Attractor/App/Tabs/TabPickerViewController.swift

//
//  TabPickerViewController.swift
//  SBrowser
//
//  Created by James Magahern on 7/30/20.
//

import UIKit

protocol TabPickerViewControllerDelegate: class
{
    func tabPicker(_ picker: TabPickerViewController, didSelectTab tab: Tab)
    func tabPicker(_ picker: TabPickerViewController, willCloseTab tab: Tab)
}

class TabPickerViewController: UIViewController, UICollectionViewDelegate
{
    let tabController: TabController!
    var selectedTab: Tab?
    
    weak var delegate: TabPickerViewControllerDelegate?
    
    typealias TabID = UUID
    
    private var collectionView: UICollectionView?
    private var dataSource: UICollectionViewDiffableDataSource<Int, TabID>?
    
    init(tabController: TabController) {
        self.tabController = tabController
        super.init(nibName: nil, bundle: nil)
        
        self.title = "Tabs"
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func loadView() {
        var listConfig = UICollectionLayoutListConfiguration(appearance: .insetGrouped)
        listConfig.trailingSwipeActionsConfigurationProvider = { [unowned self] indexPath in
            if self.dataSource?.snapshot().numberOfItems ?? 0 <= 1 {
                return nil
            }
            
            return UISwipeActionsConfiguration(actions: [ UIContextualAction(style: .destructive, title: "Close", handler: { [unowned self] (action, view, completionHandler) in
                if let item = self.dataSource?.itemIdentifier(for: indexPath), var snapshot = self.dataSource?.snapshot() {
                    if let tab = self.tabController.tab(forIdentifier: item) {
                        self.delegate?.tabPicker(self, willCloseTab: tab)
                        
                        self.tabController.closeTab(tab)
                        snapshot.deleteItems([ item ])
                        self.dataSource?.apply(snapshot, animatingDifferences: true)
                    }
                }
            })])
        }
        
        let listLayout = UICollectionViewCompositionalLayout.list(using: listConfig)
        let collectionView = UICollectionView(frame: .zero, collectionViewLayout: listLayout)
                
        let registry = UICollectionView.CellRegistration<UICollectionViewListCell, TabID> { [unowned self] (listCell, indexPath, item) in
            var config = listCell.defaultContentConfiguration()
            
            if let tab = self.tabController.tab(forIdentifier: item) {
                if let title = tab.title, title.count > 0 {
                    config.text = title
                    config.secondaryText = tab.url?.absoluteString
                } else if let url = tab.url {
                    config.text = url.absoluteString
                    config.secondaryText = url.absoluteString
                } else {
                    config.text = "New Tab"
                }
                
                config.textProperties.numberOfLines = 1
                config.secondaryTextProperties.numberOfLines = 1
                
                if let image = tab.favicon {
                    config.image = image
                } else {
                    config.image = UIImage(systemName: "safari")
                }
                
                config.imageProperties.maximumSize = CGSize(width: 21.0, height: 21.0)
                config.imageProperties.cornerRadius = 3.0
                
                if tab == self.selectedTab {
                    listCell.accessories = [ .checkmark() ]
                } else {
                    listCell.accessories = []
                }
            }
            
            listCell.contentConfiguration = config
        }
                
        let dataSource = UICollectionViewDiffableDataSource<Int, TabID>(collectionView: collectionView) { (collectionView, indexPath, item) -> UICollectionViewCell? in
            return collectionView.dequeueConfiguredReusableCell(using: registry, for: indexPath, item: item)
        }
        
        collectionView.dataSource = dataSource
        collectionView.delegate = self
        
        var snapshot = dataSource.snapshot()
        snapshot.appendSections([ 0 ])
        tabController.tabs.forEach { tab in
            snapshot.appendItems([ tab.identifier ])
        }
        
        dataSource.apply(snapshot)
        
        self.dataSource = dataSource
        self.collectionView = collectionView
        self.view = self.collectionView
        
        let newTabButton = UIBarButtonItem(systemItem: .add, primaryAction: UIAction(handler: { [unowned self] _ in
            let newTab = self.tabController.createNewTab(url: nil)
            self.delegate?.tabPicker(self, didSelectTab: newTab)
        }), menu: nil)
        
        navigationItem.rightBarButtonItem = newTabButton
    }
    
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        let tab = tabController.tabs[indexPath.row]
        delegate?.tabPicker(self, didSelectTab: tab)
    }
}