// SignalFeedView.swift
// Jarvis — home screen. Stories ranked by signal score, live connection state,
// topic filters, pull-to-refresh, infinite scroll.

import SwiftUI
import SwiftData

// Reusable wordmark: J in KisaniOrange, the rest white, weight 800, kerning -2.
struct JarvisWordmark: View {
    var size: CGFloat = 30
    var body: some View {
        (Text("J").foregroundColor(Palette.orange) + Text("arvis").foregroundColor(.white))
            .font(.system(size: size, weight: .heavy))
            .kerning(-2)
    }
}

struct SignalFeedView: View {
    @EnvironmentObject var store: StoryStore
    @EnvironmentObject var ws: WebSocketManager
    @EnvironmentObject var settings: ServerSettings
    @Environment(\.modelContext) private var modelContext

    @Query private var cachedStories: [CachedStory]
    @Query private var cachedArticles: [CachedArticle]
    @Query private var readStories: [ReadStory]
    @Query private var savedStories: [SavedStory]
    @State private var showFeeds = false
    @State private var showSettings = false
    @State private var selectedPill: StoryPill = .all
    @State private var shareStory: StorySummary?
    /// Snapshot of already-seen story ids, captured per load so the order stays
    /// stable while scrolling (and refreshes to sink newly-seen ones).
    @State private var seenSnapshot: Set<String> = []
    /// Reference-type set so marking a story seen on scroll doesn't re-render.
    @State private var seenTracker = SeenTracker()
    @State private var showRead = false

    /// Stories that have full article content cached → eligible for the green dot.
    private var cachedStoryIds: Set<String> { Set(cachedArticles.map(\.storyId)) }
    private var readStoryIds: Set<String> { Set(readStories.map(\.id)) }
    private var savedStoryIds: Set<String> { Set(savedStories.map(\.id)) }

    /// Live stories when online; cached fallback when offline. Filtered by the
    /// selected pill via backend tags — no headline keyword matching.
    private var filteredStories: [StorySummary] {
        let base: [StorySummary]
        if !store.stories.isEmpty {
            base = store.stories.sorted(by: StorySummary.feedOrder)
        } else if !ws.connectionState.isLive {
            base = cachedStories.map(StorySummary.init(cached:)).sorted(by: StorySummary.feedOrder)
        } else {
            base = []
        }
        return base.filter { $0.matches(selectedPill) }
    }

    /// The main feed: unread stories, with already-seen ones sunk below fresh ones.
    private var mainStories: [StorySummary] {
        let notRead = filteredStories.filter { !readStoryIds.contains($0.id) }
        let fresh = notRead.filter { !seenSnapshot.contains($0.id) }
        let seen = notRead.filter { seenSnapshot.contains($0.id) }
        return fresh + seen
    }

    /// Read stories, tucked into the collapsible "Read" shelf.
    private var readItems: [StorySummary] {
        filteredStories.filter { readStoryIds.contains($0.id) }
    }

    private func captureSeenSnapshot() {
        let ids = (try? modelContext.fetch(FetchDescriptor<SeenStory>()))?.map(\.id) ?? []
        seenSnapshot = Set(ids)
        seenTracker.ids = seenSnapshot
    }

    /// Hot path — runs as each row scrolls in. O(1), no disk write, no re-render:
    /// the container autosaves, and SeenStory isn't @Query'd by this view.
    private func markSeen(_ s: StorySummary) {
        guard seenTracker.ids.insert(s.id).inserted else { return }
        modelContext.insert(SeenStory(id: s.id))
    }

    private func markUnread(_ s: StorySummary) {
        let id = s.id
        if let row = (try? modelContext.fetch(
            FetchDescriptor<ReadStory>(predicate: #Predicate { $0.id == id })))?.first {
            modelContext.delete(row)
            try? modelContext.save()
        }
    }

    var body: some View {
        NavigationStack {
            ZStack {
                Color.black.ignoresSafeArea()

                VStack(spacing: 0) {
                    header
                    syncBar
                    topicPills
                    columnHeaders
                    Divider().overlay(Palette.hairline)
                    feedList
                }
            }
            .navigationBarHidden(true)
            .navigationDestination(for: StorySummary.self) { story in
                StoryDetailView(story: story)
            }
            .navigationDestination(for: ArticleRoute.self) { route in
                ArticleReaderView(route: route)
            }
            .sheet(isPresented: $showFeeds) {
                FeedManagerView()
            }
            .sheet(isPresented: $showSettings) {
                SettingsView()
            }
            .sheet(item: $shareStory) { story in
                ShareSheet(items: shareItems(story))
            }
        }
        .preferredColorScheme(.dark)
        .onChange(of: store.stories) { _, newValue in
            cacheStories(newValue)
        }
        .task { CacheMaintenance.prune(modelContext) }   // bound the caches on launch
        .task(id: selectedPill) {
            // A filter active but nothing matched in the loaded set → pull a few
            // more pages so sparse pills still populate.
            guard selectedPill != .all else { return }
            var pages = 0
            while filteredStories.isEmpty && store.hasMore && pages < 8 {
                await store.loadMore()
                pages += 1
            }
        }
    }

    // MARK: - Header

    private var header: some View {
        HStack(alignment: .center) {
            JarvisWordmark(size: 30)
            Spacer()
            ConnectionBanner(state: ws.connectionState)
            Button {
                showFeeds = true
            } label: {
                Image(systemName: "dot.radiowaves.up.forward")
                    .font(.system(size: 17, weight: .semibold))
                    .foregroundStyle(Color(hex: "888888"))
                    .frame(width: 44, height: 44)
            }
            Button {
                showSettings = true
            } label: {
                Image(systemName: "gearshape")
                    .font(.system(size: 17, weight: .semibold))
                    .foregroundStyle(Color(hex: "888888"))
                    .frame(width: 44, height: 44)
            }
        }
        .padding(.horizontal, 16)
        .padding(.top, 8)
    }

    // MARK: - Sync bar

    private var syncBar: some View {
        Text(syncText)
            .font(.system(size: 11, weight: .regular, design: .monospaced))
            .foregroundStyle(Color(hex: "5A5A5A"))
            .frame(maxWidth: .infinity, alignment: .leading)
            .padding(.horizontal, 16)
            .padding(.bottom, 12)
    }

    private var syncText: String {
        let ago = syncedMinutesAgo(store.lastSyncedAt)
        let phrase = (ago == "just now" || ago == "never") ? ago : "\(ago) ago"
        if ws.connectionState.isLive {
            return "Synced \(phrase) · \(cachedStoryIds.count) cached"
        } else {
            return "Last synced \(phrase)"
        }
    }

    // MARK: - Pills

    private var topicPills: some View {
        ScrollView(.horizontal, showsIndicators: false) {
            HStack(spacing: 8) {
                ForEach(StoryPill.allCases) { p in
                    pill(p.label, selected: selectedPill == p) { selectedPill = p }
                }
            }
            .padding(.horizontal, 16)
        }
        .padding(.bottom, 14)
    }

    private func pill(_ label: String, selected: Bool, action: @escaping () -> Void) -> some View {
        Button(action: action) {
            Text(label)
                .font(.system(size: 13, weight: .bold))
                .foregroundStyle(selected ? .black : Color(hex: "AAAAAA"))
                .padding(.horizontal, 14)
                .frame(height: 32)
                .background(selected ? Palette.orange : Palette.surface)
                .clipShape(Capsule())
        }
    }

    // MARK: - Column headers

    private var columnHeaders: some View {
        HStack {
            Text("STORY")
                .kerning(0.8)
            Spacer()
            Text("SIGNAL ↓")
                .kerning(0.8)
        }
        .font(.system(size: 10, weight: .bold, design: .monospaced))
        .foregroundStyle(Color(hex: "555555"))
        .padding(.horizontal, 16)
        .padding(.bottom, 8)
    }

    // MARK: - Feed list

    private var feedList: some View {
        List {
            if mainStories.isEmpty && readItems.isEmpty {
                emptyState.plainBlackRow()
            } else {
                ForEach(mainStories) { story in
                    mainRow(story)
                }
                if mainStories.isEmpty {
                    caughtUpRow.plainBlackRow()
                }
                if store.isLoadingMore {
                    ProgressView().tint(Palette.orange)
                        .frame(maxWidth: .infinity).padding(.vertical, 20).plainBlackRow()
                }
                readShelf
            }
        }
        .listStyle(.plain)
        .scrollContentBackground(.hidden)
        .background(Color.black)
        .animation(.snappy, value: showRead)
        .onAppear { captureSeenSnapshot() }
        .refreshable {
            captureSeenSnapshot()           // sink what you've already seen
            await store.loadStories(refresh: true)
        }
    }

    @ViewBuilder
    private func mainRow(_ story: StorySummary) -> some View {
        NavigationLink(value: story) {
            StoryRowView(story: story, isCached: cachedStoryIds.contains(story.id))
        }
        .plainBlackRow()
        .onAppear {
            markSeen(story)
            if story.id == mainStories.last?.id { Task { await store.loadMore() } }
        }
        // Swipe left: short swipe reveals Save (tap); a full/long swipe marks read.
        .swipeActions(edge: .trailing, allowsFullSwipe: true) {
            Button { markRead(story) } label: {
                Label("Mark read", systemImage: "checkmark.circle")
            }
            .tint(Color(hex: "3A5A7A"))
            Button { toggleSave(story) } label: {
                Label(isSaved(story) ? "Saved" : "Save",
                      systemImage: isSaved(story) ? "bookmark.fill" : "bookmark")
            }
            .tint(Palette.healthActive)
        }
        // Swipe right → Share.
        .swipeActions(edge: .leading, allowsFullSwipe: true) {
            Button { markRead(story); shareStory = story } label: {
                Label("Share", systemImage: "square.and.arrow.up")
            }
            .tint(Palette.orange)
        }
    }

    private var caughtUpRow: some View {
        VStack(spacing: 10) {
            Image(systemName: "checkmark.circle")
                .font(.system(size: 32)).foregroundStyle(Color(hex: "3E7E3E"))
            Text("You're all caught up").font(.system(size: 16, weight: .heavy)).foregroundStyle(.white)
            Text("Pull to refresh for more")
                .font(.system(size: 12)).foregroundStyle(Color(hex: "888888"))
        }
        .frame(maxWidth: .infinity).padding(.vertical, 70)
    }

    // Collapsible "Read" shelf at the bottom — read stories as slim rows.
    @ViewBuilder
    private var readShelf: some View {
        if !readItems.isEmpty {
            Button {
                withAnimation(.snappy) { showRead.toggle() }
            } label: {
                HStack(spacing: 8) {
                    Image(systemName: "checkmark.circle.fill")
                        .font(.system(size: 13)).foregroundStyle(Color(hex: "3E7E3E"))
                    Text("READ").font(.system(size: 11, weight: .bold, design: .monospaced)).kerning(0.8)
                    Text("\(readItems.count)")
                        .font(.system(size: 11, weight: .bold, design: .monospaced))
                        .foregroundStyle(Color(hex: "888888"))
                    Spacer()
                    Image(systemName: showRead ? "chevron.up" : "chevron.down")
                        .font(.system(size: 11, weight: .bold))
                }
                .foregroundStyle(Color(hex: "666666"))
                .padding(.horizontal, 16).padding(.vertical, 16)
                .contentShape(Rectangle())
            }
            .buttonStyle(.plain)
            .plainBlackRow()

            if showRead {
                ForEach(readItems) { story in
                    NavigationLink(value: story) {
                        StoryRowView(story: story, isCached: cachedStoryIds.contains(story.id),
                                     isRead: true, compact: true)
                    }
                    .plainBlackRow()
                    .swipeActions(edge: .trailing, allowsFullSwipe: true) {
                        Button { markUnread(story) } label: {
                            Label("Unread", systemImage: "circle")
                        }
                        .tint(Color(hex: "3A5A7A"))
                        Button { toggleSave(story) } label: {
                            Label(isSaved(story) ? "Saved" : "Save",
                                  systemImage: isSaved(story) ? "bookmark.fill" : "bookmark")
                        }
                        .tint(Palette.healthActive)
                    }
                }
            }
        }
    }

    private var emptyState: some View {
        VStack(spacing: 12) {
            if store.isLoading {
                // Actively polling the server.
                ProgressView().tint(Palette.orange)
                Text("Polling signals…")
                    .font(.system(size: 14, weight: .heavy))
                    .foregroundStyle(Color(hex: "AAAAAA"))
                hostLine
            } else if let error = store.error {
                // Reached the empty state because the fetch failed.
                emptyIcon("exclamationmark.triangle", color: Color(hex: "C25555"))
                Text("Couldn't reach the server")
                    .font(.system(size: 15, weight: .heavy)).foregroundStyle(.white)
                Text(error.errorDescription ?? "Unknown error")
                    .font(.system(size: 12)).foregroundStyle(Color(hex: "888888"))
                    .multilineTextAlignment(.center)
                hostLine
                refreshButton("Retry")
            } else if !ws.connectionState.isLive {
                emptyIcon("wifi.slash")
                Text("Offline").font(.system(size: 15, weight: .heavy)).foregroundStyle(.white)
                Text("No cached stories to show")
                    .font(.system(size: 12)).foregroundStyle(Color(hex: "888888"))
                refreshButton("Retry")
            } else if selectedPill != .all {
                emptyIcon("line.3.horizontal.decrease.circle")
                Text("No \(selectedPill.label) stories yet")
                    .font(.system(size: 15, weight: .heavy)).foregroundStyle(.white)
                if store.isLoadingMore || store.hasMore {
                    Text("Pulling more to find them…")
                        .font(.system(size: 12)).foregroundStyle(Color(hex: "888888"))
                    ProgressView().tint(Palette.orange)
                } else {
                    Text("Nothing in the feed matched")
                        .font(.system(size: 12)).foregroundStyle(Color(hex: "888888"))
                    refreshButton("Refresh")
                }
            } else {
                // Connected, loaded, genuinely nothing yet.
                emptyIcon("antenna.radiowaves.left.and.right")
                Text("No signals yet").font(.system(size: 15, weight: .heavy)).foregroundStyle(.white)
                Text("Pull to refresh")
                    .font(.system(size: 12)).foregroundStyle(Color(hex: "888888"))
                refreshButton("Refresh")
            }
        }
        .frame(maxWidth: .infinity)
        .padding(.horizontal, 32)
        .padding(.top, 80)
    }

    private func emptyIcon(_ name: String, color: Color = Color(hex: "333333")) -> some View {
        Image(systemName: name).font(.system(size: 30)).foregroundStyle(color)
    }

    @ViewBuilder private var hostLine: some View {
        if let host = settings.host {
            Text(host)
                .font(.system(size: 11, design: .monospaced))
                .foregroundStyle(Color(hex: "555555"))
        }
    }

    private func refreshButton(_ title: String) -> some View {
        Button {
            Task { await store.loadStories(refresh: true) }
        } label: {
            Text(title)
                .font(.system(size: 14, weight: .bold)).foregroundStyle(.black)
                .padding(.horizontal, 22).frame(height: 44)
                .background(Palette.orange).clipShape(Capsule())
        }
        .padding(.top, 6)
    }

    // MARK: - Swipe actions

    private func isSaved(_ s: StorySummary) -> Bool { savedStoryIds.contains(s.id) }

    /// Swipe left → toggle Save (bookmarks the story to the Saved tab).
    private func toggleSave(_ s: StorySummary) {
        let id = s.id
        if let row = (try? modelContext.fetch(
            FetchDescriptor<SavedStory>(predicate: #Predicate { $0.id == id })))?.first {
            modelContext.delete(row)
        } else {
            cacheStories([s])               // keep metadata so it renders in Saved
            modelContext.insert(SavedStory(id: id))
        }
        try? modelContext.save()
    }

    private func markRead(_ s: StorySummary) {
        let id = s.id
        let existing = try? modelContext.fetch(
            FetchDescriptor<ReadStory>(predicate: #Predicate { $0.id == id }))
        if existing?.first == nil {
            modelContext.insert(ReadStory(id: id))
            try? modelContext.save()
        }
    }

    private func shareItems(_ s: StorySummary) -> [Any] {
        var items: [Any] = ["\(s.headline)\n\n\(s.summary)\n\nvia Jarvis"]
        if let first = s.sources.first, let url = URL(string: first.url) {
            items.append(url)
        }
        return items
    }

    // MARK: - Caching

    private func cacheStories(_ stories: [StorySummary]) {
        guard !stories.isEmpty else { return }
        // One fetch + an in-memory index, instead of a query per story.
        let existing = (try? modelContext.fetch(FetchDescriptor<CachedStory>())) ?? []
        var byId = Dictionary(existing.map { ($0.id, $0) }, uniquingKeysWith: { a, _ in a })
        for summary in stories {
            if let found = byId[summary.id] {
                found.signalScore = summary.signalScore
                found.sourceCount = summary.sourceCount
                found.tags = summary.tags ?? []
                found.updatedAt = summary.updatedAt
            } else {
                let c = CachedStory(from: summary)
                modelContext.insert(c)
                byId[summary.id] = c
            }
        }
        try? modelContext.save()
    }
}

/// Session-seen ids in a reference type — mutating it doesn't trigger SwiftUI
/// updates, so marking rows seen on scroll stays cheap.
private final class SeenTracker {
    var ids = Set<String>()
}

// Map a cached story back into a StorySummary for offline rendering.
extension StorySummary {
    init(cached: CachedStory) {
        self.init(
            id: cached.id,
            headline: cached.headline,
            summary: cached.summary,
            topic: cached.topic,
            tags: cached.tags,
            signalScore: cached.signalScore,
            scoreBreakdown: ScoreBreakdown(sourceAuthority: 0, freshness: 0, localRelevance: 0,
                                           crossSourceConfirmation: 0, topicImportance: 0),
            sourceCount: cached.sourceCount,
            sources: [],
            consensus: cached.consensus,
            conflict: cached.conflict,
            updatedAt: cached.updatedAt,
            createdAt: cached.updatedAt
        )
    }
}

private extension View {
    /// Full-bleed black List row with no separator — keeps the flat feed look.
    func plainBlackRow() -> some View {
        self.listRowInsets(EdgeInsets())
            .listRowBackground(Color.black)
            .listRowSeparator(.hidden)
    }
}