Tetris/TetrisUI/CurrentPieceView.swift

//
//  CurrentPieceView.swift
//  Tetris
//
//  Created by Shadowfacts on 10/14/19.
//  Copyright © 2019 Shadowfacts. All rights reserved.
//

import SwiftUI
import TetrisKit

struct CurrentPieceView: View {
    let boardWidth: Int
    let boardHeight: Int
    @Binding var currentPiece: GamePiece?
    @Binding var droppedPiece: GamePiece?

    var body: some View {
        GridView(rows: self.boardHeight, columns: self.boardWidth) { (col, row, size) in
            if self.currentPieceAt(col, row) {
                Rectangle()
                    .foregroundColor(self.currentPiece!.tetromino.color)
                    .frame(width: size, height: size)
                    .border(self.currentPiece!.tetromino.borderColor, width: 6)
            } else if self.droppedPieceAt(col, row) {
                Rectangle()
                    .foregroundColor(.gray)
                    .frame(width: size, height: size)
            } else {
                Rectangle()
                    .foregroundColor(.clear)
                    .frame(width: size, height: size)
            }
        }
    }
    
    func currentPieceAt(_ col: Int, _ row: Int) -> Bool {
        guard let currentPiece = self.currentPiece else { return false }
        let (left, top) = currentPiece.topLeft
        let pieceHeight = currentPiece.tiles.count
        let pieceWidth = currentPiece.tiles.first!.count
        return col - left >= 0 && col - left < pieceWidth && row - top >= 0 && row - top < pieceHeight && currentPiece.tiles[row - top][col - left]
    }
    
    func droppedPieceAt(_ col: Int, _ row: Int) -> Bool {
        guard let droppedPiece = self.droppedPiece else { return false }
        let (left, top) = droppedPiece.topLeft
        let pieceHeight = droppedPiece.tiles.count
        let pieceWidth = droppedPiece.tiles.first!.count
        return col - left >= 0 && col - left < pieceWidth && row - top >= 0 && row - top < pieceHeight && droppedPiece.tiles[row - top][col - left]
    }
}

struct CurrentPieceView_Previews: PreviewProvider {
    @State static var currentPiece: GamePiece? = GamePiece(tetromino: .t)
    @State static var droppedPiece: GamePiece? = {
        var piece = GamePiece(tetromino: .t)
        return piece.moved(by: (0, 16 - piece.tiles.count))
    }()
    
    static var previews: some View {
        CurrentPieceView(boardWidth: 10, boardHeight: 16, currentPiece: $currentPiece, droppedPiece: $droppedPiece)
    }
}