package com.mindmachine.mvp

import android.app.Activity
import android.content.pm.ActivityInfo
import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.BackHandler
import androidx.activity.compose.setContent
import androidx.activity.viewModels
import androidx.compose.foundation.background
import androidx.compose.foundation.clickable
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.fillMaxHeight
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.safeDrawingPadding
import androidx.compose.foundation.layout.windowInsetsBottomHeight
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.material3.Button
import androidx.compose.material3.Card
import androidx.compose.material3.CardDefaults
import androidx.compose.material3.Checkbox
import androidx.compose.material3.DropdownMenu
import androidx.compose.material3.DropdownMenuItem
import androidx.compose.material3.ExperimentalMaterial3Api
import androidx.compose.material3.ExposedDropdownMenuBox
import androidx.compose.material3.HorizontalDivider
import androidx.compose.material3.MaterialTheme
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.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.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.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.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.viewmodel.compose.viewModel
import androidx.navigation.compose.NavHost
import androidx.navigation.compose.composable
import androidx.navigation.compose.rememberNavController
import com.mindmachine.mvp.audio.BinauralAudioEngine
import com.mindmachine.mvp.audio.HeadsetMonitor
import com.mindmachine.mvp.data.SettingsRepository
import com.mindmachine.mvp.domain.CountdownPreference
import com.mindmachine.mvp.domain.RuntimeState
import com.mindmachine.mvp.domain.SessionMode
import com.mindmachine.mvp.session.FlashColor
import com.mindmachine.mvp.session.MainViewModel
import com.mindmachine.mvp.session.SplitFlashFrame
import com.mindmachine.mvp.session.computeSplitFlashFrame
import com.mindmachine.mvp.session.flashIntervalMsToSeconds
import com.mindmachine.mvp.session.flashIntervalSecondsToMs
import com.mindmachine.mvp.session.shouldRevealSystemBarsOnTap
import com.mindmachine.mvp.session.shouldShowActiveControlsByDefault
import com.mindmachine.mvp.session.shouldUseImmersiveFullscreen
import kotlinx.coroutines.delay
import kotlin.math.roundToInt

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 vm: MainViewModel by viewModels {
        MainViewModel.Factory(SettingsRepository(applicationContext), HeadsetMonitor(applicationContext), BinauralAudioEngine())
    }

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

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun App(vm: MainViewModel = viewModel()) {
    val nav = rememberNavController()
    val ui by vm.ui.collectAsStateWithLifecycle()
    val lifecycle = LocalLifecycleOwner.current.lifecycle

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

    val startRoute = if (ui.settings.safetyAcknowledged) "home" else "welcome"
    NavHost(navController = nav, startDestination = startRoute, modifier = Modifier.background(MaterialTheme.colorScheme.background)) {
        composable("welcome") {
            SimpleScreen("MindMachine", "Blinking light + binaural audio. Stereo headphones required for binaural mode. Not a medical device.") {
                Button(onClick = { nav.navigate("safety") }) { Text("Continue") }
            }
        }
        composable("safety") {
            SafetyScreen(
                onAck = {
                    vm.acknowledgeSafety()
                    nav.navigate("home") { popUpTo(0) }
                },
                onHolder = { nav.navigate("holder") }
            )
        }
        composable("home") {
            Column(Modifier.fillMaxSize()) {
                TopAppBar(title = { Text("MindMachine") }, actions = {
                    TextButton(onClick = { nav.navigate("settings") }) { Text("Settings") }
                })
                LazyColumn(Modifier.padding(12.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
                    item {
                        TextButton(onClick = { nav.navigate("holder") }) { Text("Holder Guidance") }
                    }
                    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)
                        ) {
                            Column(Modifier.padding(12.dp)) {
                                Text(p.name, style = MaterialTheme.typography.titleMedium)
                                Text(p.description)
                                Text("${p.defaultDurationSec / 60} min • ${p.visualPatternType} • binaural ${p.binauralDifferenceHz}")
                            }
                        }
                    }
                }
            }
        }
        composable("setup") {
            SetupScreen(vm = vm, onStart = {
                vm.startSession()
                nav.navigate("active")
            }, onHolder = { nav.navigate("holder") })
        }
        composable("active") {
            ActiveSessionScreen(
                vm = vm,
                onFinish = { nav.navigate("complete") { popUpTo("setup") } },
                onBackToSetup = { nav.popBackStack("setup", inclusive = false) }
            )
        }
        composable("complete") {
            SimpleScreen(
                if (ui.endedEarly) "Session ended" else "Session complete.",
                ui.selectedPreset.name
            ) {
                Button(onClick = {
                    vm.startSession()
                    nav.navigate("active")
                }) { Text("Repeat Session") }
                OutlinedButton(onClick = { nav.navigate("home") { popUpTo(0) } }) { Text("Return Home") }
            }
        }
        composable("settings") {
            SettingsScreen(vm) { nav.popBackStack() }
        }
        composable("holder") {
            HolderScreen { nav.popBackStack() }
        }
    }
}

@Composable
fun SimpleScreen(title: String, subtitle: String, actions: @Composable ColumnScope.() -> Unit) {
    Column(
        modifier = Modifier.fillMaxSize().background(MaterialTheme.colorScheme.background).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).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\nStop immediately for discomfort, dizziness, headache, nausea, anxiety, or eye strain.\n\nBinaural mode requires stereo headphones.\n\nThis app is not a medical device.",
            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("Holder Guidance") }
    }
}

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

    Column(
        containerModifier,
        verticalArrangement = Arrangement.spacedBy(10.dp)
    ) {
        Text(ui.selectedPreset.name, style = MaterialTheme.typography.headlineSmall, color = MaterialTheme.colorScheme.onBackground)
        Text("Duration: ${cfg.durationSec / 60} min", color = MaterialTheme.colorScheme.onBackground)
        Slider(value = (cfg.durationSec / 60).toFloat(), onValueChange = { vm.setDurationMin(it.roundToInt()) }, valueRange = 1f..30f)
        Text("Mode", color = MaterialTheme.colorScheme.onBackground)
        SingleChoiceSegmentedButtonRow(modifier = Modifier.fillMaxWidth()) {
            SessionMode.values().forEachIndexed { index, mode ->
                SegmentedButton(
                    shape = androidx.compose.material3.SegmentedButtonDefaults.itemShape(index = index, count = SessionMode.values().size),
                    selected = cfg.mode == mode,
                    onClick = { vm.setMode(mode) },
                    label = { Text(mode.name.replace("_", " ")) }
                )
            }
        }
        Text(setupScreenFlashIntervalLabel(cfg.flashIntervalMs), color = MaterialTheme.colorScheme.onBackground)
        Slider(
            value = flashIntervalMsToSeconds(cfg.flashIntervalMs),
            onValueChange = { vm.setFlashIntervalMs(flashIntervalSecondsToMs(it)) },
            valueRange = 0.05f..2.0f
        )
        Text("Controls how long each frame is shown in the red/green/black pattern.", color = MaterialTheme.colorScheme.onBackground)
        Text("Carrier frequency: ${cfg.carrierFrequencyHz.roundToInt()}", color = MaterialTheme.colorScheme.onBackground)
        Slider(value = cfg.carrierFrequencyHz, onValueChange = vm::setCarrier, valueRange = 80f..400f)
        Text("Binaural difference: ${cfg.binauralDifferenceHz}", color = MaterialTheme.colorScheme.onBackground)
        Slider(value = cfg.binauralDifferenceHz, onValueChange = vm::setDifference, valueRange = 0.5f..20f)
        Text("Brightness recommendation: keep screen comfortable and avoid eye strain.", color = MaterialTheme.colorScheme.onBackground)
        TextButton(onClick = onHolder) { Text("Holder Guidance") }
        if (ui.error != null) Text(ui.error!!, color = MaterialTheme.colorScheme.error)
        Button(onClick = onStart, modifier = Modifier.fillMaxWidth().height(52.dp)) { Text("Start") }
        Spacer(Modifier.height(8.dp))
    }
}

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

internal fun setupScreenUsesScrollableContainer(): Boolean = true

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

    BackHandler {
        vm.stop()
        onBackToSetup()
    }

    val isVisualMode = ui.config.mode != SessionMode.AUDIO_ONLY
    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)
    }
    val flashFrame by rememberSplitFlashFrame(
        isRunning = ui.runtimeState == RuntimeState.RUNNING,
        mode = ui.config.mode,
        flashIntervalMs = ui.config.flashIntervalMs,
    )

    Box(
        modifier = Modifier
            .fillMaxSize()
            .background(Color.Black)
            .clickable {
                showOverlay = !showOverlay
                if (shouldRevealSystemBarsOnTap(isVisualMode, ui.runtimeState)) {
                    revealSystemBarsSignal += 1
                }
            }
    ) {
        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(
                "${ui.countdownSec}",
                modifier = Modifier.align(Alignment.Center),
                style = MaterialTheme.typography.displayLarge,
                color = Color.White
            )
        }
        if (showOverlay) {
            Column(
                Modifier
                    .align(Alignment.BottomCenter)
                    .fillMaxWidth()
                    .background(Color.Black.copy(alpha = 0.72f))
                    .padding(16.dp)
            ) {
                Text("${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 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,
    mode: SessionMode,
    flashIntervalMs: Int,
) = produceState(initialValue = SplitFlashFrame(FlashColor.BLACK, FlashColor.BLACK), isRunning, mode, flashIntervalMs) {
    if (!isRunning || mode == SessionMode.AUDIO_ONLY) {
        value = SplitFlashFrame(FlashColor.BLACK, FlashColor.BLACK)
        return@produceState
    }
    while (true) {
        withFrameNanos { frameTimeNanos ->
            value = computeSplitFlashFrame(frameTimeNanos, flashIntervalMs)
        }
    }
}

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun SettingsScreen(vm: MainViewModel, onBack: () -> Unit) {
    val ui by vm.ui.collectAsStateWithLifecycle()
    var expanded by remember { mutableStateOf(false) }
    Column(
        Modifier.fillMaxSize().background(MaterialTheme.colorScheme.background).padding(16.dp),
        verticalArrangement = Arrangement.spacedBy(12.dp)
    ) {
        Text("Settings", style = MaterialTheme.typography.headlineSmall, color = MaterialTheme.colorScheme.onBackground)
        Text("Countdown", color = MaterialTheme.colorScheme.onBackground)
        ExposedDropdownMenuBox(expanded = expanded, onExpandedChange = { expanded = it }) {
            TextButton(onClick = { expanded = true }) { Text(ui.settings.countdownPreference.name) }
            DropdownMenu(expanded = expanded, onDismissRequest = { expanded = false }) {
                CountdownPreference.values().forEach {
                    DropdownMenuItem(text = { Text(it.name) }, onClick = { vm.updateCountdown(it); expanded = false })
                }
            }
        }
        Text("Default mode", color = MaterialTheme.colorScheme.onBackground)
        Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
            SessionMode.values().forEach { mode ->
                OutlinedButton(onClick = { vm.updateDefaultMode(mode) }) { Text(mode.name) }
            }
        }
        Row(verticalAlignment = Alignment.CenterVertically) {
            Checkbox(checked = ui.settings.showHolderGuidanceBeforeSession, onCheckedChange = vm::updateGuidance)
            Text("Show holder guidance before session", color = MaterialTheme.colorScheme.onBackground)
        }
        HorizontalDivider()
        Text("About/Disclaimer: MindMachine is a prototype and not a medical device.", color = MaterialTheme.colorScheme.onBackground)
        OutlinedButton(onClick = onBack) { Text("Back") }
    }
}

@Composable
fun HolderScreen(onBack: () -> Unit) {
    Column(
        Modifier.fillMaxSize().background(MaterialTheme.colorScheme.background).padding(16.dp),
        verticalArrangement = Arrangement.spacedBy(8.dp)
    ) {
        Text("Holder Guidance", style = MaterialTheme.typography.headlineSmall, color = MaterialTheme.colorScheme.onBackground)
        Text("• Use a simple cardboard visor/holder.", color = MaterialTheme.colorScheme.onBackground)
        Text("• Keep phone stable and hands-free.", color = MaterialTheme.colorScheme.onBackground)
        Text("• Do not press device against eyes/face.", color = MaterialTheme.colorScheme.onBackground)
        Text("• Allow airflow and comfort.", color = MaterialTheme.colorScheme.onBackground)
        Text("• Test fit before session.", color = MaterialTheme.colorScheme.onBackground)
        Text("• Sit or lie down in a safe place.", color = MaterialTheme.colorScheme.onBackground)
        OutlinedButton(onClick = onBack) { Text("Back") }
    }
}