//
//  UICollectionViewExt+rx.swift
//  PaiAi
//
//  Created by LISA on 2017/5/18.
//  Copyright © 2017年 yb. All rights reserved.
//

import UIKit
import RxSwift
import RxCocoa
class FFCollectionViewReactiveArrayDataSourceSequenceWrapper<S: Sequence>
    : FFCollectionViewReactiveArrayDataSource<S.Iterator.Element>
, RxCollectionViewDataSourceType {
    typealias Element = S
    
    init(cellFactory: @escaping CellFactory) {
        super.init()
        self.cellFactory = cellFactory
    }
    func collectionView(_ collectionView: UICollectionView, observedEvent: Event<S>) {
        UIBindingObserver(UIElement: self) { collectionViewDataSource, sectionModels in
            let sections = Array(sectionModels)
            collectionViewDataSource.collectionView(collectionView, observedElements: sections)
            }.on(observedEvent)
    }
}


// Please take a look at `DelegateProxyType.swift`
class FFCollectionViewReactiveArrayDataSource<Element>
    : NSObject, UICollectionViewDataSource
, SectionedViewDataSourceType {
    
    
    var itemModels: [Element]? = nil
    typealias CellFactory = (UICollectionView, Int, Element) -> UICollectionViewCell
    typealias SupplementaryViewFactory = (UICollectionView, String, IndexPath) -> UICollectionReusableView
    func modelAtIndex(_ index: Int) -> Element? {
        return itemModels?[index]
    }
    
    func model(at indexPath: IndexPath) throws -> Any {
        precondition(indexPath.section == 0)
        guard let item = itemModels?[indexPath.item] else {
            throw RxCocoaError.itemsNotYetBound(object: self)
        }
        return item
    }
    
    var cellFactory: CellFactory
    var supplementaryViewFactory: SupplementaryViewFactory
    override init() {
        //        super.init()
        self.cellFactory =  { _, _, _ in return (nil as UICollectionViewCell?)! }
        self.supplementaryViewFactory = { _, _, _ in (nil as UICollectionReusableView?)! }
    }
    
    
    // data source
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return itemModels?.count ?? 0
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        return cellFactory(collectionView, indexPath.item, itemModels![indexPath.item])
    }
    
    func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
        return supplementaryViewFactory(collectionView, kind, indexPath)
    }
    
    
    func collectionView(_ collectionView: UICollectionView, observedElements: [Element]) {
        self.itemModels = observedElements
        collectionView.reloadData()
        collectionView.collectionViewLayout.invalidateLayout()
    }
}



extension Reactive where Base: UICollectionView {
    
    public func items<S: Sequence, Cell: UICollectionViewCell, O: ObservableType>(cellIdentifier: String, supplementaryIdentifier: String, cellType: Cell.Type = Cell.self)
        -> (_ source: O)
        -> (_ configureCell: @escaping (Int, S.Iterator.Element, Cell) -> Void, @escaping (IndexPath, UICollectionReusableView, String) -> Void)
        -> Disposable where O.E == S {
            return { source in
                return { (dataCell,supplement) in
                        let dataSource = FFCollectionViewReactiveArrayDataSourceSequenceWrapper<S>(cellFactory: {
                            (cv, i, item) in
                            let indexPath = IndexPath(item: i, section: 0)
                            let cell = cv.dequeueReusableCell(withReuseIdentifier: cellIdentifier, for: indexPath) as! Cell
                            dataCell(i, item, cell)
                            return cell
                        })
    
                        dataSource.supplementaryViewFactory = {
                            (cv, kind, indexpath) in
                            let view = cv.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: supplementaryIdentifier, for: indexpath)
                            supplement(indexpath, view, kind)
                            return view
                        }
                        return self.items(dataSource: dataSource)(source)
                }
            }
    }
}