book-reader/app/src/main/java/com/aryan/reader/MainScreen.kt

/*
 * Episteme Reader - A native Android document reader.
 * Copyright (C) 2026 Episteme
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 * mail: epistemereader@gmail.com
 */
// MainScreen.kt
package com.aryan.reader

import androidx.activity.ComponentActivity
import androidx.activity.enableEdgeToEdge
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.pager.HorizontalPager
import androidx.compose.foundation.pager.rememberPagerState
import androidx.compose.material3.Icon
import androidx.compose.material3.NavigationBar
import androidx.compose.material3.NavigationBarItem
import androidx.compose.material3.Scaffold
import androidx.compose.material3.Text
import androidx.compose.material3.windowsizeclass.WindowSizeClass
import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.SideEffect
import androidx.compose.runtime.getValue
import androidx.compose.runtime.rememberCoroutineScope
import androidx.compose.ui.Modifier
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.res.painterResource
import androidx.compose.ui.res.stringResource
import androidx.lifecycle.compose.collectAsStateWithLifecycle
import androidx.navigation.NavHostController
import kotlinx.coroutines.launch

sealed class BottomBarScreen(val route: String, val stringResId: Int, val iconResId: Int) {
    object Home : BottomBarScreen("home", R.string.nav_home, R.drawable.home)
    object Library : BottomBarScreen("library", R.string.nav_library, R.drawable.library_books)
}

private val bottomBarItems = listOf(
    BottomBarScreen.Home,
    BottomBarScreen.Library,
)

@Composable
fun MainScreen(
    viewModel: MainViewModel,
    windowSizeClass: WindowSizeClass,
    navController: NavHostController
) {
    val context = LocalContext.current

    SideEffect {
        val activity = context as? ComponentActivity
        activity?.enableEdgeToEdge()
    }

    val uiState by viewModel.uiState.collectAsStateWithLifecycle()
    val viewingShelfName = uiState.viewingShelfId

    androidx.compose.foundation.layout.Box(modifier = Modifier.fillMaxSize()) {
        if (viewingShelfName != null) {
            ShelfScreen(viewModel = viewModel)
        } else {
            val pagerState = rememberPagerState(
                initialPage = uiState.mainScreenStartPage,
                pageCount = { bottomBarItems.size }
            )
            val scope = rememberCoroutineScope()

            LaunchedEffect(uiState.mainScreenStartPage) {
                if (pagerState.currentPage != uiState.mainScreenStartPage) {
                    pagerState.animateScrollToPage(uiState.mainScreenStartPage)
                }
            }

            LaunchedEffect(pagerState.currentPage) {
                viewModel.setMainScreenPage(pagerState.currentPage)
            }

            Scaffold(
                contentWindowInsets = androidx.compose.foundation.layout.WindowInsets(0, 0, 0, 0),
                bottomBar = {
                    NavigationBar {
                        bottomBarItems.forEachIndexed { index, screen ->
                            NavigationBarItem(
                                icon = { Icon(painterResource(id = screen.iconResId), contentDescription = stringResource(screen.stringResId)) },
                                label = { Text(stringResource(screen.stringResId)) },
                                selected = pagerState.currentPage == index,
                                onClick = { scope.launch { pagerState.animateScrollToPage(index) } }
                            )
                        }
                    }
                }
            ) { innerPadding ->
                HorizontalPager(
                    state = pagerState,
                    modifier = Modifier
                        .fillMaxSize()
                        .padding(innerPadding),
                    key = { bottomBarItems[it].route },
                    beyondViewportPageCount = 1,
                    userScrollEnabled = false
                ) { page ->
                    when (page) {
                        0 -> HomeScreen(
                            viewModel = viewModel,
                            windowSizeClass = windowSizeClass,
                            navController = navController
                        )
                        1 -> LibraryScreen(viewModel = viewModel)
                    }
                }
            }
        }

        if (uiState.showTagSelectionDialogFor.isNotEmpty()) {
            TagSelectionBottomSheet(
                allTags = uiState.allTags,
                selectedBookIds = uiState.showTagSelectionDialogFor,
                booksWithTags = uiState.rawLibraryFiles,
                onCreateAndAssign = { name ->
                    viewModel.createAndAssignTag(name, uiState.showTagSelectionDialogFor)
                },
                onToggleTag = { tagId, assign ->
                    viewModel.toggleTagForBooks(tagId, uiState.showTagSelectionDialogFor, assign)
                },
                onDismiss = viewModel::closeTagSelection
            )
        }
    }
}