import SwiftData
import SwiftUI

/// Cloud library browser — navigate categories → albums → tracks from Chad Music server.
struct CloudBrowserView: View {
    @Environment(PlayerViewModel.self) private var playerVM
    @EnvironmentObject private var theme: AppTheme
    @State private var apiClient = ChadMusicAPIClient.shared

    var body: some View {
        if !apiClient.isConfigured {
            CloudNotConfiguredView()
        } else {
            CategoryListView(apiClient: apiClient)
        }
    }
}

// MARK: - Not Configured Prompt

private struct CloudNotConfiguredView: View {
    var body: some View {
        VStack(spacing: 16) {
            Spacer()
            Image(systemName: "cloud.fill")
                .font(.system(size: 48))
                .foregroundStyle(.tertiary)
            Text("Chad Music Not Configured")
                .font(.title3)
                .foregroundStyle(.secondary)
            Text("Set your server URL and API key in Settings → Chad Music.")
                .font(.callout)
                .foregroundStyle(.tertiary)
                .multilineTextAlignment(.center)
            Spacer()
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
    }
}

// MARK: - Category List

private struct CategoryListView: View {
    let apiClient: ChadMusicAPIClient

    /// Show albums and artists by default — the most useful categories.
    private let defaultCategories: [ChadCategoryType] = [.album, .artist, .genre, .year]

    var body: some View {
        VStack(alignment: .leading, spacing: 0) {
            // Header with stats
            CloudHeaderView(apiClient: apiClient)

            List {
                Section("Browse") {
                    ForEach(defaultCategories) { category in
                        NavigationLink(value: category) {
                            Label(category.displayName, systemImage: category.icon)
                        }
                    }
                }

                Section("More") {
                    ForEach(ChadCategoryType.allCases.filter { !defaultCategories.contains($0) }) { category in
                        NavigationLink(value: category) {
                            Label(category.displayName, systemImage: category.icon)
                        }
                    }
                }
            }
            .listStyle(.sidebar)
            .navigationDestination(for: ChadCategoryType.self) { category in
                CategoryDetailView(apiClient: apiClient, category: category)
            }
            .navigationDestination(for: ChadAlbum.self) { album in
                AlbumDetailView(apiClient: apiClient, album: album)
            }
            .navigationDestination(for: CategoryFilter.self) { filter in
                FilteredAlbumsView(apiClient: apiClient, filter: filter)
            }
        }
    }
}

// MARK: - Cloud Header (stats bar)

private struct CloudHeaderView: View {
    let apiClient: ChadMusicAPIClient
    @State private var stats: ChadStats?
    @State private var statsError = false

    var body: some View {
        HStack(spacing: 8) {
            Image(systemName: "cloud.fill")
                .foregroundStyle(.secondary)
            if statsError {
                Text("Could not load stats")
                    .font(.caption)
                    .foregroundStyle(.tertiary)
            } else if let stats {
                let parts = [
                    stats.tracks.map { "\($0) tracks" },
                    stats.albums.map { "\($0) albums" },
                    stats.artists.map { "\($0) artists" },
                ].compactMap { $0 }
                Text(parts.joined(separator: " · "))
                    .font(.caption)
                    .foregroundStyle(.secondary)
            } else {
                Text("Loading...")
                    .font(.caption)
                    .foregroundStyle(.tertiary)
            }
            Spacer()
        }
        .padding(.horizontal, 16)
        .padding(.vertical, 8)
        .background(.bar)
        .task {
            do {
                stats = try await apiClient.fetchStats()
            } catch {
                statsError = true
            }
        }
    }
}

// MARK: - Filtered Albums View (artist/genre/year → albums)

private struct FilteredAlbumsView: View {
    let apiClient: ChadMusicAPIClient
    let filter: CategoryFilter

    @State private var albums: [ChadAlbum] = []
    @State private var isLoading = true
    @State private var error: String?

    @Environment(\.modelContext) private var modelContext
    @Query(sort: \Playlist.dateModified, order: .reverse) private var allPlaylists: [Playlist]

    var body: some View {
        Group {
            if isLoading {
                ProgressView("Loading albums...")
                    .frame(maxWidth: .infinity, maxHeight: .infinity)
            } else if let error {
                VStack(spacing: 8) {
                    Image(systemName: "exclamationmark.triangle")
                        .font(.title)
                        .foregroundStyle(.secondary)
                    Text(error)
                        .foregroundStyle(.secondary)
                    Button("Retry") { loadAlbums() }
                }
                .frame(maxWidth: .infinity, maxHeight: .infinity)
            } else if albums.isEmpty {
                Text("No albums found")
                    .foregroundStyle(.secondary)
                    .frame(maxWidth: .infinity, maxHeight: .infinity)
            } else {
                List {
                    // Header — draggable to add all albums by this artist/genre/etc.
                    HStack {
                        VStack(alignment: .leading, spacing: 2) {
                            Text(filter.value)
                                .font(.title2.bold())
                            Text("\(albums.count) albums")
                                .font(.caption)
                                .foregroundStyle(.tertiary)
                        }
                        Spacer()
                        Menu {
                            ForEach(allPlaylists) { playlist in
                                Button(playlist.name) {
                                    addAllAlbumsToPlaylist(playlist: playlist)
                                }
                            }
                        } label: {
                            Label("Add All", systemImage: "plus.circle")
                                .font(.caption)
                        }
                        .menuStyle(.borderlessButton)
                        .fixedSize()
                    }
                    .listRowSeparator(.hidden)
                    .padding(.vertical, 4)
                    .contextMenu {
                        Menu("Add All to Playlist") {
                            ForEach(allPlaylists) { playlist in
                                Button(playlist.name) {
                                    addAllAlbumsToPlaylist(playlist: playlist)
                                }
                            }
                        }
                    }

                    // Album rows
                    ForEach(albums) { album in
                    NavigationLink(value: album) {
                        HStack {
                            VStack(alignment: .leading, spacing: 2) {
                                Text(album.title)
                                    .lineLimit(1)
                                if let artist = album.artist {
                                    Text(artist)
                                        .font(.caption)
                                        .foregroundStyle(.secondary)
                                        .lineLimit(1)
                                }
                            }
                            Spacer()
                            if let count = album.trackCount {
                                Text("\(count)")
                                    .font(.caption)
                                    .foregroundStyle(.secondary)
                            }
                        }
                    }
                    .contextMenu {
                        Menu("Add Album to Playlist") {
                            ForEach(allPlaylists) { playlist in
                                Button(playlist.name) {
                                    addAlbumToPlaylist(album, playlist: playlist)
                                }
                            }
                        }
                    }
                    .draggable(album)
                    }
                }
                .listStyle(.inset)
            }
        }
        .navigationTitle(filter.value)
        .task { loadAlbums() }
    }

    private func loadAlbums() {
        isLoading = true
        error = nil
        Task {
            do {
                albums = try await apiClient.fetchAlbums(filteredBy: filter.category.rawValue, value: filter.value)
            } catch {
                self.error = error.localizedDescription
            }
            isLoading = false
        }
    }

    private func addAlbumToPlaylist(_ album: ChadAlbum, playlist: Playlist) {
        Task.detached {
            guard let tracks = try? await apiClient.fetchAlbumTracks(albumId: album.id) else { return }
            await MainActor.run {
                let descriptor = FetchDescriptor<Track>(predicate: #Predicate<Track> { $0.isCloud == true })
                let existing = (try? modelContext.fetch(descriptor)) ?? []
                let existingById = Dictionary(uniqueKeysWithValues: existing.compactMap { t in
                    t.cloudTrackId.map { ($0, t) }
                })
                for chadTrack in tracks {
                    let track = existingById[chadTrack.id] ?? {
                        let t = Track.fromCloud(chadTrack)
                        modelContext.insert(t)
                        return t
                    }()
                    playlist.addTrack(track)
                }
            }
        }
    }

    private func addAllAlbumsToPlaylist(playlist: Playlist) {
        for album in albums {
            addAlbumToPlaylist(album, playlist: playlist)
        }
    }
}

// MARK: - Category Detail (list of albums/artists/etc.)

private struct CategoryDetailView: View {
    let apiClient: ChadMusicAPIClient
    let category: ChadCategoryType

    @State private var items: [ChadCategory] = []
    @State private var albums: [ChadAlbum] = []
    @State private var isLoading = true
    @State private var error: String?
    @State private var bulkAddingAlbum: String?  // album ID being bulk-added

    @Environment(\.modelContext) private var modelContext
    @Query(sort: \Playlist.dateModified, order: .reverse) private var allPlaylists: [Playlist]

    /// Album category returns [ChadAlbum], all others return [ChadCategory].
    private var isAlbumCategory: Bool { category == .album }

    var body: some View {
        Group {
            if isLoading {
                ProgressView("Loading \(category.displayName)...")
                    .frame(maxWidth: .infinity, maxHeight: .infinity)
            } else if let error {
                VStack(spacing: 8) {
                    Image(systemName: "exclamationmark.triangle")
                        .font(.title)
                        .foregroundStyle(.secondary)
                    Text(error)
                        .foregroundStyle(.secondary)
                    Button("Retry") { loadItems() }
                }
                .frame(maxWidth: .infinity, maxHeight: .infinity)
            } else if isAlbumCategory {
                List(albums) { album in
                    NavigationLink(value: album) {
                        HStack {
                            VStack(alignment: .leading, spacing: 2) {
                                Text(album.title)
                                    .lineLimit(1)
                                if let artist = album.artist {
                                    Text(artist)
                                        .font(.caption)
                                        .foregroundStyle(.secondary)
                                        .lineLimit(1)
                                }
                            }
                            Spacer()
                            if bulkAddingAlbum == album.id {
                                ProgressView()
                                    .controlSize(.small)
                            } else if let count = album.trackCount {
                                Text("\(count)")
                                    .font(.caption)
                                    .foregroundStyle(.secondary)
                            }
                        }
                    }
                    .contextMenu {
                        Menu("Add Album to Playlist") {
                            ForEach(allPlaylists) { playlist in
                                Button(playlist.name) {
                                    addAlbumToPlaylist(album, playlist: playlist)
                                }
                            }
                        }
                    }
                    .draggable(album)
                }
                .listStyle(.inset)
            } else {
                List(items) { item in
                    NavigationLink(value: CategoryFilter(category: category, value: item.name)) {
                        categoryRow(item)
                    }
                }
                .listStyle(.inset)
            }
        }
        .navigationTitle(category.displayName)
        .task { loadItems() }
    }

    private func categoryRow(_ item: ChadCategory) -> some View {
        HStack {
            Text(item.name)
            Spacer()
            if let count = item.count {
                Text("\(count)")
                    .font(.caption)
                    .foregroundStyle(.secondary)
            }
        }
    }

    private func loadItems() {
        isLoading = true
        error = nil
        Task {
            do {
                if isAlbumCategory {
                    albums = try await apiClient.fetchAlbums()
                } else {
                    items = try await apiClient.fetchCategory(category)
                }
            } catch {
                self.error = error.localizedDescription
            }
            isLoading = false
        }
    }

    private func addAlbumToPlaylist(_ album: ChadAlbum, playlist: Playlist) {
        bulkAddingAlbum = album.id
        Task.detached {
            let chadTracks: [ChadTrack]
            do {
                chadTracks = try await apiClient.fetchAlbumTracks(albumId: album.id)
            } catch {
                print("CloudBrowser: Failed to fetch album tracks: \(error)")
                await MainActor.run { bulkAddingAlbum = nil }
                return
            }
            await MainActor.run {
                bulkInsertCloudTracks(chadTracks, into: playlist)
                bulkAddingAlbum = nil
            }
        }
    }

    private func bulkInsertCloudTracks(_ chadTracks: [ChadTrack], into playlist: Playlist) {
        // Batch dedup: fetch all existing cloud tracks in one query
        let ids = chadTracks.map(\.id)
        let descriptor = FetchDescriptor<Track>(predicate: #Predicate<Track> { track in
            track.isCloud == true
        })
        let existingTracks = (try? modelContext.fetch(descriptor)) ?? []
        let existingById = Dictionary(uniqueKeysWithValues: existingTracks.compactMap { t in
            t.cloudTrackId.map { ($0, t) }
        })

        for chadTrack in chadTracks {
            let track = existingById[chadTrack.id] ?? {
                let newTrack = Track.fromCloud(chadTrack)
                modelContext.insert(newTrack)
                return newTrack
            }()
            playlist.addTrack(track)
        }
    }
}

// MARK: - Album Detail (track list with play buttons)

private struct AlbumDetailView: View {
    let apiClient: ChadMusicAPIClient
    let album: ChadAlbum

    @Environment(PlayerViewModel.self) private var playerVM
    @Environment(\.modelContext) private var modelContext
    @Query(sort: \Playlist.dateModified, order: .reverse) private var allPlaylists: [Playlist]
    @State private var tracks: [ChadTrack] = []
    @State private var isLoading = true
    @State private var error: String?

    var body: some View {
        Group {
            if isLoading {
                ProgressView("Loading tracks...")
                    .frame(maxWidth: .infinity, maxHeight: .infinity)
            } else if let error {
                VStack(spacing: 8) {
                    Image(systemName: "exclamationmark.triangle")
                        .font(.title)
                        .foregroundStyle(.secondary)
                    Text(error)
                        .foregroundStyle(.secondary)
                    Button("Retry") { loadTracks() }
                }
                .frame(maxWidth: .infinity, maxHeight: .infinity)
            } else {
                List {
                    // Album header — draggable to add whole album to playlist
                    VStack(alignment: .leading, spacing: 4) {
                        Text(album.title)
                            .font(.title2.bold())
                        if let artist = album.artist {
                            Text(artist)
                                .font(.title3)
                                .foregroundStyle(.secondary)
                        }
                        HStack {
                            Text("\(tracks.count) tracks")
                                .font(.caption)
                                .foregroundStyle(.tertiary)
                            Spacer()
                            Menu {
                                ForEach(allPlaylists) { playlist in
                                    Button(playlist.name) {
                                        addAllToPlaylist(playlist: playlist)
                                    }
                                }
                            } label: {
                                Label("Add All", systemImage: "plus.circle")
                                    .font(.caption)
                            }
                            .menuStyle(.borderlessButton)
                            .fixedSize()
                        }
                    }
                    .listRowSeparator(.hidden)
                    .padding(.vertical, 8)
                    .draggable(album)
                    .contextMenu {
                        Menu("Add Album to Playlist") {
                            ForEach(allPlaylists) { playlist in
                                Button(playlist.name) {
                                    addAllToPlaylist(playlist: playlist)
                                }
                            }
                        }
                    }

                    // Track rows
                    ForEach(tracks) { track in
                        CloudTrackRow(
                            track: track,
                            isPlaying: playerVM.isCloudPlayback && (
                                playerVM.currentCloudTrack?.id == track.id ||
                                playerVM.currentTrack?.cloudTrackId == track.id
                            )
                        )
                        .contentShape(Rectangle())
                        .onTapGesture {
                            playCloudTrack(track)
                        }
                        .onDrag {
                            let data = try? JSONEncoder().encode(track)
                            let provider = NSItemProvider()
                            if let data {
                                provider.registerDataRepresentation(
                                    forTypeIdentifier: "com.mixboard.chad-track",
                                    visibility: .all
                                ) { completion in
                                    completion(data, nil)
                                    return nil
                                }
                            }
                            return provider
                        }
                        .contextMenu {
                            Button {
                                playCloudTrack(track)
                            } label: {
                                Label("Play", systemImage: "play")
                            }

                            Divider()

                            Menu("Add to Playlist") {
                                ForEach(allPlaylists) { playlist in
                                    Button(playlist.name) {
                                        addToPlaylist(track, playlist: playlist)
                                    }
                                }
                            }
                        }
                    }
                }
                .listStyle(.inset)
            }
        }
        .navigationTitle(album.title)
        .task { loadTracks() }
    }

    private func loadTracks() {
        isLoading = true
        error = nil
        Task {
            do {
                tracks = try await apiClient.fetchAlbumTracks(albumId: album.id)
            } catch {
                self.error = error.localizedDescription
            }
            isLoading = false
        }
    }

    private func playCloudTrack(_ track: ChadTrack) {
        guard let url = apiClient.streamURL(for: track.url) else {
            print("CloudBrowser: Failed to build stream URL for \(track.url)")
            return
        }
        playerVM.loadAndPlayCloud(track, streamURL: url, authHeaders: apiClient.authHeaders)
    }

    private func addToPlaylist(_ chadTrack: ChadTrack, playlist: Playlist) {
        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 addAllToPlaylist(playlist: Playlist) {
        for chadTrack in tracks {
            addToPlaylist(chadTrack, playlist: playlist)
        }
    }
}

// MARK: - Cloud Track Row

private struct CloudTrackRow: View {
    let track: ChadTrack
    let isPlaying: Bool

    var body: some View {
        HStack(spacing: 12) {
            // Track number or playing indicator
            Group {
                if isPlaying {
                    Image(systemName: "speaker.wave.2.fill")
                        .foregroundStyle(Color.accentColor)
                } else if let num = track.trackNumber {
                    Text("\(num)")
                        .foregroundStyle(.secondary)
                } else {
                    Text("—")
                        .foregroundStyle(.tertiary)
                }
            }
            .font(.system(size: 12, design: .monospaced))
            .frame(width: 28, alignment: .trailing)

            // Title + artist
            VStack(alignment: .leading, spacing: 1) {
                Text(track.title)
                    .font(.system(size: 13))
                    .foregroundStyle(isPlaying ? Color.accentColor : .primary)
                    .lineLimit(1)
                if let artist = track.artist {
                    Text(artist)
                        .font(.system(size: 11))
                        .foregroundStyle(.secondary)
                        .lineLimit(1)
                }
            }

            Spacer()

            // Duration
            Text(track.formattedDuration)
                .font(.system(size: 12, design: .monospaced))
                .foregroundStyle(.secondary)
                .frame(width: 40, alignment: .trailing)
        }
        .padding(.vertical, 2)
    }
}