// FontsScreen.kt
@file:Suppress("KotlinConstantConditions")

package com.aryan.reader

import androidx.compose.foundation.background
import androidx.compose.foundation.clickable
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.PaddingValues
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.statusBarsPadding
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.items
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.automirrored.filled.ArrowBack
import androidx.compose.material.icons.filled.Add
import androidx.compose.material.icons.filled.Check
import androidx.compose.material.icons.filled.CloudDownload
import androidx.compose.material.icons.filled.Delete
import androidx.compose.material.icons.filled.Search
import androidx.compose.material3.AlertDialog
import androidx.compose.material3.ButtonDefaults
import androidx.compose.material3.Card
import androidx.compose.material3.CardDefaults
import androidx.compose.material3.CircularProgressIndicator
import androidx.compose.material3.ExperimentalMaterial3Api
import androidx.compose.material3.ExtendedFloatingActionButton
import androidx.compose.material3.HorizontalDivider
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.ModalBottomSheet
import androidx.compose.material3.OutlinedTextField
import androidx.compose.material3.Scaffold
import androidx.compose.material3.Surface
import androidx.compose.material3.Text
import androidx.compose.material3.TextButton
import androidx.compose.material3.rememberModalBottomSheetState
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.draw.clip
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.res.stringResource
import androidx.compose.ui.text.font.Font
import androidx.compose.ui.text.font.FontFamily
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import androidx.lifecycle.compose.collectAsStateWithLifecycle
import com.aryan.reader.shared.CustomFontItem
import com.aryan.reader.shared.ui.SharedAppFontSelector
import com.aryan.reader.shared.ui.SharedFontSettingsSection
import com.aryan.reader.shared.ui.SharedFontSettingsTabs
import com.aryan.reader.data.CustomFontEntity
import java.io.File

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun FontsScreen(
    viewModel: MainViewModel,
    onBackClick: () -> Unit
) {
    val fonts: List<CustomFontEntity> by viewModel.customFonts.collectAsStateWithLifecycle()
    val uiState by viewModel.uiState.collectAsStateWithLifecycle()
    val context = LocalContext.current

    val showGoogleFontsOption = !(BuildConfig.FLAVOR == "oss" && BuildConfig.IS_OFFLINE)

    // Dialog state
    var showDeleteDialog by remember { mutableStateOf(false) }
    var fontToDelete by remember { mutableStateOf<CustomFontEntity?>(null) }
    var showGoogleFontsSheet by remember { mutableStateOf(false) }
    var selectedSection by remember { mutableStateOf(SharedFontSettingsSection.READER_FONTS) }

    val pickFontLauncher = rememberFilePickerLauncher { uris ->
        uris.firstOrNull()?.let { viewModel.importFont(it) }
    }

    val fontMimeTypes = arrayOf(
        "font/ttf", "font/otf", "font/woff2",
        "application/x-font-ttf", "application/x-font-otf",
        "application/font-woff2", "application/vnd.ms-opentype",
        "application/x-font-opentype"
    )

    Scaffold(
        modifier = Modifier.statusBarsPadding(),
        topBar = {
            CustomTopAppBar(
                title = { Text(stringResource(R.string.custom_fonts)) },
                navigationIcon = {
                    IconButton(onClick = onBackClick) {
                        Icon(Icons.AutoMirrored.Filled.ArrowBack, contentDescription = stringResource(R.string.action_back))
                    }
                }
            )
        },
        floatingActionButton = {
            if (selectedSection == SharedFontSettingsSection.READER_FONTS && fonts.isNotEmpty()) {
                Column(
                    horizontalAlignment = Alignment.End,
                    verticalArrangement = Arrangement.spacedBy(16.dp)
                ) {
                    if (showGoogleFontsOption) {
                        ExtendedFloatingActionButton(
                            onClick = { showGoogleFontsSheet = true },
                            icon = { Icon(Icons.Default.CloudDownload, contentDescription = null) },
                            text = { Text(stringResource(R.string.google_fonts)) },
                            containerColor = MaterialTheme.colorScheme.secondaryContainer,
                            contentColor = MaterialTheme.colorScheme.onSecondaryContainer
                        )
                    }

                    ExtendedFloatingActionButton(
                        onClick = { pickFontLauncher.launch(fontMimeTypes) },
                        icon = { Icon(Icons.Default.Add, contentDescription = null) },
                        text = { Text(stringResource(R.string.import_font)) }
                    )
                }
            }
        }
    ) { padding ->
        Box(modifier = Modifier.fillMaxSize().padding(padding)) {
            val sharedFonts = remember(fonts) { fonts.toSharedCustomFontItems() }
            Column(modifier = Modifier.fillMaxSize()) {
                SharedFontSettingsTabs(
                    selectedSection = selectedSection,
                    onSectionChange = { selectedSection = it },
                    modifier = Modifier.padding(start = 16.dp, end = 16.dp, top = 16.dp)
                )

                when (selectedSection) {
                    SharedFontSettingsSection.READER_FONTS -> {
                        if (fonts.isEmpty()) {
                            val secondaryText = if (showGoogleFontsOption) stringResource(R.string.action_browse_google_fonts) else null
                            val secondaryClick: (() -> Unit)? = if (showGoogleFontsOption) { { showGoogleFontsSheet = true } } else null

                            EmptyState(
                                title = stringResource(R.string.no_custom_fonts),
                                message = stringResource(R.string.import_fonts_desc),
                                onSelectFileClick = { pickFontLauncher.launch(fontMimeTypes) },
                                modifier = Modifier.weight(1f),
                                secondaryButtonText = secondaryText,
                                onSecondaryClick = secondaryClick
                            )
                        } else {
                            LazyColumn(
                                modifier = Modifier.weight(1f),
                                contentPadding = PaddingValues(start = 16.dp, end = 16.dp, top = 16.dp, bottom = 88.dp),
                                verticalArrangement = Arrangement.spacedBy(12.dp)
                            ) {
                                items(fonts, key = { it.id }) { font ->
                                    FontListItem(
                                        font = font,
                                        onDelete = {
                                            fontToDelete = font
                                            showDeleteDialog = true
                                        }
                                    )
                                }
                            }
                        }
                    }

                    SharedFontSettingsSection.APP_TEXT -> {
                        SharedAppFontSelector(
                            preference = uiState.appFontPreference,
                            customFonts = sharedFonts,
                            onPreferenceChange = viewModel::setAppFontPreference,
                            fontFamilyForPreview = { font ->
                                val file = File(font.path)
                                if (file.isFile) {
                                    runCatching { FontFamily(Font(file)) }.getOrNull()
                                } else {
                                    null
                                }
                            },
                            modifier = Modifier.padding(start = 16.dp, end = 16.dp, top = 16.dp)
                        )
                    }
                }
            }

            if (uiState.isLoading) {
                Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = MaterialTheme.colorScheme.background.copy(alpha = 0.7f)
                ) {
                    Box(contentAlignment = Alignment.Center) {
                        CircularProgressIndicator()
                    }
                }
            }
        }
    }

    if (showDeleteDialog && fontToDelete != null) {
        DeleteFontConfirmationDialog(
            fontName = fontToDelete!!.displayName,
            onConfirm = {
                fontToDelete?.let { viewModel.deleteFont(it.id) }
                showDeleteDialog = false
                fontToDelete = null
            },
            onDismiss = {
                showDeleteDialog = false
                fontToDelete = null
            }
        )
    }

    if (showGoogleFontsSheet) {
        GoogleFontsBottomSheet(
            onDismiss = { showGoogleFontsSheet = false },
            existingFonts = fonts,
            getFullFontList = { viewModel.loadGoogleFontsList(context) },
            onDownloadFont = { fontName, onComplete ->
                viewModel.downloadGoogleFont(fontName, onComplete)
            }
        )
    }
}

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun GoogleFontsBottomSheet(
    onDismiss: () -> Unit,
    existingFonts: List<CustomFontEntity>,
    getFullFontList: () -> List<String>,
    onDownloadFont: (String, () -> Unit) -> Unit
) {
    val sheetState = rememberModalBottomSheetState(skipPartiallyExpanded = true)
    var searchQuery by remember { mutableStateOf("") }
    var downloadingFontName by remember { mutableStateOf<String?>(null) }

    // Curated presets to show when search is empty
    val popularPresets = remember {
        listOf(
            "Merriweather", "Open Sans", "Playfair Display", "Montserrat", "Oswald", "Raleway", "Nunito",
            "Poppins", "Ubuntu", "Fira Sans", "Quicksand", "Crimson Text",
            "Literata", "EB Garamond", "Libre Baskerville", "Inter", "Work Sans"
        )
    }

    // Lazy evaluation of the full list only when typing
    val displayList = remember(searchQuery) {
        if (searchQuery.isBlank()) {
            popularPresets
        } else {
            val allFonts = getFullFontList()
            allFonts.filter { it.contains(searchQuery, ignoreCase = true) }.take(50) // Limit to 50 for performance
        }
    }

    ModalBottomSheet(
        onDismissRequest = onDismiss,
        sheetState = sheetState,
        containerColor = MaterialTheme.colorScheme.surface
    ) {
        Column(
            modifier = Modifier
                .fillMaxWidth()
                .padding(horizontal = 16.dp, vertical = 8.dp)
        ) {
            Text(
                text = stringResource(R.string.action_browse_google_fonts),
                style = MaterialTheme.typography.titleLarge,
                fontWeight = FontWeight.Bold,
                modifier = Modifier.padding(bottom = 12.dp)
            )

            OutlinedTextField(
                value = searchQuery,
                onValueChange = { searchQuery = it },
                modifier = Modifier.fillMaxWidth(),
                placeholder = { Text(stringResource(R.string.google_fonts_search_placeholder)) },
                leadingIcon = { Icon(Icons.Default.Search, contentDescription = null) },
                singleLine = true,
                shape = RoundedCornerShape(12.dp)
            )

            Spacer(modifier = Modifier.height(16.dp))

            LazyColumn(
                modifier = Modifier.fillMaxWidth(),
                contentPadding = PaddingValues(bottom = 24.dp),
                verticalArrangement = Arrangement.spacedBy(10.dp)
            ) {
                if (searchQuery.isBlank()) {
                    item {
                        Text(
                            text = stringResource(R.string.google_fonts_popular_choices),
                            style = MaterialTheme.typography.labelMedium,
                            color = MaterialTheme.colorScheme.primary,
                            modifier = Modifier.padding(vertical = 4.dp)
                        )
                    }
                } else if (displayList.isEmpty()) {
                    item {
                        Text(
                            text = stringResource(R.string.google_fonts_no_matches, searchQuery),
                            style = MaterialTheme.typography.bodyMedium,
                            color = MaterialTheme.colorScheme.onSurfaceVariant,
                            modifier = Modifier.padding(16.dp)
                        )
                    }
                }

                items(displayList) { fontName ->
                    val isDownloaded = remember(existingFonts, fontName) {
                        existingFonts.any { it.displayName.equals(fontName, ignoreCase = true) }
                    }
                    val isDownloading = downloadingFontName == fontName

                    Row(
                        modifier = Modifier
                            .fillMaxWidth()
                            .clip(RoundedCornerShape(8.dp))
                            .clickable(enabled = !isDownloaded && !isDownloading) {
                                downloadingFontName = fontName
                                onDownloadFont(fontName) {
                                    if (downloadingFontName == fontName) {
                                        downloadingFontName = null
                                    }
                                }
                            }
                            .background(
                                if (isDownloaded) MaterialTheme.colorScheme.primaryContainer.copy(alpha = 0.2f)
                                else MaterialTheme.colorScheme.surfaceVariant.copy(alpha = 0.3f)
                            )
                            .padding(horizontal = 16.dp, vertical = 14.dp),
                        verticalAlignment = Alignment.CenterVertically,
                        horizontalArrangement = Arrangement.SpaceBetween
                    ) {
                        Text(
                            text = fontName,
                            style = MaterialTheme.typography.bodyLarge,
                            fontWeight = if (isDownloaded) FontWeight.Bold else FontWeight.Medium,
                            color = if (isDownloaded) MaterialTheme.colorScheme.primary else MaterialTheme.colorScheme.onSurface
                        )

                        Box(modifier = Modifier.padding(start = 12.dp)) {
                            when {
                                isDownloaded -> {
                                    Icon(
                                        Icons.Default.Check,
                                        contentDescription = stringResource(R.string.content_desc_already_downloaded),
                                        tint = MaterialTheme.colorScheme.primary,
                                        modifier = Modifier.size(20.dp)
                                    )
                                }
                                isDownloading -> {
                                    CircularProgressIndicator(
                                        modifier = Modifier.size(20.dp),
                                        strokeWidth = 2.dp,
                                        color = MaterialTheme.colorScheme.primary
                                    )
                                }
                                else -> {
                                    Icon(
                                        Icons.Default.CloudDownload,
                                        contentDescription = stringResource(R.string.action_download),
                                        tint = MaterialTheme.colorScheme.onSurfaceVariant,
                                        modifier = Modifier.size(20.dp)
                                    )
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}

// Existing unchanged components
@Composable
fun FontListItem(
    font: CustomFontEntity,
    onDelete: () -> Unit
) {
    val customTypeface = remember(font.path) {
        try {
            FontFamily(Font(File(font.path)))
        } catch (_: Exception) {
            null
        }
    }

    Card(
        modifier = Modifier.fillMaxWidth(),
        colors = CardDefaults.cardColors(containerColor = MaterialTheme.colorScheme.surface)
    ) {
        Column(modifier = Modifier.padding(16.dp)) {
            Row(
                modifier = Modifier.fillMaxWidth(),
                horizontalArrangement = Arrangement.SpaceBetween,
                verticalAlignment = Alignment.CenterVertically
            ) {
                Text(
                    text = font.displayName,
                    style = MaterialTheme.typography.titleMedium,
                    fontWeight = FontWeight.Bold
                )
                IconButton(onClick = onDelete, modifier = Modifier.size(24.dp)) {
                    Icon(
                        Icons.Default.Delete,
                        contentDescription = stringResource(R.string.action_delete),
                        tint = MaterialTheme.colorScheme.error
                    )
                }
            }

            HorizontalDivider(modifier = Modifier.padding(vertical = 8.dp))

            Box(
                modifier = Modifier
                    .fillMaxWidth()
                    .background(MaterialTheme.colorScheme.surfaceVariant.copy(alpha = 0.5f), MaterialTheme.shapes.small)
                    .padding(12.dp)
            ) {
                if (customTypeface != null) {
                    Text(
                        text = stringResource(R.string.font_preview_text),
                        fontFamily = customTypeface,
                        fontSize = 18.sp,
                        color = MaterialTheme.colorScheme.onSurface
                    )
                } else {
                    Text(
                        text = stringResource(R.string.font_preview_error),
                        style = MaterialTheme.typography.bodySmall,
                        color = MaterialTheme.colorScheme.error
                    )
                }
            }

            Spacer(modifier = Modifier.height(4.dp))
            Text(
                text = font.fileExtension.uppercase(),
                style = MaterialTheme.typography.labelSmall,
                color = MaterialTheme.colorScheme.outline
            )
        }
    }
}

private fun List<CustomFontEntity>.toSharedCustomFontItems(): List<CustomFontItem> {
    return filterNot { it.isDeleted }
        .sortedBy { it.displayName.lowercase() }
        .map { font ->
            CustomFontItem(
                id = font.id,
                displayName = font.displayName,
                fileName = font.fileName,
                fileExtension = font.fileExtension,
                path = font.path,
                timestamp = font.timestamp,
                isDeleted = font.isDeleted
            )
        }
}

@Composable
fun DeleteFontConfirmationDialog(
    fontName: String,
    onConfirm: () -> Unit,
    onDismiss: () -> Unit
) {
    AlertDialog(
        onDismissRequest = onDismiss,
        title = { Text(stringResource(R.string.dialog_delete_font)) },
        text = { Text(stringResource(R.string.dialog_delete_font_desc, fontName)) },
        confirmButton = {
            TextButton(
                onClick = onConfirm,
                colors = ButtonDefaults.textButtonColors(contentColor = MaterialTheme.colorScheme.error)
            ) {
                Text(stringResource(R.string.action_delete))
            }
        },
        dismissButton = {
            TextButton(onClick = onDismiss) { Text(stringResource(R.string.action_cancel)) }
        }
    )
}