Automatically add a link card for URLs in the composer (#3566)

* automatically add a link card for urls in the composer

simplify was paste check

use a set

simplify the cross platform reuse

web implementation

remove log

pasting in the middle of a block of text

proper regex

dont re-add immediately after paste and remove

don't use `byteIndex`

lfg

automatically add link card

* `mayBePaste`

* remove accidentally pasted url from comment

src/view/com/composer/text-input/text-input-util.ts

@@ -0,0 +1,59 @@
+export function addLinkCardIfNecessary({
+  uri,
+  newText,
+  cursorLocation,
+  mayBePaste,
+  onNewLink,
+  prevAddedLinks,
+}: {
+  uri: string
+  newText: string
+  cursorLocation: number
+  mayBePaste: boolean
+  onNewLink: (uri: string) => void
+  prevAddedLinks: Set<string>
+}) {
+  // It would be cool if we could just use facet.index.byteEnd, but you know... *upside down smiley*
+  const lastCharacterPosition = findIndexInText(uri, newText) + uri.length
+
+  // If the text being added is not from a paste, then we should only check if the cursor is one
+  // position ahead of the last character. However, if it is a paste we need to check both if it's
+  // the same position _or_ one position ahead. That is because iOS will add a space after a paste if
+  // pasting into the middle of a sentence!
+  const cursorLocationIsOkay =
+    cursorLocation === lastCharacterPosition + 1 || mayBePaste
+
+  // Checking previouslyAddedLinks keeps a card from getting added over and over i.e.
+  // Link card added -> Remove link card -> Press back space -> Press space -> Link card added -> and so on
+
+  // We use the isValidUrl regex below because we don't want to add embeds only if the url is valid, i.e.
+  // http://facebook is a valid url, but that doesn't mean we want to embed it. We should only embed if
+  // the url is a valid url _and_ domain. new URL() won't work for this check.
+  const shouldCheck =
+    cursorLocationIsOkay && !prevAddedLinks.has(uri) && isValidUrlAndDomain(uri)
+
+  if (shouldCheck) {
+    onNewLink(uri)
+    prevAddedLinks.add(uri)
+  }
+}
+
+// https://stackoverflow.com/questions/8667070/javascript-regular-expression-to-validate-url
+// question credit Muhammad Imran Tariq https://stackoverflow.com/users/420613/muhammad-imran-tariq
+// answer credit Christian David https://stackoverflow.com/users/967956/christian-david
+function isValidUrlAndDomain(value: string) {
+  return /^(?:(?:(?:https?|ftp):)?\/\/)(?:\S+(?::\S*)?@)?(?:(?!(?:10|127)(?:\.\d{1,3}){3})(?!(?:169\.254|192\.168)(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z\u00a1-\uffff0-9]-*)*[a-z\u00a1-\uffff0-9]+)(?:\.(?:[a-z\u00a1-\uffff0-9]-*)*[a-z\u00a1-\uffff0-9]+)*(?:\.(?:[a-z\u00a1-\uffff]{2,})))(?::\d{2,5})?(?:[/?#]\S*)?$/i.test(
+    value,
+  )
+}
+
+export function findIndexInText(term: string, text: string) {
+  // This should find patterns like:
+  // HELLO SENTENCE http://google.com/ HELLO
+  // HELLO SENTENCE http://google.com HELLO
+  // http://google.com/ HELLO.
+  // http://google.com/.
+  const pattern = new RegExp(`\\b(${term})(?![/w])`, 'i')
+  const match = pattern.exec(text)
+  return match ? match.index : -1
+}