/*
 * Copyright (C) 2021 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.example.tiptime

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.annotation.StringRes
import androidx.compose.foundation.layout.Arrangement
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.layout.size
import androidx.compose.foundation.layout.wrapContentWidth
import androidx.compose.foundation.text.KeyboardActions
import androidx.compose.foundation.text.KeyboardOptions
import androidx.compose.material.Surface
import androidx.compose.material.Switch
import androidx.compose.material.SwitchDefaults
import androidx.compose.material.Text
import androidx.compose.material.TextField
import androidx.compose.runtime.Composable
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.FocusDirection
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.platform.LocalFocusManager
import androidx.compose.ui.res.stringResource
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.input.ImeAction
import androidx.compose.ui.text.input.KeyboardType
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import com.example.tiptime.ui.theme.TipTimeTheme
import java.text.NumberFormat

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            TipTimeTheme {
                Surface(modifier = Modifier.fillMaxSize()) {
                    TipTimeScreen()
                }
            }
        }
    }
}

@Composable
fun TipTimeScreen() {
    var amountInput by remember { mutableStateOf("") }
    var tipInput by remember { mutableStateOf("") }
    var roundUp by remember { mutableStateOf(false) }

    val amount = amountInput.toDoubleOrNull() ?: 0.0
    val tipPercent = tipInput.toDoubleOrNull() ?: 0.0
    val tip = calculateTip(amount, tipPercent, roundUp)

    val focusManager = LocalFocusManager.current

    Column(
        modifier = Modifier.padding(32.dp),
        verticalArrangement = Arrangement.spacedBy(8.dp)
    ) {
        Text(
            text = stringResource(R.string.calculate_tip),
            fontSize = 24.sp,
            modifier = Modifier.align(Alignment.CenterHorizontally)
        )
        Spacer(Modifier.height(16.dp))
        EditNumberField(
            label = R.string.cost_of_service,
            keyboardOptions = KeyboardOptions.Default.copy(
                keyboardType = KeyboardType.Number,
                imeAction = ImeAction.Next
            ),
            keyboardActions = KeyboardActions(
                onNext = { focusManager.moveFocus(FocusDirection.Down) }
            ),
            value = amountInput,
            onValueChanged = { amountInput = it }
        )
        EditNumberField(
            label = R.string.how_was_the_service,
            keyboardOptions = KeyboardOptions.Default.copy(
                keyboardType = KeyboardType.Number,
                imeAction = ImeAction.Done
            ),
            keyboardActions = KeyboardActions(
                onDone = { focusManager.clearFocus() }
            ),
            value = tipInput,
            onValueChanged = { tipInput = it }
        )
        RoundTheTipRow(roundUp = roundUp, onRoundUpChanged = { roundUp = it })
        Spacer(Modifier.height(24.dp))
        Text(
            text = stringResource(R.string.tip_amount, tip),
            modifier = Modifier.align(Alignment.CenterHorizontally),
            fontSize = 20.sp,
            fontWeight = FontWeight.Bold
        )
    }
}

@Composable
fun EditNumberField(
    @StringRes label: Int,
    keyboardOptions: KeyboardOptions,
    keyboardActions: KeyboardActions,
    value: String,
    onValueChanged: (String) -> Unit,
    modifier: Modifier = Modifier
) {
    TextField(
        value = value,
        singleLine = true,
        modifier = modifier.fillMaxWidth(),
        onValueChange = onValueChanged,
        label = { Text(stringResource(label)) },
        keyboardOptions = keyboardOptions,
        keyboardActions = keyboardActions
    )
}

@Composable
fun RoundTheTipRow(
    roundUp: Boolean,
    onRoundUpChanged: (Boolean) -> Unit,
    modifier: Modifier = Modifier
) {
    Row(
        modifier = Modifier
            .fillMaxWidth()
            .size(48.dp),
        verticalAlignment = Alignment.CenterVertically
    ) {
        Text(text = stringResource(R.string.round_up_tip))
        Switch(
            modifier = modifier
                .fillMaxWidth()
                .wrapContentWidth(Alignment.End),
            checked = roundUp,
            onCheckedChange = onRoundUpChanged,
            colors = SwitchDefaults.colors(
                uncheckedThumbColor = Color.DarkGray
            )
        )
    }
}

/**
 * Calculates the tip based on the user input and format the tip amount
 * according to the local currency and display it onscreen.
 * Example would be "$10.00".
 */
private fun calculateTip(amount: Double, tipPercent: Double = 15.0, roundUp: Boolean): String {
    var tip = tipPercent / 100 * amount
    if (roundUp)
        tip = kotlin.math.ceil(tip)
    return NumberFormat.getCurrencyInstance().format(tip)
}

@Preview
@Composable
fun TipTimeScreenPreview() {
    TipTimeTheme {
        TipTimeScreen()
    }
}