pod "SwiftListTreeDataSource", "1.0.0"

var listTreeDataSource = ListTreeDataSource
   
    ()

// create data source with filtering support.
var filterableListTreeDataSource = FilterableListTreeDataSource
    
     ()

    
   

// Helper to traverse items with all nested children to include to data source.
addItems(items, itemChildren: { $0.subitems }, to: listTreeDataSource)

// Append:
listTreeDataSource.append(currentToAdd, to: referenceParent)

// Insert:
listTreeDataSource.insert([insertionBeforeItem], before: existingItem)
listTreeDataSource.insert([insertionAfterItem], after: existingItem)

// Delete:
listTreeDataSource.delete([itemToDelete])

// NOTE: Reload data source at the end of changes.
listTreeDataSource.reload()

.TreeItemType>() diffableSnaphot.appendSections([.main]) diffableSnaphot.appendItems(filterableTreeDataSource.items, toSection: .main) self.diffableDataSource.apply(diffableSnaphot, animatingDifferences: animating) } else { self.tableView.reloadData() } } ">

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return listTreeDataSource.items.count
}

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! Cell

    let item = listTreeDataSource.items[indexPath.row]

    let left = 11 + 10 * item.level
    cell.lbl?.text = item.value.title
    cell.lblLeadingConstraint.constant = CGFloat(left)
    cell.disclosureImageView.isHidden = item.subitems.isEmpty

    let transform = CGAffineTransform.init(rotationAngle: item.isExpanded ? CGFloat.pi/2.0 : 0)
    cell.disclosureImageView.transform = transform

    return cell
}

// MARK: - Example with fitering

func performSearch(with searchText: String) {
    if !searchText.isEmpty {
        self.searchBar.isLoading = true
        self.displayMode = .filtering(text: searchText)

        self.filterableTreeDataSource.filterItemsKeepingParents(by: { $0.title.lowercased().contains(searchText.lowercased()) }) { [weak self] in
            guard let self = self else { return }
            self.searchBar.isLoading = false
            self.reloadUI(animating: false)
        }
    } else {
        self.displayMode = .standard
        self.searchBar.isLoading = false
        self.filterableTreeDataSource.resetFiltering(collapsingAll: true)
        self.reloadUI(animating: false)
    }
}

func reloadUI(animating: Bool = true) {
    if isOS13Available {
        var diffableSnaphot = NSDiffableDataSourceSnapshot
   
    .TreeItemType>()
        diffableSnaphot.appendSections([.main])
        diffableSnaphot.appendItems(filterableTreeDataSource.items, toSection: .main)
        self.diffableDataSource.apply(diffableSnaphot, animatingDifferences: animating)
    } else {
        self.tableView.reloadData()
    }
}

   

/// https://en.wikipedia.org/wiki/Exponential_decay
let isPad = UIDevice.current.userInterfaceIdiom == .pad
let decayCoefficient: Double = isPad ? 150 : 40
let lvl = Double(item.level)
let left = 11 + 10 * lvl * ( exp( -lvl / max(decayCoefficient, lvl)) )
let leftOffset: CGFloat = min( CGFloat(left) , UIScreen.main.bounds.width - 120.0)
cell.lblLeadingConstraint.constant = leftOffset

// to get `testable` access to internal stuff, including to `backingStore`.
@testable import SwiftListTreeDataSource

// Make conform to `CustomDebugStringConvertible`.
extension OutlineItem: CustomDebugStringConvertible {
    public var debugDescription: String { "\(title)" }
}

// Correct usage:
let output1 = debugDescriptionTopLevel(listTreeDataSource.items) // ✅ Description for top level since `items` already flattened (one-level perspective) and include expanded children.
let output2 = debugDescriptionAllLevels(listTreeDataSource.backingStore) // ✅ Description for all levels, asked with hierarchical store as input.
let output3 = debugDescriptionExpandedLevels(listTreeDataSource.backingStore) // ✅ Description for expanded levels, asked with hierarchical store as input.
print(output3) // print output to console for example.  

// Wrong usage:
// ❌ `listTreeDataSource.items` are already flattened (one-level perspetive) and include expanded items, so methods below will return nonsense.
debugDescriptionAllLevels(listTreeDataSource.items) // ❌
debugDescriptionExpandedLevels(listTreeDataSource.items) // ❌