MindMachine/app/src/main/java/com/mindmachine/mvp/MainActivity.kt

package solutions.tretter.mindmachine

import android.app.Activity
import android.content.pm.ActivityInfo
import android.os.Bundle
import android.view.WindowManager
import androidx.activity.ComponentActivity
import androidx.activity.compose.BackHandler
import androidx.activity.compose.setContent
import androidx.activity.viewModels
import androidx.compose.foundation.background
import solutions.tretter.mindmachine.session.DurationSliderCard
import solutions.tretter.mindmachine.session.SetupTimelineEditor
import androidx.compose.foundation.clickable
import androidx.compose.foundation.gestures.detectTapGestures
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.ColumnScope
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.WindowInsets
import androidx.compose.foundation.layout.fillMaxHeight
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.width
import androidx.compose.foundation.layout.navigationBars
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.safeDrawingPadding
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.layout.statusBars
import androidx.compose.foundation.layout.windowInsetsPadding
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.verticalScroll
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.items
import androidx.compose.foundation.Image
import androidx.compose.foundation.Image
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.Add
import androidx.compose.material.icons.filled.Delete
import androidx.compose.material.icons.filled.PlayArrow
import androidx.compose.material.icons.filled.Settings
import androidx.compose.ui.res.painterResource
import androidx.compose.material3.AlertDialog
import androidx.compose.material3.Button
import androidx.compose.material3.Card
import androidx.compose.material3.CardDefaults
import androidx.compose.material3.Checkbox
import androidx.compose.material3.ExperimentalMaterial3Api
import androidx.compose.material3.HorizontalDivider
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.LinearProgressIndicator
import androidx.compose.material3.OutlinedButton
import androidx.compose.material3.SegmentedButton
import androidx.compose.material3.SingleChoiceSegmentedButtonRow
import androidx.compose.material3.Slider
import androidx.compose.material3.Text
import androidx.compose.material3.TextButton
import androidx.compose.material3.TextField
import androidx.compose.material3.TopAppBar
import androidx.compose.material3.darkColorScheme
import androidx.compose.runtime.Composable
import androidx.compose.runtime.DisposableEffect
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableIntStateOf
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.produceState
import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberUpdatedState
import androidx.compose.runtime.setValue
import androidx.compose.runtime.withFrameNanos
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.input.pointer.pointerInput
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.platform.LocalLifecycleOwner
import androidx.compose.ui.semantics.contentDescription
import androidx.compose.ui.semantics.semantics
import androidx.compose.ui.unit.dp
import androidx.compose.ui.layout.ContentScale
import androidx.core.view.WindowCompat
import androidx.core.view.WindowInsetsCompat
import androidx.core.view.WindowInsetsControllerCompat
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleEventObserver
import androidx.lifecycle.compose.collectAsStateWithLifecycle
import androidx.lifecycle.lifecycleScope
import androidx.lifecycle.viewmodel.compose.viewModel
import androidx.navigation.NavType
import androidx.navigation.compose.NavHost
import androidx.navigation.compose.composable
import androidx.navigation.compose.rememberNavController
import androidx.navigation.navArgument
import com.google.android.gms.ads.MobileAds
import solutions.tretter.mindmachine.audio.BinauralAudioEngine
import solutions.tretter.mindmachine.audio.HeadsetMonitor
import solutions.tretter.mindmachine.ads.AdBanner
import solutions.tretter.mindmachine.ads.rememberInterstitialController
import solutions.tretter.mindmachine.data.SettingsRepository
import solutions.tretter.mindmachine.data.UserProgramRepository
import solutions.tretter.mindmachine.domain.RuntimeState
import solutions.tretter.mindmachine.session.FlashColor
import solutions.tretter.mindmachine.session.MainViewModel
import solutions.tretter.mindmachine.session.SplitFlashFrame
import kotlinx.coroutines.launch
import solutions.tretter.mindmachine.session.SplitFlashSequencer
import solutions.tretter.mindmachine.session.flashIntervalMsToSeconds
import solutions.tretter.mindmachine.session.flashIntervalSecondsToMs
import solutions.tretter.mindmachine.session.formatDuration
import solutions.tretter.mindmachine.session.sessionProgressFraction
import solutions.tretter.mindmachine.session.shouldShowActiveControlsByDefault
import solutions.tretter.mindmachine.session.shouldUseImmersiveFullscreen
import kotlinx.coroutines.delay
import kotlin.math.roundToInt
import java.util.Locale


private const val SESSION_ENTRY_HOME = "home"
private const val SESSION_ENTRY_SETUP = "setup"

private val MindMachineColors = darkColorScheme(
    primary = Color(0xFF8AB4FF),
    onPrimary = Color(0xFF001B3D),
    primaryContainer = Color(0xFF004689),
    onPrimaryContainer = Color(0xFFD7E3FF),
    secondary = Color(0xFFFFD166),
    onSecondary = Color(0xFF2E2300),
    background = Color(0xFF05070D),
    onBackground = Color(0xFFF3F6FF),
    surface = Color(0xFF121621),
    onSurface = Color(0xFFF3F6FF),
    error = Color(0xFFFF6B6B),
    onError = Color(0xFF3A0002)
)

class MainActivity : ComponentActivity() {
    private val settingsRepo by lazy { SettingsRepository(applicationContext) }
    private val billingManager by lazy {
        solutions.tretter.mindmachine.billing.BillingManager(
            applicationContext,
            onNoAdsEntitlementChanged = { hasNoAds ->
                lifecycleScope.launch { settingsRepo.updateNoAds(hasNoAds) }
            },
        )
    }

    private val vm: MainViewModel by viewModels {
        MainViewModel.Factory(
            settingsRepo,
            UserProgramRepository(applicationContext),
            HeadsetMonitor(applicationContext),
            BinauralAudioEngine(),
            billingManager,
        )
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        MobileAds.initialize(this) {}
        setContent {
            MaterialTheme(colorScheme = MindMachineColors) {
                App(vm, billingManager)
            }
        }
    }
}

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun App(vm: MainViewModel = viewModel(), billingManager: solutions.tretter.mindmachine.billing.BillingManager) {
    val nav = rememberNavController()
    val ui by vm.ui.collectAsStateWithLifecycle()
    val lifecycle = LocalLifecycleOwner.current.lifecycle
    val activity = LocalContext.current as? Activity

    DisposableEffect(lifecycle, activity, ui.runtimeState) {
        val observer = LifecycleEventObserver { _, event ->
            val appActuallyBackgrounded = activity?.isChangingConfigurations != true
            if (
                event == Lifecycle.Event.ON_STOP &&
                ui.runtimeState == RuntimeState.RUNNING &&
                appActuallyBackgrounded
            ) {
                vm.pause("Session paused because app moved to background.")
            }
        }
        lifecycle.addObserver(observer)
        onDispose { lifecycle.removeObserver(observer) }
    }

    if (!ui.settingsInitialized) {
        Box(
            modifier = Modifier
                .fillMaxSize()
                .background(MaterialTheme.colorScheme.background)
        )
        return
    }

    val startRoute = if (ui.settings.safetyAcknowledged) "home" else "safety"
    NavHost(navController = nav, startDestination = startRoute, modifier = Modifier.background(MaterialTheme.colorScheme.background)) {
        composable("safety") {
            SafetyScreen(
                onAck = {
                    vm.acknowledgeSafety()
                    nav.navigate("home") { popUpTo(0) }
                },
                onHolder = { nav.navigate("holder") }
            )
        }
        composable("home") {
            var confirmDeleteProgramId by remember { mutableStateOf<String?>(null) }
            var confirmDeleteProgramName by remember { mutableStateOf("") }
            val interstitial = rememberInterstitialController(enabled = !ui.settings.noAds)

            Column(
                Modifier
                    .fillMaxSize()
                    .safeDrawingPadding()
            ) {
                TopAppBar(
                    title = {
                        Row(verticalAlignment = Alignment.CenterVertically) {
                            Image(
                                painter = painterResource(R.drawable.ic_app_logo),
                                contentDescription = "MindMachine",
                                modifier = Modifier.size(60.dp)
                            )
                            Spacer(Modifier.width(8.dp))
                            Text("MindMachine")
                        }
                    },
                    actions = {
                    IconButton(
                        onClick = {
                            vm.createNewProgramDraft()
                            nav.navigate("setup")
                        }
                    ) {
                        Icon(Icons.Filled.Add, contentDescription = "Add")
                    }
                    IconButton(onClick = { nav.navigate("settings") }) {
                        Icon(Icons.Filled.Settings, contentDescription = "Settings")
                    }
                }
                )
                LazyColumn(
                    Modifier
                        .weight(1f)
                        .padding(12.dp),
                    verticalArrangement = Arrangement.spacedBy(8.dp)
                ) {
                    item {
                        TextButton(onClick = { nav.navigate("holder") }) { Text("User Guidance/Disclaimer") }
                    }
                    items(ui.presets) { p ->
                        Card(
                            colors = CardDefaults.cardColors(
                                containerColor = MaterialTheme.colorScheme.surface,
                                contentColor = MaterialTheme.colorScheme.onSurface
                            ),
                            modifier = Modifier.fillMaxWidth().clickable {
                                vm.choosePreset(p.id)
                                nav.navigate("setup")
                            }.padding(4.dp)
                        ) {
                            Row(
                                modifier = Modifier.fillMaxWidth().padding(12.dp),
                                horizontalArrangement = Arrangement.SpaceBetween,
                                verticalAlignment = Alignment.CenterVertically,
                            ) {
                                Column(Modifier.weight(1f)) {
                                    Text(p.name, style = MaterialTheme.typography.titleMedium)
                                    Text(p.description)
                                    Text("${formatDuration(p.defaultDurationSec)} • ${p.visualPatternType} • binaural ${formatMaxTwoDecimals(p.binauralDifferenceHz)}")
                                }
                                Row(
                                    verticalAlignment = Alignment.CenterVertically,
                                    horizontalArrangement = Arrangement.spacedBy(8.dp)
                                ) {
                                    IconButton(
                                        onClick = {
                                            val go = {
                                                val started = vm.startSessionFromProgramSelection(p.id)
                                                if (started) {
                                                    nav.navigate("active/$SESSION_ENTRY_HOME")
                                                }
                                            }

                                            if (ui.settings.noAds) {
                                                go()
                                            } else {
                                                interstitial?.show(onDone = go) ?: go()
                                            }
                                        },
                                        modifier = Modifier.size(48.dp)
                                    ) {
                                        Icon(
                                            imageVector = Icons.Filled.PlayArrow,
                                            contentDescription = "Play ${p.name}",
                                            tint = Color(0xFF4CAF50),
                                            modifier = Modifier.size(38.dp)
                                        )
                                    }
                                    Box(
                                        modifier = Modifier
                                            .size(24.dp)
                                            .clickable {
                                                confirmDeleteProgramId = p.id
                                                confirmDeleteProgramName = p.name
                                            },
                                        contentAlignment = Alignment.Center
                                    ) {
                                        Icon(
                                            imageVector = Icons.Filled.Delete,
                                            contentDescription = "Delete ${p.name}",
                                            tint = Color(0xFFFF5252),
                                            modifier = Modifier.fillMaxSize()
                                        )
                                    }
                                }
                            }
                        }
                    }
                }

                AdBanner(
                    enabled = !ui.settings.noAds,
                    modifier = Modifier.fillMaxWidth()
                )
            }

            if (confirmDeleteProgramId != null) {
                AlertDialog(
                    onDismissRequest = {
                        confirmDeleteProgramId = null
                        confirmDeleteProgramName = ""
                    },
                    title = { Text("Delete program?") },
                    text = { Text("Delete \"$confirmDeleteProgramName\"?") },
                    confirmButton = {
                        TextButton(onClick = {
                            confirmDeleteProgramId?.let(vm::deleteProgram)
                            confirmDeleteProgramId = null
                            confirmDeleteProgramName = ""
                        }) {
                            Text("Delete", color = Color(0xFFFF5252))
                        }
                    },
                    dismissButton = {
                        TextButton(onClick = {
                            confirmDeleteProgramId = null
                            confirmDeleteProgramName = ""
                        }) { Text("Cancel") }
                    }
                )
            }
        }
        composable("setup") {
            val interstitial = rememberInterstitialController(enabled = !ui.settings.noAds)
            SetupScreen(
                vm = vm,
                onStart = {
                    val go = {
                        val started = vm.startSession()
                        if (started) {
                            nav.navigate("active/$SESSION_ENTRY_SETUP")
                        }
                    }

                    if (ui.settings.noAds) {
                        go()
                    } else {
                        interstitial?.show(onDone = go) ?: go()
                    }
                },
            )
        }
        composable(
            route = "active/{entryPoint}",
            arguments = listOf(navArgument("entryPoint") { type = NavType.StringType })
        ) { backStackEntry ->
            val entryPoint = backStackEntry.arguments?.getString("entryPoint") ?: SESSION_ENTRY_SETUP
            ActiveSessionScreen(
                vm = vm,
                onFinish = {
                    nav.navigate(entryPoint) {
                        popUpTo("active/$entryPoint") { inclusive = true }
                        launchSingleTop = true
                    }
                },
                onBackToEntry = {
                    vm.stop()
                    nav.navigate(entryPoint) {
                        popUpTo("active/$entryPoint") { inclusive = true }
                        launchSingleTop = true
                    }
                }
            )
        }
        composable("settings") {
            SettingsScreen(vm, onRemoveAds = { nav.navigate("remove_ads") })
        }
        composable("remove_ads") {
            RemoveAdsScreen(billingManager = billingManager, vm = vm)
        }
        composable("holder") {
            PositioningScreen()
        }
    }
}

@Composable
fun SimpleScreen(title: String, subtitle: String, actions: @Composable ColumnScope.() -> Unit) {
    Column(
        modifier = Modifier
            .fillMaxSize()
            .background(MaterialTheme.colorScheme.background)
            .safeDrawingPadding()
            .padding(16.dp),
        verticalArrangement = Arrangement.spacedBy(12.dp),
    ) {
        Text(title, style = MaterialTheme.typography.headlineMedium, color = MaterialTheme.colorScheme.onBackground)
        Text(subtitle, color = MaterialTheme.colorScheme.onBackground)
        actions()
    }
}

@Composable
fun SafetyScreen(onAck: () -> Unit, onHolder: () -> Unit) {
    var checked by remember { mutableStateOf(false) }
    Column(
        Modifier
            .fillMaxSize()
            .background(MaterialTheme.colorScheme.background)
            .safeDrawingPadding()
            .padding(16.dp)
    ) {
        Text("Read before using MindMachine", style = MaterialTheme.typography.headlineSmall, color = MaterialTheme.colorScheme.onBackground)
        Spacer(Modifier.height(12.dp))
        Text(
            "Flashing lights may be unsafe for people with epilepsy, seizure sensitivity, or migraine triggers.\n\nDo not use while driving, walking, cycling, or operating machinery.\n\nFor immersive visual sessions, keep your eyes closed. Do not stare at the screen.\n\nDo not place the phone directly on your eyes. Avoid pressure on face/eyes and ensure comfortable breathing/airflow.\n\nUse at your own risk. This app is a prototype and not a medical device.\n\nStop immediately for discomfort, dizziness, headache, nausea, anxiety, or eye strain.\n\nBinaural mode requires stereo headphones.",
            color = MaterialTheme.colorScheme.onBackground
        )
        Row(verticalAlignment = Alignment.CenterVertically) {
            Checkbox(checked = checked, onCheckedChange = { checked = it })
            Text("I understand the risks and will stop immediately if I feel discomfort.", color = MaterialTheme.colorScheme.onBackground)
        }
        Button(onClick = onAck, enabled = checked, modifier = Modifier.semantics { contentDescription = "I Understand" }) { Text("I Understand") }
        TextButton(onClick = onHolder) { Text("Positioning Guidance") }
    }
}

@Composable
fun SetupScreen(
    vm: MainViewModel,
    onStart: () -> Unit,
) {
    val ui by vm.ui.collectAsStateWithLifecycle()
    val scrollState = rememberScrollState()
    val containerModifier = Modifier
        .fillMaxSize()
        .background(MaterialTheme.colorScheme.background)
        .windowInsetsPadding(WindowInsets.statusBars)
        .windowInsetsPadding(WindowInsets.navigationBars)
        .then(if (setupScreenUsesScrollableContainer()) Modifier.verticalScroll(scrollState) else Modifier)
        .padding(horizontal = 16.dp, vertical = 12.dp)

    var programName by remember(ui.selectedPreset.id) { mutableStateOf(ui.selectedPreset.name) }

    val hasUnsavedChanges = setupScreenHasUnsavedChanges(
        hasUnsavedTimelineChanges = ui.hasUnsavedChanges,
        editedProgramName = programName,
        savedProgramName = ui.savedProgramName,
    )

    Column(
        modifier = containerModifier,
        verticalArrangement = Arrangement.spacedBy(14.dp),
    ) {
        Text(
            ui.selectedPreset.name,
            style = MaterialTheme.typography.headlineSmall,
            color = MaterialTheme.colorScheme.onBackground,
        )

        TextField(
            value = programName,
            onValueChange = { programName = it },
            label = { Text("Program name") },
            modifier = Modifier.fillMaxWidth(),
        )

        DurationSliderCard(
            durationSec = ui.timeline.durationSec,
            onDurationSecChanged = { vm.setDurationSec(it) },
        )

        // Integrated timeline editor (no separate screen).
        SetupTimelineEditor(
            state = ui.timeline,
            onStateChanged = vm::updateTimeline,
            onCurveGranularityChanged = vm::setCurveGranularitySec,
        )

        Row(horizontalArrangement = Arrangement.spacedBy(8.dp), modifier = Modifier.fillMaxWidth()) {
            if (hasUnsavedChanges) {
                OutlinedButton(onClick = { vm.saveCurrentProgram(programName) }, modifier = Modifier.weight(1f).height(52.dp)) {
                    Text("Save")
                }
            } else {
                Button(onClick = onStart, modifier = Modifier.weight(1f).height(52.dp)) { Text("Start") }
            }
        }
        if (ui.error != null) Text(ui.error!!, color = if (ui.error!!.startsWith("Saved")) Color(0xFF72E39A) else MaterialTheme.colorScheme.error)
        Spacer(Modifier.height(8.dp))
    }
}

internal fun setupScreenFlashIntervalLabel(flashIntervalMs: Int): String =
    "Flash interval: ${"%.2f".format(flashIntervalMsToSeconds(flashIntervalMs))} s"

internal fun formatMaxTwoDecimals(value: Float): String =
    String.format(Locale.US, "%.2f", value).trimEnd('0').trimEnd('.')

internal fun setupScreenHasUnsavedChanges(
    hasUnsavedTimelineChanges: Boolean,
    editedProgramName: String,
    savedProgramName: String,
): Boolean {
    val nameChanged = editedProgramName.trim() != savedProgramName.trim()
    return hasUnsavedTimelineChanges || nameChanged
}

internal fun setupScreenUsesScrollableContainer(): Boolean = true

@Composable
fun ActiveSessionScreen(vm: MainViewModel, onFinish: () -> Unit, onBackToEntry: () -> Unit) {
    val ui by vm.ui.collectAsStateWithLifecycle()
    if (ui.runtimeState == RuntimeState.COMPLETED) onFinish()

    BackHandler {
        onBackToEntry()
    }

    val isVisualMode = true
    val context = LocalContext.current
    DisposableEffect(isVisualMode) {
        val activity = context as? Activity
        val previous = activity?.requestedOrientation
        if (isVisualMode) {
            activity?.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_SENSOR_LANDSCAPE
        }
        onDispose {
            if (isVisualMode) {
                activity?.requestedOrientation = previous ?: ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED
            }
        }
    }

    val immersiveFullscreen = shouldUseImmersiveFullscreen(isVisualMode, ui.runtimeState)
    var revealSystemBarsSignal by remember { mutableIntStateOf(0) }
    ApplyImmersiveMode(
        enabled = immersiveFullscreen,
        revealSignal = revealSystemBarsSignal,
    )

    var showOverlay by remember(ui.runtimeState) { mutableStateOf(shouldShowActiveControlsByDefault(ui.runtimeState)) }
    LaunchedEffect(ui.runtimeState) {
        showOverlay = shouldShowActiveControlsByDefault(ui.runtimeState)
    }
    var brightnessOverlayVisible by remember { mutableStateOf(false) }
    var brightnessOverlayToken by remember { mutableIntStateOf(0) }

    LaunchedEffect(brightnessOverlayToken) {
        if (!brightnessOverlayVisible) return@LaunchedEffect
        delay(2500)
        brightnessOverlayVisible = false
    }

    ApplyKeepScreenOn(enabled = true)

    ApplyScreenBrightnessOverride(
        enabled = true,
        brightnessPercent = ui.settings.immersiveBrightnessPercent,
    )

    val flashFrame by rememberSplitFlashFrame(
        isRunning = ui.runtimeState == RuntimeState.RUNNING,
        flashOnMs = ui.runtimeParams.flashOnMs,
        flashOffMs = ui.runtimeParams.flashOffMs,
    )

    val progress = sessionProgressFraction(
        durationSec = ui.timeline.durationSec,
        remainingSec = ui.remainingSec,
    )

    Box(
        modifier = Modifier
            .fillMaxSize()
            .background(Color.Black)
            .then(if (immersiveFullscreen) Modifier else Modifier.safeDrawingPadding())
            .pointerInput(immersiveFullscreen) {
                detectTapGestures {
                    brightnessOverlayVisible = true
                    brightnessOverlayToken++
                    if (!immersiveFullscreen) {
                        showOverlay = !showOverlay
                    }
                }
            }
    ) {
        if (isVisualMode) {
            Row(Modifier.fillMaxSize()) {
                Box(
                    modifier = Modifier
                        .weight(1f)
                        .fillMaxHeight()
                        .background(flashFrame.left.toComposeColor())
                )
                Box(
                    modifier = Modifier
                        .weight(1f)
                        .fillMaxHeight()
                        .background(flashFrame.right.toComposeColor())
                )
            }
        }

        if (ui.runtimeState == RuntimeState.COUNTDOWN) {
            Text(
                "${ui.countdownSec}",
                modifier = Modifier.align(Alignment.Center),
                style = MaterialTheme.typography.displayLarge,
                color = Color.White
            )
        }

        if (immersiveFullscreen && ui.settings.showImmersiveProgressBar) {
            LinearProgressIndicator(
                progress = { progress },
                modifier = Modifier
                    .align(Alignment.BottomCenter)
                    .fillMaxWidth()
                    .height(5.dp),
                trackColor = Color.White.copy(alpha = 0.2f),
                color = Color.White,
            )
        }

        if (brightnessOverlayVisible) {
            Column(
                Modifier
                    .align(Alignment.TopCenter)
                    .padding(top = 24.dp)
                    .fillMaxWidth(0.45f)
                    .background(Color.Black.copy(alpha = 0.72f))
                    .padding(horizontal = 12.dp, vertical = 10.dp)
            ) {
                Text(
                    text = "Brightness ${ui.settings.immersiveBrightnessPercent}%",
                    color = Color.White,
                    style = MaterialTheme.typography.bodyMedium,
                )
                Slider(
                    value = ui.settings.immersiveBrightnessPercent.toFloat(),
                    onValueChange = {
                        vm.updateImmersiveBrightnessPercent(it.roundToInt())
                        brightnessOverlayVisible = true
                        brightnessOverlayToken++
                    },
                    valueRange = 5f..100f,
                )
            }
        }

        if (showOverlay) {
            Column(
                Modifier
                    .align(Alignment.BottomCenter)
                    .fillMaxWidth()
                    .background(Color.Black.copy(alpha = 0.72f))
                    .padding(16.dp)
            ) {
                Text("${ui.selectedPreset.name} • ${ui.remainingSec}s", color = Color.White)
                if (ui.runtimeState == RuntimeState.RUNNING) {
                    Button(onClick = { vm.pause() }, modifier = Modifier.fillMaxWidth()) { Text("Pause") }
                } else {
                    Button(onClick = { vm.resume() }, modifier = Modifier.fillMaxWidth()) { Text("Resume") }
                }
                OutlinedButton(
                    onClick = {
                        vm.stop()
                        onFinish()
                    },
                    modifier = Modifier.fillMaxWidth()
                ) { Text("Stop") }
                if (ui.interruptionReason != null) {
                    Text(ui.interruptionReason!!, color = Color.White)
                    if (ui.runtimeState == RuntimeState.INTERRUPTED) {
                        OutlinedButton(onClick = { vm.switchToVisualOnlyAndResume() }, modifier = Modifier.fillMaxWidth()) {
                            Text("Resume Visual-only")
                        }
                    }
                }
            }
        }
    }
}

@Composable
private fun ApplyKeepScreenOn(enabled: Boolean) {
    val activity = LocalContext.current as? Activity ?: return
    val window = activity.window

    DisposableEffect(window, enabled) {
        if (enabled) {
            window.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
        } else {
            window.clearFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
        }
        onDispose {
            window.clearFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
        }
    }
}

@Composable
private fun ApplyScreenBrightnessOverride(enabled: Boolean, brightnessPercent: Int) {
    val activity = LocalContext.current as? Activity ?: return
    val window = activity.window

    DisposableEffect(window) {
        onDispose {
            val reset = window.attributes
            reset.screenBrightness = -1f
            window.attributes = reset
        }
    }

    LaunchedEffect(enabled, brightnessPercent) {
        val params = window.attributes
        params.screenBrightness = if (enabled) {
            (brightnessPercent.coerceIn(5, 100) / 100f)
        } else {
            -1f
        }
        window.attributes = params
    }
}

@Composable
private fun ApplyImmersiveMode(enabled: Boolean, revealSignal: Int) {
    val context = LocalContext.current
    val activity = context as? Activity ?: return
    val window = activity.window
    val controller = remember(window) { WindowInsetsControllerCompat(window, window.decorView) }

    DisposableEffect(window) {
        onDispose {
            controller.show(WindowInsetsCompat.Type.systemBars())
            WindowCompat.setDecorFitsSystemWindows(window, true)
        }
    }

    LaunchedEffect(enabled) {
        if (enabled) {
            WindowCompat.setDecorFitsSystemWindows(window, false)
            controller.systemBarsBehavior = WindowInsetsControllerCompat.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE
            controller.hide(WindowInsetsCompat.Type.systemBars())
        } else {
            controller.show(WindowInsetsCompat.Type.systemBars())
            WindowCompat.setDecorFitsSystemWindows(window, true)
        }
    }

    LaunchedEffect(revealSignal, enabled) {
        if (!enabled || revealSignal == 0) return@LaunchedEffect
        controller.show(WindowInsetsCompat.Type.systemBars())
        delay(2500)
        if (enabled) {
            controller.hide(WindowInsetsCompat.Type.systemBars())
        }
    }
}

private fun FlashColor.toComposeColor(): Color = when (this) {
    FlashColor.RED -> Color.Red
    FlashColor.GREEN -> Color.Green
    FlashColor.BLACK -> Color.Black
}

@Composable
private fun rememberSplitFlashFrame(
    isRunning: Boolean,
    flashOnMs: Int,
    flashOffMs: Int,
): androidx.compose.runtime.State<SplitFlashFrame> {
    val latestFlashOnMs = rememberUpdatedState(flashOnMs)
    val latestFlashOffMs = rememberUpdatedState(flashOffMs)

    return produceState(initialValue = SplitFlashFrame(FlashColor.BLACK, FlashColor.BLACK), isRunning) {
        if (!isRunning) {
            value = SplitFlashFrame(FlashColor.BLACK, FlashColor.BLACK)
            return@produceState
        }

        // Lock the sequencer's time base to Compose's frame clock.
        // Mixing System.nanoTime() (start) with withFrameNanos() (updates) can introduce
        // an arbitrary offset that looks like irregular intervals.
        val sequencer = SplitFlashSequencer(
            startTimeNanos = 0L,
            flashOnMs = latestFlashOnMs.value,
            flashOffMs = latestFlashOffMs.value,
        )

        var started = false

        while (true) {
            withFrameNanos { frameTimeNanos ->
                if (!started) {
                    // Initialize phaseStartNanos to the first real frame timestamp.
                    // This keeps phase transitions aligned to the same monotonic clock.
                    sequencer.frameAt(frameTimeNanos)
                    started = true
                }
                sequencer.updateIntervals(latestFlashOnMs.value, latestFlashOffMs.value)
                value = sequencer.frameAt(frameTimeNanos)
            }
        }
    }
}

@Composable
fun SettingsScreen(vm: MainViewModel, onRemoveAds: () -> Unit) {
    val ui by vm.ui.collectAsStateWithLifecycle()
    val scrollState = rememberScrollState()
    Column(
        Modifier
            .fillMaxSize()
            .background(MaterialTheme.colorScheme.background)
            .safeDrawingPadding()
            .verticalScroll(scrollState)
            .padding(16.dp),
        verticalArrangement = Arrangement.spacedBy(12.dp)
    ) {
        Text("Settings", style = MaterialTheme.typography.headlineSmall, color = MaterialTheme.colorScheme.onBackground)

        Text("Countdown: ${ui.settings.countdownSeconds}s", color = MaterialTheme.colorScheme.onBackground)
        Slider(
            value = ui.settings.countdownSeconds.toFloat(),
            onValueChange = { vm.updateCountdownSeconds(it.roundToInt()) },
            valueRange = 0f..10f,
            steps = 9,
        )

        Row(verticalAlignment = Alignment.CenterVertically) {
            Checkbox(
                checked = ui.settings.forceAudioWithoutHeadphones,
                onCheckedChange = vm::updateForceAudioWithoutHeadphones,
            )
            Text("force audio without headphones", color = MaterialTheme.colorScheme.onBackground)
        }

        Row(verticalAlignment = Alignment.CenterVertically) {
            Checkbox(checked = ui.settings.showImmersiveProgressBar, onCheckedChange = vm::updateShowImmersiveProgressBar)
            Text("Show immersive bottom progress bar", color = MaterialTheme.colorScheme.onBackground)
        }

        Button(onClick = onRemoveAds) {
            Text(if (ui.settings.noAds) "Ads removed" else "Remove ads")
        }

        HorizontalDivider()
        Text(
            "About/Disclaimer: MindMachine is a prototype and not a medical device. Use at your own risk. For immersive visual sessions, keep your eyes closed.",
            color = MaterialTheme.colorScheme.onBackground
        )
    }
}

@Composable
fun RemoveAdsScreen(billingManager: solutions.tretter.mindmachine.billing.BillingManager, vm: MainViewModel) {
    val ui by vm.ui.collectAsStateWithLifecycle()
    val activity = LocalContext.current as? Activity
    val details by billingManager.productDetails.collectAsStateWithLifecycle()

    Column(
        Modifier
            .fillMaxSize()
            .background(MaterialTheme.colorScheme.background)
            .safeDrawingPadding()
            .padding(16.dp),
        verticalArrangement = Arrangement.spacedBy(12.dp)
    ) {
        Text("Remove Ads", style = MaterialTheme.typography.headlineSmall, color = MaterialTheme.colorScheme.onBackground)
        Text(
            if (ui.settings.noAds) "You already have ads removed." else "MindMachine is free with ads. You can remove ads via subscription or one-time purchase.",
            color = MaterialTheme.colorScheme.onBackground
        )

        Button(
            enabled = activity != null && !ui.settings.noAds,
            onClick = {
                activity?.let { billingManager.launchPurchase(it, solutions.tretter.mindmachine.billing.BillingProducts.SUB_REMOVE_ADS_MONTHLY) }
            }
        ) {
            Text(details[solutions.tretter.mindmachine.billing.BillingProducts.SUB_REMOVE_ADS_MONTHLY]?.name ?: "Subscribe: $1/month")
        }

        Button(
            enabled = activity != null && !ui.settings.noAds,
            onClick = {
                activity?.let { billingManager.launchPurchase(it, solutions.tretter.mindmachine.billing.BillingProducts.INAPP_REMOVE_ADS_FOREVER) }
            }
        ) {
            Text(details[solutions.tretter.mindmachine.billing.BillingProducts.INAPP_REMOVE_ADS_FOREVER]?.name ?: "Buy: $20 one-time")
        }

        TextButton(onClick = { billingManager.refresh() }) { Text("Restore / Refresh purchases") }

        Text(
            "Note: Purchases only work when the app is installed from Google Play (Internal testing/Production). Debug sideloaded builds won’t complete real billing flows.",
            color = MaterialTheme.colorScheme.onBackground.copy(alpha = 0.8f)
        )
    }
}

@Composable
fun PositioningScreen() {
    val scrollState = rememberScrollState()
    Column(
        Modifier
            .fillMaxSize()
            .background(MaterialTheme.colorScheme.background)
            .safeDrawingPadding()
            .verticalScroll(scrollState)
            .padding(16.dp),
        verticalArrangement = Arrangement.spacedBy(8.dp)
    ) {
        Text("Positioning Guidance", style = MaterialTheme.typography.headlineSmall, color = MaterialTheme.colorScheme.onBackground)

        Image(
            painter = painterResource(R.drawable.positioning_guide),
            contentDescription = "Positioning guide",
            contentScale = ContentScale.Fit,
            modifier = Modifier
                .fillMaxWidth()
                .height(260.dp)
                .padding(vertical = 6.dp)
        )

        Text("• Lie on your back in a safe, comfortable place.", color = MaterialTheme.colorScheme.onBackground)
        Text("• Rest the phone across the upper nose/forehead area so it stays stable.", color = MaterialTheme.colorScheme.onBackground)
        Text("• Keep your eyes closed during immersive visual sessions.", color = MaterialTheme.colorScheme.onBackground)

        Text("Warnings", style = MaterialTheme.typography.titleMedium, color = MaterialTheme.colorScheme.onBackground)
        Text("• Flashing lights may be unsafe for people with epilepsy, seizure sensitivity, or migraine triggers.", color = MaterialTheme.colorScheme.onBackground)
        Text("• Do not stare at the screen, for immersive visual sessions, keep your eyes closed.", color = MaterialTheme.colorScheme.onBackground)
        Text("• Stop immediately for discomfort, dizziness, headache, nausea, anxiety, or eye strain.", color = MaterialTheme.colorScheme.onBackground)

        Spacer(Modifier.height(12.dp))
        Text("Disclaimer", style = MaterialTheme.typography.titleMedium, color = MaterialTheme.colorScheme.onBackground)
        Text(
            "MindMachine is provided \"as is\" for informational and experimental purposes only, without warranties of any kind. You assume all risks of use. MindMachine is not a medical device and does not provide medical advice. To the maximum extent permitted by law, the developers and distributors disclaim all liability for any claims, damages, losses, or injuries arising from or related to use of the app.",
            color = MaterialTheme.colorScheme.onBackground
        )
    }
}