feat: add preferences and send empty state

shared/src/jvmMain/kotlin/com/vnidrop/app/core/FilePicker.jvm.kt

@@ -2,9 +2,12 @@ package com.vnidrop.app.core
 
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.remember
+import java.awt.EventQueue
 import java.awt.FileDialog
 import java.awt.Frame
+import java.awt.KeyboardFocusManager
 import java.io.File
+import javax.swing.JFileChooser
 
 @Composable
 actual fun rememberShareFilePicker(
@@ -13,17 +16,29 @@ actual fun rememberShareFilePicker(
 ): ShareFilePicker = remember(onFilePicked, onError) {
 	object : ShareFilePicker {
 		override fun pickFile() {
-			try {
-				val dialog = FileDialog(null as Frame?, "Select file to share", FileDialog.LOAD)
-				dialog.isVisible = true
-				val directory = dialog.directory
-				val file = dialog.file
-				if (directory != null && file != null) {
-					val selected = File(directory, file)
-					onFilePicked(PickedShareFile(selected.absolutePath, selected.name))
-				}
-			} catch (error: Throwable) {
-				onError(error.message ?: error.toString())
+			openPicker(onError) {
+				pickShareFile()?.let(onFilePicked)
+			}
+		}
+	}
+}
+
+@Composable
+actual fun rememberReceiveFolderPicker(
+	onFolderPicked: (ReceiveFolder) -> Unit,
+	onError: (String) -> Unit,
+): ReceiveFolderPicker = remember(onFolderPicked, onError) {
+	object : ReceiveFolderPicker {
+		override fun pickFolder() {
+			openPicker(onError) {
+				val selected = pickDirectory() ?: return@openPicker
+				onFolderPicked(
+					ReceiveFolder(
+						kind = ReceiveFolderKind.FileSystemPath,
+						value = selected.absolutePath,
+						displayName = selected.name.ifBlank { selected.absolutePath },
+					),
+				)
 			}
 		}
 	}
@@ -37,3 +52,85 @@ actual suspend fun sharePickedFile(
 ) {
 	repository.sharePath(file.value, transferName, senderName)
 }
+
+private fun openPicker(
+	onError: (String) -> Unit,
+	block: () -> Unit,
+) {
+	EventQueue.invokeLater {
+		try {
+			block()
+		} catch (error: Throwable) {
+			onError(error.message ?: error.toString())
+		}
+	}
+}
+
+private fun nativeFileDialog(title: String): FileDialog =
+	FileDialog(activeFrame(), title, FileDialog.LOAD)
+
+private fun activeFrame(): Frame? {
+	val activeWindow = KeyboardFocusManager.getCurrentKeyboardFocusManager().activeWindow
+	return activeWindow as? Frame
+		?: Frame.getFrames().firstOrNull { it.isActive || it.isFocused }
+		?: Frame.getFrames().firstOrNull { it.isVisible }
+}
+
+private fun pickShareFile(): PickedShareFile? {
+	val dialog = nativeFileDialog("Select file to share")
+	return try {
+		dialog.isVisible = true
+		val directory = dialog.directory
+		val file = dialog.file
+		if (directory != null && file != null) {
+			val selected = File(directory, file)
+			PickedShareFile(selected.absolutePath, selected.name)
+		} else {
+			null
+		}
+	} finally {
+		dialog.dispose()
+	}
+}
+
+private fun pickDirectory(): File? =
+	if (isMacOs()) {
+		val dialog = withMacDirectoryDialog {
+			nativeFileDialog("Select receive folder").apply { isVisible = true }
+		}
+		try {
+			val directory = dialog.directory ?: return null
+			dialog.file
+				?.let { File(directory, it) }
+				?: File(directory)
+		} finally {
+			dialog.dispose()
+		}
+	} else {
+		val chooser = JFileChooser().apply {
+			dialogTitle = "Select receive folder"
+			fileSelectionMode = JFileChooser.DIRECTORIES_ONLY
+			isAcceptAllFileFilterUsed = false
+		}
+		if (chooser.showOpenDialog(null) == JFileChooser.APPROVE_OPTION) chooser.selectedFile else null
+	}
+
+private fun <T> withMacDirectoryDialog(block: () -> T): T {
+	if (!isMacOs()) return block()
+
+	val key = "apple.awt.fileDialogForDirectories"
+	val previous = System.getProperty(key)
+	System.setProperty(key, "true")
+	return try {
+		block()
+	} finally {
+		if (previous == null) {
+			System.clearProperty(key)
+		} else {
+			System.setProperty(key, previous)
+		}
+	}
+}
+
+private fun isMacOs(): Boolean =
+	System.getProperty("os.name").startsWith("Mac", ignoreCase = true)

shared/src/jvmMain/kotlin/com/vnidrop/app/core/FileSystemService.jvm.kt

@@ -0,0 +1,30 @@
+package com.vnidrop.app.core
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import uniffi.vnidrop.ReceiveOutputSink
+import java.io.File
+
+@Composable
+actual fun rememberFileSystemService(): FileSystemService =
+	remember { JvmFileSystemService() }
+
+private class JvmFileSystemService : FileSystemService {
+	override fun defaultReceiveFolder(): ReceiveFolder =
+		ReceiveFolder(
+			kind = ReceiveFolderKind.FileSystemPath,
+			value = File(System.getProperty("user.home"), "Downloads").absolutePath,
+			displayName = "Downloads",
+		)
+
+	override suspend fun validateReceiveFolder(folder: ReceiveFolder): FolderAccessStatus {
+		if (folder.kind != ReceiveFolderKind.FileSystemPath) return FolderAccessStatus.Unavailable
+		return runCatching {
+			val directory = File(folder.value)
+			if (!directory.exists()) directory.mkdirs()
+			if (directory.isDirectory && directory.canWrite()) FolderAccessStatus.Writable else FolderAccessStatus.Unavailable
+		}.getOrDefault(FolderAccessStatus.Unavailable)
+	}
+
+	override fun createReceiveOutputSink(folder: ReceiveFolder): ReceiveOutputSink? = null
+}