// Copyright © 2021 Metabolist. All rights reserved.

import AVKit
import Combine
import SDWebImage
import UIKit
import ViewModels
import Vision

final class EditAttachmentViewController: UIViewController {
    private let textView = UITextView()
    private let detectTextFromPictureButton = UIButton(type: .system)
    private let detectTextFromPictureProgressView = UIProgressView()
    private let viewModel: AttachmentViewModel
    private let parentViewModel: CompositionViewModel
    private var cancellables = Set<AnyCancellable>()

    init(viewModel: AttachmentViewModel, parentViewModel: CompositionViewModel) {
        self.viewModel = viewModel
        self.parentViewModel = parentViewModel

        super.init(nibName: nil, bundle: nil)
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    deinit {
        if let playerViewController =
            children.first(where: { $0 is AVPlayerViewController }) as? AVPlayerViewController {
            playerViewController.player?.isMuted = true
            AVAudioSession.decrementPresentedPlayerViewControllerCount()
        }
    }

    // swiftlint:disable:next function_body_length
    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .systemBackground

        let trailingView: UIView

        switch viewModel.attachment.type {
        case .image, .gifv:
            trailingView = EditThumbnailView(viewModel: viewModel)
            view.addSubview(trailingView)
        default:
            let playerViewController = AVPlayerViewController()
            let player: AVPlayer

            if viewModel.attachment.type == .video {
                player = PlayerCache.shared.player(url: viewModel.attachment.url.url)
            } else {
                player = AVPlayer(url: viewModel.attachment.url.url)
            }

            player.isMuted = false
            playerViewController.player = player

            trailingView = playerViewController.view
            addChild(playerViewController)
            view.addSubview(trailingView)
            playerViewController.didMove(toParent: self)
            AVAudioSession.incrementPresentedPlayerViewControllerCount()
        }

        trailingView.translatesAutoresizingMaskIntoConstraints = false

        let stackView = UIStackView()

        view.addSubview(stackView)
        stackView.translatesAutoresizingMaskIntoConstraints = false
        stackView.axis = .vertical
        stackView.spacing = .defaultSpacing

        let describeLabel = UILabel()

        stackView.addArrangedSubview(describeLabel)
        describeLabel.adjustsFontForContentSizeCategory = true
        describeLabel.font = .preferredFont(forTextStyle: .headline)
        describeLabel.numberOfLines = 0
        describeLabel.textAlignment = .center

        switch viewModel.attachment.type {
        case .audio:
            describeLabel.text = NSLocalizedString("attachment.edit.description.audio", comment: "")
        case .video:
            describeLabel.text = NSLocalizedString("attachment.edit.description.video", comment: "")
        default:
            describeLabel.text = NSLocalizedString("attachment.edit.description", comment: "")
        }

        stackView.addArrangedSubview(textView)
        textView.adjustsFontForContentSizeCategory = true
        textView.font = .preferredFont(forTextStyle: .body)
        textView.layer.borderWidth = .hairline
        textView.layer.borderColor = UIColor.separator.cgColor
        textView.layer.cornerRadius = .defaultCornerRadius
        textView.delegate = self
        textView.text = viewModel.editingDescription
        textView.accessibilityLabel = describeLabel.text

        let lowerStackView = UIStackView()

        stackView.addArrangedSubview(lowerStackView)
        lowerStackView.spacing = .defaultSpacing

        let remainingCharactersLabel = UILabel()

        lowerStackView.addArrangedSubview(remainingCharactersLabel)
        remainingCharactersLabel.adjustsFontForContentSizeCategory = true
        remainingCharactersLabel.font = .preferredFont(forTextStyle: .subheadline)

        lowerStackView.addArrangedSubview(detectTextFromPictureButton)
        detectTextFromPictureButton.setTitle(
            NSLocalizedString("attachment.edit.detect-text-from-picture", comment: ""),
            for: .normal)
        detectTextFromPictureButton.titleLabel?.adjustsFontSizeToFitWidth = true
        detectTextFromPictureButton.titleLabel?.numberOfLines = 0
        detectTextFromPictureButton.addAction(
            UIAction { [weak self] _ in self?.detectTextFromPicture() },
            for: .touchUpInside)
        detectTextFromPictureButton.isHidden = viewModel.attachment.type != .image

        stackView.addArrangedSubview(detectTextFromPictureProgressView)
        detectTextFromPictureProgressView.isHidden = true

        NSLayoutConstraint.activate([
            stackView.leadingAnchor.constraint(equalTo: view.layoutMarginsGuide.leadingAnchor),
            stackView.topAnchor.constraint(equalTo: view.layoutMarginsGuide.topAnchor, constant: .defaultSpacing),
            trailingView.leadingAnchor.constraint(equalTo: stackView.trailingAnchor, constant: .defaultSpacing),
            stackView.bottomAnchor.constraint(
                equalTo: view.layoutMarginsGuide.bottomAnchor,
                constant: -.defaultSpacing),
            trailingView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
            trailingView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor),
            trailingView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor),
            trailingView.widthAnchor.constraint(equalTo: stackView.widthAnchor, multiplier: 3 / 2)
        ])

        viewModel.$descriptionRemainingCharacters
            .sink {
                remainingCharactersLabel.text = String($0)
                remainingCharactersLabel.textColor = $0 < 0 ? .systemRed : .label
            }
            .store(in: &cancellables)

        textView.becomeFirstResponder()
    }

    override func didMove(toParent parent: UIViewController?) {
        super.didMove(toParent: parent)

        let cancelButton = UIBarButtonItem(
            systemItem: .cancel,
            primaryAction: UIAction { [weak self] _ in
                self?.presentingViewController?.dismiss(animated: true)
            })
        let doneButton = UIBarButtonItem(
            systemItem: .done,
            primaryAction: UIAction { [weak self] _ in
                guard let self = self else { return }

                self.parentViewModel.update(attachmentViewModel: self.viewModel)
                self.presentingViewController?.dismiss(animated: true)
            })

        parent?.navigationItem.leftBarButtonItem = cancelButton
        parent?.navigationItem.rightBarButtonItem = doneButton
        parent?.navigationItem.title = NSLocalizedString("attachment.edit.title", comment: "")
    }
}

extension EditAttachmentViewController: UITextViewDelegate {
    func textViewDidChange(_ textView: UITextView) {
        viewModel.editingDescription = textView.text
    }
}

private extension EditAttachmentViewController {
    enum TextDetectionOutput {
        case progress(Double)
        case result(String)
    }

    func detectTextFromPicture() {
        SDWebImageManager.shared.loadImage(
            with: viewModel.attachment.url.url,
            options: [],
            progress: nil) { [weak self] image, _, _, _, _, _ in
            guard let self = self, let cgImage = image?.cgImage else { return }

            self.detectText(cgImage: cgImage)
                .sink {
                    if case let .failure(error) = $0 {
                        self.present(alertItem: .init(error: error))
                    }
                } receiveValue: { [weak self] in
                    guard let self = self else { return }

                    switch $0 {
                    case let .progress(progress):
                        self.detectTextFromPictureButton.isHidden = true
                        self.detectTextFromPictureProgressView.isHidden = false
                        self.detectTextFromPictureProgressView.progress = Float(progress)
                    case let .result(result):
                        self.detectTextFromPictureButton.isHidden = false
                        self.detectTextFromPictureProgressView.isHidden = true
                        self.textView.text += result
                        self.textViewDidChange(self.textView)
                    }
                }
                .store(in: &self.cancellables)
        }
    }

    func detectText(cgImage: CGImage) -> AnyPublisher<TextDetectionOutput, Error> {
        let subject = PassthroughSubject<TextDetectionOutput, Error>()

        let recognizeTextRequest = VNRecognizeTextRequest { request, error in
            if let error = error {
                DispatchQueue.main.async {
                    subject.send(completion: .failure(error))
                }

                return
            }

            let recognizedTextObservations = request.results as? [VNRecognizedTextObservation] ?? []
            let result = recognizedTextObservations
                .compactMap { $0.topCandidates(1).first?.string }
                .joined(separator: " ")

            DispatchQueue.main.async {
                subject.send(.result(result))
                subject.send(completion: .finished)
            }
        }

        recognizeTextRequest.recognitionLevel = .accurate
        recognizeTextRequest.usesLanguageCorrection = true
        recognizeTextRequest.progressHandler = { _, progress, error in
            DispatchQueue.main.async {
                if let error = error {
                    subject.send(completion: .failure(error))

                    return
                }

                subject.send(.progress(progress))
            }
        }

        let handler = VNImageRequestHandler(cgImage: cgImage, options: [:])

        do {
            try handler.perform([recognizeTextRequest])
        } catch {
            subject.send(completion: .failure(error))
        }

        return subject.eraseToAnyPublisher()
    }
}