feat(comments): support custom giscus themes (#1526)

Co-authored-by: Aaron Pham <Aaronpham0103@gmail.com>
Co-authored-by: Aaron Pham <contact@aarnphm.xyz>

quartz/components/scripts/comments.inline.ts

@@ -13,7 +13,7 @@ const changeTheme = (e: CustomEventMap["themechange"]) => {
     {
       giscus: {
         setConfig: {
-          theme: theme,
+          theme: getThemeUrl(getThemeName(theme)),
         },
       },
     },
@@ -21,12 +21,36 @@ const changeTheme = (e: CustomEventMap["themechange"]) => {
   )
 }
 
+const getThemeName = (theme: string) => {
+  if (theme !== "dark" && theme !== "light") {
+    return theme
+  }
+  const giscusContainer = document.querySelector(".giscus") as GiscusElement
+  if (!giscusContainer) {
+    return theme
+  }
+  const darkGiscus = giscusContainer.dataset.darkTheme ?? "dark"
+  const lightGiscus = giscusContainer.dataset.lightTheme ?? "light"
+  return theme === "dark" ? darkGiscus : lightGiscus
+}
+
+const getThemeUrl = (theme: string) => {
+  const giscusContainer = document.querySelector(".giscus") as GiscusElement
+  if (!giscusContainer) {
+    return `https://giscus.app/themes/${theme}.css`
+  }
+  return `${giscusContainer.dataset.themeUrl ?? "https://giscus.app/themes"}/${theme}.css`
+}
+
 type GiscusElement = Omit<HTMLElement, "dataset"> & {
   dataset: DOMStringMap & {
     repo: `${string}/${string}`
     repoId: string
     category: string
     categoryId: string
+    themeUrl: string
+    lightTheme: string
+    darkTheme: string
     mapping: "url" | "title" | "og:title" | "specific" | "number" | "pathname"
     strict: string
     reactionsEnabled: string
@@ -57,7 +81,7 @@ document.addEventListener("nav", () => {
 
   const theme = document.documentElement.getAttribute("saved-theme")
   if (theme) {
-    giscusScript.setAttribute("data-theme", theme)
+    giscusScript.setAttribute("data-theme", getThemeUrl(getThemeName(theme)))
   }
 
   giscusContainer.appendChild(giscusScript)