package org.terst.feedreader.ui

import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.width
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.items
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.ArrowBack
import androidx.compose.material.icons.filled.Delete
import androidx.compose.material.icons.filled.Visibility
import androidx.compose.material.icons.filled.VisibilityOff
import androidx.compose.material3.Button
import androidx.compose.material3.CircularProgressIndicator
import androidx.compose.material3.DropdownMenu
import androidx.compose.material3.DropdownMenuItem
import androidx.compose.material3.ExperimentalMaterial3Api
import androidx.compose.material3.HorizontalDivider
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.ListItem
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.OutlinedTextField
import androidx.compose.material3.Scaffold
import androidx.compose.material3.Slider
import androidx.compose.material3.Text
import androidx.compose.material3.TopAppBar
import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.collectAsState
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberCoroutineScope
import androidx.compose.runtime.setValue
import androidx.compose.ui.Modifier
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.text.input.PasswordVisualTransformation
import androidx.compose.ui.text.input.VisualTransformation
import androidx.compose.ui.unit.dp
import kotlinx.coroutines.launch
import org.terst.feedreader.data.AppDatabase
import org.terst.feedreader.data.DEFAULT_READER_FONT_SIZE_PX
import org.terst.feedreader.data.FeedEntity
import org.terst.feedreader.data.FilterAction
import org.terst.feedreader.data.FilterRuleEntity
import org.terst.feedreader.data.Net
import org.terst.feedreader.data.READER_FONT_SIZE_RANGE_PX
import org.terst.feedreader.data.Settings
import org.terst.feedreader.stash.StashClient
import org.terst.feedreader.stash.StashVerifyResult
import kotlin.math.roundToInt

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun SettingsScreen(onBack: () -> Unit) {
    val context = LocalContext.current
    val db = remember { AppDatabase.get(context) }
    val settings = remember { Settings(context) }
    val scope = rememberCoroutineScope()

    var stashUrl by remember { mutableStateOf("") }
    var stashKey by remember { mutableStateOf("") }
    var stashKeyVisible by remember { mutableStateOf(false) }
    var isVerifyingStash by remember { mutableStateOf(false) }
    var stashStatus by remember { mutableStateOf<String?>(null) }
    var fontSizePx by remember { mutableStateOf(DEFAULT_READER_FONT_SIZE_PX) }
    LaunchedEffect(Unit) {
        stashUrl = settings.stashBaseUrlNow()
        stashKey = settings.stashApiKeyNow()
        fontSizePx = settings.readerFontSizePxNow()
    }

    var newRulePattern by remember { mutableStateOf("") }
    var newRuleAction by remember { mutableStateOf(FilterAction.MUTE) }
    var actionMenuExpanded by remember { mutableStateOf(false) }
    val rules by db.filterRuleDao().observeAll().collectAsState(initial = emptyList())
    val feeds by db.feedDao().observeAll().collectAsState(initial = emptyList())
    val feedTitleById = remember(feeds) { feeds.associate { it.id to it.title } }
    // null = applies to every feed (the only option before this scope picker existed).
    var newRuleFeedId by remember { mutableStateOf<String?>(null) }
    var feedMenuExpanded by remember { mutableStateOf(false) }

    Scaffold(
        topBar = {
            TopAppBar(
                title = { Text("Settings") },
                navigationIcon = {
                    IconButton(onClick = onBack) {
                        Icon(Icons.Default.ArrowBack, contentDescription = "Back")
                    }
                }
            )
        }
    ) { padding ->
        LazyColumn(modifier = Modifier.fillMaxWidth().padding(padding)) {
            item {
                Column(modifier = Modifier.padding(16.dp)) {
                    Text("FeeDreader", style = MaterialTheme.typography.titleMedium)
                    Spacer(modifier = Modifier.height(4.dp))
                    Text(
                        "FeeDreader exists to avoid tracking, manipulation, and junk fees. If an " +
                            "article's full text is something you could just as easily find with a " +
                            "search, reader mode will pull it up here too.",
                        style = MaterialTheme.typography.bodyMedium
                    )
                }
                HorizontalDivider()
            }

            item {
                Column(modifier = Modifier.padding(16.dp)) {
                    Text("Reading", style = MaterialTheme.typography.titleMedium)
                    Spacer(modifier = Modifier.height(8.dp))
                    Text("Font size: ${fontSizePx}px", style = MaterialTheme.typography.bodyMedium)
                    Slider(
                        value = fontSizePx.toFloat(),
                        onValueChange = { fontSizePx = it.roundToInt() },
                        valueRange = READER_FONT_SIZE_RANGE_PX.first.toFloat()..READER_FONT_SIZE_RANGE_PX.last.toFloat(),
                        steps = READER_FONT_SIZE_RANGE_PX.last - READER_FONT_SIZE_RANGE_PX.first - 1,
                        // Persist on release, not on every onValueChange -- a drag crosses many
                        // integer values in a fraction of a second, and there's no reason to hit
                        // DataStore that often for a value nothing reads until the next article load.
                        onValueChangeFinished = { scope.launch { settings.setReaderFontSizePx(fontSizePx) } }
                    )
                }
                HorizontalDivider()
            }

            item {
                Column(modifier = Modifier.padding(16.dp)) {
                    Text("Stash", style = MaterialTheme.typography.titleMedium)
                    Spacer(modifier = Modifier.height(8.dp))
                    OutlinedTextField(
                        value = stashUrl,
                        onValueChange = { stashUrl = it },
                        label = { Text("Base URL") },
                        placeholder = { Text("https://stash.example.com") },
                        modifier = Modifier.fillMaxWidth()
                    )
                    Spacer(modifier = Modifier.height(8.dp))
                    OutlinedTextField(
                        value = stashKey,
                        onValueChange = { stashKey = it; stashStatus = null },
                        label = { Text("API key") },
                        singleLine = true,
                        visualTransformation = if (stashKeyVisible) VisualTransformation.None else PasswordVisualTransformation(),
                        trailingIcon = {
                            IconButton(onClick = { stashKeyVisible = !stashKeyVisible }) {
                                Icon(
                                    if (stashKeyVisible) Icons.Default.VisibilityOff else Icons.Default.Visibility,
                                    contentDescription = if (stashKeyVisible) "Hide API key" else "Show API key"
                                )
                            }
                        },
                        modifier = Modifier.fillMaxWidth()
                    )
                    Spacer(modifier = Modifier.height(8.dp))
                    Button(
                        enabled = !isVerifyingStash,
                        onClick = {
                            scope.launch {
                                isVerifyingStash = true
                                stashStatus = null
                                val client = StashClient(Net.client, stashUrl.trim(), stashKey.trim())
                                when (val result = client.verifyCredentials()) {
                                    is StashVerifyResult.Valid -> {
                                        settings.setStash(stashUrl.trim(), stashKey.trim())
                                        stashStatus = "Verified and saved"
                                    }
                                    is StashVerifyResult.Invalid -> {
                                        stashStatus = result.message
                                    }
                                }
                                isVerifyingStash = false
                            }
                        },
                        modifier = Modifier.fillMaxWidth()
                    ) {
                        if (isVerifyingStash) {
                            CircularProgressIndicator(modifier = Modifier.height(20.dp).width(20.dp))
                        } else {
                            Text("Verify and save")
                        }
                    }
                    stashStatus?.let {
                        Spacer(modifier = Modifier.height(8.dp))
                        Text(it, style = MaterialTheme.typography.bodySmall)
                    }
                }
                HorizontalDivider()
            }

            item {
                Column(modifier = Modifier.padding(16.dp)) {
                    Text("Filter rules", style = MaterialTheme.typography.titleMedium)
                    Spacer(modifier = Modifier.height(8.dp))
                    Row(modifier = Modifier.fillMaxWidth()) {
                        OutlinedTextField(
                            value = newRulePattern,
                            onValueChange = { newRulePattern = it },
                            label = { Text("Keyword") },
                            modifier = Modifier.weight(1f)
                        )
                        Spacer(modifier = Modifier.width(8.dp))
                        Box {
                            Button(onClick = { actionMenuExpanded = true }) {
                                Text(if (newRuleAction == FilterAction.MUTE) "Mute" else "Highlight")
                            }
                            DropdownMenu(expanded = actionMenuExpanded, onDismissRequest = { actionMenuExpanded = false }) {
                                DropdownMenuItem(text = { Text("Mute") }, onClick = { newRuleAction = FilterAction.MUTE; actionMenuExpanded = false })
                                DropdownMenuItem(text = { Text("Highlight") }, onClick = { newRuleAction = FilterAction.HIGHLIGHT; actionMenuExpanded = false })
                            }
                        }
                    }
                    Spacer(modifier = Modifier.height(8.dp))
                    FeedScopePicker(
                        feeds = feeds,
                        selectedFeedId = newRuleFeedId,
                        expanded = feedMenuExpanded,
                        onExpandedChange = { feedMenuExpanded = it },
                        onSelect = { newRuleFeedId = it }
                    )
                    Spacer(modifier = Modifier.height(8.dp))
                    Button(
                        enabled = newRulePattern.isNotBlank(),
                        onClick = {
                            scope.launch {
                                db.filterRuleDao().insert(
                                    FilterRuleEntity(
                                        pattern = newRulePattern.trim(),
                                        action = newRuleAction,
                                        feedId = newRuleFeedId,
                                        createdAt = System.currentTimeMillis()
                                    )
                                )
                                newRulePattern = ""
                                newRuleFeedId = null
                            }
                        },
                        modifier = Modifier.fillMaxWidth()
                    ) { Text("Add rule") }
                }
            }

            items(rules, key = { it.id }) { rule ->
                ListItem(
                    headlineContent = { Text(rule.pattern) },
                    supportingContent = {
                        val actionLabel = if (rule.action == FilterAction.MUTE) "Mute" else "Highlight"
                        val scopeLabel = rule.feedId?.let { feedTitleById[it] ?: it } ?: "All feeds"
                        Text("$actionLabel · $scopeLabel")
                    },
                    trailingContent = {
                        IconButton(onClick = { scope.launch { db.filterRuleDao().delete(rule.id) } }) {
                            Icon(Icons.Default.Delete, contentDescription = "Delete rule")
                        }
                    }
                )
                HorizontalDivider()
            }
        }
    }
}

/** Scope picker for a new filter rule: "All feeds" (feedId = null) or one specific feed. */
@Composable
private fun FeedScopePicker(
    feeds: List<FeedEntity>,
    selectedFeedId: String?,
    expanded: Boolean,
    onExpandedChange: (Boolean) -> Unit,
    onSelect: (String?) -> Unit
) {
    Box {
        Button(onClick = { onExpandedChange(true) }, modifier = Modifier.fillMaxWidth()) {
            Text(feeds.find { it.id == selectedFeedId }?.title ?: "All feeds")
        }
        DropdownMenu(expanded = expanded, onDismissRequest = { onExpandedChange(false) }) {
            DropdownMenuItem(
                text = { Text("All feeds") },
                onClick = { onSelect(null); onExpandedChange(false) }
            )
            feeds.forEach { feed ->
                DropdownMenuItem(
                    text = { Text(feed.title) },
                    onClick = { onSelect(feed.id); onExpandedChange(false) }
                )
            }
        }
    }
}