Improve stableness

app/src/main/java/com/jerboa/JerboaAppState.kt

@@ -0,0 +1,237 @@
+package com.jerboa
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.Stable
+import androidx.compose.runtime.State
+import androidx.compose.runtime.derivedStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewmodel.compose.viewModel
+import androidx.navigation.NavBackStackEntry
+import androidx.navigation.NavHostController
+import androidx.navigation.compose.rememberNavController
+import com.jerboa.datatypes.types.CommentView
+import com.jerboa.datatypes.types.Community
+import com.jerboa.datatypes.types.PostView
+import com.jerboa.datatypes.types.PrivateMessageView
+import com.jerboa.model.ReplyItem
+import com.jerboa.ui.components.common.Route
+import kotlinx.coroutines.CoroutineScope
+import java.net.URLEncoder
+import java.nio.charset.StandardCharsets
+
+@Composable
+fun rememberJerboaAppState(
+    coroutineScope: CoroutineScope = rememberCoroutineScope(),
+    navController: NavHostController = rememberNavController(),
+): JerboaAppState {
+    return remember(
+        navController,
+        coroutineScope,
+    ) {
+        JerboaAppState(
+            navController,
+            coroutineScope,
+        )
+    }
+}
+
+@Stable
+class JerboaAppState(
+    val navController: NavHostController,
+    val coroutineScope: CoroutineScope,
+) {
+
+    fun toPrivateMessageReply(
+        channel: RouteChannel<PrivateMessageDeps>,
+        privateMessageView: PrivateMessageView,
+    ) {
+        channel.put(privateMessageView)
+        navController.navigate(Route.PRIVATE_MESSAGE_REPLY)
+    }
+
+    fun toCommentReport(id: Int) {
+        navController.navigate(Route.CommentReportArgs.makeRoute(id = "$id"))
+    }
+
+    fun toPostReport(id: Int) {
+        navController.navigate(Route.PostReportArgs.makeRoute(id = "$id"))
+    }
+
+    fun toSettings() = navController.navigate(Route.SETTINGS)
+
+    fun toAccountSettings() = navController.navigate(Route.ACCOUNT_SETTINGS)
+
+    fun toLookAndFeel() = navController.navigate(Route.LOOK_AND_FEEL)
+
+    fun toAbout() = navController.navigate(Route.ABOUT)
+
+    fun toCrashLogs() = navController.navigate(Route.CRASH_LOGS)
+
+    fun toView(url: String) {
+        val encodedUrl = URLEncoder.encode(url, StandardCharsets.UTF_8.name())
+        navController.navigate(Route.ViewArgs.makeRoute(encodedUrl))
+    }
+
+    fun toPostEdit(
+        channel: RouteChannel<PostEditDeps>,
+        postView: PostView,
+    ) {
+        channel.put(postView)
+        navController.navigate(Route.POST_EDIT)
+    }
+
+    fun toCommentEdit(
+        channel: RouteChannel<CommentEditDeps>,
+        commentView: CommentView,
+    ) {
+        channel.put(commentView)
+        navController.navigate(Route.COMMENT_EDIT)
+    }
+
+    fun toSiteSideBar() = navController.navigate(Route.SITE_SIDEBAR)
+
+    fun toCommentReply(
+        channel: RouteChannel<CommentReplyDeps>,
+        replyItem: ReplyItem,
+        isModerator: Boolean,
+    ) {
+        channel.put(replyItem)
+        navController.navigate(Route.CommentReplyArgs.makeRoute(isModerator = "$isModerator"))
+    }
+
+    fun toComment(id: Int) {
+        navController.navigate(Route.CommentArgs.makeRoute(id = "$id"))
+    }
+
+    fun toCreatePost(
+        channel: RouteChannel<CreatePostDeps>,
+        community: Community?,
+    ) {
+        channel.put(community)
+        navController.navigate(Route.CREATE_POST)
+    }
+
+    fun toPost(id: Int) {
+        navController.navigate(Route.PostArgs.makeRoute(id = "$id"))
+    }
+
+    fun toLogin() = navController.navigate(Route.LOGIN)
+
+    fun toHome() = navController.navigate(Route.HOME) { popUpTo(navController.graph.id) }
+
+    fun toInbox() = navController.navigate(Route.INBOX)
+
+    fun toCommunity(id: Int) {
+        navController.navigate(Route.CommunityFromIdArgs.makeRoute(id = "$id"))
+    }
+
+    fun toCommunitySideBar() = navController.navigate(Route.COMMUNITY_SIDEBAR)
+
+    fun toProfile(id: Int, saved: Boolean = false) {
+        navController.navigate(Route.ProfileFromIdArgs.makeRoute(id = "$id", saved = "$saved"))
+    }
+
+    fun toCommunityList(select: Boolean = Route.CommunityListArgs.SELECT_DEFAULT) {
+        navController.navigate(Route.CommunityListArgs.makeRoute(select = "$select"))
+    }
+
+    fun popBackStack(): Boolean = navController.popBackStack()
+
+    fun navigateUp(): Boolean = navController.navigateUp()
+
+    fun openLink(url: String, useCustomTabs: Boolean, usePrivateTabs: Boolean) {
+        openLink(url, navController, useCustomTabs, usePrivateTabs)
+    }
+
+    fun<T> addReturn(key: String, value: T) {
+        navController.previousBackStackEntry?.savedStateHandle?.set(key, gson.toJson(value))
+    }
+
+    fun getBackStackEntry(route: String): NavBackStackEntry {
+        return navController.getBackStackEntry(route)
+    }
+
+    fun toPostWithPopUpTo(postId: Int) {
+        navController.navigate(
+            Route.PostArgs.makeRoute(id = "$postId"),
+        ) {
+            popUpTo(Route.CREATE_POST) { inclusive = true }
+        }
+    }
+
+    fun navigate(route: String) {
+        navController.navigate(route)
+    }
+}
+
+// A view model stored higher up the tree used for moving navigation arguments from one route
+// to another. Since this will be reused, the value inside this should be moved out ASAP.
+// The value inside this will also not survive process death, so should be saved elsewhere.
+class RouteChannel<D> : ViewModel() {
+    private var value: D? = null
+
+    fun put(value: D) {
+        this.value = value
+    }
+
+    fun take(): D? {
+        val value = this.value
+        this.value = null
+        return value
+    }
+}
+
+typealias CreatePostDeps = Community?
+
+typealias CommentReplyDeps = ReplyItem
+
+typealias CommentEditDeps = CommentView
+
+typealias PostEditDeps = PostView
+
+typealias PrivateMessageDeps = PrivateMessageView
+
+@Composable
+fun<D> JerboaAppState.rootChannel(): RouteChannel<D> {
+    // This will create a ViewModel<D> on the fly and will be stored on the nav stack entry
+    //  with route = Route.Graph.ROOT.
+    val root = remember(this.navController.currentBackStackEntry) { this.navController.getBackStackEntry(Route.Graph.ROOT) }
+    return viewModel(root)
+}
+
+@Composable
+inline fun <reified D> JerboaAppState.takeDepsFromRoot(): State<D> {
+    // HACK: the autogen types aren't serializable or parcelable. If they were we don't
+    //  have to do this manual conversion to json and back.
+    // TODO: Fix this once autogen types are serializable or parcelable
+
+    val deps = rootChannel<D>().take()
+
+    // This will survive process death
+    val depsJson = rememberSaveable { gson.toJson(deps) }
+
+    // After process death, deps will be null
+    return remember(depsJson) {
+        derivedStateOf {
+            deps ?: gson.fromJson(depsJson, D::class.java)
+        }
+    }
+}
+
+@Composable
+inline fun<reified T> JerboaAppState.ConsumeReturn(
+    key: String,
+    crossinline consumeBlock: (T) -> Unit,
+) {
+    LaunchedEffect(key) {
+        val savedStateHandle = navController.currentBackStackEntry?.savedStateHandle
+        if (savedStateHandle?.contains(key) == true) {
+            consumeBlock(gson.fromJson(savedStateHandle.get<String>(key), T::class.java))
+            savedStateHandle.remove<String>(key)
+        }
+    }
+}