//

// CollectionViewDataSource.swift

// DataSourceKit

//

// Created by Yosuke Ishikawa on 2018/09/02.

// Copyright © 2018年 Yosuke Ishikawa. All rights reserved.

//

import UIKit

open class CollectionViewDataSource<CellDeclaration>: NSObject, UICollectionViewDataSource {

open var cellDeclarations = [] as [CellDeclaration]

private var registeredReuseIdentifiers = [] as [String]

private let binderFromDeclaration: (CellDeclaration) -> CellBinder

public init(binderFromDeclaration: @escaping (CellDeclaration) -> CellBinder) {

self.binderFromDeclaration = binderFromDeclaration

super.init()

}

open func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

return cellDeclarations.count

}

open func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

let cellBinder = binderFromDeclaration(cellDeclarations[indexPath.item])

if !registeredReuseIdentifiers.contains(cellBinder.reuseIdentifier) {

switch cellBinder.registrationMethod {

case let .nib(nib):

collectionView.register(nib, forCellWithReuseIdentifier: cellBinder.reuseIdentifier)

case let .class(cellClass):

collectionView.register(cellClass, forCellWithReuseIdentifier: cellBinder.reuseIdentifier)

case .none:

break

}

registeredReuseIdentifiers.append(cellBinder.reuseIdentifier)

}

let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellBinder.reuseIdentifier, for: indexPath)

cellBinder.configureCell(cell)

return cell

}

}

extension CollectionViewDataSource where CellDeclaration == CellBinder {

// Add meaningless parameter to avoid error `Members of constrained extensions

// cannot be declared @objc`, which is caused by collision to init() of NSObject.

public convenience init(binderFromBinder: @escaping (CellBinder) -> CellBinder = { $0 }) {

self.init(binderFromDeclaration: binderFromBinder)

}

}