//
//  AssetComparisonViewController.swift
//  PhotoRank
//
//  Created by Shadowfacts on 8/3/19.
//  Copyright © 2019 Shadowfacts. All rights reserved.
//

import UIKit
import Photos

class AssetComparisonViewController: UIViewController {

    let allAssets: [PHAsset]
    var assetScores = [String: Int]()
    let assetPairs: [[PHAsset]]
    var currentPairIndex: Int = 0 {
        didSet {
            currentAssetPair = assetPairs[currentPairIndex]
            currentlySelected = 0
        }
    }
    
    var currentlySelected: Int = 0 {
        didSet {
            largeImage.image = currentImagePair[currentlySelected]
        }
    }
    
    var currentAssetPair: [PHAsset]! {
        didSet {
            loadImages()
        }
    }
    var currentImagePair: [UIImage?] = [nil, nil] {
        didSet {
            largeImage.image = currentImagePair[currentlySelected]
        }
    }
    
    let largeImage = LargeImageViewController()

    @IBOutlet var imageContainerView: UIView!
    
    init(assets: [PHAsset]) {
        guard assets.count >= 2 else { fatalError("AssetComparisonViewController requires at least 2 assets") }
        self.allAssets = assets
        self.assetPairs = assets.allPairs()
        self.currentAssetPair = assetPairs.first!

        super.init(nibName: "AssetComparisonViewController", bundle: .main)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        largeImage.view.translatesAutoresizingMaskIntoConstraints = false
        imageContainerView.addSubview(largeImage.view)
        NSLayoutConstraint.activate([
            largeImage.view.leadingAnchor.constraint(equalTo: imageContainerView.leadingAnchor),
            largeImage.view.topAnchor.constraint(equalTo: imageContainerView.topAnchor),
            imageContainerView.trailingAnchor.constraint(equalTo: largeImage.view.trailingAnchor),
            imageContainerView.bottomAnchor.constraint(equalTo: largeImage.view.bottomAnchor),
        ])
        addChild(largeImage)
        
        toolbarItems = [
            UIBarButtonItem(title: "Skip", style: .plain, target: self, action: #selector(moveToNextPair)),
            UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil),
            UIBarButtonItem(title: "Switch", style: .plain, target: self, action: #selector(switchButtonPressed)),
            UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil),
            UIBarButtonItem(title: "Pick", style: .plain, target: self, action: #selector(pickButtonPressed))
        ]
        
        loadImages()
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        navigationController!.isToolbarHidden = false
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        
        navigationController!.isToolbarHidden = true
    }
    
    func loadImages() {
        self.currentlySelected = 0
        self.currentImagePair = [nil, nil]
        PhotosHelper.requestFullSizeImage(for: currentAssetPair[0]) { (image) in
            DispatchQueue.main.async {
                self.currentImagePair = [image, self.currentImagePair[1]]
            }
        }
        PhotosHelper.requestFullSizeImage(for: currentAssetPair[1]) { (image) in
            DispatchQueue.main.async {
                self.currentImagePair = [self.currentImagePair[0], image]
            }
        }
    }
    
    @objc func switchButtonPressed() {
        currentlySelected = currentlySelected == 0 ? 1 : 0
    }
    
    @objc func moveToNextPair() {
        if currentPairIndex == assetPairs.count - 1 {
            print("finished: \(assetScores)")
            // sorts assets by score in descending order
            let sorted = allAssets
                .map { ($0, assetScores[$0.localIdentifier] ?? 0) }
                .sorted { (first, second) -> Bool in
                    return first.1 > second.1
                }
            let rankings = RankingsTableViewController(rankings: sorted)
            show(rankings, sender: nil)
        } else {
            currentPairIndex += 1
        }
    }
    
    @objc func pickButtonPressed() {
        let identifier = currentAssetPair[currentlySelected].localIdentifier
        let current = assetScores[identifier] ?? 0
        assetScores[identifier] = current + 1
        
        moveToNextPair()
    }

}