//
// Swiftfin is subject to the terms of the Mozilla Public
// License, v2.0. If a copy of the MPL was not distributed with this
// file, you can obtain one at https://mozilla.org/MPL/2.0/.
//
// Copyright (c) 2022 Jellyfin & Jellyfin Contributors
//

import JellyfinAPI
import SwiftUI

// TODO: Needs replacement/reworking
struct SmallMediaStreamSelectionView: View {

	enum Layer: Hashable {
		case subtitles
		case audio
		case playbackSpeed
	}

	enum MediaSection: Hashable {
		case titles
		case items
	}

	@ObservedObject
	var viewModel: VideoPlayerViewModel

	@State
	private var updateFocusedLayer: Layer = .subtitles

	@FocusState
	private var subtitlesFocused: Bool
	@FocusState
	private var audioFocused: Bool
	@FocusState
	private var playbackSpeedFocused: Bool
	@FocusState
	private var focusedSection: MediaSection?
	@FocusState
	private var focusedLayer: Layer? {
		willSet {
			updateFocusedLayer = newValue!

			if focusedSection == .titles {
				lastFocusedLayer = newValue!
			}
		}
	}

	@State
	private var lastFocusedLayer: Layer = .subtitles

	var body: some View {
		ZStack(alignment: .bottom) {
			LinearGradient(gradient: Gradient(colors: [.clear, .black.opacity(0.8), .black]),
			               startPoint: .top,
			               endPoint: .bottom)
				.ignoresSafeArea()
				.frame(height: 300)

			VStack {

				Spacer()

				HStack {

					// MARK: Subtitle Header

					Button {
						updateFocusedLayer = .subtitles
						focusedLayer = .subtitles
					} label: {
						if updateFocusedLayer == .subtitles {
							HStack(spacing: 15) {
								Image(systemName: "captions.bubble")
								L10n.subtitles.text
							}
							.padding()
							.background(Color.white)
							.foregroundColor(.black)
						} else {
							HStack(spacing: 15) {
								Image(systemName: "captions.bubble")
								L10n.subtitles.text
							}
							.padding()
						}
					}
					.buttonStyle(PlainButtonStyle())
					.background(Color.clear)
					.focused($focusedLayer, equals: .subtitles)
					.focused($subtitlesFocused)
					.onChange(of: subtitlesFocused) { isFocused in
						if isFocused {
							focusedLayer = .subtitles
						}
					}

					// MARK: Audio Header

					Button {
						updateFocusedLayer = .audio
						focusedLayer = .audio
					} label: {
						if updateFocusedLayer == .audio {
							HStack(spacing: 15) {
								Image(systemName: "speaker.wave.3")
								L10n.audio.text
							}
							.padding()
							.background(Color.white)
							.foregroundColor(.black)
						} else {
							HStack(spacing: 15) {
								Image(systemName: "speaker.wave.3")
								L10n.audio.text
							}
							.padding()
						}
					}
					.buttonStyle(PlainButtonStyle())
					.background(Color.clear)
					.focused($focusedLayer, equals: .audio)
					.focused($audioFocused)
					.onChange(of: audioFocused) { isFocused in
						if isFocused {
							focusedLayer = .audio
						}
					}

					// MARK: Playback Speed Header

					Button {
						updateFocusedLayer = .playbackSpeed
						focusedLayer = .playbackSpeed
					} label: {
						if updateFocusedLayer == .playbackSpeed {
							HStack(spacing: 15) {
								Image(systemName: "speedometer")
								L10n.playbackSpeed.text
							}
							.padding()
							.background(Color.white)
							.foregroundColor(.black)
						} else {
							HStack(spacing: 15) {
								Image(systemName: "speedometer")
								L10n.playbackSpeed.text
							}
							.padding()
						}
					}
					.buttonStyle(PlainButtonStyle())
					.background(Color.clear)
					.focused($focusedLayer, equals: .playbackSpeed)
					.focused($playbackSpeedFocused)
					.onChange(of: playbackSpeedFocused) { isFocused in
						if isFocused {
							focusedLayer = .playbackSpeed
						}
					}

					Spacer()
				}
				.padding()
				.focusSection()
				.focused($focusedSection, equals: .titles)
				.onChange(of: focusedSection) { _ in
					if focusedSection == .titles {
						if lastFocusedLayer == .subtitles {
							subtitlesFocused = true
						} else if lastFocusedLayer == .audio {
							audioFocused = true
						} else if lastFocusedLayer == .playbackSpeed {
							playbackSpeedFocused = true
						}
					}
				}

				if updateFocusedLayer == .subtitles && lastFocusedLayer == .subtitles {
					// MARK: Subtitles

					ScrollView(.horizontal) {
						HStack {
							if viewModel.subtitleStreams.isEmpty {
								Button {} label: {
									L10n.none.text
								}
							} else {
								ForEach(viewModel.subtitleStreams, id: \.self) { subtitleStream in
									Button {
										viewModel.selectedSubtitleStreamIndex = subtitleStream.index ?? -1
									} label: {
										if subtitleStream.index == viewModel.selectedSubtitleStreamIndex {
											Label(subtitleStream.displayTitle ?? L10n.noTitle, systemImage: "checkmark")
										} else {
											Text(subtitleStream.displayTitle ?? L10n.noTitle)
										}
									}
								}
							}
						}
						.padding(.vertical)
						.focusSection()
						.focused($focusedSection, equals: .items)
					}
				} else if updateFocusedLayer == .audio && lastFocusedLayer == .audio {
					// MARK: Audio

					ScrollView(.horizontal) {
						HStack {
							if viewModel.audioStreams.isEmpty {
								Button {} label: {
									Text("None")
								}
							} else {
								ForEach(viewModel.audioStreams, id: \.self) { audioStream in
									Button {
										viewModel.selectedAudioStreamIndex = audioStream.index ?? -1
									} label: {
										if audioStream.index == viewModel.selectedAudioStreamIndex {
											Label(audioStream.displayTitle ?? L10n.noTitle, systemImage: "checkmark")
										} else {
											Text(audioStream.displayTitle ?? L10n.noTitle)
										}
									}
								}
							}
						}
						.padding(.vertical)
						.focusSection()
						.focused($focusedSection, equals: .items)
					}
				} else if updateFocusedLayer == .playbackSpeed && lastFocusedLayer == .playbackSpeed {
					// MARK: Rates

					ScrollView(.horizontal) {
						HStack {
							ForEach(PlaybackSpeed.allCases, id: \.self) { playbackSpeed in
								Button {
									viewModel.playbackSpeed = playbackSpeed
								} label: {
									if playbackSpeed == viewModel.playbackSpeed {
										Label(playbackSpeed.displayTitle, systemImage: "checkmark")
									} else {
										Text(playbackSpeed.displayTitle)
									}
								}
							}
						}
						.padding(.vertical)
						.focusSection()
						.focused($focusedSection, equals: .items)
					}
				}
			}
		}
	}
}