/*
 * Copyright 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
 *
 *      https://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.google.accompanist.sample.pager

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.PaddingValues
import androidx.compose.foundation.layout.aspectRatio
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.material.MaterialTheme
import androidx.compose.material.Scaffold
import androidx.compose.material.Surface
import androidx.compose.material.Text
import androidx.compose.material.TopAppBar
import androidx.compose.runtime.Composable
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.res.stringResource
import androidx.compose.ui.unit.dp
import com.google.accompanist.pager.ExperimentalPagerApi
import com.google.accompanist.pager.HorizontalPager
import com.google.accompanist.pager.rememberPagerState
import com.google.accompanist.sample.AccompanistSampleTheme
import com.google.accompanist.sample.R

class HorizontalPagerLoopingSample : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContent {
            AccompanistSampleTheme {
                Surface {
                    Sample()
                }
            }
        }
    }
}

@OptIn(ExperimentalPagerApi::class)
@Composable
private fun Sample() {
    Scaffold(
        topBar = {
            TopAppBar(
                title = { Text(stringResource(R.string.horiz_pager_title_looping)) },
                backgroundColor = MaterialTheme.colors.surface,
            )
        },
        modifier = Modifier.fillMaxSize()
    ) { padding ->
        Column(Modifier.fillMaxSize().padding(padding)) {
            // Display 10 items
            val pageCount = 10

            // We start the pager in the middle of the raw number of pages
            val startIndex = Int.MAX_VALUE / 2
            val pagerState = rememberPagerState(initialPage = startIndex)

            HorizontalPager(
                // Set the raw page count to a really large number
                count = Int.MAX_VALUE,
                state = pagerState,
                // Add 32.dp horizontal padding to 'center' the pages
                contentPadding = PaddingValues(horizontal = 32.dp),
                // Add some horizontal spacing between items
                itemSpacing = 4.dp,
                modifier = Modifier
                    .weight(1f)
                    .fillMaxWidth()
            ) { index ->
                // We calculate the page from the given index
                val page = (index - startIndex).floorMod(pageCount)
                PagerSampleItem(
                    page = page,
                    modifier = Modifier
                        .fillMaxWidth()
                        .aspectRatio(1f)
                )
            }

            ActionsRow(
                pagerState = pagerState,
                modifier = Modifier.align(Alignment.CenterHorizontally)
            )
        }
    }
}

private fun Int.floorMod(other: Int): Int = when (other) {
    0 -> this
    else -> this - floorDiv(other) * other
}
