import SwiftUI

/// The item table: the filter tabs, the rows, and what to do with one.
struct ItemListView: View {
    @ObservedObject var store: LibraryStore
    @ObservedObject var playback: Playback
    /// The file asked for, or nil for the item's first playable one.
    var play: (IPX.Entry, IPX.Enclosure?) -> Void

    var body: some View {
        VStack(spacing: 0) {
            header
            list
        }
        .background(Glass.Wash())
        .navigationTitle(store.title)
        #if !targetEnvironment(macCatalyst)
        .navigationBarTitleDisplayMode(.inline)
        #endif
        .toolbar { toolbar }
        .searchable(text: $store.search, prompt: "Search \(store.title)")
    }

    // MARK: - header

    private var header: some View {
        VStack(spacing: 8) {
            Picker("Show", selection: $store.filter) {
                ForEach(IPX.Filter.allCases, id: \.self) { f in
                    Text(f.rawValue.capitalized).tag(f)
                }
            }
            .pickerStyle(.segmented)
            .disabled(store.place == .listening)

            HStack(spacing: 6) {
                Text(summary).font(.caption).foregroundStyle(Glass.faint)
                Spacer()
                if store.loading { ProgressView().controlSize(.mini) }
            }
        }
        .padding(.horizontal, 14)
        .padding(.vertical, 8)
        .glassPane(Glass.sticky)
    }

    private var summary: String {
        if let failure = store.failure { return failure }
        let unread = store.entries.filter { !$0.read }.count
        return "\(store.total) items, \(unread) unread on this page"
    }

    // MARK: - rows

    private var list: some View {
        // No selection binding: it swallowed the tap before the NavigationLink could act on
        // it, so a row highlighted and went nowhere. Navigation is the link's job.
        List {
            ForEach(store.entries) { entry in
                // A destination built here rather than a value matched to one elsewhere:
                // the value form pushed nothing and gave no reason, and there is nothing to
                // get wrong about a link that carries its own destination.
                NavigationLink {
                    ItemDetailView(store: store, playback: playback, entry: entry, play: play)
                } label: {
                    row(entry)
                }
                    .onAppear {
                        // Paging by the last row rather than a button: fifty at a time is the
                        // server's page size, and a long list should not need a tap to continue.
                        if entry.id == store.entries.last?.id { store.loadMore() }
                    }
            }
            if store.canLoadMore {
                HStack { Spacer(); ProgressView(); Spacer() }
                    .listRowBackground(Color.clear)
            }
        }
        .listStyle(.plain)
        .scrollContentBackground(.hidden)
        .refreshable { await store.refreshFeeds(); store.reload() }
        .overlay { if store.entries.isEmpty && !store.loading { empty } }
    }

    /// Written out rather than ContentUnavailableView, which is iOS 17 and this still runs on 16.
    private var empty: some View {
        VStack(spacing: 8) {
            Image(systemName: store.search.isEmpty ? "tray" : "magnifyingglass")
                .font(.largeTitle).foregroundStyle(Glass.faint)
            Text(store.search.isEmpty ? "Nothing here" : "No matches")
                .font(.headline).foregroundStyle(Glass.dim)
            Text(store.search.isEmpty ? "Nothing in this view yet."
                                      : "Nothing matches \u{201c}\(store.search)\u{201d}.")
                .font(.footnote).foregroundStyle(Glass.faint)
        }
        .multilineTextAlignment(.center)
        .padding()
    }

    private func row(_ entry: IPX.Entry) -> some View {
        HStack(spacing: 10) {
            // The unread dot, and the EQ bars in its place for whatever is playing, as the page
            // marks the current item.
            Group {
                if playback.nowPlaying?.guid == entry.guid {
                    Image(systemName: "waveform").foregroundStyle(Glass.highlight)
                } else if !entry.read {
                    Circle().fill(Glass.highlight).frame(width: 8, height: 8)
                } else {
                    Color.clear.frame(width: 8, height: 8)
                }
            }
            .frame(width: 14)

            VStack(alignment: .leading, spacing: 2) {
                Text(entry.title ?? "(untitled)")
                    .font(.callout.weight(entry.read ? .regular : .semibold))
                    .foregroundStyle(entry.read ? Glass.dim : Glass.text)
                    .lineLimit(2)
                Text(subtitle(entry)).font(.caption2).foregroundStyle(Glass.faint).lineLimit(1)
            }

            Spacer(minLength: 6)

            if entry.flagged {
                Image(systemName: "pin.fill").font(.caption2).foregroundStyle(Glass.accent)
            }
            if entry.playable != nil {
                Button { play(entry, nil) } label: { Image(systemName: "play.circle") }
                    .buttonStyle(.plain).foregroundStyle(Glass.accent)
                    .accessibilityLabel("Play")
            }
        }
        .padding(.vertical, 3)
        .listRowBackground(Color.clear)
        .contentShape(Rectangle())
        .swipeActions(edge: .leading) {
            Button { store.setRead(entry, !entry.read) } label: {
                Label(entry.read ? "Unread" : "Read",
                      systemImage: entry.read ? "envelope.badge" : "checkmark")
            }
            .tint(Glass.accent)
        }
        .swipeActions(edge: .trailing) {
            Button { store.setPinned(entry, !entry.flagged) } label: {
                Label(entry.flagged ? "Unpin" : "Pin", systemImage: "pin")
            }
            .tint(Glass.highlight)
        }
    }

    /// Feed, episode number, and how much is left if it has been started.
    private func subtitle(_ entry: IPX.Entry) -> String {
        var bits: [String] = []
        if store.place.feedId == nil, let feed = store.feed(entry.feedId) { bits.append(feed.name) }
        let number = [entry.season.map { "S\($0)" }, entry.episode.map { "E\($0)" }]
            .compactMap { $0 }.joined()
        if !number.isEmpty { bits.append(number) }
        if let d = entry.duration, d > 0 {
            bits.append(entry.position > 10 ? "\(clock(d - entry.position)) left" : clock(d))
        }
        if let published = entry.published {
            bits.append(Date(timeIntervalSince1970: TimeInterval(published))
                .formatted(date: .abbreviated, time: .omitted))
        }
        return bits.joined(separator: " · ")
    }

    private func clock(_ seconds: Int) -> String {
        let (h, m, s) = (seconds / 3600, (seconds % 3600) / 60, seconds % 60)
        return h > 0 ? String(format: "%d:%02d:%02d", h, m, s) : String(format: "%d:%02d", m, s)
    }

    // MARK: - toolbar

    @ToolbarContentBuilder private var toolbar: some ToolbarContent {
        ToolbarItemGroup {
            Button { store.scan() } label: { Image(systemName: "arrow.trianglehead.2.clockwise") }
                .help("Check for new items")
            Button { store.readAll() } label: { Image(systemName: "checkmark.circle") }
                .help("Mark everything here read")
            Menu {
                Picker("Sort by", selection: $store.sort) {
                    Text("Published").tag(IPX.Sort.published)
                    Text("Title").tag(IPX.Sort.title)
                    Text("Feed").tag(IPX.Sort.feed)
                    Text("Size").tag(IPX.Sort.size)
                    Text("Type").tag(IPX.Sort.type)
                }
                Picker("Order", selection: $store.direction) {
                    Text("Newest first").tag(IPX.Direction.desc)
                    Text("Oldest first").tag(IPX.Direction.asc)
                }
            } label: {
                Image(systemName: "arrow.up.arrow.down")
            }
            .help("Sort")
        }
    }
}