//
//  GridViewController.swift
//  CapCollector
//
//  Created by Christoph on 07.01.19.
//  Copyright © 2019 CH. All rights reserved.
//

import UIKit

class GridViewController: UIViewController {
    
    private let columns = 40
    
    static let len: CGFloat = 60
    
    private lazy var rowHeight = GridViewController.len * 0.866
    
    private lazy var margin = GridViewController.len - rowHeight
    
    private var myView: UIView!
    
    private var canvasSize: CGSize = .zero
    
    @IBOutlet weak var scrollView: UIScrollView!

    private var selectedTile: Int? = nil

    private weak var selectionView: RoundedButton!
    
    override var preferredInterfaceOrientationForPresentation: UIInterfaceOrientation {
        return .portrait
    }
    
    override var shouldAutorotate: Bool {
        return true
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let width = CGFloat(columns) * GridViewController.len + GridViewController.len / 2
        let height = (CGFloat(Cap.totalCapCount) / CGFloat(columns)).rounded(.up) * rowHeight + margin
        canvasSize = CGSize(width: width, height: height)
        myView = UIView(frame: CGRect(origin: .zero, size: canvasSize))
        
        
        scrollView.addSubview(myView)
        scrollView.contentSize = canvasSize
        scrollView.delegate = self
        scrollView.zoomScale = 0.5
        scrollView.maximumZoomScale = 1
        setZoomRange()
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        updateTiles()
        
        let tapRecognizer = UITapGestureRecognizer(target: self, action: #selector(handleTap))
        myView.addGestureRecognizer(tapRecognizer)
    }
    
    override func viewDidLayoutSubviews() {
        setZoomRange()
        updateTiles()
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
    
        Cap.save()
    }
    
    private func setZoomRange() {
        let size = scrollView.frame.size
        let a = size.width / canvasSize.width
        let b = size.height / canvasSize.height
        let scale = min(a,b)
        scrollView.minimumZoomScale = min(a,b)
        if scrollView.zoomScale < scale {
            scrollView.setZoomScale(scale, animated: true)
        }
    }
    
    @objc func handleTap(_ sender: UITapGestureRecognizer) {
        
        let loc = sender.location(in: myView)
        let y = loc.y
        let s = y.truncatingRemainder(dividingBy: rowHeight)
        let row = Int(y / rowHeight)
        guard s > margin else {
            return
        }
        let column: CGFloat
        if row.isEven {
            column = loc.x / GridViewController.len
        } else {
            column = (loc.x - GridViewController.len / 2) / GridViewController.len
        }
        handleTileTapped(tile: row * columns + Int(column))
    }
    
    private func handleTileTapped(tile: Int) {
        if let selected = selectedTile {
            switchTiles(oldTile: selected, newTile: tile)
        } else {
            showSelection(tile: tile)
        }
    }

    private var installedTiles = [Int : RoundedImageView]()
    
    private func showSelection(tile: Int) {
        clearTileSelection()
        
        if let view = installedTiles[tile] {
            view.borderWidth = 3
            view.borderColor = AppDelegate.tintColor
            selectedTile = tile
        } else {
            selectedTile = nil
        }
    }
    
    private func tileIsVisible(tile: Int, in rect: CGRect) -> Bool {
        return rect.intersects(frame(for: tile))
    }
    
    private func makeTile(_ tile: Int) {
        let view = RoundedImageView(frame: frame(for: tile))
        myView.addSubview(view)
        view.image = Cap.tileImage(tile: tile)
        installedTiles[tile] = view
    }
    
    private func frame(for tile: Int) -> CGRect {
        let row = tile / columns
        let column = tile - row * columns
        let x = CGFloat(column) * GridViewController.len + (row.isEven ? 0 : GridViewController.len / 2)
        let y = CGFloat(row) * rowHeight
        return CGRect(x: x, y: y, width: GridViewController.len, height: GridViewController.len)
    }
    
    private func switchTiles(oldTile: Int, newTile: Int) {
        if oldTile != newTile {
            Cap.switchTiles(oldTile, newTile)
            installedTiles[oldTile]?.image = Cap.tileImage(tile: oldTile)
            installedTiles[newTile]?.image = Cap.tileImage(tile: newTile)
        }
        clearTileSelection()
    }
    
    private func clearTileSelection() {
        guard let tile = selectedTile else {
            return
        }
        installedTiles[tile]?.borderWidth = 0
        selectedTile = nil
    }
    
    private func showTiles(in rect: CGRect) {
        for i in 0..<Cap.totalCapCount {
            if tileIsVisible(tile: i, in: rect) {
                if installedTiles[i] != nil {
                    continue
                }
                makeTile(i)
            } else if let tile = installedTiles[i] {
                tile.removeFromSuperview()
                installedTiles[i] = nil
            }
        }
    }
    
    private func updateTiles() {
        guard #available(iOS 12.0, *) else {
            return
        }
        let scale = scrollView.zoomScale
        let offset = scrollView.contentOffset
        let size = scrollView.visibleSize
        
        let scaledOrigin = CGPoint(x: offset.x / scale, y: offset.y / scale)
        let scaledSize = CGSize(width: size.width / scale, height: size.height / scale)
        let rect = CGRect(origin: scaledOrigin, size: scaledSize)
        
        showTiles(in: rect)
    }
}

extension GridViewController: UIScrollViewDelegate {

    func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        return myView
    }
    
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        updateTiles()
    }
}

private extension Int {
    
    var isEven: Bool {
        return self % 2 == 0
    }
}

extension GridViewController: Logger {
    
    static let logToken: String = "[Grid]"
    
}