Composable Preferences rewrite

app/build.gradle.kts

@@ -1,6 +1,7 @@
 import org.gradle.internal.jvm.Jvm
 import org.gradle.internal.os.OperatingSystem
 import org.gradle.nativeplatform.platform.internal.DefaultNativePlatform
+import org.jetbrains.compose.ExperimentalComposeLibrary
 import org.jetbrains.compose.desktop.application.dsl.TargetFormat
 import org.jetbrains.compose.desktop.application.tasks.AbstractJPackageTask
 import org.jetbrains.compose.internal.de.undercouch.gradle.tasks.download.Download
@@ -119,6 +120,8 @@ dependencies {
     implementation(libs.markdown)
     implementation(libs.markdownJVM)
 
+    @OptIn(ExperimentalComposeLibrary::class)
+    testImplementation(compose.uiTest)
     testImplementation(kotlin("test"))
     testImplementation(libs.mockitoKotlin)
     testImplementation(libs.junitJupiter)

app/src/processing/app/Preferences.kt

@@ -2,56 +2,183 @@ package processing.app
 
 import androidx.compose.runtime.*
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.FlowPreview
+import kotlinx.coroutines.flow.debounce
+import kotlinx.coroutines.flow.dropWhile
 import kotlinx.coroutines.launch
 import java.io.File
 import java.io.InputStream
 import java.nio.file.*
 import java.util.Properties
 
+/*
+    The ReactiveProperties class extends the standard Java Properties class
+    to provide reactive capabilities using Jetpack Compose's mutableStateMapOf.
+    This allows UI components to automatically update when preference values change.
+*/
+class ReactiveProperties: Properties() {
+    val snapshotStateMap = mutableStateMapOf<String, String>()
+
+    override fun setProperty(key: String, value: String) {
+        super.setProperty(key, value)
+        snapshotStateMap[key] = value
+    }
+
+    override fun getProperty(key: String): String? {
+        return snapshotStateMap[key] ?: super.getProperty(key)
+    }
+
+    operator fun get(key: String): String? = getProperty(key)
+
+    operator fun set(key: String, value: String) {
+        setProperty(key, value)
+    }
+}
+
+/*
+    A CompositionLocal to provide access to the ReactiveProperties instance
+    throughout the composable hierarchy.
+ */
+val LocalPreferences = compositionLocalOf<ReactiveProperties> { error("No preferences provided") }
 
 const val PREFERENCES_FILE_NAME = "preferences.txt"
 const val DEFAULTS_FILE_NAME = "defaults.txt"
 
-fun PlatformStart(){
-    Platform.inst ?: Platform.init()
-}
+/*
+    This composable function sets up a preferences provider that manages application settings.
+    It initializes the preferences from a file, watches for changes to that file, and saves
+    any updates back to the file. It uses a ReactiveProperties class to allow for reactive
+    updates in the UI when preferences change.
 
+    usage:
+    PreferencesProvider {
+        // Your app content here
+    }
+
+    to access preferences:
+    val preferences = LocalPreferences.current
+    val someSetting = preferences["someKey"] ?: "defaultValue"
+    preferences["someKey"] = "newValue"
+
+    This will automatically save to the preferences file and update any UI components
+    that are observing that key.
+
+    to override the preferences file (for testing, etc)
+        System.setProperty("processing.app.preferences.file", "/path/to/your/preferences.txt")
+    to override the debounce time (in milliseconds)
+        System.setProperty("processing.app.preferences.debounce", "200")
+
+ */
+@OptIn(FlowPreview::class)
 @Composable
-fun loadPreferences(): Properties{
-    PlatformStart()
+fun PreferencesProvider(content: @Composable () -> Unit){
+    val preferencesFileOverride: File? = System.getProperty("processing.app.preferences.file")?.let { File(it) }
+    val preferencesDebounceOverride: Long? = System.getProperty("processing.app.preferences.debounce")?.toLongOrNull()
 
-    val settingsFolder = Platform.getSettingsFolder()
-    val preferencesFile = settingsFolder.resolve(PREFERENCES_FILE_NAME)
+    // Initialize the platform (if not already done) to ensure we have access to the settings folder
+    remember {
+        Platform.init()
+    }
 
+    // Grab the preferences file, creating it if it doesn't exist
+    // TODO: This functionality should be separated from the `Preferences` class itself
+    val settingsFolder = Platform.getSettingsFolder()
+    val preferencesFile = preferencesFileOverride ?: settingsFolder.resolve(PREFERENCES_FILE_NAME)
     if(!preferencesFile.exists()){
+        preferencesFile.mkdirs()
         preferencesFile.createNewFile()
     }
-    watchFile(preferencesFile)
 
-    return Properties().apply {
-        load(ClassLoader.getSystemResourceAsStream(DEFAULTS_FILE_NAME) ?: InputStream.nullInputStream())
-        load(preferencesFile.inputStream())
+    val update = watchFile(preferencesFile)
+
+
+    val properties = remember(preferencesFile, update) {
+        ReactiveProperties().apply {
+            val defaultsStream = ClassLoader.getSystemResourceAsStream(DEFAULTS_FILE_NAME)
+                ?: InputStream.nullInputStream()
+            load(defaultsStream
+                .reader(Charsets.UTF_8)
+            )
+            load(preferencesFile
+                .inputStream()
+                .reader(Charsets.UTF_8)
+            )
+        }
+    }
+
+    val initialState = remember(properties) { properties.snapshotStateMap.toMap() }
+
+    // Listen for changes to the preferences and save them to file
+    LaunchedEffect(properties) {
+        snapshotFlow { properties.snapshotStateMap.toMap() }
+            .dropWhile { it == initialState }
+            .debounce(preferencesDebounceOverride ?: 100)
+            .collect {
+
+                // Save the preferences to file, sorted alphabetically
+                preferencesFile.outputStream().use { output ->
+                    output.write(
+                        properties.entries
+                            .sortedWith(compareBy(String.CASE_INSENSITIVE_ORDER) { it.key.toString() })
+                            .joinToString("\n") { (key, value) -> "$key=$value" }
+                            .toByteArray()
+                    )
+                }
+            }
+    }
+
+    CompositionLocalProvider(LocalPreferences provides properties){
+        content()
     }
+
 }
 
+/*
+    This composable function watches a specified file for modifications. When the file is modified,
+    it updates a state variable with the latest WatchEvent. This can be useful for triggering UI updates
+    or other actions in response to changes in the file.
+
+    To watch the file at the fasted speed (for testing) set the following system property:
+        System.setProperty("processing.app.watchfile.forced", "true")
+ */
 @Composable
 fun watchFile(file: File): Any? {
+    val forcedWatch: Boolean = System.getProperty("processing.app.watchfile.forced").toBoolean()
+
     val scope = rememberCoroutineScope()
     var event by remember(file) {  mutableStateOf<WatchEvent<*>?> (null) }
 
     DisposableEffect(file){
         val fileSystem = FileSystems.getDefault()
         val watcher = fileSystem.newWatchService()
+
         var active = true
 
+        // In forced mode we just poll the last modified time of the file
+        // This is not efficient but works better for testing with temp files
+        val toWatch = { file.lastModified() }
+        var state = toWatch()
+
         val path = file.toPath()
         val parent = path.parent
         val key = parent.register(watcher, StandardWatchEventKinds.ENTRY_MODIFY)
         scope.launch(Dispatchers.IO) {
             while (active) {
-                for (modified in key.pollEvents()) {
-                    if (modified.context() != path.fileName) continue
-                    event = modified
+                if(forcedWatch) {
+                    if(toWatch() == state) continue
+                    state = toWatch()
+                    event = object : WatchEvent<Path> {
+                        override fun count(): Int = 1
+                        override fun context(): Path = file.toPath().fileName
+                        override fun kind(): WatchEvent.Kind<Path> = StandardWatchEventKinds.ENTRY_MODIFY
+                        override fun toString(): String = "ForcedEvent(${context()})"
+                    }
+                    continue
+                }else{
+                    for (modified in key.pollEvents()) {
+                        if (modified.context() != path.fileName) continue
+                        event = modified
+                    }
                 }
             }
         }
@@ -62,12 +189,4 @@ fun watchFile(file: File): Any? {
         }
     }
     return event
-}
-val LocalPreferences = compositionLocalOf<Properties> { error("No preferences provided") }
-@Composable
-fun PreferencesProvider(content: @Composable () -> Unit){
-    val preferences = loadPreferences()
-    CompositionLocalProvider(LocalPreferences provides preferences){
-        content()
-    }
 }