('t must be a Function');

    if (typeof originalPath !== 'string')
      throw new Error('originalPath must be a String');

    let key = this.config[path];

    // it should traverse up and split by / till it finds a parent route
    if (!key)
      if (
        (!ctx || !ctx.status || ctx.status === 200) &&
        (path === '/' || path.slice(0, path.lastIndexOf('/')) === '')
      )
        throw new Error(`path "${path}" needs a meta config key defined`);
      else
        return this.getByPath(
          path.slice(0, path.lastIndexOf('/')) || '/',
          t,
          originalPath,
          ctx
        );

    // translate the meta information
    key = key.map((string) => {
      // this has built in support for @ladjs/i18n via `ctx.request.t`
      if (t) {
        // replace `|` pipe character because
        // translation will interpret as ranged interval
        // <https://github.com/mashpie/i18n-node/issues/274>
        string = string.replace(/\|/g, '&#124;');
        string = t(string);
      }

      return sanitizeHtml(string, {
        allowedTags: [],
        allowedAttributes: {}
      });
    });

    return { title: key[0], description: key[1] };
  }

  middleware(ctx, next) {
    // return early if there was no `ctx.render` bound
    if (!ctx.render) return next();

    // provide a default `ctx.state.meta` object used in routes/middleware
    ctx.state.meta = ctx.state.meta || {};

    //
    // lookup page title and description
    //
    // this has built in support for @ladjs/i18n
    // since it exposes `ctx.pathWithoutLocale`
    const { getByPath, logger, levelForMissing } = this;
    const { render } = ctx;
    // override existing render but if and only if
    // title and description weren't both set
    ctx.render = function (...args) {
      // if we already had a title/description (e.g. 404) then return early
      if (isSANB(ctx.state.meta.title) && isSANB(ctx.state.meta.description))
        return render.call(ctx, ...args);

      // otherwise lookup the meta config
      let data = {};
      try {
        data = getByPath(
          ctx.pathWithoutLocale || ctx.path || '/',
          ctx.request.t,
          null,
          ctx
        );
      } catch (err) {
        logger[levelForMissing](err);
        data = getByPath('/', ctx.request.t, null, ctx);
      }

      Object.assign(ctx.state.meta, data);
      return render.call(ctx, ...args);
    };

    return next();
  }
}

module.exports = Meta;