add comment system

layouts/partials/comment.html

@@ -0,0 +1,4 @@
+{{ $enableComment := .Params.comment | default .Site.Params.comment.enable }}
+{{ if and $enableComment .Site.Params.comment.provider }}
+  {{ partial (printf "comments/%s.html" .Site.Params.comment.provider) . }}
+{{ end }}

layouts/partials/comments/disqus.html

@@ -0,0 +1,57 @@
+<script>
+  var disqus_config = function () {
+    this.page.url = '{{ .Permalink }}';
+    this.page.identifier = '{{ .RelPermalink }}';
+  };
+
+  function addDisqus() {
+    let disqusThread = document.createElement('div');
+    let paragraph = document.createElement('p');
+
+    disqusThread.id = 'disqus_thread';
+    paragraph.className = 'text-center text-muted small';
+    paragraph.innerHTML = 'Comments powered by <a href="https://disqus.com/">Disqus</a>.';
+    disqusThread.appendChild(paragraph);
+
+    const footer = document.querySelector('footer');
+    footer.insertAdjacentElement("beforebegin", disqusThread);
+  }
+
+  {{/* Auto switch theme */}}
+  function reloadDisqus(event) {
+    if (event.source === window && event.data && event.data.id === Theme.ID) {
+      {{/* Disqus hasn't been loaded */}}
+      if (typeof DISQUS === 'undefined') {
+        return;
+      }
+
+      if (document.readyState == 'complete') {
+        DISQUS.reset({ reload: true, config: disqus_config });
+      }
+    }
+  }
+
+  addDisqus();
+
+  if (Theme.switchable) {
+    addEventListener('message', reloadDisqus);
+  }
+
+  {{/* Lazy loading */}}
+  var disqusObserver = new IntersectionObserver(
+    function (entries) {
+      if (entries[0].isIntersecting) {
+        var d = document,
+          s = d.createElement('script');
+        s.src = 'https://{{ .Site.Params.comments.disqus.shortname }}.disqus.com/embed.js';
+        s.setAttribute('data-timestamp', +new Date());
+        (d.head || d.body).appendChild(s);
+
+        disqusObserver.disconnect();
+      }
+    },
+    { threshold: [0] }
+  );
+
+  disqusObserver.observe(document.getElementById('disqus_thread'));
+</script>

layouts/partials/comments/giscus.html

@@ -0,0 +1,54 @@
+<script>
+  (function () {
+    const themeMapper = Theme.getThemeMapper('light', 'dark_dimmed');
+    const initTheme = themeMapper[Theme.visualState];
+
+    let lang = '{{ .Site.Params.comments.giscus.lang | default .Site.Language.Lang }}';
+    {{/* https://github.com/giscus/giscus/tree/main/locales */}}
+    if (lang.length > 2 && !lang.startsWith('zh')) {
+      lang = lang.slice(0, 2);
+    }
+
+    let giscusAttributes = {
+      src: 'https://giscus.app/client.js',
+      'data-repo': '{{ .Site.Params.comments.giscus.repo }}',
+      'data-repo-id': '{{ .Site.Params.comments.giscus.repo_id }}',
+      'data-category': '{{ .Site.Params.comments.giscus.category }}',
+      'data-category-id': '{{ .Site.Params.comments.giscus.category_id }}',
+      'data-mapping': '{{ .Site.Params.comments.giscus.mapping | default "pathname" }}',
+      'data-strict': '{{ .Site.Params.comments.giscus.strict | default "0" }}',
+      'data-reactions-enabled': '{{ .Site.Params.comments.giscus.reactions_enabled | default "1" }}',
+      'data-emit-metadata': '0',
+      'data-theme': initTheme,
+      'data-input-position': '{{ .Site.Params.comments.giscus.input_position | default "bottom" }}',
+      'data-lang': lang,
+      'data-loading': 'lazy',
+      crossorigin: 'anonymous',
+      async: ''
+    };
+
+    let giscusNode = document.createElement('script');
+    Object.entries(giscusAttributes).forEach(([key, value]) =>
+      giscusNode.setAttribute(key, value)
+    );
+
+    const $footer = document.querySelector('footer');
+    $footer.insertAdjacentElement("beforebegin", giscusNode);
+
+    addEventListener('message', (event) => {
+      if (event.source === window && event.data && event.data.id === Theme.ID) {
+        const newTheme = themeMapper[Theme.visualState];
+
+        const message = {
+          setConfig: {
+            theme: newTheme
+          }
+        };
+
+        const giscus =
+          document.getElementsByClassName('giscus-frame')[0].contentWindow;
+        giscus.postMessage({ giscus: message }, 'https://giscus.app');
+      }
+    });
+  })();
+</script>

layouts/partials/comments/utterances.html

@@ -0,0 +1,37 @@
+<script>
+  (function () {
+    const origin = 'https://utteranc.es';
+    const themeMapper = Theme.getThemeMapper('github-light', 'github-dark');
+    const initTheme = themeMapper[Theme.visualState];
+
+    let script = document.createElement('script');
+    script.src = 'https://utteranc.es/client.js';
+    script.setAttribute('repo', '{{ .Site.Params.comments.utterances.repo }}');
+    script.setAttribute('issue-term', '{{ .Site.Params.comments.utterances.issue_term }}');
+    script.setAttribute('theme', initTheme);
+    script.crossOrigin = 'anonymous';
+    script.async = true;
+
+    const $footer = document.querySelector('footer');
+    $footer.insertAdjacentElement('beforebegin', script);
+
+    addEventListener('message', (event) => {
+      let newTheme;
+
+      {{/*
+        Credit to <https://github.com/utterance/utterances/issues/170#issuecomment-594036347>
+      */}}
+      if (event.source === window && event.data && event.data.id === Theme.ID) {
+        newTheme = themeMapper[Theme.visualState];
+
+        const message = {
+          type: 'set-theme',
+          theme: newTheme
+        };
+
+        const utterances = document.querySelector('.utterances-frame').contentWindow;
+        utterances.postMessage(message, origin);
+      }
+    });
+  })();
+</script>