update readme

Author: imkdir

ArkDemo/HomeFeed.swift

@@ -8,7 +8,6 @@
 
 import Foundation
 import Ark
-import AsyncDisplayKit
 
 enum HomeFeed: SectionInflator {
 

Assets/Ark.png

@@ -1,2 +1,171 @@
 # Ark
 
+**Ark** provides an option to adopt high performance of both **Texture** and **IGListKit**, without any boilerplate code stand in the way.
+
+## Internal Workflow
+![Ark](Assets/Ark.png)
+
+1. an instance of `A` which implements **SectionInflator** protocol.
+2. applying a new snapshot triggers diff processing.
+3. instance of `ASCollectionNode` from _Texture_.
+4. call `performBatchUpdates` on *collectionNode* with diff results.
+5. instance of **SectionInflator** provides an array of **AnyNodable** elements.
+6. instance of **AnyNodable** will map to an instance of `ASCellNode` in *collectionNode*.
+7. *collectionNode*'s delegate methods create a new event passed into **rx.nodeEventChannel**.
+8. showing an example what a custom cell node looks like.
+9. custom node maps user action to an event in **rx.nodeEventChannel**.
+10. differentiate user actions by enum `NodeEvent.Action`.
+11. subscribe to **rx.nodeEventChannel** on instance of **DiffableDataSource** for future events (more details later).
+
+## Transition to Ark
+
+### Prerequisite
+1. [Texture](https://github.com/texturegroup/texture), especially  [_LayoutSpecs_](https://texturegroup.org/docs/layout2-layoutspec-types.html).
+2. [RxSwift](https://github.com/ReactiveX/RxSwift)
+
+### Setup
+1. Set `ASCollectionNode` as ViewController's _root_ node.
+
+	```swift
+	import AsyncDisplayKit
+	
+	class ViewController: ASDKViewController<ASCollectionNode> {
+		required init?(coder: NSCoder) { // storyboard
+			// create layout instance
+			let node = ASCollectionNode(collectionViewLayout: layout)
+			super.init(node)
+		}
+	}
+	```
+	
+2. Create an instance of `DiffableDataSource`.
+	
+	```swift
+	import Ark
+	
+	class ViewController: ASDKViewController<ASCollectionNode> {
+		private lazy var dataSource = DiffableDataSource<HomeFeed>(collectionNode: node)
+		
+		// ...
+	}
+	```
+	
+3. Implements `SectionInflator` for your _HomeFeed_ type.
+
+	```swift
+	import Ark
+	
+	enum HomeFeed: SectionInflator {
+		case banner(Banner)[^]
+		case subjects(SubjectFeed)
+		
+		var diffIdentifier: AnyHashbale {
+			switch self {
+			case .banner(let banner):
+				return banner.diffIdentifier
+			case .subjects(let feed):
+				return feed.date
+			}
+		}
+		
+		var items: [AnyNodable] {
+			switch self {
+			case .banner(let banner):
+				return [AnyNodable(banner)]
+			case .subjects(let feed):
+				return feed.subjects.map(AnyNodable.init)
+			}
+		}
+	}
+	```
+	
+4. Implements `Nodable` for your _Banner_ type.
+
+	```swift
+	struct Banner: Nodable {
+		let imageName: String
+		
+		var diffIdentifier: AnyHashable {
+			imageName
+		}
+		
+		func nodeBlock(with channel: NodeEventChannel, indexPath: IndexPath) -> ASCellNodeBlock {
+			let image = UIImage(named: imageName)! // main thread operation
+			return { Node(image: image) }
+		}
+		
+		final class Node: ASCellNode {
+			var imageNode: ASImageNode
+			
+			init(image: UIImage) {
+				self.imageNode = ASImageNode()
+				
+				super.init()
+				
+				automaticallyManagesSubnodes = true
+				backgroundColor = .systemBackground
+				
+				imageNode.image = image
+				imageNode.cornerRadius = 4
+				imageNode.contentMode = .scaleAspectFit
+			}
+			
+			override func layoutSpecThatFits(_ constrainedSize: ASSizeRange) -> ASLayoutSpec {
+				ASWrapperLayoutSpec(layoutElement: imageNode)
+			}
+		}
+	}
+	```
+
+5. Subscribe on `rx.nodeEventChannel` of `dataSource` to handle collection node's delegate methods callback and other target actions, for example, to move the selected subject to the bottom of the section:
+
+	```swift
+	dataSource
+		.rx.nodeEventChannel()
+		.subscribe(onNext: { [unowned self] (event: GenericNodeEvent<SubjectFeed.Subject>) in
+			let targetSection = event.indexPath.section
+			guard case .subjects(let feed) = self.sections[targetSection],
+				let index = feed.subjects.firstIndex(of: event.model) else {
+				return
+			}
+			if case .selected = event.action {
+				var subjects = feed.subjects
+				subjects.remove(at: index)
+				subjects.append(event.model)
+				let newFeed: HomeFeed = .subjects(.init(date: feed.date, subjects: subjects))
+				self.sections[targetSection] = newFeed
+			}
+		})
+		.disposed(by: disposeBag)
+	```
+Note that in `onNext` closure you should specify the `Nodable` type, and it will be called when events related to or from that type's node arrives.
+
+6. Call `apply(_:animatingDifferences:completion:)` on `dataSource`, Isn't this what you have been waiting for?
+
+	```swift
+	private var sections: [HomeFeed] = [] {
+		didSet {
+			updateUI(animated: true)
+		}
+	}
+	
+	private fun updateUI(animated: Bool = false) {
+		dataSource.apply(.init(sections: sections), animatingDifferences: true, completion: nil)
+	}
+	```
+
+## TODO:
+
+- [ ] Support Installation via CocoaPods
+
+## References
++ [ListDiff: Swift port of IGListKit's IGListDiff](https://github.com/lxcid/ListDiff)
+
+## Index
++ [DiffableDataSource](https://github.com/imkdir/Ark/blob/master/Ark/DiffableDataSource.swift#L45)
++ [DiffableDataSourceSnapshot](https://github.com/imkdir/Ark/blob/6c83355663b9c0c9eadbd2b84512e3528d5ac981/Ark/DiffableDataSource.swift#L15)
++ [NodeEventChannel](https://github.com/imkdir/Ark/blob/6c83355663b9c0c9eadbd2b84512e3528d5ac981/Ark/DiffableDataSource.swift#L34)
++ [SectionInflator](https://github.com/imkdir/Ark/blob/6c83355663b9c0c9eadbd2b84512e3528d5ac981/Ark/Nodable.swift#L17)
++ [Nodable](https://github.com/imkdir/Ark/blob/6c83355663b9c0c9eadbd2b84512e3528d5ac981/Ark/Nodable.swift#L24)
++ [AnyNodable](https://github.com/imkdir/Ark/blob/master/Ark/AnyNodable.swift#L84)
++ [GenericNodeEvent](https://github.com/imkdir/Ark/blob/6c83355663b9c0c9eadbd2b84512e3528d5ac981/Ark/NodeEvent.swift#L33)