// Copyright © 2020 Metabolist. All rights reserved.

import Combine
import Kingfisher
import UIKit
import ViewModels

final class CompositionView: UIView {
    let avatarImageView = UIImageView()
    let spoilerTextField = UITextField()
    let textView = UITextView()
    let attachmentUploadView = AttachmentUploadView()
    let attachmentsCollectionView: UICollectionView

    private let viewModel: CompositionViewModel
    private let parentViewModel: NewStatusViewModel
    private var cancellables = Set<AnyCancellable>()

    private lazy var attachmentsDataSource: CompositionAttachmentsDataSource = {
        CompositionAttachmentsDataSource(
            collectionView: attachmentsCollectionView) { [weak self] in
            self?.viewModel.attachmentViewModel(indexPath: $0)
        }
    }()

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

        let itemSize = NSCollectionLayoutSize(
            widthDimension: .fractionalWidth(0.2),
            heightDimension: .fractionalHeight(1.0))
        let item = NSCollectionLayoutItem(layoutSize: itemSize)
        let groupSize = NSCollectionLayoutSize(
            widthDimension: .fractionalWidth(1.0),
            heightDimension: .fractionalWidth(0.2))
        let group = NSCollectionLayoutGroup.horizontal(
            layoutSize: groupSize,
            subitems: [item])

        group.interItemSpacing = .fixed(.defaultSpacing)

        let section = NSCollectionLayoutSection(group: group)
        let attachmentsLayout = UICollectionViewCompositionalLayout(section: section)
        attachmentsCollectionView = UICollectionView(frame: .zero, collectionViewLayout: attachmentsLayout)

        super.init(frame: .zero)

        initialSetup()
    }

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

extension CompositionView {
    var id: CompositionViewModel.Id { viewModel.id }
}

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

private extension CompositionView {
    static let attachmentUploadViewHeight: CGFloat = 100

    // swiftlint:disable:next function_body_length
    func initialSetup() {
        tag = viewModel.id.hashValue

        addSubview(avatarImageView)
        avatarImageView.translatesAutoresizingMaskIntoConstraints = false
        avatarImageView.layer.cornerRadius = .avatarDimension / 2
        avatarImageView.clipsToBounds = true

        let stackView = UIStackView()
        let inputAccessoryView = CompositionInputAccessoryView(viewModel: viewModel, parentViewModel: parentViewModel)

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

        stackView.addArrangedSubview(spoilerTextField)
        spoilerTextField.backgroundColor = .secondarySystemBackground
        spoilerTextField.layer.cornerRadius = .defaultCornerRadius
        spoilerTextField.adjustsFontForContentSizeCategory = true
        spoilerTextField.font = .preferredFont(forTextStyle: .body)
        spoilerTextField.placeholder = NSLocalizedString("status.spoiler-text-placeholder", comment: "")
        spoilerTextField.inputAccessoryView = inputAccessoryView
        spoilerTextField.addAction(
            UIAction { [weak self] _ in
                guard let self = self, let text = self.spoilerTextField.text else { return }

                self.viewModel.contentWarning = text
            },
            for: .editingChanged)

        stackView.addArrangedSubview(textView)
        textView.backgroundColor = .secondarySystemBackground
        textView.layer.cornerRadius = .defaultCornerRadius
        textView.isScrollEnabled = false
        textView.adjustsFontForContentSizeCategory = true
        textView.font = .preferredFont(forTextStyle: .body)
//        textView.textContainer.lineFragmentPadding = 0
        textView.inputAccessoryView = inputAccessoryView
        textView.inputAccessoryView?.sizeToFit()
        textView.delegate = self
        textView.setContentHuggingPriority(.required, for: .vertical)

        stackView.addArrangedSubview(attachmentsCollectionView)
        attachmentsCollectionView.dataSource = attachmentsDataSource

        stackView.addArrangedSubview(attachmentUploadView)

        textView.text = viewModel.text
        spoilerTextField.text = viewModel.contentWarning

        viewModel.$displayContentWarning
            .sink { [weak self] in
                guard let self = self else { return }

                if self.spoilerTextField.isHidden && self.textView.isFirstResponder && $0 {
                    self.spoilerTextField.becomeFirstResponder()
                } else if !self.spoilerTextField.isHidden && self.spoilerTextField.isFirstResponder && !$0 {
                    self.textView.becomeFirstResponder()
                }

                self.spoilerTextField.isHidden = !$0
            }
            .store(in: &cancellables)

        parentViewModel.$identification.map(\.identity.image)
            .sink { [weak self] in self?.avatarImageView.kf.setImage(with: $0) }
            .store(in: &cancellables)

        viewModel.$attachmentViewModels
            .receive(on: DispatchQueue.main) // hack to punt to next run loop, consider refactoring
            .sink { [weak self] in
                self?.attachmentsDataSource.apply($0.map(\.attachment).snapshot())
                self?.attachmentsCollectionView.isHidden = $0.isEmpty
            }
            .store(in: &cancellables)

        viewModel.$attachmentUpload
            .sink { [weak self] in self?.attachmentUploadView.attachmentUpload = $0 }
            .store(in: &cancellables)

        let guide = UIDevice.current.userInterfaceIdiom == .pad ? readableContentGuide : layoutMarginsGuide
        let constraints = [
            avatarImageView.heightAnchor.constraint(equalToConstant: .avatarDimension),
            avatarImageView.widthAnchor.constraint(equalToConstant: .avatarDimension),
            avatarImageView.topAnchor.constraint(equalTo: guide.topAnchor),
            avatarImageView.leadingAnchor.constraint(equalTo: guide.leadingAnchor),
            avatarImageView.bottomAnchor.constraint(lessThanOrEqualTo: guide.bottomAnchor),
            stackView.leadingAnchor.constraint(equalTo: avatarImageView.trailingAnchor, constant: .defaultSpacing),
            stackView.topAnchor.constraint(equalTo: guide.topAnchor),
            stackView.trailingAnchor.constraint(equalTo: guide.trailingAnchor),
            stackView.bottomAnchor.constraint(lessThanOrEqualTo: guide.bottomAnchor),
            attachmentsCollectionView.heightAnchor.constraint(
                equalTo: attachmentsCollectionView.widthAnchor,
                multiplier: 1 / 4),
            attachmentUploadView.heightAnchor.constraint(equalToConstant: Self.attachmentUploadViewHeight)
        ]

        if UIDevice.current.userInterfaceIdiom == .pad {
            for constraint in constraints {
                constraint.priority = .justBelowMax
            }
        }

        NSLayoutConstraint.activate(constraints)
    }
}