/**
 * TipCalculatorApp — Compose state + TextField input + hoisted state.
 */

import androidx.compose.foundation.layout.*
import androidx.compose.foundation.text.KeyboardOptions
import androidx.compose.material3.*
import androidx.compose.runtime.*
import androidx.compose.ui.Modifier
import androidx.compose.ui.text.input.KeyboardType
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import kotlin.math.ceil

@Composable
fun TipCalculatorApp() {
    var amountInput by remember { mutableStateOf("") }
    var percentInput by remember { mutableStateOf("15") }
    var roundUp by remember { mutableStateOf(false) }

    val amount = amountInput.toDoubleOrNull() ?: 0.0
    val percent = percentInput.toDoubleOrNull() ?: 0.0
    val rawTip = amount * percent / 100
    val tip = if (roundUp) ceil(rawTip) else rawTip

    Column(Modifier.padding(16.dp), verticalArrangement = Arrangement.spacedBy(12.dp)) {
        Text("Tip Calculator", fontSize = 24.sp, fontWeight = FontWeight.Bold)

        OutlinedTextField(
            value = amountInput,
            onValueChange = { amountInput = it },
            label = { Text("Bill amount") },
            keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.Number),
            singleLine = true
        )

        OutlinedTextField(
            value = percentInput,
            onValueChange = { percentInput = it },
            label = { Text("Tip %") },
            keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.Number),
            singleLine = true
        )

        Row(verticalAlignment = androidx.compose.ui.Alignment.CenterVertically) {
            Text("Round up", modifier = Modifier.weight(1f))
            Switch(checked = roundUp, onCheckedChange = { roundUp = it })
        }

        Divider()

        Text("Tip: %.2f".format(tip), fontSize = 22.sp, fontWeight = FontWeight.Bold)
        Text("Total: %.2f".format(amount + tip), fontSize = 18.sp)
    }
}

@Preview(showBackground = true)
@Composable
fun TipCalculatorPreview() { TipCalculatorApp() }