EmojiInputController.swift

//
//  EmojiInputController.swift
//  LoopKit
//
//  Copyright © 2017 LoopKit Authors. All rights reserved.
//

import UIKit


public class EmojiInputController: UIInputViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout, IdentifiableClass {

    @IBOutlet private weak var collectionView: UICollectionView!

    @IBOutlet private weak var sectionIndex: UIStackView!

    public weak var delegate: EmojiInputControllerDelegate?

    var emojis: EmojiDataSource!

    static func instance(withEmojis emojis: EmojiDataSource) -> EmojiInputController {
        let bundle = Bundle(for: self)
        let storyboard = UIStoryboard(name: className, bundle: bundle)
        let controller = storyboard.instantiateInitialViewController() as! EmojiInputController
        controller.emojis = emojis
        return controller
    }

    public override func viewDidLoad() {
        super.viewDidLoad()

        inputView = view as? UIInputView
        inputView?.allowsSelfSizing = true
        view.translatesAutoresizingMaskIntoConstraints = false

        if let layout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout {
            layout.sectionHeadersPinToVisibleBounds = true
            layout.sectionFootersPinToVisibleBounds = true
        }

        setupSectionIndex()

        // Scroll to medium absorption
        DispatchQueue.main.async {
            self.collectionView.scrollToItem(at: IndexPath(row: 0, section: 1), at: .left, animated: false)
        }
    }

    private func setupSectionIndex() {
        sectionIndex.removeAllArrangedSubviews()

        for section in emojis.sections {
            let label = UILabel(frame: .zero)
            label.text = section.indexSymbol
            sectionIndex.addArrangedSubview(label)
        }
    }

    @IBOutlet weak var deleteButton: UIButton! {
        didSet {
            let image = UIImage(systemName: "delete.left", compatibleWith: traitCollection)
            deleteButton.setImage(image, for: .normal)
        }
    }

    // MARK: - Actions

    @IBAction func switchKeyboard(_ sender: Any) {
        delegate?.emojiInputControllerDidAdvanceToStandardInputMode(self)
    }

    @IBAction func deleteBackward(_ sender: Any) {
        inputView?.playInputClick​()
        textDocumentProxy.deleteBackward()
    }

    @IBAction func indexTouched(_ sender: UIGestureRecognizer) {
        let xLocation = max(0, sender.location(in: sectionIndex).x / sectionIndex.frame.width)
        let items = sectionIndex.arrangedSubviews.count
        let section = min(items - 1, Int(xLocation * CGFloat(items)))

        collectionView.scrollToItem(at: IndexPath(item: 0, section: section), at: .left, animated: false)
    }

    // MARK: - UICollectionViewDataSource

    public func numberOfSections(in collectionView: UICollectionView) -> Int {
        return emojis.sections.count
    }

    public func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return emojis.sections[section].items.count
    }

    public func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
        let cell = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: kind == UICollectionView.elementKindSectionHeader ? EmojiInputHeaderView.className : "Footer", for: indexPath)

        if let cell = cell as? EmojiInputHeaderView {
            cell.titleLabel.text = emojis.sections[indexPath.section].title.localizedUppercase
        }

        return cell
    }

    public func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: EmojiInputCell.className, for: indexPath) as! EmojiInputCell

        cell.label.text = emojis.sections[indexPath.section].items[indexPath.row]

        return cell
    }

    // MARK: - UICollectionViewDelegateFlowLayout

    // MARK: - UICollectionViewDelegate

    public func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        collectionView.deselectItem(at: indexPath, animated: true)
        inputView?.playInputClick​()
        textDocumentProxy.insertText(emojis.sections[indexPath.section].items[indexPath.row])

        delegate?.emojiInputControllerDidSelectItemInSection(indexPath.section)
    }
}


public protocol EmojiInputControllerDelegate: AnyObject {
    func emojiInputControllerDidAdvanceToStandardInputMode(_ controller: EmojiInputController)

    func emojiInputControllerDidSelectItemInSection(_ section: Int)
}

// MARK: - Default Implementations
extension EmojiInputControllerDelegate {
    public func emojiInputControllerDidSelectItemInSection(_ section: Int) { }
}

extension UIInputView: UIInputViewAudioFeedback {
    public var enableInputClicksWhenVisible: Bool { return true }

    func playInputClick​() {
        let device = UIDevice.current
        device.playInputClick()
    }
}

private extension UIStackView {
    func removeAllArrangedSubviews() {
        for view in arrangedSubviews {
            view.removeFromSuperview()
        }
    }
}