Add Find By Username and Find By Phone Number interstitials.

Co-authored-by: Greyson Parrelli <greyson@signal.org>

app/src/main/java/org/thoughtcrime/securesms/phonenumbers/PhoneNumberVisualTransformation.kt

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.thoughtcrime.securesms.phonenumbers
+
+import androidx.compose.ui.text.AnnotatedString
+import androidx.compose.ui.text.input.OffsetMapping
+import androidx.compose.ui.text.input.TransformedText
+import androidx.compose.ui.text.input.VisualTransformation
+import com.google.i18n.phonenumbers.AsYouTypeFormatter
+import com.google.i18n.phonenumbers.PhoneNumberUtil
+
+/**
+ * Formats the input number according to the regionCode. Assumes the input is all digits.
+ */
+class PhoneNumberVisualTransformation(
+  regionCode: String
+) : VisualTransformation {
+
+  private val asYouTypeFormatter: AsYouTypeFormatter = PhoneNumberUtil.getInstance().getAsYouTypeFormatter(regionCode)
+
+  override fun filter(text: AnnotatedString): TransformedText {
+    asYouTypeFormatter.clear()
+    val output = text.map { asYouTypeFormatter.inputDigit(it) }.lastOrNull() ?: text.text
+
+    return TransformedText(
+      AnnotatedString(output),
+      PhoneNumberOffsetMapping(output)
+    )
+  }
+
+  /**
+   * Each character in our phone number is either a digit or a transformed offset.
+   */
+  private class PhoneNumberOffsetMapping(
+    private val transformed: String
+  ) : OffsetMapping {
+    override fun originalToTransformed(offset: Int): Int {
+      // We need a different algorithm here. We need to take UNTIL we've hit offset digits, and then return the resulting length.
+      var remaining = (offset + 1)
+      return transformed.takeWhile {
+        if (it.isDigit()) {
+          remaining--
+        }
+
+        remaining != 0
+      }.length
+    }
+
+    override fun transformedToOriginal(offset: Int): Int {
+      val substring = transformed.substring(0, offset)
+      val characterCount = substring.count { !it.isDigit() }
+      return offset - characterCount
+    }
+  }
+}