Add view for browsing and unfollowing followed hashtags (#2794)

* Add view for browsing and unfollowing followed hashtags.
Implements #2785

* Improve list interface

* Remove superfluous suspend modifier

* Migrate to paginated loading for followed tags view

* Update app/src/main/java/com/keylesspalace/tusky/components/followedtags/FollowedTagsViewModel.kt

Co-authored-by: Konrad Pozniak <connyduck@users.noreply.github.com>

* Fix unhandled exception when opening the followed tags view while offline

Co-authored-by: Konrad Pozniak <connyduck@users.noreply.github.com>

app/src/main/AndroidManifest.xml

@@ -133,6 +133,7 @@
         <activity android:name=".ListsActivity" />
         <activity android:name=".LicenseActivity" />
         <activity android:name=".FiltersActivity" />
+        <activity android:name=".components.followedtags.FollowedTagsActivity" />
         <activity
             android:name=".components.report.ReportActivity"
             android:windowSoftInputMode="stateAlwaysHidden|adjustResize" />

app/src/main/java/com/keylesspalace/tusky/components/followedtags/FollowedTagsActivity.kt

@@ -0,0 +1,148 @@
+package com.keylesspalace.tusky.components.followedtags
+
+import android.os.Bundle
+import android.util.Log
+import androidx.activity.viewModels
+import androidx.lifecycle.lifecycleScope
+import androidx.paging.LoadState
+import androidx.recyclerview.widget.DividerItemDecoration
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.SimpleItemAnimator
+import at.connyduck.calladapter.networkresult.fold
+import com.google.android.material.snackbar.Snackbar
+import com.keylesspalace.tusky.BaseActivity
+import com.keylesspalace.tusky.R
+import com.keylesspalace.tusky.databinding.ActivityFollowedTagsBinding
+import com.keylesspalace.tusky.di.ViewModelFactory
+import com.keylesspalace.tusky.interfaces.HashtagActionListener
+import com.keylesspalace.tusky.network.MastodonApi
+import com.keylesspalace.tusky.util.hide
+import com.keylesspalace.tusky.util.show
+import com.keylesspalace.tusky.util.viewBinding
+import com.keylesspalace.tusky.util.visible
+import kotlinx.coroutines.flow.collectLatest
+import kotlinx.coroutines.launch
+import java.io.IOException
+import javax.inject.Inject
+
+class FollowedTagsActivity : BaseActivity(), HashtagActionListener {
+    @Inject
+    lateinit var api: MastodonApi
+
+    @Inject
+    lateinit var viewModelFactory: ViewModelFactory
+
+    private val binding by viewBinding(ActivityFollowedTagsBinding::inflate)
+    private val viewModel: FollowedTagsViewModel by viewModels { viewModelFactory }
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+
+        setContentView(binding.root)
+        setSupportActionBar(binding.includedToolbar.toolbar)
+        supportActionBar?.run {
+            setTitle(R.string.title_followed_hashtags)
+            // Back button
+            setDisplayHomeAsUpEnabled(true)
+            setDisplayShowHomeEnabled(true)
+        }
+
+        setupAdapter().let { adapter ->
+            setupRecyclerView(adapter)
+
+            lifecycleScope.launch {
+                viewModel.pager.collectLatest { pagingData ->
+                    adapter.submitData(pagingData)
+                }
+            }
+        }
+    }
+
+    private fun setupRecyclerView(adapter: FollowedTagsAdapter) {
+        binding.followedTagsView.adapter = adapter
+        binding.followedTagsView.setHasFixedSize(true)
+        binding.followedTagsView.layoutManager = LinearLayoutManager(this)
+        binding.followedTagsView.addItemDecoration(DividerItemDecoration(this, DividerItemDecoration.VERTICAL))
+        (binding.followedTagsView.itemAnimator as SimpleItemAnimator).supportsChangeAnimations = false
+    }
+
+    private fun setupAdapter(): FollowedTagsAdapter {
+        return FollowedTagsAdapter(this, viewModel).apply {
+            addLoadStateListener { loadState ->
+                binding.followedTagsProgressBar.visible(loadState.refresh == LoadState.Loading && itemCount == 0)
+
+                if (loadState.refresh is LoadState.Error) {
+                    binding.followedTagsView.hide()
+                    binding.followedTagsMessageView.show()
+                    val errorState = loadState.refresh as LoadState.Error
+                    if (errorState.error is IOException) {
+                        binding.followedTagsMessageView.setup(R.drawable.elephant_offline, R.string.error_network) { retry() }
+                    } else {
+                        binding.followedTagsMessageView.setup(R.drawable.elephant_error, R.string.error_generic) { retry() }
+                    }
+                    Log.w(TAG, "error loading followed hashtags", errorState.error)
+                } else {
+                    binding.followedTagsView.show()
+                    binding.followedTagsMessageView.hide()
+                }
+            }
+        }
+    }
+
+    private fun follow(tagName: String, position: Int) {
+        lifecycleScope.launch {
+            api.followTag(tagName).fold(
+                {
+                    viewModel.tags.add(position, it)
+                    viewModel.currentSource?.invalidate()
+                },
+                {
+                    Snackbar.make(
+                        this@FollowedTagsActivity,
+                        binding.followedTagsView,
+                        getString(R.string.error_following_hashtag_format, tagName),
+                        Snackbar.LENGTH_SHORT
+                    )
+                        .show()
+                }
+            )
+        }
+    }
+
+    override fun unfollow(tagName: String, position: Int) {
+        lifecycleScope.launch {
+            api.unfollowTag(tagName).fold(
+                {
+                    viewModel.tags.removeAt(position)
+                    Snackbar.make(
+                        this@FollowedTagsActivity,
+                        binding.followedTagsView,
+                        getString(R.string.confirmation_hashtag_unfollowed, tagName),
+                        Snackbar.LENGTH_LONG
+                    )
+                        .setAction(R.string.action_undo) {
+                            follow(tagName, position)
+                        }
+                        .show()
+                    viewModel.currentSource?.invalidate()
+                },
+                {
+                    Snackbar.make(
+                        this@FollowedTagsActivity,
+                        binding.followedTagsView,
+                        getString(
+                            R.string.error_unfollowing_hashtag_format,
+                            tagName
+                        ),
+                        Snackbar.LENGTH_SHORT
+                    )
+                        .show()
+                }
+            )
+        }
+    }
+
+    companion object {
+        const val TAG = "FollowedTagsActivity"
+    }
+}

app/src/main/java/com/keylesspalace/tusky/components/followedtags/FollowedTagsAdapter.kt

@@ -0,0 +1,38 @@
+package com.keylesspalace.tusky.components.followedtags
+
+import android.view.LayoutInflater
+import android.view.ViewGroup
+import android.widget.ImageButton
+import android.widget.TextView
+import androidx.paging.PagingDataAdapter
+import androidx.recyclerview.widget.DiffUtil
+import com.keylesspalace.tusky.R
+import com.keylesspalace.tusky.databinding.ItemFollowedHashtagBinding
+import com.keylesspalace.tusky.interfaces.HashtagActionListener
+import com.keylesspalace.tusky.util.BindingHolder
+
+class FollowedTagsAdapter(
+    private val actionListener: HashtagActionListener,
+    private val viewModel: FollowedTagsViewModel,
+) : PagingDataAdapter<String, BindingHolder<ItemFollowedHashtagBinding>>(STRING_COMPARATOR) {
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): BindingHolder<ItemFollowedHashtagBinding> =
+        BindingHolder(ItemFollowedHashtagBinding.inflate(LayoutInflater.from(parent.context), parent, false))
+
+    override fun onBindViewHolder(holder: BindingHolder<ItemFollowedHashtagBinding>, position: Int) {
+        viewModel.tags[position].let { tag ->
+            holder.itemView.findViewById<TextView>(R.id.followed_tag).text = tag.name
+            holder.itemView.findViewById<ImageButton>(R.id.followed_tag_unfollow).setOnClickListener {
+                actionListener.unfollow(tag.name, position)
+            }
+        }
+    }
+
+    override fun getItemCount(): Int = viewModel.tags.size
+
+    companion object {
+        val STRING_COMPARATOR = object : DiffUtil.ItemCallback<String>() {
+            override fun areItemsTheSame(oldItem: String, newItem: String): Boolean = oldItem == newItem
+            override fun areContentsTheSame(oldItem: String, newItem: String): Boolean = oldItem == newItem
+        }
+    }
+}

app/src/main/java/com/keylesspalace/tusky/components/followedtags/FollowedTagsPagingSource.kt

@@ -0,0 +1,16 @@
+package com.keylesspalace.tusky.components.followedtags
+
+import androidx.paging.PagingSource
+import androidx.paging.PagingState
+
+class FollowedTagsPagingSource(private val viewModel: FollowedTagsViewModel) : PagingSource<String, String>() {
+    override fun getRefreshKey(state: PagingState<String, String>): String? = null
+
+    override suspend fun load(params: LoadParams<String>): LoadResult<String, String> {
+        return if (params is LoadParams.Refresh) {
+            LoadResult.Page(viewModel.tags.map { it.name }, null, viewModel.nextKey)
+        } else {
+            LoadResult.Page(emptyList(), null, null)
+        }
+    }
+}

app/src/main/java/com/keylesspalace/tusky/components/followedtags/FollowedTagsRemoteMediator.kt

@@ -0,0 +1,57 @@
+package com.keylesspalace.tusky.components.followedtags
+
+import androidx.paging.ExperimentalPagingApi
+import androidx.paging.LoadType
+import androidx.paging.PagingState
+import androidx.paging.RemoteMediator
+import com.keylesspalace.tusky.entity.HashTag
+import com.keylesspalace.tusky.network.MastodonApi
+import com.keylesspalace.tusky.util.HttpHeaderLink
+import retrofit2.HttpException
+import retrofit2.Response
+
+@OptIn(ExperimentalPagingApi::class)
+class FollowedTagsRemoteMediator(
+    private val api: MastodonApi,
+    private val viewModel: FollowedTagsViewModel,
+) : RemoteMediator<String, String>() {
+    override suspend fun load(
+        loadType: LoadType,
+        state: PagingState<String, String>
+    ): MediatorResult {
+        return try {
+            val response = request(loadType)
+                ?: return MediatorResult.Success(endOfPaginationReached = true)
+
+            return applyResponse(response)
+        } catch (e: Exception) {
+            MediatorResult.Error(e)
+        }
+    }
+
+    private suspend fun request(loadType: LoadType): Response<List<HashTag>>? {
+        return when (loadType) {
+            LoadType.PREPEND -> null
+            LoadType.APPEND -> api.followedTags(maxId = viewModel.nextKey)
+            LoadType.REFRESH -> {
+                viewModel.nextKey = null
+                viewModel.tags.clear()
+                api.followedTags()
+            }
+        }
+    }
+
+    private fun applyResponse(response: Response<List<HashTag>>): MediatorResult {
+        val tags = response.body()
+        if (!response.isSuccessful || tags == null) {
+            return MediatorResult.Error(HttpException(response))
+        }
+
+        val links = HttpHeaderLink.parse(response.headers()["Link"])
+        viewModel.nextKey = HttpHeaderLink.findByRelationType(links, "next")?.uri?.getQueryParameter("max_id")
+        viewModel.tags.addAll(tags)
+        viewModel.currentSource?.invalidate()
+
+        return MediatorResult.Success(endOfPaginationReached = viewModel.nextKey == null)
+    }
+}

app/src/main/java/com/keylesspalace/tusky/components/followedtags/FollowedTagsViewModel.kt

@@ -0,0 +1,33 @@
+package com.keylesspalace.tusky.components.followedtags
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import androidx.paging.ExperimentalPagingApi
+import androidx.paging.Pager
+import androidx.paging.PagingConfig
+import androidx.paging.cachedIn
+import com.keylesspalace.tusky.di.Injectable
+import com.keylesspalace.tusky.entity.HashTag
+import com.keylesspalace.tusky.network.MastodonApi
+import javax.inject.Inject
+
+class FollowedTagsViewModel @Inject constructor (
+    api: MastodonApi
+) : ViewModel(), Injectable {
+    val tags: MutableList<HashTag> = mutableListOf()
+    var nextKey: String? = null
+    var currentSource: FollowedTagsPagingSource? = null
+
+    @OptIn(ExperimentalPagingApi::class)
+    val pager = Pager(
+        config = PagingConfig(pageSize = 100),
+        remoteMediator = FollowedTagsRemoteMediator(api, this),
+        pagingSourceFactory = {
+            FollowedTagsPagingSource(
+                viewModel = this
+            ).also { source ->
+                currentSource = source
+            }
+        },
+    ).flow.cachedIn(viewModelScope)
+}

app/src/main/java/com/keylesspalace/tusky/components/preference/AccountPreferencesFragment.kt

@@ -30,6 +30,7 @@ import com.keylesspalace.tusky.R
 import com.keylesspalace.tusky.TabPreferenceActivity
 import com.keylesspalace.tusky.appstore.EventHub
 import com.keylesspalace.tusky.appstore.PreferenceChangedEvent
+import com.keylesspalace.tusky.components.followedtags.FollowedTagsActivity
 import com.keylesspalace.tusky.components.instancemute.InstanceListActivity
 import com.keylesspalace.tusky.components.login.LoginActivity
 import com.keylesspalace.tusky.components.notifications.currentAccountNeedsMigration
@@ -95,6 +96,20 @@ class AccountPreferencesFragment : PreferenceFragmentCompat(), Injectable {
                 }
             }
 
+            preference {
+                setTitle(R.string.title_followed_hashtags)
+                setIcon(R.drawable.ic_hashtag)
+                setOnPreferenceClickListener {
+                    val intent = Intent(context, FollowedTagsActivity::class.java)
+                    activity?.startActivity(intent)
+                    activity?.overridePendingTransition(
+                        R.anim.slide_from_right,
+                        R.anim.slide_to_left
+                    )
+                    true
+                }
+            }
+
             preference {
                 setTitle(R.string.action_view_mutes)
                 setIcon(R.drawable.ic_mute_24dp)

app/src/main/java/com/keylesspalace/tusky/di/ActivitiesModule.kt

@@ -31,6 +31,7 @@ import com.keylesspalace.tusky.components.account.AccountActivity
 import com.keylesspalace.tusky.components.announcements.AnnouncementsActivity
 import com.keylesspalace.tusky.components.compose.ComposeActivity
 import com.keylesspalace.tusky.components.drafts.DraftsActivity
+import com.keylesspalace.tusky.components.followedtags.FollowedTagsActivity
 import com.keylesspalace.tusky.components.instancemute.InstanceListActivity
 import com.keylesspalace.tusky.components.login.LoginActivity
 import com.keylesspalace.tusky.components.login.LoginWebViewActivity
@@ -103,6 +104,9 @@ abstract class ActivitiesModule {
     @ContributesAndroidInjector
     abstract fun contributesFiltersActivity(): FiltersActivity
 
+    @ContributesAndroidInjector
+    abstract fun contributesFollowedTagsActivity(): FollowedTagsActivity
+
     @ContributesAndroidInjector(modules = [FragmentBuildersModule::class])
     abstract fun contributesReportActivity(): ReportActivity
 

app/src/main/java/com/keylesspalace/tusky/di/ViewModelFactory.kt

@@ -10,6 +10,7 @@ import com.keylesspalace.tusky.components.announcements.AnnouncementsViewModel
 import com.keylesspalace.tusky.components.compose.ComposeViewModel
 import com.keylesspalace.tusky.components.conversation.ConversationsViewModel
 import com.keylesspalace.tusky.components.drafts.DraftsViewModel
+import com.keylesspalace.tusky.components.followedtags.FollowedTagsViewModel
 import com.keylesspalace.tusky.components.login.LoginWebViewViewModel
 import com.keylesspalace.tusky.components.report.ReportViewModel
 import com.keylesspalace.tusky.components.scheduled.ScheduledStatusViewModel
@@ -126,5 +127,10 @@ abstract class ViewModelModule {
     @ViewModelKey(LoginWebViewViewModel::class)
     internal abstract fun loginWebViewViewModel(viewModel: LoginWebViewViewModel): ViewModel
 
+    @Binds
+    @IntoMap
+    @ViewModelKey(FollowedTagsViewModel::class)
+    internal abstract fun followedTagsViewModel(viewModel: FollowedTagsViewModel): ViewModel
+
     // Add more ViewModels here
 }

app/src/main/java/com/keylesspalace/tusky/interfaces/HashtagActionListener.kt

@@ -0,0 +1,5 @@
+package com.keylesspalace.tusky.interfaces
+
+interface HashtagActionListener {
+    fun unfollow(tagName: String, position: Int)
+}

app/src/main/java/com/keylesspalace/tusky/network/MastodonApi.kt

@@ -668,6 +668,14 @@ interface MastodonApi {
     @GET("api/v1/tags/{name}")
     suspend fun tag(@Path("name") name: String): NetworkResult<HashTag>
 
+    @GET("api/v1/followed_tags")
+    suspend fun followedTags(
+        @Query("min_id") minId: String? = null,
+        @Query("since_id") sinceId: String? = null,
+        @Query("max_id") maxId: String? = null,
+        @Query("limit") limit: Int? = null,
+    ): Response<List<HashTag>>
+
     @POST("api/v1/tags/{name}/follow")
     suspend fun followTag(@Path("name") name: String): NetworkResult<HashTag>
 

app/src/main/res/layout/activity_followed_tags.xml

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context="com.keylesspalace.tusky.components.followedtags.FollowedTagsActivity">
+
+    <include
+        android:id="@+id/includedToolbar"
+        layout="@layout/toolbar_basic" />
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/followedTagsView"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        tools:itemCount="5"
+        tools:listitem="@layout/item_followed_hashtag"
+        app:layout_behavior="@string/appbar_scrolling_view_behavior"
+        />
+
+    <com.keylesspalace.tusky.view.BackgroundMessageView
+        android:id="@+id/followedTagsMessageView"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        app:layout_behavior="@string/appbar_scrolling_view_behavior"
+        />
+
+    <ProgressBar
+        android:id="@+id/followedTagsProgressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        app:layout_behavior="@string/appbar_scrolling_view_behavior"
+        />
+
+</androidx.coordinatorlayout.widget.CoordinatorLayout>

app/src/main/res/layout/item_followed_hashtag.xml

@@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="72dp"
+    android:gravity="center_vertical"
+    android:paddingLeft="16dp"
+    android:paddingRight="16dp"
+    >
+
+    <ImageButton
+        android:id="@+id/followed_tag_unfollow"
+        style="@style/TuskyImageButton"
+        android:layout_width="32dp"
+        android:layout_height="32dp"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintRight_toRightOf="parent"
+        android:background="?attr/selectableItemBackgroundBorderless"
+        android:contentDescription="@string/action_unfollow"
+        android:padding="4dp"
+        app:srcCompat="@drawable/ic_person_remove_24dp"
+        />
+
+    <TextView
+        android:id="@+id/followed_tag"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintLeft_toLeftOf="parent"
+        app:layout_constraintRight_toRightOf="parent"
+        android:gravity="center_vertical"
+        android:ellipsize="end"
+        android:maxLines="1"
+        android:textColor="?android:textColorSecondary"
+        android:textSize="?attr/status_text_medium"
+        tools:text="#hashtag" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/values/strings.xml

@@ -24,6 +24,7 @@
     <string name="error_sender_account_gone">Error sending post.</string>
     <string name="error_following_hashtag_format">Error following #%s</string>
     <string name="error_unfollowing_hashtag_format">Error unfollowing #%s</string>
+    <string name="error_following_hashtags_unsupported">This instance does not support following hashtags.</string>
 
     <string name="title_login">Login</string>
     <string name="title_home">Home</string>
@@ -50,6 +51,7 @@
     <string name="title_scheduled_posts">Scheduled posts</string>
     <string name="title_announcements">Announcements</string>
     <string name="title_licenses">Licenses</string>
+    <string name="title_followed_hashtags">Followed Hashtags</string>
 
     <string name="post_username_format">\@%s</string>
     <string name="post_boosted_format">%s boosted</string>
@@ -176,6 +178,7 @@
     <string name="confirmation_unblocked">User unblocked</string>
     <string name="confirmation_unmuted">User unmuted</string>
     <string name="confirmation_domain_unmuted">%s unhidden</string>
+    <string name="confirmation_hashtag_unfollowed">#%s unfollowed</string>
 
     <string name="post_sent">Sent!</string>
     <string name="post_sent_long">Reply sent successfully.</string>
@@ -676,5 +679,6 @@
 
     <string name="instance_rule_info">By logging in you agree to the rules of %s.</string>
     <string name="instance_rule_title">%s rules</string>
+    <string name="action_unfollow_hashtag_format">Unfollow #%s?</string>
 
 </resources>