fix: copy code in non-secure contexts (#792)

Co-authored-by: Divyansh Singh <40380293+brc-dd@users.noreply.github.com>

src/client/theme-default/composables/copy-code.ts

@@ -20,6 +20,50 @@ export function useCopyCode() {
     )
 }
 
+async function copyToClipboard(text: string) {
+  try {
+    return navigator.clipboard.writeText(text)
+  } catch {
+    const element = document.createElement('textarea')
+    const previouslyFocusedElement = document.activeElement
+
+    element.value = text
+
+    // Prevent keyboard from showing on mobile
+    element.setAttribute('readonly', '')
+
+    element.style.contain = 'strict'
+    element.style.position = 'absolute'
+    element.style.left = '-9999px'
+    element.style.fontSize = '12pt' // Prevent zooming on iOS
+
+    const selection = document.getSelection()
+    const originalRange = selection
+      ? selection.rangeCount > 0 && selection.getRangeAt(0)
+      : null
+
+    document.body.appendChild(element)
+    element.select()
+
+    // Explicit selection workaround for iOS
+    element.selectionStart = 0
+    element.selectionEnd = text.length
+
+    document.execCommand('copy')
+    document.body.removeChild(element)
+
+    if (originalRange) {
+      selection!.removeAllRanges() // originalRange can't be truthy when selection is falsy
+      selection!.addRange(originalRange)
+    }
+
+    // Get the focus back on the previously focused element, if any
+    if (previouslyFocusedElement) {
+      ;(previouslyFocusedElement as HTMLElement).focus()
+    }
+  }
+}
+
 function handleElement(el: HTMLElement) {
   el.onclick = () => {
     const parent = el.parentElement
@@ -38,7 +82,7 @@ function handleElement(el: HTMLElement) {
       text = text.replace(/^ *\$ /gm, '')
     }
 
-    navigator.clipboard.writeText(text).then(() => {
+    copyToClipboard(text).then(() => {
       el.classList.add('copied')
       setTimeout(() => {
         el.classList.remove('copied')