import SwiftUI
import TVAnarchyCore

/// Horizontal upcoming-episode rail — only items after the current one.
struct PlayerQueueRail: View {
    @Bindable var controller: PlayerController
    @Bindable var library: LibraryController
    @Bindable var playlist: PlaylistController

    private var paths: [String] {
        if !controller.playbackQueuePaths.isEmpty { return controller.playbackQueuePaths }
        return playlist.queue.map(\.path)
    }

    private var upcoming: [(offset: Int, path: String)] {
        guard paths.count > 1 else { return [] }
        let cur = currentIndex ?? -1
        let start = cur + 1
        guard start < paths.count else { return [] }
        return paths.enumerated().compactMap { idx, path in
            idx >= start ? (idx, path) : nil
        }
    }

    var body: some View {
        if !upcoming.isEmpty {
            VStack(alignment: .leading, spacing: 6) {
                HStack(spacing: 6) {
                    Text("Up next")
                        .font(.caption)
                        .foregroundStyle(.secondary)
                    Text("· \(upcoming.count) episode\(upcoming.count == 1 ? "" : "s")")
                        .font(.caption2)
                        .foregroundStyle(.tertiary)
                }
                ScrollViewReader { proxy in
                    ScrollView(.horizontal, showsIndicators: upcoming.count > 4) {
                        HStack(spacing: 8) {
                            ForEach(upcoming, id: \.path) { item in
                                queueChip(path: item.path, index: item.offset)
                                    .id(item.path)
                            }
                        }
                    }
                    .onAppear {
                        if let first = upcoming.first?.path {
                            proxy.scrollTo(first, anchor: .leading)
                        }
                    }
                    .onChange(of: currentIndex) {
                        if let first = upcoming.first?.path {
                            withAnimation(.easeOut(duration: 0.2)) {
                                proxy.scrollTo(first, anchor: .leading)
                            }
                        }
                    }
                }
            }
        }
    }

    private func queueChip(path: String, index: Int) -> some View {
        let parts = PlayerController.queueChipParts(for: path, library: library)
        return VStack(alignment: .leading, spacing: 3) {
            if !parts.code.isEmpty {
                Text(parts.code)
                    .font(.caption2.bold().monospacedDigit())
                    .foregroundStyle(.secondary)
            }
            Text(parts.title.isEmpty ? PlayerController.label(for: path, library: library) : parts.title)
                .font(.caption)
                .lineLimit(2)
                .frame(minWidth: 130, maxWidth: 170, alignment: .leading)
        }
        .padding(.horizontal, 10).padding(.vertical, 8)
        .background(Color.white.opacity(0.06), in: RoundedRectangle(cornerRadius: 8))
        .overlay {
            RoundedRectangle(cornerRadius: 8)
                .strokeBorder(.white.opacity(0.1), lineWidth: 1)
        }
        .help(PlayerController.label(for: path, library: library))
    }

    private var currentIndex: Int? {
        if !controller.playbackQueuePaths.isEmpty,
           paths == controller.playbackQueuePaths {
            return controller.currentQueueIndex
        }
        if paths == playlist.queue.map(\.path),
           let pos = controller.activeSnapshot.status.playlistPos {
            return pos
        }
        return nil
    }
}