Show story media previews in the destination picker on the V3 media send flow.

app/src/main/java/org/thoughtcrime/securesms/mediasend/v3/MediaSendV3ForwardFragment.kt

@@ -5,22 +5,51 @@
 
 package org.thoughtcrime.securesms.mediasend.v3
 
+import android.net.Uri
 import android.os.Bundle
 import android.view.View
 import android.view.ViewGroup
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
 import androidx.core.content.ContextCompat
 import androidx.fragment.app.Fragment
+import androidx.fragment.app.FragmentManager
 import androidx.fragment.app.activityViewModels
+import androidx.lifecycle.lifecycleScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import org.signal.core.util.ContentTypeUtil
 import org.signal.core.util.getParcelableArrayListCompat
+import org.signal.core.util.logging.Log
+import org.signal.mediasend.EditorState
 import org.signal.mediasend.MediaRecipientId
 import org.signal.mediasend.MediaSendActivityContract
 import org.signal.mediasend.MediaSendRecipient
+import org.signal.mediasend.MediaSendState
 import org.signal.mediasend.MediaSendViewModel
 import org.thoughtcrime.securesms.R
+import org.thoughtcrime.securesms.contacts.paged.ArbitraryRepository
+import org.thoughtcrime.securesms.contacts.paged.ContactSearchConfiguration
+import org.thoughtcrime.securesms.contacts.paged.ContactSearchData
 import org.thoughtcrime.securesms.contacts.paged.ContactSearchKey
+import org.thoughtcrime.securesms.contacts.paged.ContactSearchState
 import org.thoughtcrime.securesms.conversation.mutiselect.forward.MultiselectForwardFragment
 import org.thoughtcrime.securesms.conversation.mutiselect.forward.MultiselectForwardFragmentArgs
+import org.thoughtcrime.securesms.conversation.mutiselect.forward.SearchConfigurationProvider
+import org.thoughtcrime.securesms.mediasend.v2.stories.StoryMediaPreviews
+import org.thoughtcrime.securesms.scribbles.ImageEditorFragment
 import org.thoughtcrime.securesms.stories.Stories
+import org.thoughtcrime.securesms.util.adapter.mapping.MappingModel
+import org.thoughtcrime.securesms.util.adapter.mapping.compose.MappingEntryProvider
+import org.thoughtcrime.securesms.util.adapter.mapping.compose.rememberMappingEntryProvider
 import org.signal.core.ui.R as CoreUiR
 
 /**
@@ -29,18 +58,51 @@ import org.signal.core.ui.R as CoreUiR
  *
  * Implements the callback interface and uses the shared [MediaSendViewModel] to drive
  * the send flow forward.
+ *
+ * For story sends this also acts as the [SearchConfigurationProvider], swapping the default
+ * destination list for the stories-only list and prepending a preview of the media being posted.
  */
-class MediaSendV3ForwardFragment : Fragment(R.layout.multiselect_forward_activity), MultiselectForwardFragment.Callback {
+class MediaSendV3ForwardFragment : Fragment(R.layout.multiselect_forward_activity), MultiselectForwardFragment.Callback, SearchConfigurationProvider {
+
+  companion object {
+    private val TAG = Log.tag(MediaSendV3ForwardFragment::class)
+
+    private const val PREVIEW_ITEM = "preview_item"
+
+    /** The number of selected media items rendered into the destination picker preview. */
+    private const val PREVIEW_COUNT = 2
+
+    /**
+     * Fixed height of the preview row, so the list does not shift when the asynchronously rendered
+     * previews arrive. Matches the tallest thumbnail in [StoryMediaPreviews] plus its vertical padding.
+     */
+    private val PREVIEW_HEIGHT = 260.dp
+  }
 
   private val viewModel: MediaSendViewModel by activityViewModels {
     MediaSendViewModel.Factory(args = MediaSendActivityContract.Args.fromIntent(requireActivity().intent))
   }
 
+  /**
+   * The rendered story previews. Backed by compose state because rendering the image editor models happens off the main
+   * thread, after the picker has already been composed.
+   */
+  private var storyPreviews: List<Uri> by mutableStateOf(emptyList())
+
+  private val isStory: Boolean get() = viewModel.state.value.isStory
+
+  private val hasPreviewableMedia: Boolean get() = viewModel.state.value.selectedMedia.isNotEmpty()
+
   override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
     super.onViewCreated(view, savedInstanceState)
 
+    val state = viewModel.state.value
+
+    if (state.isStory && storyPreviews.isEmpty()) {
+      renderStoryPreviews(state)
+    }
+
     if (savedInstanceState == null) {
-      val state = viewModel.state.value
       val forwardFragment = MultiselectForwardFragment.create(
         MultiselectForwardFragmentArgs(
           title = R.string.MediaReviewFragment__send_to,
@@ -84,4 +146,97 @@ class MediaSendV3ForwardFragment : Fragment(R.layout.multiselect_forward_activit
   override fun getStorySendRequirements(): Stories.MediaTransform.SendRequirements? {
     return viewModel.getStorySendRequirements().toAppSendRequirements()
   }
+
+  override fun getSearchConfiguration(fragmentManager: FragmentManager, contactSearchState: ContactSearchState): ContactSearchConfiguration? {
+    if (!isStory) {
+      return null
+    }
+
+    return ContactSearchConfiguration.build {
+      query = contactSearchState.query
+
+      addSection(
+        ContactSearchConfiguration.Section.Arbitrary(setOf(PREVIEW_ITEM))
+      )
+
+      addSection(
+        ContactSearchConfiguration.Section.Stories(
+          groupStories = contactSearchState.groupStories,
+          includeHeader = true,
+          headerAction = Stories.getHeaderAction(fragmentManager)
+        )
+      )
+    }
+  }
+
+  override fun getArbitraryRepository(): ArbitraryRepository? {
+    if (!isStory) {
+      return null
+    }
+
+    return object : ArbitraryRepository {
+      /**
+       * Reported as present as soon as there is media to preview, rather than once the previews have finished rendering.
+       * The section size is only sampled while the paged data source is being built, so a size that flipped from zero to
+       * one later on would never be picked up.
+       */
+      override fun getSize(section: ContactSearchConfiguration.Section.Arbitrary, query: String?): Int = if (hasPreviewableMedia) 1 else 0
+
+      override fun getData(
+        section: ContactSearchConfiguration.Section.Arbitrary,
+        query: String?,
+        startIndex: Int,
+        endIndex: Int,
+        totalSearchSize: Int
+      ): List<ContactSearchData.Arbitrary> = if (hasPreviewableMedia) listOf(ContactSearchData.Arbitrary(PREVIEW_ITEM)) else emptyList()
+
+      override fun getMappingModel(arbitrary: ContactSearchData.Arbitrary): MappingModel<*> = PreviewEntryMappingModel()
+    }
+  }
+
+  @Composable
+  override fun getAdditionalEntries(): MappingEntryProvider<Any> {
+    return rememberMappingEntryProvider {
+      entry<PreviewEntryMappingModel> {
+        Box(
+          modifier = Modifier
+            .fillMaxWidth()
+            .height(PREVIEW_HEIGHT)
+        ) {
+          StoryMediaPreviews(previews = storyPreviews)
+        }
+      }
+    }
+  }
+
+  /**
+   * Renders the first [PREVIEW_COUNT] selected media into single-session blobs so the picker shows what is actually
+   * being posted, edits included. Items that aren't routed through the image editor are previewed as-is.
+   */
+  private fun renderStoryPreviews(state: MediaSendState) {
+    val context = requireContext().applicationContext
+
+    viewLifecycleOwner.lifecycleScope.launch {
+      storyPreviews = withContext(Dispatchers.IO) {
+        state.selectedMedia.take(PREVIEW_COUNT).map { media ->
+          val editorState = state.editorStateMap[media.uri]
+          if (ContentTypeUtil.isImageType(media.contentType) && editorState is EditorState.Image) {
+            try {
+              ImageEditorFragment.renderToSingleSessionBlob(context, editorState.model)
+            } catch (e: Exception) {
+              Log.w(TAG, "Failed to render story preview. Falling back to the original media.", e)
+              media.uri
+            }
+          } else {
+            media.uri
+          }
+        }
+      }
+    }
+  }
+
+  private class PreviewEntryMappingModel : MappingModel<PreviewEntryMappingModel> {
+    override fun areItemsTheSame(newItem: PreviewEntryMappingModel): Boolean = true
+    override fun areContentsTheSame(newItem: PreviewEntryMappingModel): Boolean = true
+  }
 }