From df581f4c51a164639b146166139d713a8c0f71d8 Mon Sep 17 00:00:00 2001
From: Christian Basler <chrigu.meyer@gmail.com>
Date: Sat, 13 Jan 2018 21:59:20 +0100
Subject: [PATCH] Use observer pattern for label change

---
 app/build.gradle                              |  2 +-
 .../apps/abit/AbstractItemListFragment.kt     |  2 -
 .../java/ch/dissem/apps/abit/ListHolder.kt    |  2 -
 .../java/ch/dissem/apps/abit/MainActivity.kt  | 63 +++++----------
 .../dissem/apps/abit/MessageDetailActivity.kt |  8 +-
 .../dissem/apps/abit/MessageListFragment.kt   | 78 +++++--------------
 .../ch/dissem/apps/abit/service/Singleton.kt  | 51 +++++++++++-
 .../ch/dissem/apps/abit/util/Observable.kt    | 37 +++++++++
 8 files changed, 130 insertions(+), 113 deletions(-)
 create mode 100644 app/src/main/java/ch/dissem/apps/abit/util/Observable.kt

diff --git a/app/build.gradle b/app/build.gradle
index 4b08511..ed4fd3f 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -17,7 +17,7 @@ android {
     buildToolsVersion "26.0.2"
 
     defaultConfig {
-        applicationId "ch.dissem.apps." + appName.toLowerCase()
+        applicationId "ch.dissem.apps.${appName.toLowerCase()}"
         minSdkVersion 19
         targetSdkVersion 27
         versionCode 17
diff --git a/app/src/main/java/ch/dissem/apps/abit/AbstractItemListFragment.kt b/app/src/main/java/ch/dissem/apps/abit/AbstractItemListFragment.kt
index a9cd265..2e919d2 100644
--- a/app/src/main/java/ch/dissem/apps/abit/AbstractItemListFragment.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/AbstractItemListFragment.kt
@@ -127,8 +127,6 @@ abstract class AbstractItemListFragment<L, T> : ListFragment(), ListHolder<L> {
         activatedPosition = position
     }
 
-    override var currentLabel: L? = null
-
     override fun showPreviousList() = false
 
     /**
diff --git a/app/src/main/java/ch/dissem/apps/abit/ListHolder.kt b/app/src/main/java/ch/dissem/apps/abit/ListHolder.kt
index 6e57319..a72ad87 100644
--- a/app/src/main/java/ch/dissem/apps/abit/ListHolder.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/ListHolder.kt
@@ -24,7 +24,5 @@ interface ListHolder<L> {
 
     fun setActivateOnItemClick(activateOnItemClick: Boolean)
 
-    var currentLabel: L?
-
     fun showPreviousList(): Boolean
 }
diff --git a/app/src/main/java/ch/dissem/apps/abit/MainActivity.kt b/app/src/main/java/ch/dissem/apps/abit/MainActivity.kt
index 9296101..2e288dd 100644
--- a/app/src/main/java/ch/dissem/apps/abit/MainActivity.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/MainActivity.kt
@@ -30,6 +30,7 @@ import ch.dissem.apps.abit.drawer.ProfileSelectionListener
 import ch.dissem.apps.abit.listener.ListSelectionListener
 import ch.dissem.apps.abit.repository.AndroidLabelRepository.Companion.LABEL_ARCHIVE
 import ch.dissem.apps.abit.service.Singleton
+import ch.dissem.apps.abit.service.Singleton.currentLabel
 import ch.dissem.apps.abit.synchronization.SyncAdapter
 import ch.dissem.apps.abit.util.Labels
 import ch.dissem.apps.abit.util.NetworkUtils
@@ -89,9 +90,6 @@ class MainActivity : AppCompatActivity(), ListSelectionListener<Serializable> {
     var hasDetailPane: Boolean = false
         private set
 
-    var selectedLabel: Label? = null
-        private set
-
     private lateinit var bmc: BitmessageContext
     private lateinit var accountHeader: AccountHeader
 
@@ -280,14 +278,16 @@ class MainActivity : AppCompatActivity(), ListSelectionListener<Serializable> {
 
             uiThread {
                 if (intent.hasExtra(EXTRA_SHOW_LABEL)) {
-                    selectedLabel = intent.getSerializableExtra(EXTRA_SHOW_LABEL) as Label
-                } else if (selectedLabel == null) {
-                    selectedLabel = labels[0]
+                    currentLabel.value = intent.getSerializableExtra(EXTRA_SHOW_LABEL) as Label
+                } else if (currentLabel.value == null) {
+                    currentLabel.value = labels[0]
                 }
                 for (label in labels) {
                     addLabelEntry(label)
                 }
-                drawer.setSelection(selectedLabel?.id as Long)
+                currentLabel.value?.let {
+                    drawer.setSelection(it.id as Long)
+                }
                 updateUnread()
             }
         }
@@ -295,16 +295,9 @@ class MainActivity : AppCompatActivity(), ListSelectionListener<Serializable> {
 
     override fun onBackPressed() {
         val listFragment = supportFragmentManager.findFragmentById(R.id.item_list)
-        if (listFragment is ListHolder<*>) {
-            val listHolder = listFragment as ListHolder<*>
-            if (listHolder.showPreviousList()) {
-                drawer.getDrawerItem(listHolder.currentLabel)?.let {
-                    drawer.setSelection(it)
-                }
-                return
-            }
+        if (listFragment !is ListHolder<*> || !listFragment.showPreviousList()) {
+            super.onBackPressed()
         }
-        super.onBackPressed()
     }
 
     private inner class DrawerItemClickListener : Drawer.OnDrawerItemClickListener {
@@ -312,13 +305,9 @@ class MainActivity : AppCompatActivity(), ListSelectionListener<Serializable> {
             val itemList = supportFragmentManager.findFragmentById(R.id.item_list)
             val tag = item.tag
             if (tag is Label) {
-                selectedLabel = tag
-                if (itemList is MessageListFragment) {
-                    itemList.updateList(tag)
-                } else {
-                    val listFragment = MessageListFragment()
-                    changeList(listFragment)
-                    listFragment.updateList(tag)
+                currentLabel.value = tag
+                if (itemList !is MessageListFragment) {
+                    changeList(MessageListFragment())
                 }
                 return false
             } else if (item is Nameable<*>) {
@@ -347,33 +336,23 @@ class MainActivity : AppCompatActivity(), ListSelectionListener<Serializable> {
         }
     }
 
-    override fun onSaveInstanceState(savedInstanceState: Bundle) {
-        super.onSaveInstanceState(savedInstanceState)
-        savedInstanceState.putSerializable("selectedLabel", selectedLabel)
-    }
-
-    override fun onRestoreInstanceState(savedInstanceState: Bundle) {
-        selectedLabel = savedInstanceState.getSerializable("selectedLabel") as? Label
-
-        selectedLabel?.let { selectedLabel ->
-            drawer.getDrawerItem(selectedLabel)?.let { selectedItem ->
-                drawer.setSelection(selectedItem)
-            }
-        }
-        super.onRestoreInstanceState(savedInstanceState)
-    }
-
     override fun onResume() {
         updateUnread()
         if (Preferences.isFullNodeActive(this) && Preferences.isConnectionAllowed(this@MainActivity)) {
             NetworkUtils.enableNode(this, false)
         }
         Singleton.getMessageListener(this).resetNotification()
+        currentLabel.addObserver(this) { label ->
+            if (label != null) {
+                drawer.setSelection(label.id as Long)
+            }
+        }
         active = true
         super.onResume()
     }
 
     override fun onPause() {
+        currentLabel.removeObserver(this)
         super.onPause()
         active = false
     }
@@ -471,9 +450,7 @@ class MainActivity : AppCompatActivity(), ListSelectionListener<Serializable> {
             // for the selected item ID.
             val detailIntent = when (item) {
                 is Plaintext -> {
-                    Intent(this, MessageDetailActivity::class.java).apply {
-                        putExtra(EXTRA_SHOW_LABEL, selectedLabel)
-                    }
+                    Intent(this, MessageDetailActivity::class.java)
                 }
                 is BitmessageAddress -> Intent(this, AddressDetailActivity::class.java)
                 else -> throw IllegalArgumentException("Plaintext or BitmessageAddress expected, but was ${item::class.simpleName}")
@@ -521,7 +498,7 @@ class MainActivity : AppCompatActivity(), ListSelectionListener<Serializable> {
          * Runs the given code in the main activity context, if it currently exists. Otherwise,
          * it's ignored.
          */
-        fun apply(run: MainActivity.() -> Unit){
+        fun apply(run: MainActivity.() -> Unit) {
             instance?.get()?.let { run.invoke(it) }
         }
     }
diff --git a/app/src/main/java/ch/dissem/apps/abit/MessageDetailActivity.kt b/app/src/main/java/ch/dissem/apps/abit/MessageDetailActivity.kt
index f8586cb..62d2cec 100644
--- a/app/src/main/java/ch/dissem/apps/abit/MessageDetailActivity.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/MessageDetailActivity.kt
@@ -5,8 +5,6 @@ import android.os.Bundle
 import android.support.v4.app.NavUtils
 import android.view.MenuItem
 
-import ch.dissem.bitmessage.entity.valueobject.Label
-
 
 /**
  * An activity representing a single Message detail screen. This
@@ -18,7 +16,6 @@ import ch.dissem.bitmessage.entity.valueobject.Label
  * more than a [MessageDetailFragment].
  */
 class MessageDetailActivity : DetailActivity() {
-    private var label: Label? = null
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -33,7 +30,6 @@ class MessageDetailActivity : DetailActivity() {
         // http://developer.android.com/guide/components/fragments.html
         //
         if (savedInstanceState == null) {
-            label = intent.getSerializableExtra(MainActivity.EXTRA_SHOW_LABEL) as Label?
             // Create the detail fragment and add it to the activity
             // using a fragment transaction.
             val arguments = Bundle()
@@ -49,9 +45,7 @@ class MessageDetailActivity : DetailActivity() {
 
     override fun onOptionsItemSelected(item: MenuItem) = when (item.itemId) {
         android.R.id.home -> {
-            val parentIntent = Intent(this, MainActivity::class.java)
-            parentIntent.putExtra(MainActivity.EXTRA_SHOW_LABEL, label)
-            NavUtils.navigateUpTo(this, parentIntent)
+            NavUtils.navigateUpTo(this, Intent(this, MainActivity::class.java))
             true
         }
         else -> super.onOptionsItemSelected(item)
diff --git a/app/src/main/java/ch/dissem/apps/abit/MessageListFragment.kt b/app/src/main/java/ch/dissem/apps/abit/MessageListFragment.kt
index a579cd3..b63e991 100644
--- a/app/src/main/java/ch/dissem/apps/abit/MessageListFragment.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/MessageListFragment.kt
@@ -32,6 +32,7 @@ import ch.dissem.apps.abit.adapter.SwipeableMessageAdapter
 import ch.dissem.apps.abit.listener.ListSelectionListener
 import ch.dissem.apps.abit.repository.AndroidMessageRepository
 import ch.dissem.apps.abit.service.Singleton
+import ch.dissem.apps.abit.service.Singleton.currentLabel
 import ch.dissem.apps.abit.util.FabUtils
 import ch.dissem.bitmessage.entity.Plaintext
 import ch.dissem.bitmessage.entity.valueobject.Label
@@ -87,8 +88,6 @@ class MessageListFragment : Fragment(), ListHolder<Label> {
         }
     }
 
-    override var currentLabel: Label? = null
-
     private var emptyTrashMenuItem: MenuItem? = null
     private lateinit var messageRepo: AndroidMessageRepository
     private var activateOnItemClick: Boolean = false
@@ -99,7 +98,7 @@ class MessageListFragment : Fragment(), ListHolder<Label> {
         isLoading = true
         swipeableMessageAdapter?.let { messageAdapter ->
             doAsync {
-                val messages = messageRepo.findMessages(currentLabel, messageAdapter.itemCount, PAGE_SIZE)
+                val messages = messageRepo.findMessages(currentLabel.value, messageAdapter.itemCount, PAGE_SIZE)
                 onUiThread {
                     messageAdapter.addAll(messages)
                     isLoading = false
@@ -121,21 +120,13 @@ class MessageListFragment : Fragment(), ListHolder<Label> {
         initFab(activity)
         messageRepo = Singleton.getMessageRepository(activity)
 
-        if (backStack.isEmpty() && currentLabel == null) {
-            doUpdateList(activity.selectedLabel)
-        }
+        currentLabel.addObserver(this) { new -> doUpdateList(new) }
+        doUpdateList(currentLabel.value)
     }
 
-    override fun updateList(label: Label) {
-        if (currentLabel != null && currentLabel != label && (backStack.isEmpty() || currentLabel != backStack.peek())) {
-            backStack.push(currentLabel)
-        }
-        if (!isResumed) {
-            currentLabel = label
-            return
-        }
-
-        doUpdateList(label)
+    override fun onPause() {
+        currentLabel.removeObserver(this)
+        super.onPause()
     }
 
     private fun doUpdateList(label: Label?) {
@@ -146,7 +137,6 @@ class MessageListFragment : Fragment(), ListHolder<Label> {
             swipeableMessageAdapter?.notifyDataSetChanged()
             return
         }
-        currentLabel = label
         emptyTrashMenuItem?.isVisible = label.type == Label.Type.TRASH
         mainActivity?.apply {
             if ("archive" == label.toString()) {
@@ -238,36 +228,7 @@ class MessageListFragment : Fragment(), ListHolder<Label> {
         recyclerViewSwipeManager = swipeManager
         this.swipeableMessageAdapter = adapter
 
-        Singleton.labeler.listener = { message, added, removed ->
-            swipeableMessageAdapter?.let { swipeableMessageAdapter ->
-                when {
-                    currentLabel?.type == Label.Type.TRASH && added.all { it.type == Label.Type.TRASH } && removed.any { it.type == Label.Type.TRASH } -> {
-                        // work-around for messages that are deleted from trash
-                        swipeableMessageAdapter.remove(message)
-                    }
-                    currentLabel?.type == Label.Type.UNREAD && added.all { it.type == Label.Type.TRASH } -> {
-                        // work-around for messages that are deleted from unread, which already have the unread label removed
-                        swipeableMessageAdapter.remove(message)
-                    }
-                    added.contains(currentLabel) -> {
-                        // in most cases, top should be the correct position, but time will show if
-                        // the message should be properly sorted in
-                        swipeableMessageAdapter.addFirst(message)
-                    }
-                    removed.contains(currentLabel) -> {
-                        swipeableMessageAdapter.remove(message)
-                    }
-                    removed.any { it.type == Label.Type.UNREAD } || added.any { it.type == Label.Type.UNREAD } -> {
-                        swipeableMessageAdapter.update(message)
-                    }
-                }
-            }
-            if (removed.any { it.type == Label.Type.UNREAD } || added.any { it.type == Label.Type.UNREAD }) {
-                MainActivity.apply {
-                    updateUnread()
-                }
-            }
-        }
+        Singleton.updateMessageListAdapterInListener(adapter)
     }
 
     private fun initFab(context: MainActivity) {
@@ -326,24 +287,27 @@ class MessageListFragment : Fragment(), ListHolder<Label> {
     }
 
     override fun onOptionsItemSelected(item: MenuItem): Boolean {
-        currentLabel?.let { currentLabel ->
-            when (item.itemId) {
-                R.id.empty_trash -> {
-                    if (currentLabel.type != Label.Type.TRASH) return true
+        when (item.itemId) {
+            R.id.empty_trash -> {
+                currentLabel.value?.let { label ->
+                    if (label.type != Label.Type.TRASH) return true
 
                     doAsync {
-                        for (message in messageRepo.findMessages(currentLabel)) {
+                        for (message in messageRepo.findMessages(label)) {
                             messageRepo.remove(message)
                         }
 
-                        uiThread { updateList(currentLabel) }
+                        uiThread { doUpdateList(label) }
                     }
-                    return true
                 }
-                else -> return false
+                return true
             }
+            else -> return false
         }
-        return false
+    }
+
+    override fun updateList(label: Label) {
+        currentLabel.value = label
     }
 
     override fun setActivateOnItemClick(activateOnItemClick: Boolean) {
@@ -354,7 +318,7 @@ class MessageListFragment : Fragment(), ListHolder<Label> {
     override fun showPreviousList() = if (backStack.isEmpty()) {
         false
     } else {
-        doUpdateList(backStack.pop())
+        currentLabel.value = backStack.pop()
         true
     }
 }
diff --git a/app/src/main/java/ch/dissem/apps/abit/service/Singleton.kt b/app/src/main/java/ch/dissem/apps/abit/service/Singleton.kt
index 59c60c6..6e48cad 100644
--- a/app/src/main/java/ch/dissem/apps/abit/service/Singleton.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/service/Singleton.kt
@@ -21,14 +21,17 @@ import android.widget.Toast
 import ch.dissem.apps.abit.MainActivity
 import ch.dissem.apps.abit.R
 import ch.dissem.apps.abit.adapter.AndroidCryptography
+import ch.dissem.apps.abit.adapter.SwipeableMessageAdapter
 import ch.dissem.apps.abit.adapter.SwitchingProofOfWorkEngine
 import ch.dissem.apps.abit.listener.MessageListener
 import ch.dissem.apps.abit.pow.ServerPowEngine
 import ch.dissem.apps.abit.repository.*
 import ch.dissem.apps.abit.util.Constants
+import ch.dissem.apps.abit.util.Observable
 import ch.dissem.bitmessage.BitmessageContext
 import ch.dissem.bitmessage.entity.BitmessageAddress
 import ch.dissem.bitmessage.entity.payload.Pubkey
+import ch.dissem.bitmessage.entity.valueobject.Label
 import ch.dissem.bitmessage.networking.nio.NioNetworkHandler
 import ch.dissem.bitmessage.ports.DefaultLabeler
 import ch.dissem.bitmessage.utils.ConversationService
@@ -36,12 +39,54 @@ import ch.dissem.bitmessage.utils.TTL
 import ch.dissem.bitmessage.utils.UnixTime.DAY
 import org.jetbrains.anko.doAsync
 import org.jetbrains.anko.uiThread
+import java.lang.ref.WeakReference
 
 /**
  * Provides singleton objects across the application.
  */
 object Singleton {
-    val labeler = DefaultLabeler()
+    var currentLabel = Observable<Label?>(null).apply {
+        addObserver(this) { _ -> swipeableMessageAdapter = null }
+    }
+
+    private var swipeableMessageAdapter: WeakReference<SwipeableMessageAdapter>? = null
+    val labeler = DefaultLabeler().apply {
+        listener = { message, added, removed ->
+            swipeableMessageAdapter?.get()?.let { swipeableMessageAdapter ->
+                currentLabel.value?.let { label ->
+                    when {
+                        label.type == Label.Type.TRASH
+                            && added.all { it.type == Label.Type.TRASH }
+                            && removed.any { it.type == Label.Type.TRASH } -> {
+                            // work-around for messages that are deleted from trash
+                            swipeableMessageAdapter.remove(message)
+                        }
+                        label.type == Label.Type.UNREAD
+                            && added.all { it.type == Label.Type.TRASH } -> {
+                            // work-around for messages that are deleted from unread, which already have the unread label removed
+                            swipeableMessageAdapter.remove(message)
+                        }
+                        added.contains(label) -> {
+                            // in most cases, top should be the correct position, but time will show if
+                            // the message should be properly sorted in
+                            swipeableMessageAdapter.addFirst(message)
+                        }
+                        removed.contains(label) -> {
+                            swipeableMessageAdapter.remove(message)
+                        }
+                        removed.any { it.type == Label.Type.UNREAD } || added.any { it.type == Label.Type.UNREAD } -> {
+                            swipeableMessageAdapter.update(message)
+                        }
+                    }
+                }
+            }
+            if (removed.any { it.type == Label.Type.UNREAD } || added.any { it.type == Label.Type.UNREAD }) {
+                MainActivity.apply {
+                    updateUnread()
+                }
+            }
+        }
+    }
     var bitmessageContext: BitmessageContext? = null
         private set
     private var conversationService: ConversationService? = null
@@ -75,6 +120,10 @@ object Singleton {
             }
         }
 
+    fun updateMessageListAdapterInListener(adapter: SwipeableMessageAdapter) {
+        swipeableMessageAdapter = WeakReference(adapter)
+    }
+
     fun getMessageListener(ctx: Context) = init({ messageListener }, { messageListener = it }) { MessageListener(ctx) }
 
     fun getLabelRepository(ctx: Context) = getBitmessageContext(ctx).labels as AndroidLabelRepository
diff --git a/app/src/main/java/ch/dissem/apps/abit/util/Observable.kt b/app/src/main/java/ch/dissem/apps/abit/util/Observable.kt
new file mode 100644
index 0000000..1e35955
--- /dev/null
+++ b/app/src/main/java/ch/dissem/apps/abit/util/Observable.kt
@@ -0,0 +1,37 @@
+package ch.dissem.apps.abit.util
+
+import kotlin.properties.Delegates
+
+/**
+ * A simple observable implementation that should be mostly
+ */
+class Observable<T>(value: T) {
+    private val observers = mutableMapOf<Any, (T) -> Unit>()
+
+    var value: T by Delegates.observable(value, { _, old, new ->
+        if (old != new) {
+            observers.values.forEach { it.invoke(new) }
+        }
+    })
+
+    /**
+     * The key will make sure the observer can easily be removed. Usually the key should be either
+     * the object that created the observer, or the observer itself, if it's easily available.
+     *
+     * Note that a map is used for observers, so if you define more than one observer with the same
+     * key, all previous ones will be removed. Also, the observers will be notified in no specific
+     * order.
+     *
+     * To prevent memory leaks, the observer must be removed if it isn't used anymore.
+     */
+    fun addObserver(key: Any, observer: (T) -> Unit) {
+        observers.put(key, observer)
+    }
+
+    /**
+     * Remove the observer that was registered with the given key.
+     */
+    fun removeObserver(key: Any) {
+        observers.remove(key)
+    }
+}