/* global hexo */

'use strict'

hexo.extend.filter.register(
  'after_post_render',
  function (data) {
    const config = this.config
    const url = new URL(config.url)
    const siteHost = url.hostname || config.url

    // Match 'a' tags that don't contain html children.
    const regPureATag = /<a([^>]*)href="([^"]*)"([^>]*)>([^<]*)<\/a>/gim

    data.content = data.content.replace(
      regPureATag,
      function (match, attrBegin, href, attrEnd, html) {
        // Exit if the href attribute doesn't exists.
        if (!href) return match

        let link = ''
        try {
          link = new URL(href)
        } catch (e) {
          // Invalid url, e.g. Anchor link.
          return match
        }

        // Exit if the url has same host with `config.url`, which means isn't an external link.
        if (!link.protocol || link.hostname === siteHost) return match

        return `<a class="link" ${attrBegin} href="${href}" ${attrEnd}>${html}<i class="fas fa-external-link-alt"></i></a>`
      }
    )
  },
  0
)