package soy.iko.opencode.ui.server

import androidx.activity.compose.BackHandler
import androidx.compose.animation.AnimatedVisibility
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.Row
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.imePadding
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.layout.widthIn
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.text.KeyboardActions
import androidx.compose.foundation.text.KeyboardOptions
import androidx.compose.foundation.verticalScroll
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.automirrored.filled.ArrowBack
import androidx.compose.material.icons.filled.Visibility
import androidx.compose.material.icons.filled.VisibilityOff
import androidx.compose.material.icons.filled.Wifi
import androidx.compose.material3.AlertDialog
import androidx.compose.material3.Button
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.OutlinedButton
import androidx.compose.material3.OutlinedTextField
import androidx.compose.material3.Scaffold
import androidx.compose.material3.Switch
import androidx.compose.material3.Text
import androidx.compose.material3.TextButton
import androidx.compose.material3.TopAppBar
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.saveable.rememberSaveable
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.platform.testTag
import androidx.compose.ui.semantics.contentDescription
import androidx.compose.ui.semantics.semantics
import androidx.compose.ui.text.input.ImeAction
import androidx.compose.ui.text.input.KeyboardType
import androidx.compose.ui.text.input.PasswordVisualTransformation
import androidx.compose.ui.text.input.VisualTransformation
import androidx.compose.ui.res.stringResource
import androidx.compose.ui.unit.dp
import androidx.lifecycle.compose.collectAsStateWithLifecycle
import androidx.lifecycle.viewmodel.compose.viewModel
import soy.iko.opencode.data.network.NsdDiscovery
import soy.iko.opencode.di.AppContainer
import soy.iko.opencode.R
import soy.iko.opencode.ui.vmFactory

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun ServerEditScreen(
    container: AppContainer,
    profileId: String?,
    onDone: () -> Unit,
    sourceId: String? = null,
) {
    val vm: ServerEditViewModel =
        viewModel(factory = vmFactory { ServerEditViewModel(container, profileId, sourceId) })
    val state by vm.state.collectAsStateWithLifecycle()
    var showDiscardConfirm by rememberSaveable { mutableStateOf(false) }
    var passwordVisible by rememberSaveable { mutableStateOf(false) }

    fun safeExit() {
        when {
            // A save is in flight: ignore the back gesture (matching the BackHandler guard
            // below). Popping here would cancel the save's viewModelScope coroutine and
            // silently abandon the write; the VM calls onDone itself once the save lands.
            state.saving -> Unit
            state.isDirty -> showDiscardConfirm = true
            else -> onDone()
        }
    }

    // Intercept the system back gesture when the form has unsaved changes so the user
    // gets a chance to keep editing instead of losing their work silently. Stays enabled
    // (as a no-op) while a save is in flight so the gesture can't propagate to the NavHost
    // and cancel the save's viewModelScope coroutine mid-write — matching safeExit()'s guard.
    BackHandler(enabled = (state.isDirty || state.saving) && !showDiscardConfirm) {
        if (!state.saving) showDiscardConfirm = true
    }

    Scaffold(
        topBar = {
            TopAppBar(
                title = { Text(if (state.isNew) stringResource(R.string.add_server) else stringResource(R.string.edit_server)) },
                navigationIcon = {
                    IconButton(onClick = ::safeExit) {
                        Icon(Icons.AutoMirrored.Filled.ArrowBack, contentDescription = stringResource(R.string.back))
                    }
                },
            )
        },
    ) { padding ->
        if (!state.loaded) {
            val loadingLabel = stringResource(R.string.loading)
            Box(modifier = Modifier.fillMaxSize().padding(padding), contentAlignment = Alignment.Center) {
                CircularProgressIndicator(Modifier.semantics { contentDescription = loadingLabel })
            }
        } else {
            ServerEditForm(
                state = state,
                passwordVisible = passwordVisible,
                onTogglePassword = { passwordVisible = !passwordVisible },
                padding = padding,
                vm = vm,
                onDone = onDone,
            )
        }
    }

    if (showDiscardConfirm) {
        AlertDialog(
            onDismissRequest = { showDiscardConfirm = false },
            title = { Text(stringResource(R.string.discard_title)) },
            text = { Text(stringResource(R.string.discard_text)) },
            confirmButton = {
                TextButton(onClick = {
                    showDiscardConfirm = false
                    onDone()
                }) { Text(stringResource(R.string.discard), color = MaterialTheme.colorScheme.error) }
            },
            dismissButton = {
                TextButton(onClick = { showDiscardConfirm = false }) { Text(stringResource(R.string.keep_editing)) }
            },
        )
    }
}

@Composable
private fun ServerEditForm(
    state: ServerEditState,
    passwordVisible: Boolean,
    onTogglePassword: () -> Unit,
    padding: androidx.compose.foundation.layout.PaddingValues,
    vm: ServerEditViewModel,
    onDone: () -> Unit,
) {
    val haptics = androidx.compose.ui.platform.LocalHapticFeedback.current
    // canSave parses the base URL with java.net.URI (which throws — and fills a stack trace —
    // on the common half-typed URL). Memoize on baseUrl so it runs once per edit instead of
    // being re-parsed at each of the enabled= call sites on every keystroke's recomposition.
    val canSave = remember(state.baseUrl, state.certPin) { state.canSave }
    Column(
        modifier = Modifier
            .padding(padding)
            .imePadding()
            .widthIn(max = 600.dp)
            .padding(16.dp)
            .verticalScroll(rememberScrollState()),
        verticalArrangement = Arrangement.spacedBy(12.dp),
    ) {
        OutlinedTextField(
            value = state.label,
            onValueChange = { v -> vm.update { it.copy(label = v) } },
            label = { Text(stringResource(R.string.label_optional)) },
            singleLine = true,
            keyboardOptions = KeyboardOptions(imeAction = ImeAction.Next),
            modifier = Modifier.fillMaxWidth().testTag("server_label"),
        )
        OutlinedTextField(
            value = state.baseUrl,
            onValueChange = { v -> vm.update { it.copy(baseUrl = v, error = null, probeReachable = null) } },
            label = { Text(stringResource(R.string.base_url)) },
            placeholder = { Text(stringResource(R.string.base_url_hint)) },
            singleLine = true,
            isError = state.baseUrl.isNotBlank() && !isValidUrl(state.baseUrl),
            supportingText = {
                if (state.baseUrl.isNotBlank() && !isValidUrl(state.baseUrl)) {
                    // Offer a one-tap "http://" fix for bare host:port input instead of a
                    // generic error, so the user doesn't have to know the URL needs a scheme.
                    val suggestion = suggestUrlScheme(state.baseUrl)
                    if (suggestion != null) {
                        TextButton(
                            onClick = { vm.update { it.copy(baseUrl = suggestion, probeReachable = null) } },
                            contentPadding = androidx.compose.foundation.layout.PaddingValues(horizontal = 0.dp),
                        ) {
                            Text(stringResource(R.string.suggest_scheme))
                        }
                    } else {
                        Text(stringResource(R.string.invalid_url))
                    }
                }
            },
            keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.Uri, imeAction = ImeAction.Done),
            modifier = Modifier.fillMaxWidth().testTag("server_url"),
        )
        OutlinedButton(
            onClick = { vm.probe() },
            enabled = canSave && !state.probing && !state.saving,
            modifier = Modifier.fillMaxWidth().testTag("server_probe"),
        ) {
            if (state.probing) {
                CircularProgressIndicator(
                    modifier = Modifier.size(20.dp),
                    strokeWidth = 2.dp,
                )
                Text(stringResource(R.string.checking), modifier = Modifier.padding(start = 8.dp))
            } else {
                Text(stringResource(R.string.check_connectivity))
            }
        }
        // Positive feedback when the probe found the server reachable without auth, so
        // the user knows the connection works before saving (closes the loop that the
        // prior "silently does nothing" Reachable path left open).
        if (state.probeReachable == true && !state.authFieldsVisible) {
            Text(
                stringResource(R.string.server_reachable),
                style = MaterialTheme.typography.bodySmall,
                color = MaterialTheme.colorScheme.primary,
                modifier = Modifier.fillMaxWidth(),
            )
        }
        DiscoverySection(
            onPick = { url -> vm.update { it.copy(baseUrl = url, error = null, probeReachable = null) } },
        )
        if (!state.authFieldsVisible) {
            Text(
                stringResource(R.string.auth_help),
                style = MaterialTheme.typography.bodySmall,
                color = MaterialTheme.colorScheme.onSurfaceVariant,
                modifier = Modifier.fillMaxWidth(),
            )
        }
        AnimatedVisibility(visible = state.authFieldsVisible) {
            AuthFields(
                state = state,
                passwordVisible = passwordVisible,
                onTogglePassword = onTogglePassword,
                onUpdate = vm::update,
                onTestCredentials = vm::testCredentials,
                onImeDone = { if (canSave && !state.saving) vm.saveAndConnect(onDone) },
            )
        }
        SecurityFields(state = state, onUpdate = vm::update)
        Row(
            modifier = Modifier.fillMaxWidth(),
            horizontalArrangement = Arrangement.spacedBy(12.dp),
        ) {
            OutlinedButton(
                onClick = {
                    haptics.performHapticFeedback(androidx.compose.ui.hapticfeedback.HapticFeedbackType.LongPress)
                    vm.save(onDone)
                },
                enabled = canSave && !state.saving,
                modifier = Modifier.weight(1f),
            ) {
                if (state.saving) {
                    CircularProgressIndicator(
                        modifier = Modifier.size(20.dp),
                        color = MaterialTheme.colorScheme.primary,
                        strokeWidth = 2.dp,
                    )
                    Text(stringResource(R.string.saving), modifier = Modifier.padding(start = 8.dp))
                } else {
                    Text(stringResource(R.string.save))
                }
            }
            Button(
                onClick = {
                    haptics.performHapticFeedback(androidx.compose.ui.hapticfeedback.HapticFeedbackType.LongPress)
                    vm.saveAndConnect(onDone)
                },
                enabled = canSave && !state.saving,
                modifier = Modifier.weight(1f),
            ) {
                Text(stringResource(R.string.save_and_connect))
            }
        }
        state.error?.let { message ->
            Text(
                message,
                color = MaterialTheme.colorScheme.error,
                style = MaterialTheme.typography.bodySmall,
                modifier = Modifier.fillMaxWidth(),
            )
        }
    }
}

@Composable
private fun AuthFields(
    state: ServerEditState,
    passwordVisible: Boolean,
    onTogglePassword: () -> Unit,
    onUpdate: ((ServerEditState) -> ServerEditState) -> Unit,
    onTestCredentials: () -> Unit,
    onImeDone: () -> Unit,
) {
    val showPasswordLabel = stringResource(R.string.show_password)
    val hidePasswordLabel = stringResource(R.string.hide_password)
    // Memoize the URI parse on baseUrl so the test-credentials button doesn't re-parse it on
    // every keystroke's recomposition (see ServerEditForm).
    val canSave = remember(state.baseUrl, state.certPin) { state.canSave }
    Column(verticalArrangement = Arrangement.spacedBy(12.dp)) {
        Text(
            stringResource(R.string.auth_required),
            style = MaterialTheme.typography.bodySmall,
            color = MaterialTheme.colorScheme.error,
        )
        OutlinedTextField(
            value = state.username,
            onValueChange = { v -> onUpdate { it.copy(username = v) } },
            label = { Text(stringResource(R.string.username_optional)) },
            singleLine = true,
            keyboardOptions = KeyboardOptions(imeAction = ImeAction.Next),
            modifier = Modifier.fillMaxWidth().testTag("server_username"),
        )
        OutlinedTextField(
            value = state.password,
            onValueChange = { v -> onUpdate { it.copy(password = v) } },
            label = { Text(stringResource(R.string.password_optional)) },
            singleLine = true,
            visualTransformation = if (passwordVisible) VisualTransformation.None else PasswordVisualTransformation(),
            trailingIcon = {
                IconButton(onClick = onTogglePassword) {
                    Icon(
                        if (passwordVisible) Icons.Filled.VisibilityOff else Icons.Filled.Visibility,
                        contentDescription = if (passwordVisible) hidePasswordLabel else showPasswordLabel,
                    )
                }
            },
            keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.Password, imeAction = ImeAction.Done),
            keyboardActions = KeyboardActions(onDone = { onImeDone() }),
            modifier = Modifier.fillMaxWidth().testTag("server_password"),
        )
        OutlinedButton(
            onClick = onTestCredentials,
            // Require at least one credential field: testCredentials() no-ops when both are
            // blank, so without this the button is tappable but silently does nothing.
            enabled = canSave && !state.testingCredentials && !state.saving &&
                (state.username.isNotBlank() || state.password.isNotBlank()),
            modifier = Modifier.fillMaxWidth().testTag("server_test_creds"),
        ) {
            if (state.testingCredentials) {
                CircularProgressIndicator(
                    modifier = Modifier.size(20.dp),
                    strokeWidth = 2.dp,
                )
                Text(stringResource(R.string.testing_credentials), modifier = Modifier.padding(start = 8.dp))
            } else {
                Text(stringResource(R.string.test_credentials))
            }
        }
        state.credentialsResult?.let { ok ->
            Text(
                stringResource(if (ok) R.string.credentials_ok else R.string.credentials_rejected),
                style = MaterialTheme.typography.bodySmall,
                color = if (ok) MaterialTheme.colorScheme.primary else MaterialTheme.colorScheme.error,
            )
        }
    }
}

/** Optional TLS hardening for this server: force HTTPS (upgrade cleartext) and pin the
 *  server certificate. Both are off by default so the common localhost/HTTP setup is
 *  unaffected. */
@Composable
private fun SecurityFields(
    state: ServerEditState,
    onUpdate: (((ServerEditState) -> ServerEditState)) -> Unit,
) {
    Column(verticalArrangement = Arrangement.spacedBy(8.dp), modifier = Modifier.fillMaxWidth()) {
        Text(
            stringResource(R.string.server_security),
            style = MaterialTheme.typography.titleSmall,
            color = MaterialTheme.colorScheme.primary,
        )
        Row(modifier = Modifier.fillMaxWidth(), verticalAlignment = Alignment.CenterVertically) {
            Column(modifier = Modifier.weight(1f)) {
                Text(stringResource(R.string.require_https), style = MaterialTheme.typography.bodyLarge)
                Text(
                    stringResource(R.string.require_https_desc),
                    style = MaterialTheme.typography.bodySmall,
                    color = MaterialTheme.colorScheme.onSurfaceVariant,
                )
            }
            Switch(
                checked = state.requireHttps,
                onCheckedChange = { v -> onUpdate { it.copy(requireHttps = v) } },
            )
        }
        OutlinedTextField(
            value = state.certPin,
            onValueChange = { v -> onUpdate { it.copy(certPin = v) } },
            label = { Text(stringResource(R.string.cert_pin)) },
            placeholder = { Text(stringResource(R.string.cert_pin_hint)) },
            singleLine = true,
            isError = !state.certPinValid,
            supportingText = {
                Text(
                    stringResource(if (state.certPinValid) R.string.cert_pin_desc else R.string.cert_pin_invalid),
                    style = MaterialTheme.typography.bodySmall,
                    color = if (state.certPinValid) MaterialTheme.colorScheme.onSurfaceVariant
                        else MaterialTheme.colorScheme.error,
                )
            },
            keyboardOptions = KeyboardOptions(imeAction = ImeAction.Done),
            modifier = Modifier.fillMaxWidth().testTag("server_cert_pin"),
        )
    }
}

/**
 * Optional LAN discovery: browses for opencode servers advertised via mDNS (`--mdns`) and
 * offers each as a one-tap fill for the base URL. Collapsed by default so the discovery (and
 * its multicast traffic) only runs while the section is expanded — the collection stops when
 * the section is collapsed or the screen leaves composition.
 */
@Composable
private fun DiscoverySection(onPick: (String) -> Unit) {
    val context = LocalContext.current
    var expanded by rememberSaveable { mutableStateOf(false) }
    Column(modifier = Modifier.fillMaxWidth()) {
        TextButton(
            onClick = { expanded = !expanded },
            contentPadding = androidx.compose.foundation.layout.PaddingValues(horizontal = 0.dp),
        ) {
            Icon(Icons.Filled.Wifi, contentDescription = null, modifier = Modifier.size(18.dp))
            Text(stringResource(R.string.discover_on_network), modifier = Modifier.padding(start = 8.dp))
        }
        if (expanded) {
            val discovery = remember { NsdDiscovery(context) }
            val servers by remember(discovery) { discovery.discover() }
                .collectAsStateWithLifecycle(initialValue = emptyList())
            if (servers.isEmpty()) {
                Row(
                    verticalAlignment = Alignment.CenterVertically,
                    modifier = Modifier.padding(vertical = 8.dp),
                ) {
                    CircularProgressIndicator(modifier = Modifier.size(16.dp), strokeWidth = 2.dp)
                    Text(
                        stringResource(R.string.searching_network),
                        style = MaterialTheme.typography.bodySmall,
                        color = MaterialTheme.colorScheme.onSurfaceVariant,
                        modifier = Modifier.padding(start = 8.dp),
                    )
                }
            } else {
                servers.forEach { server ->
                    Column(
                        modifier = Modifier
                            .fillMaxWidth()
                            .clickable { onPick(server.baseUrl) }
                            .padding(vertical = 8.dp),
                    ) {
                        Text(server.name, style = MaterialTheme.typography.bodyMedium)
                        Text(
                            server.baseUrl,
                            style = MaterialTheme.typography.bodySmall,
                            color = MaterialTheme.colorScheme.onSurfaceVariant,
                        )
                    }
                }
            }
        }
    }
}