RxSwift/RxCocoa/iOS/UICollectionView+Rx.swift

//
//  UICollectionView+Rx.swift
//  RxCocoa
//
//  Created by Krunoslav Zaher on 4/2/15.
//  Copyright (c) 2015 Krunoslav Zaher. All rights reserved.
//

#if os(iOS) || os(tvOS)

import Foundation
#if !RX_NO_MODULE
import RxSwift
#endif
import UIKit

// Items

extension UICollectionView {
    
    /**
    Binds sequences of elements to collection view items.
    
    - parameter source: Observable sequence of items.
    - parameter cellFactory: Transform between sequence elements and view cells.
    - returns: Disposable object that can be used to unbind.
    */
    public func rx_itemsWithCellFactory<S: SequenceType, O: ObservableType where O.E == S>
        (source: O)
        (cellFactory: (UICollectionView, Int, S.Generator.Element) -> UICollectionViewCell)
        -> Disposable {
        let dataSource = RxCollectionViewReactiveArrayDataSourceSequenceWrapper<S>(cellFactory: cellFactory)
        return self.rx_itemsWithDataSource(dataSource)(source: source)
    }
    
    /**
    Binds sequences of elements to collection view items.
    
    - parameter cellIdentifier: Identifier used to dequeue cells.
    - parameter source: Observable sequence of items.
    - parameter configureCell: Transform between sequence elements and view cells.
    - returns: Disposable object that can be used to unbind.
    */
    public func rx_itemsWithCellIdentifier<S: SequenceType, Cell: UICollectionViewCell, O : ObservableType where O.E == S>
        (cellIdentifier: String)
        (source: O)
        (configureCell: (Int, S.Generator.Element, Cell) -> Void)
        -> Disposable {
        let dataSource = RxCollectionViewReactiveArrayDataSourceSequenceWrapper<S> { (cv, i, item) in
            let indexPath = NSIndexPath(forItem: i, inSection: 0)
            let cell = cv.dequeueReusableCellWithReuseIdentifier(cellIdentifier, forIndexPath: indexPath) as! Cell
            configureCell(i, item, cell)
            return cell
        }
        
        return self.rx_itemsWithDataSource(dataSource)(source: source)
    }
    
    /**
    Binds sequences of elements to collection view items using a custom reactive data used to perform the transformation.
    
    - parameter dataSource: Data source used to transform elements to view cells.
    - parameter source: Observable sequence of items.
    - returns: Disposable object that can be used to unbind.
    */
    public func rx_itemsWithDataSource<DataSource: protocol<RxCollectionViewDataSourceType, UICollectionViewDataSource>, S: SequenceType, O: ObservableType where DataSource.Element == S, O.E == S>
        (dataSource: DataSource)
        (source: O)
        -> Disposable  {
        return source.subscribeProxyDataSourceForObject(self, dataSource: dataSource, retainDataSource: false) { [weak self] (_: RxCollectionViewDataSourceProxy, event) -> Void in
            guard let collectionView = self else {
                return
            }
            dataSource.collectionView(collectionView, observedEvent: event)
        }
    }
}

extension UICollectionView {
   
    /**
    Factory method that enables subclasses to implement their own `rx_delegate`.
    
    - returns: Instance of delegate proxy that wraps `delegate`.
    */
    override func rx_createDelegateProxy() -> RxScrollViewDelegateProxy {
        return RxCollectionViewDelegateProxy(parentObject: self)
    }
    
    /**
    Reactive wrapper for `dataSource`.
    
    For more information take a look at `DelegateProxyType` protocol documentation.
    */
    public var rx_dataSource: DelegateProxy {
        get {
            return proxyForObject(self) as RxCollectionViewDataSourceProxy
        }
    }
    
    /**
    Installs data source as forwarding delegate on `rx_dataSource`. 
    
    It enables using normal delegate mechanism with reactive delegate mechanism.
    
    - parameter dataSource: Data source object.
    - returns: Disposable object that can be used to unbind the data source.
    */
    public func rx_setDataSource(dataSource: UICollectionViewDataSource)
        -> Disposable {
        let proxy: RxCollectionViewDataSourceProxy = proxyForObject(self)
        return installDelegate(proxy, delegate: dataSource, retainDelegate: false, onProxyForObject: self)
    }
   
    /**
    Reactive wrapper for `delegate` message `collectionView:didSelectItemAtIndexPath:`.
    */
    public var rx_itemSelected: ControlEvent<NSIndexPath> {
        let source = rx_delegate.observe("collectionView:didSelectItemAtIndexPath:")
            .map { a in
                return a[1] as! NSIndexPath
            }
        
        return ControlEvent(source: source)
    }
    
    /**
    Reactive wrapper for `delegate` message `collectionView:didSelectItemAtIndexPath:`.
    
    It can be only used when one of the `rx_itemsWith*` methods is used to bind observable sequence.
    
         collectionView.rx_modelSelected(MyModel.self)
            .map { ...

    If custom data source is being bound, new `rx_modelSelected` wrapper needs to be written also.
    
        public func rx_myModelSelected<T>() -> ControlEvent<T> {
            let source: Observable<T> = rx_itemSelected.map { indexPath in
                    let dataSource: MyDataSource = self.rx_dataSource.forwardToDelegate() as! MyDataSource
    
                    return dataSource.modelAtIndex(indexPath.item)!
                }
            
            return ControlEvent(source: source)
        }
    
    */
    public func rx_modelSelected<T>(modelType: T.Type) -> ControlEvent<T> {
        let source: Observable<T> = rx_itemSelected.flatMap { [weak self] indexPath -> Observable<T> in
            guard let view = self else {
                return empty()
            }

            return just(try view.rx_modelAtIndexPath(indexPath))
        }
        
        return ControlEvent(source: source)
    }
    
    /**
    Syncronous helper method for retrieving a model at indexPath through a reactive data source
    */
    public func rx_modelAtIndexPath<T>(indexPath: NSIndexPath) throws -> T {
        let dataSource: RxCollectionViewReactiveArrayDataSource<T> = castOrFatalError(self.rx_dataSource.forwardToDelegate(), message: "This method only works in case one of the `rx_itemsWith*` methods was used.")
        
        guard let element = dataSource.modelAtIndex(indexPath.item) else {
            throw RxCocoaError.ItemsNotYetBound(object: self)
        }
        
        return element
    }
}
#endif

#if os(tvOS)

extension UICollectionView {
    
    /**
     Reactive wrapper for `delegate` message `collectionView:didUpdateFocusInContext:withAnimationCoordinator:`.
     */
    public var rx_didUpdateFocusInContextWithAnimationCoordinator: ControlEvent<(context: UIFocusUpdateContext, animationCoordinator: UIFocusAnimationCoordinator)> {
        
        let source = rx_delegate.observe("collectionView:didUpdateFocusInContext:withAnimationCoordinator:")
            .map { a -> (context: UIFocusUpdateContext, animationCoordinator: UIFocusAnimationCoordinator) in
                let context = a[1] as! UIFocusUpdateContext
                let animationCoordinator = a[2] as! UIFocusAnimationCoordinator
                return (context: context, animationCoordinator: animationCoordinator)
        }

        return ControlEvent(source: source)
    }
}
#endif