package soy.iko.opencode.ui.screens

import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Column
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.imePadding
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.size
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.filled.Lock
import androidx.compose.material.icons.filled.Person
import androidx.compose.material.icons.filled.Terminal
import androidx.compose.material.icons.filled.Visibility
import androidx.compose.material.icons.filled.VisibilityOff
import androidx.compose.material3.Button
import androidx.compose.material3.CircularProgressIndicator
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.OutlinedTextField
import androidx.compose.material3.Text
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.focus.FocusRequester
import androidx.compose.ui.focus.focusRequester
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.text.style.TextAlign
import androidx.compose.ui.unit.dp
import soy.iko.opencode.core.Event
import soy.iko.opencode.core.UiState

@Composable
fun ConnectScreen(state: UiState, dispatch: (Event) -> Unit) {
    val focusRequester = remember { FocusRequester() }
    var passwordVisible by remember { mutableStateOf(false) }

    // Focus the server URL field when the screen opens, but only when it's empty
    // so we don't steal focus (and pop the keyboard) on a return visit.
    LaunchedEffect(Unit) {
        if (state.serverUrl.isEmpty()) focusRequester.requestFocus()
    }

    Column(
        modifier = Modifier
            .fillMaxSize()
            .verticalScroll(rememberScrollState())
            .imePadding()
            .padding(horizontal = 28.dp),
        verticalArrangement = Arrangement.Center,
        horizontalAlignment = Alignment.CenterHorizontally,
    ) {
        Icon(
            Icons.Filled.Terminal,
            contentDescription = null,
            tint = MaterialTheme.colorScheme.primary,
            modifier = Modifier.size(72.dp),
        )
        Spacer(Modifier.height(16.dp))
        Text(
            text = "opencode",
            style = MaterialTheme.typography.displaySmall,
            color = MaterialTheme.colorScheme.primary,
        )
        Text(
            text = "Connect to your opencode server",
            style = MaterialTheme.typography.bodyMedium,
            color = MaterialTheme.colorScheme.onSurfaceVariant,
            textAlign = TextAlign.Center,
        )

        Spacer(Modifier.height(32.dp))

        OutlinedTextField(
            value = state.serverUrl,
            onValueChange = { dispatch(Event.ServerUrlChanged(it)) },
            label = { Text("Server URL") },
            placeholder = { Text("http://192.168.1.10:4096") },
            singleLine = true,
            modifier = Modifier.fillMaxWidth().focusRequester(focusRequester),
            keyboardOptions = KeyboardOptions(
                keyboardType = KeyboardType.Uri,
                imeAction = if (state.authRequired) ImeAction.Next else ImeAction.Go,
            ),
            keyboardActions = KeyboardActions(onGo = { dispatch(Event.Connect) }),
            enabled = !state.loading,
        )

        // Point first-time users at the expected address format. Hidden once they
        // start typing so it doesn't compete with the field's own contents.
        if (state.serverUrl.isEmpty()) {
            Spacer(Modifier.height(6.dp))
            Text(
                text = "Enter the URL of your opencode server (e.g. http://192.168.1.10:4096)",
                style = MaterialTheme.typography.bodySmall,
                color = MaterialTheme.colorScheme.onSurfaceVariant,
                textAlign = TextAlign.Center,
            )
        }

        // Nudge the user if the URL looks like it's missing a scheme — a bare host:port
        // won't connect. Informational (tertiary), not an error, since it's a heuristic.
        if (state.serverUrl.isNotBlank() && "://" !in state.serverUrl && !state.serverUrl.startsWith("http")) {
            Spacer(Modifier.height(6.dp))
            Text(
                text = "Tip: Add http:// if connecting to a local server",
                style = MaterialTheme.typography.bodySmall,
                color = MaterialTheme.colorScheme.tertiary,
                textAlign = TextAlign.Center,
            )
        }

        if (state.authRequired) {
            Spacer(Modifier.height(12.dp))
            OutlinedTextField(
                value = state.username,
                onValueChange = { dispatch(Event.UsernameChanged(it)) },
                label = { Text("Username") },
                singleLine = true,
                leadingIcon = { Icon(Icons.Filled.Person, contentDescription = null) },
                modifier = Modifier.fillMaxWidth(),
                keyboardOptions = KeyboardOptions(imeAction = ImeAction.Next),
                enabled = !state.loading,
            )
            Spacer(Modifier.height(12.dp))
            OutlinedTextField(
                value = state.password,
                onValueChange = { dispatch(Event.PasswordChanged(it)) },
                label = { Text("Password") },
                singleLine = true,
                visualTransformation = if (passwordVisible) VisualTransformation.None else PasswordVisualTransformation(),
                leadingIcon = { Icon(Icons.Filled.Lock, contentDescription = null) },
                trailingIcon = {
                    IconButton(onClick = { passwordVisible = !passwordVisible }) {
                        Icon(
                            imageVector = if (passwordVisible) Icons.Filled.VisibilityOff else Icons.Filled.Visibility,
                            contentDescription = if (passwordVisible) "Hide password" else "Show password",
                        )
                    }
                },
                modifier = Modifier.fillMaxWidth(),
                keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.Password, imeAction = ImeAction.Go),
                keyboardActions = KeyboardActions(onGo = { dispatch(Event.Connect) }),
                enabled = !state.loading,
            )
            Spacer(Modifier.height(4.dp))
            Text(
                text = "This server requires authentication.",
                style = MaterialTheme.typography.bodySmall,
                color = MaterialTheme.colorScheme.onSurfaceVariant,
            )
        }

        Spacer(Modifier.height(24.dp))

        Button(
            onClick = { dispatch(Event.Connect) },
            enabled = !state.loading && state.serverUrl.isNotBlank(),
            modifier = Modifier.fillMaxWidth(),
        ) {
            if (state.loading) {
                CircularProgressIndicator(
                    modifier = Modifier.height(20.dp),
                    strokeWidth = 2.dp,
                    color = MaterialTheme.colorScheme.onPrimary,
                )
            } else {
                Text(if (state.authRequired) "Sign in" else "Connect")
            }
        }

        // Surface the error inline as well, so it stays visible while the user
        // corrects the form (the snackbar is transient).
        if (state.error != null && !state.loading) {
            Spacer(Modifier.height(8.dp))
            Text(
                text = state.error,
                style = MaterialTheme.typography.bodySmall,
                color = MaterialTheme.colorScheme.error,
                textAlign = TextAlign.Center,
            )
        }
    }
}