ai-app/app/androidApp/src/main/kotlin/com/example/aiapp/SetupsScreen.kt

package com.example.aiapp

import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.Spacer
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.lazy.LazyColumn
import androidx.compose.material3.AlertDialog
import androidx.compose.material3.Card
import androidx.compose.material3.CircularProgressIndicator
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.OutlinedTextField
import androidx.compose.material3.Text
import androidx.compose.material3.TextButton
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.rememberCoroutineScope
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext

/**
 * The machines this backend can run things on.
 *
 * Note what this screen cannot do: name a program. Providers are what the server found when it
 * asked the machine, so adding one is "here is how to reach it" and never "here is what to run" --
 * which is what keeps the enrolled token from being able to introduce commands.
 */
@Composable
fun SetupsScreen(settings: ServerSettings, reloadToken: Int) {
    val scope = rememberCoroutineScope()
    var state by remember { mutableStateOf<LoadState<List<Setup>>>(LoadState.Loading) }
    var adding by remember { mutableStateOf(false) }
    var renaming by remember { mutableStateOf<Setup?>(null) }
    var confirmingDelete by remember { mutableStateOf<Setup?>(null) }
    var busy by remember { mutableStateOf<String?>(null) }
    var actionError by remember { mutableStateOf<String?>(null) }

    suspend fun reload() {
        state =
            try {
                withContext(Dispatchers.IO) { LoadState.Loaded(fetchSetups(settings)) }
            } catch (e: ApiException) {
                LoadState.failed(e)
            }
    }

    LaunchedEffect(reloadToken) { reload() }

    Column(Modifier.fillMaxSize().padding(16.dp)) {
        // The heading and Back are the tab row's now; adding a machine is this tab's own work
        // and stays with the list it adds to.
        Row(verticalAlignment = Alignment.CenterVertically, modifier = Modifier.fillMaxWidth()) {
            TextButton(onClick = { adding = true }) { Text("Add machine") }
        }
        Spacer(Modifier.height(8.dp))

        actionError?.let {
            Text(it, color = MaterialTheme.colorScheme.error)
            Spacer(Modifier.height(8.dp))
        }
        busy?.let {
            Row(verticalAlignment = Alignment.CenterVertically) {
                CircularProgressIndicator(Modifier.height(16.dp).padding(end = 8.dp))
                Text(it, style = MaterialTheme.typography.bodySmall)
            }
            Spacer(Modifier.height(8.dp))
        }

        when (val current = state) {
            is LoadState.Loading -> CircularProgressIndicator()
            is LoadState.Error -> Text(current.message, color = MaterialTheme.colorScheme.error)
            is LoadState.Loaded ->
                LazyColumn(Modifier.fillMaxSize()) {
                    uniqueItems(current.value, key = { it.id }) { setup ->
                        SetupCard(
                            setup = setup,
                            onRename = { renaming = setup },
                            onRediscover = {
                                scope.launch {
                                    busy = "Asking ${setup.name} what it has…"
                                    actionError =
                                        runCatching {
                                            withContext(Dispatchers.IO) {
                                                updateSetup(
                                                    settings,
                                                    setup.id,
                                                    rediscover = true,
                                                )
                                            }
                                        }
                                            .exceptionOrNull()
                                            ?.message
                                    busy = null
                                    reload()
                                }
                            },
                            onDelete = { confirmingDelete = setup },
                        )
                    }
                }
        }
    }

    if (adding) {
        AddSetupDialog(
            onDismiss = { adding = false },
            onAdd = { name, ssh ->
                adding = false
                scope.launch {
                    busy = "Asking $name what it has…"
                    actionError =
                        runCatching {
                            withContext(Dispatchers.IO) { addSetup(settings, name, ssh) }
                        }
                            .exceptionOrNull()
                            ?.message
                    busy = null
                    reload()
                }
            },
            onTest = { ssh -> withContext(Dispatchers.IO) { probeSetup(settings, ssh) } },
        )
    }

    renaming?.let { setup ->
        RenameDialog(
            setup = setup,
            onDismiss = { renaming = null },
            onRename = { name ->
                renaming = null
                scope.launch {
                    actionError =
                        runCatching {
                            withContext(Dispatchers.IO) {
                                updateSetup(settings, setup.id, name = name)
                            }
                        }
                            .exceptionOrNull()
                            ?.message
                    reload()
                }
            },
        )
    }

    confirmingDelete?.let { setup ->
        AlertDialog(
            onDismissRequest = { confirmingDelete = null },
            title = { Text("Remove \"${setup.name}\"?") },
            text = {
                Text(
                    "The machine is left alone -- this only stops this app offering it. " +
                        "Sessions still running on it must be deleted first."
                )
            },
            confirmButton = {
                TextButton(
                    onClick = {
                        confirmingDelete = null
                        scope.launch {
                            actionError =
                                runCatching {
                                    withContext(Dispatchers.IO) { deleteSetup(settings, setup.id) }
                                }
                                    .exceptionOrNull()
                                    ?.message
                            reload()
                        }
                    }
                ) {
                    Text("Remove")
                }
            },
            dismissButton = {
                TextButton(onClick = { confirmingDelete = null }) { Text("Cancel") }
            },
        )
    }
}

@Composable
private fun SetupCard(
    setup: Setup,
    onRename: () -> Unit,
    onRediscover: () -> Unit,
    onDelete: () -> Unit,
) {
    Card(Modifier.fillMaxWidth().padding(vertical = 4.dp)) {
        Column(Modifier.padding(12.dp)) {
            Text(setup.name, style = MaterialTheme.typography.titleSmall)
            Text(
                // Not "this machine": the seeded setup is *called* that,
                // and the card read "this machine / this machine". The
                // line has to say something the name cannot also be.
                setup.address ?: "runs where the backend does",
                style = MaterialTheme.typography.bodySmall,
                color = MaterialTheme.colorScheme.onSurfaceVariant,
            )
            Spacer(Modifier.height(4.dp))
            Text(
                if (setup.providers.isEmpty()) {
                    "Nothing found on it. Install something and rediscover."
                } else {
                    setup.providers.joinToString(" · ") { it.name }
                },
                style = MaterialTheme.typography.bodySmall,
            )
            Row(verticalAlignment = Alignment.CenterVertically) {
                TextButton(onClick = onRename) { Text("Rename") }
                TextButton(onClick = onRediscover) { Text("Rediscover") }
                Spacer(Modifier.weight(1f))
                TextButton(onClick = onDelete) { Text("Remove") }
            }
        }
    }
}

@Composable
private fun AddSetupDialog(
    onDismiss: () -> Unit,
    onAdd: (String, SshDetails?) -> Unit,
    onTest: suspend (SshDetails?) -> List<Provider>,
) {
    val scope = rememberCoroutineScope()
    var name by remember { mutableStateOf("") }
    var address by remember { mutableStateOf("") }
    var identity by remember { mutableStateOf("") }
    var tested by remember { mutableStateOf<String?>(null) }
    var testing by remember { mutableStateOf(false) }

    fun details(): SshDetails? =
        address
            .trim()
            .takeIf { it.isNotEmpty() }
            ?.let { typed ->
                val (host, typedPort) = splitHostAndPort(typed)
                SshDetails(
                    address = host,
                    port = typedPort,
                    identityFile = identity.trim().ifEmpty { null },
                )
            }

    AlertDialog(
        onDismissRequest = onDismiss,
        title = { Text("Add a machine") },
        text = {
            Column {
                Text(
                    "Leave the address blank for the machine the backend runs on. " +
                        "What it can run is discovered, not typed.",
                    style = MaterialTheme.typography.bodySmall,
                    color = MaterialTheme.colorScheme.onSurfaceVariant,
                )
                Spacer(Modifier.height(8.dp))
                OutlinedTextField(
                    value = name,
                    onValueChange = { name = it },
                    label = { Text("Name") },
                    singleLine = true,
                )
                OutlinedTextField(
                    value = address,
                    onValueChange = { address = it },
                    // Just the shape. What a blank one means is said once, in the text above
                    // this form -- repeating it here wrapped the label onto a second line and
                    // made this field taller than the two beside it for no information.
                    label = { Text("user@host[:port]") },
                    singleLine = true,
                )
                OutlinedTextField(
                    value = identity,
                    onValueChange = { identity = it },
                    label = { Text("Key path on the backend") },
                    singleLine = true,
                )
                tested?.let {
                    Spacer(Modifier.height(8.dp))
                    Text(it, style = MaterialTheme.typography.bodySmall)
                }
            }
        },
        confirmButton = {
            TextButton(enabled = name.isNotBlank(), onClick = { onAdd(name.trim(), details()) }) {
                Text("Add")
            }
        },
        dismissButton = {
            Row {
                // Tried before saving, so a wrong address or an
                // unauthorised key is caught while this form is still on
                // screen rather than at the first spawn.
                TextButton(
                    enabled = !testing,
                    onClick = {
                        testing = true
                        tested = "Asking…"
                        scope.launch {
                            tested =
                                runCatching { onTest(details()) }
                                    .fold(
                                        onSuccess = { found ->
                                            if (found.isEmpty()) {
                                                "Reached it, but found nothing it can run."
                                            } else {
                                                "Found ${found.joinToString(", ") { it.name }}"
                                            }
                                        },
                                        onFailure = { it.message ?: "Couldn't reach it" },
                                    )
                            testing = false
                        }
                    },
                ) {
                    Text("Test")
                }
                TextButton(onClick = onDismiss) { Text("Cancel") }
            }
        },
    )
}

@Composable
private fun RenameDialog(setup: Setup, onDismiss: () -> Unit, onRename: (String) -> Unit) {
    var name by remember { mutableStateOf(setup.name) }
    AlertDialog(
        onDismissRequest = onDismiss,
        title = { Text("Rename") },
        text = {
            Column {
                OutlinedTextField(
                    value = name,
                    onValueChange = { name = it },
                    label = { Text("Name") },
                    singleLine = true,
                )
                Spacer(Modifier.height(8.dp))
                Text(
                    "Sessions already running on it keep working -- they refer to the machine, " +
                        "not to what it is called.",
                    style = MaterialTheme.typography.bodySmall,
                    color = MaterialTheme.colorScheme.onSurfaceVariant,
                )
            }
        },
        confirmButton = {
            TextButton(enabled = name.isNotBlank(), onClick = { onRename(name.trim()) }) {
                Text("Rename")
            }
        },
        dismissButton = { TextButton(onClick = onDismiss) { Text("Cancel") } },
    )
}

/**
 * Splits `user@host:port` into its two halves, with the port left null when none was typed.
 *
 * One field rather than two because that is how an address is written and read everywhere else --
 * and because a port that is almost always 22 does not deserve a box of its own on a phone
 * keyboard. Null rather than 22: the backend already decides the default, and writing 22 here would
 * put a second answer to that question in a second place.
 *
 * A colon only means "port" when it can. A bracketed IPv6 literal is unwrapped as ssh writes it,
 * `[::1]:22`; a bare `::1` keeps every colon, because an address with several is an address, not an
 * address and a port. So the rule is: brackets, or exactly one colon followed by digits.
 */
private fun splitHostAndPort(typed: String): Pair<String, Int?> {
    if (typed.startsWith("[")) {
        val close = typed.indexOf(']')
        if (close > 0) {
            val host = typed.substring(1, close)
            val rest = typed.substring(close + 1)
            val port = rest.removePrefix(":").toIntOrNull().takeIf { rest.startsWith(":") }
            return host to port
        }
    }
    if (typed.count { it == ':' } == 1) {
        val host = typed.substringBeforeLast(':')
        val port = typed.substringAfterLast(':').toIntOrNull()
        if (port != null && host.isNotEmpty()) return host to port
    }
    return typed to null
}