For #4007 - Add ShareController for handling ShareFragment's business logic

`ShareController` defines a contract with all possible `ShareFragment`'s
behavior changes and comes with a default implementation -
`DefaultShareController`.
It is to be delegated by all `ShareFragment`s contained Views' Interactors
following any user interactions.

app/src/main/java/org/mozilla/fenix/share/ShareController.kt

@@ -0,0 +1,104 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.share
+
+import android.content.Intent
+import android.content.Intent.ACTION_SEND
+import android.content.Intent.EXTRA_TEXT
+import android.content.Intent.FLAG_ACTIVITY_NEW_TASK
+import androidx.appcompat.app.AlertDialog
+import androidx.fragment.app.Fragment
+import androidx.navigation.NavController
+import mozilla.components.concept.sync.Device
+import mozilla.components.concept.sync.DeviceEventOutgoing
+import mozilla.components.concept.sync.OAuthAccount
+import org.mozilla.fenix.R
+import org.mozilla.fenix.ext.nav
+import org.mozilla.fenix.share.listadapters.AppShareOption
+
+/**
+ * [ShareFragment] controller.
+ *
+ * Delegated by View Interactors, handles container business logic and operates changes on it.
+ */
+interface ShareController {
+    fun handleShareClosed()
+    fun handleShareToApp(app: AppShareOption)
+    fun handleAddNewDevice()
+    fun handleShareToDevice(device: Device)
+    fun handleShareToAllDevices(devices: List<Device>)
+    fun handleSignIn()
+}
+
+/**
+ * Default behavior of [ShareController]. Other implementations are possible.
+ *
+ * @param fragment the [ShareFragment] instance this controller handles business logic for.
+ * @param tabs the list of [ShareTab]s that can be shared.
+ * @param account the [OAuthAccount] to which tabs can be shared.
+ * @param navController - [NavController] used for navigation.
+ * @param dismiss - callback signalling sharing can be closed.
+ */
+class DefaultShareController(
+    private val fragment: Fragment,
+    private val tabs: List<ShareTab>,
+    private val account: OAuthAccount?,
+    private val navController: NavController,
+    private val dismiss: () -> Unit
+) : ShareController {
+    override fun handleShareClosed() {
+        dismiss()
+    }
+
+    override fun handleShareToApp(app: AppShareOption) {
+        val shareText = tabs.joinToString("\n") { tab -> tab.url }
+
+        val intent = Intent(ACTION_SEND).apply {
+            putExtra(EXTRA_TEXT, shareText)
+            type = "text/plain"
+            flags = FLAG_ACTIVITY_NEW_TASK
+            setClassName(app.packageName, app.activityName)
+        }
+        fragment.startActivity(intent)
+        dismiss()
+    }
+
+    override fun handleAddNewDevice() {
+        AlertDialog.Builder(fragment.requireContext()).apply {
+            setMessage(R.string.sync_connect_device_dialog)
+            setPositiveButton(R.string.sync_confirmation_button) { dialog, _ -> dialog.cancel() }
+            create()
+        }.show()
+    }
+
+    override fun handleShareToDevice(device: Device) {
+        sendTab(device.id)
+        (fragment.activity as ShareFragment.TabsSharedCallback).onTabsShared(tabs.size)
+        dismiss()
+    }
+
+    override fun handleShareToAllDevices(devices: List<Device>) {
+        devices.forEach { device -> sendTab(device.id) }
+        (fragment.activity as ShareFragment.TabsSharedCallback).onTabsShared(tabs.size)
+        dismiss()
+    }
+
+    override fun handleSignIn() {
+        val directions = ShareFragmentDirections.actionShareFragmentToTurnOnSyncFragment()
+        navController.nav(R.id.shareFragment, directions)
+        dismiss()
+    }
+
+    private fun sendTab(deviceId: String) {
+        account?.run {
+            tabs.forEach { tab ->
+                deviceConstellation().sendEventToDeviceAsync(
+                    deviceId,
+                    DeviceEventOutgoing.SendTab(tab.title, tab.url)
+                )
+            }
+        }
+    }
+}

app/src/main/java/org/mozilla/fenix/share/ShareFragment.kt

@@ -16,6 +16,7 @@ import android.view.View
 import android.view.ViewGroup
 import androidx.appcompat.app.AppCompatDialogFragment
 import androidx.lifecycle.lifecycleScope
+import androidx.navigation.fragment.findNavController
 import kotlinx.android.parcel.Parcelize
 import kotlinx.android.synthetic.main.fragment_share.view.*
 import kotlinx.coroutines.Deferred
@@ -27,6 +28,7 @@ import mozilla.components.concept.sync.DeviceType
 import mozilla.components.service.fxa.manager.FxaAccountManager
 import org.mozilla.fenix.R
 import org.mozilla.fenix.ext.components
+import org.mozilla.fenix.ext.requireComponents
 import org.mozilla.fenix.share.listadapters.AppShareOption
 import org.mozilla.fenix.share.listadapters.SyncShareOption
 
@@ -79,8 +81,17 @@ class ShareFragment : AppCompatDialogFragment() {
         }
 
         val tabs = args.tabs?.toList() ?: listOf(ShareTab(args.url!!, args.title ?: ""))
+        val account = requireComponents.backgroundServices.accountManager.authenticatedAccount()
 
-        shareInteractor = ShareInteractor()
+        shareInteractor = ShareInteractor(
+            DefaultShareController(
+                fragment = this,
+                tabs = tabs,
+                navController = findNavController(),
+                account = account,
+                dismiss = ::dismiss
+            )
+        )
 
         if (isSharingToDevicesAvailable(requireContext().applicationContext)) {
             shareToAccountDevicesView = ShareToAccountDevicesView(view.devicesShareLayout, shareInteractor)

app/src/main/java/org/mozilla/fenix/share/ShareInteractor.kt

@@ -10,28 +10,30 @@ import org.mozilla.fenix.share.listadapters.AppShareOption
 /**
  * Interactor for the share screen.
  */
-class ShareInteractor : ShareCloseInteractor, ShareToAccountDevicesInteractor, ShareToAppsInteractor {
+class ShareInteractor(
+    private val controller: ShareController
+) : ShareCloseInteractor, ShareToAccountDevicesInteractor, ShareToAppsInteractor {
     override fun onShareClosed() {
-        TODO("not yet!? implemented")
+        controller.handleShareClosed()
     }
 
     override fun onSignIn() {
-        TODO("not yet!? implemented")
+        controller.handleSignIn()
     }
 
     override fun onAddNewDevice() {
-        TODO("not yet!? implemented")
+        controller.handleAddNewDevice()
     }
 
     override fun onShareToDevice(device: Device) {
-        TODO("not yet!? implemented")
+        controller.handleShareToDevice(device)
     }
 
     override fun onShareToAllDevices(devices: List<Device>) {
-        TODO("not yet!? implemented")
+        controller.handleShareToAllDevices(devices)
     }
 
     override fun onShareToApp(appToShareTo: AppShareOption) {
-        TODO("not yet!? implemented")
+        controller.handleShareToApp(appToShareTo)
     }
 }