import SwiftData
import SwiftUI
import UniformTypeIdentifiers

/// Sidebar — playlist folders and playlists with drag & drop.
struct SidebarView: View {
    @Binding var selectedPlaylist: Playlist?
    @Binding var showNewPlaylistSheet: Bool
    @Binding var showCloudBrowser: Bool

    @Environment(PlaylistViewModel.self) private var playlistVM
    @Environment(\.modelContext) private var modelContext
    @EnvironmentObject private var theme: AppTheme

    @Query(sort: \Track.title) private var allTracks: [Track]
    @Query(sort: \Playlist.dateModified, order: .reverse) private var allPlaylists: [Playlist]
    @Query(sort: \PlaylistFolder.dateCreated) private var folders: [PlaylistFolder]

    @State private var showNewFolderAlert = false
    @State private var newFolderName = ""

    /// Playlists not in any folder.
    private var unfolderedPlaylists: [Playlist] {
        allPlaylists.filter { $0.folder == nil }
    }

    var body: some View {
        List(selection: $selectedPlaylist) {
            // Cloud Library
            Section("Cloud") {
                Button {
                    showCloudBrowser = true
                    selectedPlaylist = nil
                } label: {
                    Label("Chad Music", systemImage: "cloud.fill")
                        .foregroundStyle(showCloudBrowser ? Color.accentColor : .primary)
                }
                .buttonStyle(.plain)
            }

            Section("Playlists") {
                // Folders
                ForEach(folders) { folder in
                    FolderRowView(
                        folder: folder,
                        selectedPlaylist: $selectedPlaylist,
                        onDrop: { providers, playlist in
                            handleDrop(providers: providers, playlist: playlist)
                        }
                    )
                }

                // Playlists not in a folder
                ForEach(unfolderedPlaylists) { playlist in
                    playlistRow(playlist)
                }

                // Actions
                HStack(spacing: 16) {
                    Button {
                        showNewPlaylistSheet = true
                    } label: {
                        Image(systemName: "plus.circle.fill")
                            .font(.system(size: 18))
                    }
                    .buttonStyle(.plain)
                    .help("New Playlist")

                    Button {
                        newFolderName = ""
                        showNewFolderAlert = true
                    } label: {
                        Image(systemName: "folder.badge.plus")
                            .font(.system(size: 18))
                    }
                    .buttonStyle(.plain)
                    .help("New Folder")
                }
                .foregroundStyle(theme.secondaryText)
            }
        }
        .listStyle(.sidebar)
        .navigationTitle("MixBoard")
        .alert("New Folder", isPresented: $showNewFolderAlert) {
            TextField("Folder name", text: $newFolderName)
            Button("Cancel", role: .cancel) {}
            Button("Create") {
                guard !newFolderName.isEmpty else { return }
                let folder = PlaylistFolder(name: newFolderName)
                modelContext.insert(folder)
                try? modelContext.save()
            }
        }
    }

    // MARK: - Playlist Row

    private func playlistRow(_ playlist: Playlist) -> some View {
        PlaylistRow(playlist: playlist)
            .tag(playlist)
            .draggable(playlist.id.uuidString)
            .onDrop(of: [.chadTrack, .chadAlbum, .utf8PlainText], isTargeted: nil) { providers in
                handleDrop(providers: providers, playlist: playlist)
                return true
            }
            .contextMenu {
                playlistContextMenu(playlist)
            }
    }

    private func handleDrop(providers: [NSItemProvider], playlist: Playlist) {
        print("SidebarView: handleDrop called with \(providers.count) providers for playlist '\(playlist.name)'")
        for provider in providers {
            print("  Provider types: \(provider.registeredTypeIdentifiers)")
            // Cloud track
            if provider.hasItemConformingToTypeIdentifier("com.mixboard.chad-track") {
                print("  → Matched chad-track")
                provider.loadDataRepresentation(forTypeIdentifier: "com.mixboard.chad-track") { data, error in
                    if let error { print("  → Load error: \(error)"); return }
                    guard let data, let track = try? JSONDecoder().decode(ChadTrack.self, from: data) else {
                        print("  → Decode failed")
                        return
                    }
                    print("  → Decoded track: \(track.title)")
                    Task { @MainActor in
                        self.addCloudTracksToPlaylist([track], playlist: playlist)
                    }
                }
            }
            // Cloud album
            else if provider.hasItemConformingToTypeIdentifier("com.mixboard.chad-album") {
                provider.loadDataRepresentation(forTypeIdentifier: "com.mixboard.chad-album") { data, _ in
                    guard let data, let album = try? JSONDecoder().decode(ChadAlbum.self, from: data) else { return }
                    Task { @MainActor in
                        addCloudAlbumsToPlaylist([album], playlist: playlist)
                    }
                }
            }
            // Local track ID (string)
            else if provider.hasItemConformingToTypeIdentifier("public.utf8-plain-text") {
                provider.loadItem(forTypeIdentifier: "public.utf8-plain-text") { item, _ in
                    guard let data = item as? Data, let idString = String(data: data, encoding: .utf8) else { return }
                    Task { @MainActor in
                        addTracksToPlaylist(trackIDs: [idString], playlist: playlist)
                    }
                }
            }
        }
    }

    @ViewBuilder
    private func playlistContextMenu(_ playlist: Playlist) -> some View {
        // Set as mix target
        let mixShortcuts: [ShortcutAction] = [.addToMix1, .addToMix2, .addToMix3]
        Menu("Set as Mix Target") {
            ForEach(0..<3, id: \.self) { slot in
                let isCurrent = playlistVM.mixTargets[slot]?.id == playlist.id
                let hint = KeyboardShortcutConfig.shared.binding(for: mixShortcuts[slot]).displayString
                Button(isCurrent ? "✓ Mix \(slot + 1)" : "Mix \(slot + 1) (\(hint))") {
                    playlistVM.setMixTarget(slot, playlist: playlist)
                    playlistVM.showStatus("\"\(playlist.name)\" → Mix \(slot + 1)")
                }
            }
        }

        Divider()

        // Move to folder
        if !folders.isEmpty {
            Menu("Move to Folder") {
                ForEach(folders) { folder in
                    Button(folder.name) {
                        playlist.folder = folder
                        try? modelContext.save()
                    }
                }
                Divider()
                Button("No Folder") {
                    playlist.folder = nil
                    try? modelContext.save()
                }
            }
        }

        Divider()

        Button("Delete Playlist", role: .destructive) {
            playlistVM.deletePlaylist(playlist, context: modelContext)
        }
    }

    private func addTracksToPlaylist(trackIDs: [String], playlist: Playlist) {
        for idString in trackIDs {
            guard let uuid = UUID(uuidString: idString),
                  let track = allTracks.first(where: { $0.id == uuid }) else { continue }
            playlistVM.addTrack(track, to: playlist, context: modelContext)
        }
    }

    private func addCloudTracksToPlaylist(_ chadTracks: [ChadTrack], playlist: Playlist) {
        for chadTrack in chadTracks {
            let cloudId = chadTrack.id
            let descriptor = FetchDescriptor<Track>(predicate: #Predicate { $0.cloudTrackId == cloudId })
            let existing = try? modelContext.fetch(descriptor).first
            let track = existing ?? Track.fromCloud(chadTrack)
            if existing == nil {
                modelContext.insert(track)
            }
            playlist.addTrack(track)
        }
    }

    private func addCloudAlbumsToPlaylist(_ albums: [ChadAlbum], playlist: Playlist) {
        Task {
            let client = ChadMusicAPIClient.shared
            for album in albums {
                guard let tracks = try? await client.fetchAlbumTracks(albumId: album.id) else { continue }
                addCloudTracksToPlaylist(tracks, playlist: playlist)
            }
        }
    }
}

// MARK: - Folder Row

private struct FolderRowView: View {
    let folder: PlaylistFolder
    @Binding var selectedPlaylist: Playlist?
    let onDrop: ([NSItemProvider], Playlist) -> Void

    @Environment(PlaylistViewModel.self) private var playlistVM
    @Environment(\.modelContext) private var modelContext
    @EnvironmentObject private var theme: AppTheme

    @Query(sort: \PlaylistFolder.dateCreated) private var allFolders: [PlaylistFolder]

    @State private var isExpanded: Bool = true
    @State private var showRenameAlert = false
    @State private var renameName = ""

    var body: some View {
        DisclosureGroup(isExpanded: $isExpanded) {
            ForEach(folder.sortedPlaylists) { playlist in
                PlaylistRow(playlist: playlist)
                    .tag(playlist)
                    .draggable(playlist.id.uuidString)
                    .onDrop(of: [.chadTrack, .chadAlbum, .utf8PlainText], isTargeted: nil) { providers in
                        onDrop(providers, playlist)
                        return true
                    }
                    .contextMenu {
                        // Set as mix target
                        let mixShortcuts: [ShortcutAction] = [.addToMix1, .addToMix2, .addToMix3]
                        Menu("Set as Mix Target") {
                            ForEach(0..<3, id: \.self) { slot in
                                let isCurrent = playlistVM.mixTargets[slot]?.id == playlist.id
                                let hint = KeyboardShortcutConfig.shared.binding(for: mixShortcuts[slot]).displayString
                                Button(isCurrent ? "✓ Mix \(slot + 1)" : "Mix \(slot + 1) (\(hint))") {
                                    playlistVM.setMixTarget(slot, playlist: playlist)
                                    playlistVM.showStatus("\"\(playlist.name)\" → Mix \(slot + 1)")
                                }
                            }
                        }

                        Divider()

                        Button("Remove from Folder") {
                            playlist.folder = nil
                            try? modelContext.save()
                        }

                        // Move to different folder
                        let otherFolders = allFolders.filter { $0.id != folder.id }
                        if !otherFolders.isEmpty {
                            Menu("Move to Folder") {
                                ForEach(otherFolders) { f in
                                    Button(f.name) {
                                        playlist.folder = f
                                        try? modelContext.save()
                                    }
                                }
                            }
                        }

                        Divider()

                        Button("Delete Playlist", role: .destructive) {
                            modelContext.delete(playlist)
                            try? modelContext.save()
                        }
                    }
            }
        } label: {
            HStack(spacing: 6) {
                Image(systemName: "folder.fill")
                    .foregroundStyle(theme.accent)
                    .font(.system(size: 14))

                Text(folder.name)
                    .foregroundStyle(theme.primaryText)

                Text("(\(folder.playlists.count))")
                    .font(.caption2)
                    .foregroundStyle(theme.tertiaryText)
            }
            .contentShape(Rectangle())
            .contextMenu {
                Button("Rename Folder...") {
                    renameName = folder.name
                    showRenameAlert = true
                }
                Divider()
                Button("Delete Folder", role: .destructive) {
                    for pl in folder.playlists {
                        pl.folder = nil
                    }
                    modelContext.delete(folder)
                    try? modelContext.save()
                }
            }
        }
        .dropDestination(for: String.self) { items, _ in
            handlePlaylistDrop(items)
            return true
        }
        .alert("Rename Folder", isPresented: $showRenameAlert) {
            TextField("Folder name", text: $renameName)
            Button("Cancel", role: .cancel) {}
            Button("Rename") {
                folder.name = renameName
                try? modelContext.save()
            }
        }
        .onAppear {
            isExpanded = folder.isExpanded
        }
        .onChange(of: isExpanded) { _, newValue in
            folder.isExpanded = newValue
            try? modelContext.save()
        }
    }

    private func handlePlaylistDrop(_ items: [String]) {
        // Items are playlist UUID strings — move them into this folder
        for idString in items {
            guard let uuid = UUID(uuidString: idString) else { continue }

            let descriptor = FetchDescriptor<Playlist>(predicate: #Predicate { $0.id == uuid })
            if let playlist = try? modelContext.fetch(descriptor).first {
                playlist.folder = folder
            }
        }
        try? modelContext.save()
    }
}

// MARK: - Playlist Row

private struct PlaylistRow: View {
    let playlist: Playlist
    @EnvironmentObject private var theme: AppTheme
    @Environment(PlaylistViewModel.self) private var playlistVM

    /// Which mix slot(s) this playlist is assigned to (0, 1, 2), if any.
    private var assignedSlots: [Int] {
        (0..<3).filter { playlistVM.mixTargets[$0]?.id == playlist.id }
    }

    var body: some View {
        HStack {
            Image(systemName: assignedSlots.isEmpty ? "music.note.list" : "target")
                .foregroundStyle(assignedSlots.isEmpty ? (Color(hex: playlist.color) ?? theme.accent) : theme.accent)

            VStack(alignment: .leading, spacing: 2) {
                Text(playlist.name)
                    .foregroundStyle(theme.primaryText)
                    .lineLimit(1)

                Text("\(playlist.trackCount) tracks · \(playlist.formattedTotalDuration)")
                    .font(.caption2)
                    .foregroundStyle(theme.secondaryText)
            }

            Spacer(minLength: 4)

            // Show mix slot badges
            ForEach(assignedSlots, id: \.self) { slot in
                Text("\(slot + 1)")
                    .font(.system(size: 9, weight: .bold, design: .rounded))
                    .frame(width: 16, height: 16)
                    .foregroundStyle(mixTargetColors[slot])
                    .background(mixTargetColors[slot].opacity(0.15))
                    .clipShape(RoundedRectangle(cornerRadius: 3))
            }
        }
    }
}

// MARK: - Color Extension

extension Color {
    init?(hex: String) {
        let hex = hex.trimmingCharacters(in: CharacterSet.alphanumerics.inverted)
        var int: UInt64 = 0
        Scanner(string: hex).scanHexInt64(&int)
        let r, g, b: Double
        switch hex.count {
        case 6:
            r = Double((int >> 16) & 0xFF) / 255
            g = Double((int >> 8) & 0xFF) / 255
            b = Double(int & 0xFF) / 255
        default:
            return nil
        }
        self.init(red: r, green: g, blue: b)
    }
}