Add pasting URLs on selected text as Markdown links

Author: steffen

README.md

@@ -1,6 +1,7 @@
 # Paste Markdown objects
 
 - Paste spreadsheet cells and HTML tables as a Markdown tables.
+- Paste URLs on selected text as Markdown links.
 - Paste image URLs as Markdown image links.
 - Paste markdown as markdown. See [`@github/quote-selection`/Preserving markdown syntax](https://github.com/github/quote-selection/tree/9ae5f88f5bc3021f51d2dc9981eca83ce7cfe04f#preserving-markdown-syntax) for details.
 

src/index.ts

@@ -1,4 +1,5 @@
-import {install as installLink, uninstall as uninstallLink} from './paste-markdown-image-link'
+import {install as installImageLink, uninstall as uninstallImageLink} from './paste-markdown-image-link'
+import {install as installLink, uninstall as uninstallLink} from './paste-markdown-link'
 import {install as installTable, uninstall as uninstallTable} from './paste-markdown-table'
 import {install as installText, uninstall as uninstallText} from './paste-markdown-text'
 
@@ -8,12 +9,14 @@ interface Subscription {
 
 export default function subscribe(el: HTMLElement): Subscription {
   installTable(el)
+  installImageLink(el)
   installLink(el)
   installText(el)
 
   return {
     unsubscribe: () => {
       uninstallTable(el)
+      uninstallImageLink(el)
       uninstallLink(el)
       uninstallText(el)
     }

src/paste-markdown-link.ts

@@ -0,0 +1,54 @@
+import {insertText} from './text'
+
+export function install(el: HTMLElement): void {
+  el.addEventListener('paste', onPaste)
+}
+
+export function uninstall(el: HTMLElement): void {
+  el.removeEventListener('paste', onPaste)
+}
+
+function onPaste(event: ClipboardEvent) {
+  const transfer = event.clipboardData
+  if (!transfer || !hasPlainText(transfer)) return
+
+  const field = event.currentTarget
+  if (!(field instanceof HTMLTextAreaElement)) return
+
+  const text = transfer.getData('text/plain')
+  if (!text) return
+
+  if (isWithinLink(field)) return
+
+  event.stopPropagation()
+  event.preventDefault()
+
+  const selectedText = field.value.substring(field.selectionStart, field.selectionEnd)
+
+  insertText(field, linkify(selectedText, text), false)
+}
+
+function hasPlainText(transfer: DataTransfer): boolean {
+  return Array.from(transfer.types).indexOf('text/plain') >= 0
+}
+
+function isWithinLink(textarea: HTMLTextAreaElement): boolean {
+  const selectionStart = textarea.selectionStart || 0
+
+  if (selectionStart > 1) {
+    const previousChars = textarea.value.substring(selectionStart - 2, selectionStart)
+    return previousChars === ']('
+  } else {
+    return false
+  }
+}
+
+function linkify(selectedText: string, text: string): string {
+  return selectedText.length && isURL(text) ? `[${selectedText}](${text})` : text
+}
+
+const URL_RE = /^https?:\/\//i
+
+function isURL(url: string): boolean {
+  return URL_RE.test(url)
+}

src/text.ts

@@ -1,8 +1,8 @@
-export function insertText(textarea: HTMLInputElement | HTMLTextAreaElement, text: string): void {
+export function insertText(textarea: HTMLInputElement | HTMLTextAreaElement, text: string, addNewline = true): void {
   const beginning = textarea.value.substring(0, textarea.selectionStart || 0)
   const remaining = textarea.value.substring(textarea.selectionEnd || 0)
 
-  const newline = beginning.length === 0 || beginning.match(/\n$/) ? '' : '\n'
+  const newline = !addNewline || beginning.length === 0 || beginning.match(/\n$/) ? '' : '\n'
   const textBeforeCursor = beginning + newline + text
 
   textarea.value = textBeforeCursor + remaining