State Management

/**
 * Remember a value across recompositions.
 */
@Composable
fun <T> remember(calculation: () -> T): T

/**
 * Remember a value with a single key for cache invalidation.
 */
@Composable
fun <T> remember(
    key1: Any?,
    calculation: () -> T
): T

/**
 * Remember a value with two keys for cache invalidation.
 */
@Composable
fun <T> remember(
    key1: Any?,
    key2: Any?,
    calculation: () -> T
): T

/**
 * Remember a value with three keys for cache invalidation.
 */
@Composable
fun <T> remember(
    key1: Any?,
    key2: Any?,
    key3: Any?,
    calculation: () -> T
): T

/**
 * Remember a value with arbitrary keys for cache invalidation.
 */
@Composable
fun <T> remember(
    vararg keys: Any?,
    calculation: () -> T
): T

/**
 * Create a mutable state holder with structural equality policy.
 */
fun <T> mutableStateOf(
    value: T,
    policy: SnapshotMutationPolicy<T> = structuralEqualityPolicy()
): MutableState<T>

/**
 * Create a mutable state holder with referential equality policy.
 */
fun <T> mutableStateOf(
    value: T,
    policy: SnapshotMutationPolicy<T> = referentialEqualityPolicy()
): MutableState<T>

/**
 * A state holder that represents a value and allows observation of changes.
 */
interface State<out T> {
    val value: T
}

/**
 * A mutable state holder that can be read and written.
 */
interface MutableState<T> : State<T> {
    override var value: T
    operator fun component1(): T
    operator fun component2(): (T) -> Unit
}

/**
 * Create a derived state that is calculated from other state values.
 */
@Composable
fun <T> derivedStateOf(calculation: () -> T): State<T>

/**
 * Mutation policies for state management.
 */
fun <T> structuralEqualityPolicy(): SnapshotMutationPolicy<T>
fun <T> referentialEqualityPolicy(): SnapshotMutationPolicy<T>
fun <T> neverEqualPolicy(): SnapshotMutationPolicy<T>

/**
 * Policy for determining when state changes trigger recomposition.
 */
interface SnapshotMutationPolicy<T> {
    fun equivalent(a: T, b: T): Boolean
    fun merge(previous: T, current: T, applied: T): T?
}

// Basic state management
@Composable
fun StateExample() {
    // Simple state with remember and mutableStateOf
    var count by remember { mutableStateOf(0) }
    var text by remember { mutableStateOf("") }
    
    Column(
        modifier = Modifier.padding(16.dp),
        verticalArrangement = Arrangement.spacedBy(16.dp)
    ) {
        Text("Count: $count")
        
        Row {
            Button(onClick = { count++ }) {
                Text("Increment")
            }
            Button(onClick = { count-- }) {
                Text("Decrement")
            }
            Button(onClick = { count = 0 }) {
                Text("Reset")
            }
        }
        
        TextField(
            value = text,
            onValueChange = { text = it },
            label = { Text("Enter text") }
        )
        
        Text("Text length: ${text.length}")
    }
}

// Derived state example
@Composable
fun DerivedStateExample() {
    var firstName by remember { mutableStateOf("") }
    var lastName by remember { mutableStateOf("") }
    
    // Derived state that recalculates when firstName or lastName changes
    val fullName by derivedStateOf { 
        "$firstName $lastName".trim()
    }
    
    Column(modifier = Modifier.padding(16.dp)) {
        TextField(
            value = firstName,
            onValueChange = { firstName = it },
            label = { Text("First Name") }
        )
        
        TextField(
            value = lastName,
            onValueChange = { lastName = it },
            label = { Text("Last Name") }
        )
        
        Text("Full Name: $fullName")
        Text("Name is ${if (fullName.isNotEmpty()) "not " else ""}empty")
    }
}

// State with keys for cache invalidation
@Composable
fun KeyedStateExample(userId: String) {
    // State that resets when userId changes
    var userPreferences by remember(userId) {
        mutableStateOf(loadUserPreferences(userId))
    }
    
    // Expensive calculation that only recalculates when specific values change
    val processedData by remember(userPreferences.theme, userPreferences.language) {
        derivedStateOf {
            processUserData(userPreferences.theme, userPreferences.language)
        }
    }
    
    // UI using the state...
}

fun loadUserPreferences(userId: String): UserPreferences = TODO()
fun processUserData(theme: String, language: String): ProcessedData = TODO()

/**
 * Launch a coroutine tied to the composition lifecycle.
 */
@Composable
fun LaunchedEffect(
    key1: Any?,
    block: suspend CoroutineScope.() -> Unit
)

/**
 * Launch a coroutine with multiple keys.
 */
@Composable
fun LaunchedEffect(
    key1: Any?,
    key2: Any?,
    block: suspend CoroutineScope.() -> Unit
)

/**
 * Launch a coroutine with arbitrary keys.
 */
@Composable
fun LaunchedEffect(
    vararg keys: Any?,
    block: suspend CoroutineScope.() -> Unit
)

/**
 * Create and remember a coroutine scope tied to the composition.
 */
@Composable
fun rememberCoroutineScope(): CoroutineScope

/**
 * Create a disposable effect that cleans up when keys change or composition exits.
 */
@Composable
fun DisposableEffect(
    key1: Any?,
    effect: DisposableEffectScope.() -> DisposableEffectResult
)

/**
 * Create a disposable effect with multiple keys.
 */
@Composable
fun DisposableEffect(
    key1: Any?,
    key2: Any?,
    effect: DisposableEffectScope.() -> DisposableEffectResult
)

/**
 * Create a disposable effect with arbitrary keys.
 */
@Composable
fun DisposableEffect(
    vararg keys: Any?,
    effect: DisposableEffectScope.() -> DisposableEffectResult
)

/**
 * Scope for disposable effects.
 */
interface DisposableEffectScope {
    /**
     * Create a disposal callback.
     */
    fun onDispose(onDisposeEffect: () -> Unit): DisposableEffectResult
}

/**
 * Result of a disposable effect.
 */
interface DisposableEffectResult

/**
 * Create a side effect that runs after every recomposition.
 */
@Composable
fun SideEffect(effect: () -> Unit)

// LaunchedEffect for one-time or key-dependent side effects
@Composable
fun LaunchedEffectExample(userId: String) {
    var userData by remember { mutableStateOf<UserData?>(null) }
    var isLoading by remember { mutableStateOf(false) }
    var error by remember { mutableStateOf<String?>(null) }
    
    // Launch effect when userId changes
    LaunchedEffect(userId) {
        isLoading = true
        error = null
        try {
            userData = fetchUserData(userId)
        } catch (e: Exception) {
            error = e.message
        } finally {
            isLoading = false
        }
    }
    
    // One-time effect (runs only once)
    LaunchedEffect(Unit) {
        // Initialize analytics, start location updates, etc.
        initializeApp()
    }
    
    when {
        isLoading -> Text("Loading...")
        error != null -> Text("Error: $error", color = Color.Red)
        userData != null -> UserDataDisplay(userData!!)
        else -> Text("No data")
    }
}

// DisposableEffect for cleanup
@Composable
fun DisposableEffectExample() {
    val lifecycleOwner = LocalLifecycleOwner.current
    
    DisposableEffect(lifecycleOwner) {
        val observer = LifecycleEventObserver { _, event ->
            when (event) {
                Lifecycle.Event.ON_START -> {
                    // Start location updates, register listeners, etc.
                }
                Lifecycle.Event.ON_STOP -> {
                    // Stop location updates, unregister listeners, etc.
                }
                else -> {}
            }
        }
        
        lifecycleOwner.lifecycle.addObserver(observer)
        
        onDispose {
            lifecycleOwner.lifecycle.removeObserver(observer)
        }
    }
}

// RememberCoroutineScope for event-driven coroutines
@Composable
fun CoroutineScopeExample() {
    val scope = rememberCoroutineScope()
    var result by remember { mutableStateOf("") }
    
    Column {
        Button(onClick = {
            scope.launch {
                result = "Loading..."
                try {
                    delay(2000) // Simulate network call
                    result = "Data loaded successfully!"
                } catch (e: Exception) {
                    result = "Error: ${e.message}"
                }
            }
        }) {
            Text("Load Data")
        }
        
        Text(result)
    }
}

// SideEffect for non-compose state synchronization
@Composable
fun SideEffectExample(value: String) {
    // Update external system whenever value changes
    SideEffect {
        // This runs after every recomposition where value might have changed
        updateExternalSystem(value)
    }
}

suspend fun fetchUserData(userId: String): UserData = TODO()
fun initializeApp() = TODO()
fun updateExternalSystem(value: String) = TODO()

/**
 * Remember a value that survives configuration changes.
 */
@Composable
fun <T : Any> rememberSaveable(
    vararg inputs: Any?,
    saver: Saver<T, out Any> = autoSaver(),
    key: String? = null,
    init: () -> T
): T

/**
 * Remember a mutable state that survives configuration changes.
 */
@Composable
fun <T : Any> rememberSaveable(
    vararg inputs: Any?,
    stateSaver: Saver<T, out Any> = autoSaver(),
    key: String? = null,
    init: () -> MutableState<T>
): MutableState<T>

/**
 * Interface for saving and restoring state.
 */
interface Saver<Original, Saveable : Any> {
    fun save(value: Original): Saveable?
    fun restore(value: Saveable): Original?
}

/**
 * Create a Saver using save and restore functions.
 */
fun <Original, Saveable : Any> Saver(
    save: (value: Original) -> Saveable?,
    restore: (value: Saveable) -> Original?
): Saver<Original, Saveable>

/**
 * Create a list saver for collections.
 */
fun <Original, Saveable : Any> listSaver(
    save: (value: Original) -> List<Saveable>,
    restore: (list: List<Saveable>) -> Original?
): Saver<Original, Any>

/**
 * Create a map saver for complex objects.
 */
fun <T : Any> mapSaver(
    save: (value: T) -> Map<String, Any?>,
    restore: (map: Map<String, Any?>) -> T?
): Saver<T, Any>

/**
 * Automatic saver that works with basic types.
 */
fun <T> autoSaver(): Saver<T, Any>

// Basic saveable state
@Composable
fun SaveableStateExample() {
    // This state survives configuration changes
    var count by rememberSaveable { mutableStateOf(0) }
    var text by rememberSaveable { mutableStateOf("") }
    
    Column {
        Text("Count: $count (survives rotation)")
        Button(onClick = { count++ }) {
            Text("Increment")
        }
        
        TextField(
            value = text,
            onValueChange = { text = it },
            label = { Text("Persistent text") }
        )
    }
}

// Custom saver for complex objects
data class UserProfile(
    val name: String,
    val email: String,
    val age: Int
)

val UserProfileSaver = Saver<UserProfile, Map<String, Any>>(
    save = { profile ->
        mapOf(
            "name" to profile.name,
            "email" to profile.email,
            "age" to profile.age
        )
    },
    restore = { map ->
        UserProfile(
            name = map["name"] as String,
            email = map["email"] as String,
            age = map["age"] as Int
        )
    }
)

@Composable
fun CustomSaverExample() {
    var userProfile by rememberSaveable(saver = UserProfileSaver) {
        mutableStateOf(UserProfile("", "", 0))
    }
    
    Column {
        TextField(
            value = userProfile.name,
            onValueChange = { userProfile = userProfile.copy(name = it) },
            label = { Text("Name") }
        )
        
        TextField(
            value = userProfile.email,
            onValueChange = { userProfile = userProfile.copy(email = it) },
            label = { Text("Email") }
        )
        
        // Age input field...
    }
}

// List saver example
val IntListSaver = listSaver<List<Int>, Int>(
    save = { it },
    restore = { it }
)

@Composable
fun ListSaverExample() {
    var numbers by rememberSaveable(saver = IntListSaver) {
        mutableStateOf(listOf<Int>())
    }
    
    Column {
        Button(onClick = { 
            numbers = numbers + (numbers.size + 1)
        }) {
            Text("Add Number")
        }
        
        LazyColumn {
            items(numbers) { number ->
                Text("Number: $number")
            }
        }
    }
}

/**
 * Snapshot state management for batch updates.
 */
object Snapshot {
    /**
     * Take a snapshot of the current state.
     */
    fun takeSnapshot(readObserver: ((Any) -> Unit)? = null): Snapshot
    
    /**
     * Send and apply all changes in a snapshot.
     */
    fun sendApplyNotifications()
    
    /**
     * Create a mutable snapshot for making changes.
     */
    fun takeMutableSnapshot(
        readObserver: ((Any) -> Unit)? = null,
        writeObserver: ((Any) -> Unit)? = null
    ): MutableSnapshot
    
    /**
     * Observe state reads within a block.
     */
    fun <T> observe(
        readObserver: ((Any) -> Unit)?,
        writeObserver: ((Any) -> Unit)? = null,
        block: () -> T
    ): T
    
    /**
     * Run a block without triggering state reads.
     */
    fun <T> withoutReadObservation(block: () -> T): T
    
    /**
     * Run a block with all mutations applied immediately.
     */
    fun <T> withMutableSnapshot(block: MutableSnapshot.() -> T): T
}

/**
 * Create a snapshot state list.
 */
fun <T> mutableStateListOf(vararg elements: T): SnapshotStateList<T>

/**
 * Create a snapshot state map.
 */
fun <K, V> mutableStateMapOf(vararg pairs: Pair<K, V>): SnapshotStateMap<K, V>

/**
 * A list that participates in snapshot state management.
 */
interface SnapshotStateList<T> : MutableList<T>, State<List<T>>

/**
 * A map that participates in snapshot state management.
 */
interface SnapshotStateMap<K, V> : MutableMap<K, V>, State<Map<K, V>>

// State hoisting pattern
@Composable
fun TodoApp() {
    var todos by remember { mutableStateOf(emptyList<Todo>()) }
    var newTodoText by remember { mutableStateOf("") }
    
    Column {
        TodoInput(
            text = newTodoText,
            onTextChange = { newTodoText = it },
            onAddTodo = { 
                if (newTodoText.isNotBlank()) {
                    todos = todos + Todo(id = generateId(), text = newTodoText)
                    newTodoText = ""
                }
            }
        )
        
        TodoList(
            todos = todos,
            onToggleTodo = { todoId ->
                todos = todos.map { todo ->
                    if (todo.id == todoId) {
                        todo.copy(completed = !todo.completed)
                    } else {
                        todo
                    }
                }
            },
            onDeleteTodo = { todoId ->
                todos = todos.filter { it.id != todoId }
            }
        )
    }
}

@Composable
fun TodoInput(
    text: String,
    onTextChange: (String) -> Unit,
    onAddTodo: () -> Unit
) {
    Row {
        TextField(
            value = text,
            onValueChange = onTextChange,
            label = { Text("New todo") },
            modifier = Modifier.weight(1f)
        )
        Button(onClick = onAddTodo) {
            Text("Add")
        }
    }
}

@Composable
fun TodoList(
    todos: List<Todo>,
    onToggleTodo: (String) -> Unit,
    onDeleteTodo: (String) -> Unit
) {
    LazyColumn {
        items(todos) { todo ->
            TodoItem(
                todo = todo,
                onToggle = { onToggleTodo(todo.id) },
                onDelete = { onDeleteTodo(todo.id) }
            )
        }
    }
}

// Using SnapshotStateList for collection state
@Composable
fun StateListExample() {
    val items = remember { mutableStateListOf<String>() }
    
    Column {
        Button(onClick = { 
            items.add("Item ${items.size + 1}")
        }) {
            Text("Add Item")
        }
        
        LazyColumn {
            itemsIndexed(items) { index, item ->
                Row {
                    Text(item, modifier = Modifier.weight(1f))
                    Button(onClick = { items.removeAt(index) }) {
                        Text("Remove")
                    }
                }
            }
        }
    }
}

data class Todo(val id: String, val text: String, val completed: Boolean = false)
fun generateId(): String = UUID.randomUUID().toString()