feat: add copy buttons for code blocks (#217)

* feat: copy button on snippet code

* refactor: update func name, styles and refactor backToTop

Rename the function name `copyButton` to `attachCopyButtons`. Update copy button styles. Fix broken `backToTop` function by attaching `astro:after-swap` event listener.

---------

Co-authored-by: Sat Naing <satnaingdev@gmail.com>

src/layouts/PostDetails.astro

@@ -100,10 +100,57 @@ const layoutProps = {
 </style>
 
 <script is:inline>
-  /* When the user clicks on the "Back to Top" button,
+  /** Attaches copy buttons to code blocks in the document,
-   * scroll to the top of the document */
+   * allowing users to copy code easily. */
+  function attachCopyButtons() {
+    let copyButtonLabel = "Copy";
+    let codeBlocks = Array.from(document.querySelectorAll("pre"));
+
+    for (let codeBlock of codeBlocks) {
+      let wrapper = document.createElement("div");
+      wrapper.style.position = "relative";
+
+      let copyButton = document.createElement("button");
+      copyButton.className =
+        "copy-code absolute right-3 -top-3 rounded bg-skin-card px-2 py-1 text-xs leading-4 text-skin-base font-medium";
+      copyButton.innerHTML = copyButtonLabel;
+      codeBlock.setAttribute("tabindex", "0");
+      codeBlock.appendChild(copyButton);
+
+      // wrap codebock with relative parent element
+      codeBlock.parentNode.insertBefore(wrapper, codeBlock);
+      wrapper.appendChild(codeBlock);
+
+      copyButton.addEventListener("click", async () => {
+        await copyCode(codeBlock, copyButton);
+      });
+    }
+
+    async function copyCode(block, button) {
+      let code = block.querySelector("code");
+      let text = code.innerText;
+
+      await navigator.clipboard.writeText(text);
+
+      // visual feedback that task is completed
+      button.innerText = "Copied";
+
+      setTimeout(() => {
+        button.innerText = copyButtonLabel;
+      }, 700);
+    }
+  }
+  attachCopyButtons();
+  document.addEventListener("astro:after-swap", attachCopyButtons);
+
+  /** Scrolls the document to the top when
+   * the "Back to Top" button is clicked. */
+  function backToTop() {
     document.querySelector("#back-to-top")?.addEventListener("click", () => {
       document.body.scrollTop = 0; // For Safari
       document.documentElement.scrollTop = 0; // For Chrome, Firefox, IE and Opera
     });
+  }
+  backToTop();
+  document.addEventListener("astro:after-swap", backToTop);
 </script>