Merge pull request #6 from github/quote-on-copy

Quote Markdown text on clipboard copy

Author: dgraham

quote-selection.js

@@ -22,6 +22,7 @@ export function install(container: Element) {
   installed += containers.has(container) ? 0 : 1
   containers.set(container, 1)
   document.addEventListener('keydown', quoteSelection)
+  container.addEventListener('copy', onCopy)
 }
 
 export function uninstall(container: Element) {
@@ -30,6 +31,29 @@ export function uninstall(container: Element) {
   if (!installed) {
     document.removeEventListener('keydown', quoteSelection)
   }
+  container.removeEventListener('copy', onCopy)
+}
+
+function onCopy(event: ClipboardEvent) {
+  const target = event.target
+  if (!(target instanceof HTMLElement)) return
+  if (isFormField(target)) return
+
+  const transfer = event.clipboardData
+  if (!transfer) return
+
+  const selection = window.getSelection()
+  let range
+  try {
+    range = selection.getRangeAt(0)
+  } catch (err) {
+    return
+  }
+  const quoted = extractQuote(selection.toString(), range)
+  if (!quoted) return
+
+  transfer.setData('text/plain', quoted.selectionText)
+  event.preventDefault()
 }
 
 function eventIsNotRelevant(event: KeyboardEvent): boolean {
@@ -72,17 +96,47 @@ function quoteSelection(event: KeyboardEvent): void {
 }
 
 export function quote(text: string, range: Range): boolean {
+  const quoted = extractQuote(text, range)
+  if (!quoted) return false
+
+  const {container, selectionText} = quoted
+
+  const dispatched = container.dispatchEvent(
+    new CustomEvent('quote-selection', {
+      bubbles: true,
+      cancelable: true,
+      detail: {range, selectionText}
+    })
+  )
+
+  if (!dispatched) {
+    return true
+  }
+
+  const field = findTextarea(container)
+  if (!field) return false
+
+  insertQuote(selectionText, field)
+  return true
+}
+
+type Quote = {
+  container: Element,
+  selectionText: string
+}
+
+function extractQuote(text: string, range: Range): ?Quote {
   let selectionText = text.trim()
-  if (!selectionText) return false
+  if (!selectionText) return
 
   let focusNode = range.startContainer
-  if (!focusNode) return false
+  if (!focusNode) return
 
   if (focusNode.nodeType !== Node.ELEMENT_NODE) focusNode = focusNode.parentNode
-  if (!(focusNode instanceof Element)) return false
+  if (!(focusNode instanceof Element)) return
 
   const container = findContainer(focusNode)
-  if (!container) return false
+  if (!container) return
 
   const markdownSelector = container.getAttribute('data-quote-markdown')
   if (markdownSelector != null) {
@@ -97,21 +151,10 @@ export function quote(text: string, range: Range): boolean {
     }
   }
 
-  const dispatched = container.dispatchEvent(
-    new CustomEvent('quote-selection', {
-      bubbles: true,
-      cancelable: true,
-      detail: {range, selectionText}
-    })
-  )
-
-  if (!dispatched) {
-    return true
-  }
-
-  const field = findTextarea(container)
-  if (!field) return false
+  return {selectionText, container}
+}
 
+function insertQuote(selectionText: string, field: HTMLTextAreaElement) {
   let quotedText = `> ${selectionText.replace(/\n/g, '\n> ')}\n\n`
   if (field.value) {
     quotedText = `${field.value}\n\n${quotedText}`
@@ -120,8 +163,6 @@ export function quote(text: string, range: Range): boolean {
   field.focus()
   field.selectionStart = field.value.length
   field.scrollTop = field.scrollHeight
-
-  return true
 }
 
 function visible(el: HTMLElement): boolean {