Temperature Unit Converter

}

fun convertTemperature(input: String, fromCelsius: Boolean): ConversionResult {
    val value = input.trim().toDoubleOrNull()
    if (value == null || !value.isFinite()) {
        return ConversionResult.Error("Enter a finite temperature. Negative values are allowed.")
    }
    val converted = if (fromCelsius) value * (9.0 / 5.0) + 32.0 else (value - 32.0) * (5.0 / 9.0)
    if (!converted.isFinite()) {
        return ConversionResult.Error("This temperature is too large to convert.")
    }
    return ConversionResult.Success(converted, if (fromCelsius) "°F" else "°C")
}

        return ConversionResult.Error("Enter a finite temperature. Negative values are allowed.")
    }
    val converted = if (fromCelsius) value * (9.0 / 5.0) + 32.0 else (value - 32.0) * (5.0 / 9.0)
    if (!converted.isFinite()) {
        return ConversionResult.Error("This temperature is too large to convert.")
    }
    return ConversionResult.Success(converted, if (fromCelsius) "°F" else "°C")
}

@Composable
fun TemperatureConverter() {
    var input by rememberSaveable { mutableStateOf("0") }
    var fromCelsius by rememberSaveable { mutableStateOf(true) }
    var showResult by rememberSaveable { mutableStateOf(false) }
    val result = convertTemperature(input, fromCelsius)

    Text("Choose the input scale, then enter a temperature.")
    DirectionOption("Celsius to Fahrenheit", fromCelsius) { fromCelsius = true; showResult = false }
    DirectionOption("Fahrenheit to Celsius", !fromCelsius) { fromCelsius = false; showResult = false }
    OutlinedTextField(
        value = input,
        onValueChange = { input = it; showResult = false },
        label = { Text(if (fromCelsius) "Temperature (°C)" else "Temperature (°F)") },
        supportingText = { Text("Use a dot for decimals. You can type a minus sign.") },
        keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.Text),
        singleLine = true,
        modifier = Modifier.fillMaxWidth()
    )
    Row(horizontalArrangement = Arrangement.spacedBy(12.dp)) {
        Button(onClick = { showResult = true }) { Text("Convert") }
        OutlinedButton(onClick = { input = ""; fromCelsius = true; showResult = false }) { Text("Clear") }
    }
    if (!showResult) Text("Tap Convert to calculate the current input.")
    if (showResult) when (result) {
        is ConversionResult.Error -> Text(result.message, color = MaterialTheme.colorScheme.error)

@Composable
private fun DirectionOption(label: String, selected: Boolean, onSelect: () -> Unit) {
    Row(
        modifier = Modifier.fillMaxWidth().selectable(selected = selected, role = Role.RadioButton, onClick = onSelect),
        verticalAlignment = Alignment.CenterVertically,
        horizontalArrangement = Arrangement.spacedBy(8.dp)
    ) {
        RadioButton(selected = selected, onClick = null)
        Text(label)
    }
}

        value = input,
        onValueChange = { input = it; showResult = false },
        label = { Text(if (fromCelsius) "Temperature (°C)" else "Temperature (°F)") },
        supportingText = { Text("Use a dot for decimals. You can type a minus sign.") },
        keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.Text),
        singleLine = true,
        modifier = Modifier.fillMaxWidth()
    )
    Row(horizontalArrangement = Arrangement.spacedBy(12.dp)) {
        Button(onClick = { showResult = true }) { Text("Convert") }
        OutlinedButton(onClick = { input = ""; fromCelsius = true; showResult = false }) { Text("Clear") }
    }
    if (!showResult) Text("Tap Convert to calculate the current input.")
    if (showResult) when (result) {
        is ConversionResult.Error -> Text(result.message, color = MaterialTheme.colorScheme.error)
        is ConversionResult.Success -> Text(
            "${String.format(Locale.US, "%.6g", if (result.value == 0.0) 0.0 else result.value)} ${result.unit}",
            style = MaterialTheme.typography.headlineMedium
        )
    }
    Text("Changing direction keeps the typed number and interprets it in the newly selected input scale.")
    Text("The result is rounded to six significant digits. This exercise converts numeric values; it does not model physical limits.")
}

@Composable
private fun DirectionOption(label: String, selected: Boolean, onSelect: () -> Unit) {

    }

    @Test fun negativeFortyIsTheSameOnBothScales() {
        assertEquals(-40.0, (convertTemperature("-40", true) as ConversionResult.Success).value, 0.000001)
        assertEquals(-40.0, (convertTemperature("-40", false) as ConversionResult.Success).value, 0.000001)
    }

    @Test fun decimalsAreNotTruncated() {
        assertEquals(98.6, (convertTemperature("37", true) as ConversionResult.Success).value, 0.000001)
    }

    @Test fun rejectsBlankNonNumericNonFiniteAndOverflow() {
        listOf("", "-", "abc", "NaN", "Infinity", "1.7e308").forEach {
            assertTrue(convertTemperature(it, true) is ConversionResult.Error)
        }
    }
}