package soy.iko.opencode.ui.chat

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.PaddingValues
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.items
import androidx.compose.foundation.lazy.rememberLazyListState
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.automirrored.filled.ArrowBack
import androidx.compose.material.icons.automirrored.filled.Send
import androidx.compose.material.icons.filled.SmartToy
import androidx.compose.material.icons.filled.Stop
import androidx.compose.material.icons.filled.Terminal
import androidx.compose.material.icons.filled.Tune
import androidx.compose.material3.CircularProgressIndicator
import androidx.compose.material3.ExperimentalMaterial3Api
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.OutlinedTextField
import androidx.compose.material3.Scaffold
import androidx.compose.material3.SnackbarHost
import androidx.compose.material3.SnackbarHostState
import androidx.compose.material3.Surface
import androidx.compose.material3.Text
import androidx.compose.material3.TopAppBar
import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import androidx.lifecycle.compose.collectAsStateWithLifecycle
import androidx.lifecycle.viewmodel.compose.viewModel
import soy.iko.opencode.di.AppContainer
import soy.iko.opencode.ui.vmFactory

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun ChatScreen(
    container: AppContainer,
    sessionId: String,
    onBack: () -> Unit,
) {
    val vm: ChatViewModel = viewModel(factory = vmFactory { ChatViewModel(container, sessionId) })
    val messages by vm.messages.collectAsStateWithLifecycle()
    val running by vm.running.collectAsStateWithLifecycle()
    val error by vm.error.collectAsStateWithLifecycle()
    val models by vm.models.collectAsStateWithLifecycle()
    val selectedModel by vm.selectedModel.collectAsStateWithLifecycle()
    val connectionState by vm.connectionState.collectAsStateWithLifecycle()
    val pendingPermission by vm.pendingPermission.collectAsStateWithLifecycle()
    val agents by vm.agents.collectAsStateWithLifecycle()
    val selectedAgent by vm.selectedAgent.collectAsStateWithLifecycle()
    val commands by vm.commands.collectAsStateWithLifecycle()

    val listState = rememberLazyListState()
    val snackbar = remember { SnackbarHostState() }
    var input by remember { mutableStateOf("") }
    var showModelPicker by remember { mutableStateOf(false) }
    var showAgentPicker by remember { mutableStateOf(false) }
    var showCommandPicker by remember { mutableStateOf(false) }

    // Keep the newest content in view as parts stream in.
    LaunchedEffect(messages.size, messages.lastOrNull()?.parts?.size) {
        if (messages.isNotEmpty()) listState.animateScrollToItem(messages.lastIndex)
    }
    LaunchedEffect(error) {
        error?.let {
            snackbar.showSnackbar(it)
            vm.clearError()
        }
    }

    Scaffold(
        topBar = {
            TopAppBar(
                title = {
                    Column(modifier = Modifier.clickable(enabled = models.isNotEmpty()) { showModelPicker = true }) {
                        Text("Session")
                        Text(
                            buildString {
                                append(selectedModel?.modelLabel ?: "default model")
                                selectedAgent?.let { append("  •  $it") }
                            },
                            style = MaterialTheme.typography.labelSmall,
                            color = MaterialTheme.colorScheme.onSurfaceVariant,
                        )
                    }
                },
                navigationIcon = {
                    IconButton(onClick = onBack) {
                        Icon(Icons.AutoMirrored.Filled.ArrowBack, contentDescription = "Back")
                    }
                },
                actions = {
                    IconButton(onClick = { showCommandPicker = true }, enabled = commands.isNotEmpty()) {
                        Icon(Icons.Filled.Terminal, contentDescription = "Commands")
                    }
                    IconButton(onClick = { showAgentPicker = true }, enabled = agents.isNotEmpty()) {
                        Icon(Icons.Filled.SmartToy, contentDescription = "Choose agent")
                    }
                    IconButton(onClick = { showModelPicker = true }, enabled = models.isNotEmpty()) {
                        Icon(Icons.Filled.Tune, contentDescription = "Choose model")
                    }
                },
            )
        },
        snackbarHost = { SnackbarHost(snackbar) },
        bottomBar = {
            ChatInputBar(
                value = input,
                onValueChange = { input = it },
                running = running,
                enabled = vm.connected,
                onSend = {
                    vm.send(input)
                    input = ""
                },
                onAbort = { vm.abort() },
            )
        },
    ) { padding ->
        Box(modifier = Modifier.fillMaxSize().padding(padding)) {
            if (!vm.connected) {
                Text(
                    "Not connected.",
                    modifier = Modifier.align(Alignment.Center).padding(24.dp),
                    color = MaterialTheme.colorScheme.error,
                )
            } else {
                ConnectionBanner(
                    state = connectionState,
                    modifier = Modifier.align(Alignment.TopCenter),
                )
                LazyColumn(
                    state = listState,
                    modifier = Modifier.fillMaxSize(),
                    contentPadding = PaddingValues(16.dp),
                    verticalArrangement = Arrangement.spacedBy(16.dp),
                ) {
                    items(messages, key = { it.info.id }) { message ->
                        MessageBubble(message)
                    }
                    if (running) {
                        item(key = "__typing") {
                            Row(verticalAlignment = Alignment.CenterVertically) {
                                CircularProgressIndicator(Modifier.size(16.dp), strokeWidth = 2.dp)
                                Text("  working…", style = MaterialTheme.typography.labelMedium)
                            }
                        }
                    }
                }
            }
        }
    }

    if (showModelPicker) {
        ModelPickerSheet(
            options = models,
            selected = selectedModel,
            onSelect = { vm.selectModel(it) },
            onDismiss = { showModelPicker = false },
        )
    }

    if (showAgentPicker) {
        AgentPickerSheet(
            agents = agents,
            selected = selectedAgent,
            onSelect = { vm.selectAgent(it?.name) },
            onDismiss = { showAgentPicker = false },
        )
    }

    if (showCommandPicker) {
        CommandPickerSheet(
            commands = commands,
            onSelect = { vm.runCommand(it) },
            onDismiss = { showCommandPicker = false },
        )
    }

    pendingPermission?.let { permission ->
        PermissionDialog(
            permission = permission,
            onRespond = { response -> vm.respondPermission(permission, response) },
        )
    }
}

@Composable
private fun ConnectionBanner(
    state: soy.iko.opencode.data.network.EventStreamClient.ConnectionState,
    modifier: Modifier = Modifier,
) {
    val text = when (state) {
        soy.iko.opencode.data.network.EventStreamClient.ConnectionState.Connecting -> "Connecting…"
        soy.iko.opencode.data.network.EventStreamClient.ConnectionState.Disconnected -> "Reconnecting…"
        soy.iko.opencode.data.network.EventStreamClient.ConnectionState.Connected -> null
    }
    if (text != null) {
        Surface(
            modifier = modifier.fillMaxWidth(),
            color = MaterialTheme.colorScheme.tertiaryContainer,
        ) {
            Row(
                modifier = Modifier.fillMaxWidth().padding(vertical = 6.dp),
                horizontalArrangement = Arrangement.Center,
                verticalAlignment = Alignment.CenterVertically,
            ) {
                CircularProgressIndicator(Modifier.size(12.dp), strokeWidth = 2.dp)
                Text(
                    "  $text",
                    style = MaterialTheme.typography.labelMedium,
                    color = MaterialTheme.colorScheme.onTertiaryContainer,
                )
            }
        }
    }
}

@Composable
private fun ChatInputBar(
    value: String,
    onValueChange: (String) -> Unit,
    running: Boolean,
    enabled: Boolean,
    onSend: () -> Unit,
    onAbort: () -> Unit,
) {
    Surface(tonalElevation = 3.dp) {
        Row(
            modifier = Modifier.fillMaxWidth().padding(8.dp),
            verticalAlignment = Alignment.Bottom,
        ) {
            OutlinedTextField(
                value = value,
                onValueChange = onValueChange,
                modifier = Modifier.weight(1f),
                placeholder = { Text("Message opencode…") },
                enabled = enabled,
                maxLines = 6,
            )
            if (running) {
                IconButton(onClick = onAbort, modifier = Modifier.padding(start = 4.dp)) {
                    Icon(Icons.Filled.Stop, contentDescription = "Stop")
                }
            } else {
                IconButton(
                    onClick = onSend,
                    enabled = enabled && value.isNotBlank(),
                    modifier = Modifier.padding(start = 4.dp),
                ) {
                    Icon(Icons.AutoMirrored.Filled.Send, contentDescription = "Send")
                }
            }
        }
    }
}