Add content watcher for aztec text

aztec/src/main/kotlin/org/wordpress/aztec/AztecContentChangeWatcher.kt

@@ -0,0 +1,33 @@
+package org.wordpress.aztec
+
+import java.lang.ref.WeakReference
+
+class AztecContentChangeWatcher {
+    private val observers = mutableListOf<WeakReference<AztecTextChangeObserver>>()
+    fun registerObserver(observer: AztecTextChangeObserver) {
+        if (observers.none { it.get() == observer }) {
+            observers.add(WeakReference(observer))
+        }
+    }
+
+    fun unregisterObserver(observer: AztecTextChangeObserver) {
+        observers.removeAll { it.get() == observer }
+    }
+
+    internal fun notifyContentChanged() {
+        val iterator = observers.iterator()
+        while (iterator.hasNext()) {
+            val item = iterator.next()
+            val foundObserver = item.get()
+            if (foundObserver == null) {
+                iterator.remove()
+            } else {
+                foundObserver.onContentChanged()
+            }
+        }
+    }
+
+    interface AztecTextChangeObserver {
+        fun onContentChanged()
+    }
+}

aztec/src/main/kotlin/org/wordpress/aztec/AztecText.kt

@@ -293,6 +293,8 @@ open class AztecText : AppCompatEditText, TextWatcher, UnknownHtmlSpan.OnUnknown
 
     private var focusOnVisible = true
 
+    val contentChangeWatcher = AztecContentChangeWatcher()
+
     interface OnSelectionChangedListener {
         fun onSelectionChanged(selStart: Int, selEnd: Int)
     }
@@ -497,6 +499,8 @@ open class AztecText : AppCompatEditText, TextWatcher, UnknownHtmlSpan.OnUnknown
                     // use HTML from the new text to set the state of the editText directly
                     fromHtml(toFormattedHtml(newText), false)
 
+                    contentChangeWatcher.notifyContentChanged()
+
                     // re-enable MediaDeleted listener
                     enableMediaDeletedListener()
                     // re-enable this very filter
@@ -565,6 +569,7 @@ open class AztecText : AppCompatEditText, TextWatcher, UnknownHtmlSpan.OnUnknown
                 setText("")
                 enableTextChangedListener()
             }
+            contentChangeWatcher.notifyContentChanged()
         }
         return wasStyleRemoved
     }
@@ -627,6 +632,7 @@ open class AztecText : AppCompatEditText, TextWatcher, UnknownHtmlSpan.OnUnknown
             }
 
             override fun afterTextChanged(text: Editable) {
+                contentChangeWatcher.notifyContentChanged()
                 if (isTextChangedListenerDisabled()) {
                     return
                 }
@@ -1024,6 +1030,8 @@ open class AztecText : AppCompatEditText, TextWatcher, UnknownHtmlSpan.OnUnknown
                         .forEach { it.toggle() }
             }
         }
+
+        contentChangeWatcher.notifyContentChanged()
     }
 
     fun contains(format: ITextFormat, selStart: Int = selectionStart, selEnd: Int = selectionEnd): Boolean {
@@ -1128,10 +1136,12 @@ open class AztecText : AppCompatEditText, TextWatcher, UnknownHtmlSpan.OnUnknown
 
     fun redo() {
         history.redo(this)
+        contentChangeWatcher.notifyContentChanged()
     }
 
     fun undo() {
         history.undo(this)
+        contentChangeWatcher.notifyContentChanged()
     }
 
     // Helper ======================================================================================
@@ -1618,6 +1628,7 @@ open class AztecText : AppCompatEditText, TextWatcher, UnknownHtmlSpan.OnUnknown
                 fromHtml(newHtml, false)
                 inlineFormatter.joinStyleSpans(0, length())
             }
+            contentChangeWatcher.notifyContentChanged()
         }
     }
 
@@ -1643,6 +1654,7 @@ open class AztecText : AppCompatEditText, TextWatcher, UnknownHtmlSpan.OnUnknown
         } else {
             linkFormatter.addLink(url, anchor, openInNewWindow, selectionStart, selectionEnd)
         }
+        contentChangeWatcher.notifyContentChanged()
     }
 
     fun removeLink() {

aztec/src/test/kotlin/org/wordpress/aztec/AztecContentChangeWatcherTest.kt

@@ -0,0 +1,73 @@
+package org.wordpress.aztec
+
+import org.junit.Assert.*
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+
+@RunWith(JUnit4::class)
+class AztecContentChangeWatcherTest {
+    private lateinit var aztecContentChangeWatcher: AztecContentChangeWatcher
+    @Before
+    fun setUp() {
+        aztecContentChangeWatcher = AztecContentChangeWatcher()
+    }
+
+    @Test
+    fun `notifies registered observer`() {
+        // Given
+        var contentChanged = false
+        setupRegisteredObserver {
+            contentChanged = true
+        }
+
+        // When
+        aztecContentChangeWatcher.notifyContentChanged()
+
+        // Then
+        assertTrue(contentChanged)
+    }
+
+    @Test
+    fun `does not notify unregistered observer`() {
+        // Given
+        var contentChanged = false
+        val observer = setupRegisteredObserver {
+            contentChanged = true
+        }
+
+        // When
+        aztecContentChangeWatcher.unregisterObserver(observer)
+        aztecContentChangeWatcher.notifyContentChanged()
+
+        // Then
+        assertFalse(contentChanged)
+    }
+
+    @Test
+    fun `observer is garbage collected and reference is lost`() {
+        // Given
+        var contentChanged = false
+        setupRegisteredObserver {
+            contentChanged = true
+        }
+        System.gc()
+
+        // When
+        aztecContentChangeWatcher.notifyContentChanged()
+
+        // Then
+        assertFalse(contentChanged)
+    }
+
+    private fun setupRegisteredObserver(onContentChanged: () -> Unit): AztecContentChangeWatcher.AztecTextChangeObserver {
+        val observer = object : AztecContentChangeWatcher.AztecTextChangeObserver {
+            override fun onContentChanged() {
+                onContentChanged()
+            }
+        }
+        aztecContentChangeWatcher.registerObserver(observer)
+        return observer
+    }
+}