Texture/examples_extra/ASDKgram-Swift/ASDKgram-Swift/PhotoFeedTableViewController.swift

//
//  PhotoFeedTableViewController.swift
//  ASDKgram-Swift
//
//  Created by Calum Harris on 06/01/2017.
//
//  Copyright (c) 2014-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under the BSD-style license found in the
//  LICENSE file in the root directory of this source tree. An additional grant
//  of patent rights can be found in the PATENTS file in the same directory.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
//  FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
//   ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
//  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

import UIKit

class PhotoFeedTableViewController: UITableViewController {
	
	var activityIndicator: UIActivityIndicatorView!
	var photoFeed: PhotoFeedModel
	
	init() {
		photoFeed = PhotoFeedModel(initWithPhotoFeedModelType: .photoFeedModelTypePopular, requiredImageSize: screenSizeForWidth)
		super.init(nibName: nil, bundle: nil)
		self.navigationItem.title = "UIKit"
		
	}
	
	required init?(coder aDecoder: NSCoder) {
		fatalError("init(coder:) has not been implemented")
	}
	
	override func viewDidLoad() {
		super.viewDidLoad()
		setupActivityIndicator()
		configureTableView()
		fetchNewBatch()
		navigationController?.hidesBarsOnSwipe = true
	}
	
	func fetchNewBatch() {
		activityIndicator.startAnimating()
		photoFeed.updateNewBatchOfPopularPhotos() { additions, connectionStatus in
			switch connectionStatus {
			case .connected:
				self.activityIndicator.stopAnimating()
				self.addRowsIntoTableView(newPhotoCount: additions)
			case .noConnection:
				self.activityIndicator.stopAnimating()
				break
			}
		}
	}
	
	var screenSizeForWidth: CGSize = {
		let screenRect = UIScreen.main.bounds
		let screenScale = UIScreen.main.scale
		return CGSize(width: screenRect.size.width * screenScale, height: screenRect.size.width * screenScale)
	}()
	
	// helper functions
	func setupActivityIndicator() {
		let activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .gray)
		self.activityIndicator = activityIndicator
		self.tableView.addSubview(activityIndicator)
		activityIndicator.translatesAutoresizingMaskIntoConstraints = false
		NSLayoutConstraint.activate([
			activityIndicator.centerXAnchor.constraint(equalTo: self.tableView.centerXAnchor),
			activityIndicator.centerYAnchor.constraint(equalTo: self.tableView.centerYAnchor)
			])
	}
	
	func configureTableView() {
		tableView.register(PhotoTableViewCell.self, forCellReuseIdentifier: "photoCell")
		tableView.allowsSelection = false
		tableView.rowHeight = UITableViewAutomaticDimension
		tableView.separatorStyle = .none
	}
}

extension PhotoFeedTableViewController {
	
	func addRowsIntoTableView(newPhotoCount newPhotos: Int) {
		
		let indexRange = (photoFeed.photos.count - newPhotos..<photoFeed.photos.count)
		let indexPaths = indexRange.map { IndexPath(row: $0, section: 0) }
		tableView.insertRows(at: indexPaths, with: .none)
	}
	
	// TableView Data Source
	
	override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
		return photoFeed.photos.count
	}
	
	override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
		guard let cell = tableView.dequeueReusableCell(withIdentifier: "photoCell", for: indexPath) as? PhotoTableViewCell else { fatalError("Wrong cell type") }
		cell.photoModel = photoFeed.photos[indexPath.row]
		return cell
	}
	
	override func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
		return PhotoTableViewCell.height(for: photoFeed.photos[indexPath.row], withWidth: self.view.frame.size.width)
	}
	
	override func scrollViewDidScroll(_ scrollView: UIScrollView) {
		
		let currentOffSetY = scrollView.contentOffset.y
		let contentHeight = scrollView.contentSize.height
		let screenHeight = UIScreen.main.bounds.size.height
		let screenfullsBeforeBottom = (contentHeight - currentOffSetY) / screenHeight
		if screenfullsBeforeBottom < 2.5 {
			self.fetchNewBatch()
		}
	}
}