Add 2048 Game

Examples/2048 Game/SwiftUI2048/Models/BlockMatrix.swift

@@ -0,0 +1,127 @@
+//
+//  BlockMatrix.swift
+//  SwiftUI2048
+//
+//  Created by Hongyu on 6/5/19.
+//  Copyright © 2019 Cyandev. All rights reserved.
+//
+
+import Foundation
+
+protocol Block {
+    
+    associatedtype Value
+    
+    var number: Value { get set }
+    
+}
+
+struct IndexedBlock<T> {
+    
+    let index: (Int, Int)
+    let item: T?
+
+}
+
+struct BlockMatrix<T> : CustomDebugStringConvertible where T: Block {
+    
+    typealias Index = (Int, Int)
+    
+    fileprivate var matrix: [[T?]]
+    
+    init() {
+        matrix = [[T?]]()
+        for _ in 0..<4 {
+            var row = [T?]()
+            for _ in 0..<4 {
+                row.append(nil)
+            }
+            matrix.append(row)
+        }
+    }
+    
+    var debugDescription: String {
+        matrix.map { row -> String in
+            row.map {
+                if $0 == nil {
+                    return " "
+                } else {
+                    return String(describing: $0!.number)
+                }
+            }.joined(separator: "\t")
+        }.joined(separator: "\n")
+    }
+    
+    var flatten: [IndexedBlock<T>] {
+        return self.matrix.enumerated().flatMap { (y: Int, element: [T?]) in
+            element.enumerated().map { (x: Int, element: T?) in
+                return IndexedBlock(index: (x, y), item: element)
+            }
+        }
+    }
+    
+    subscript(index: Self.Index) -> T? {
+        guard isIndexValid(index) else {
+            return nil
+        }
+        
+        return matrix[index.1][index.0]
+    }
+    
+    /// Move the block to specific location and leave the original location blank.
+    /// - Parameter from: Source location
+    /// - Parameter to: Destination location
+    mutating func move(from: Self.Index, to: Self.Index) {
+        guard isIndexValid(from) && isIndexValid(to) else {
+            // TODO: Throw an error?
+            return
+        }
+        
+        guard let source = self[from] else {
+            return
+        }
+        
+        matrix[to.1][to.0] = source
+        matrix[from.1][from.0] = nil
+    }
+    
+    /// Move the block to specific location, change its value and leave the original location blank.
+    /// - Parameter from: Source location
+    /// - Parameter to: Destination location
+    /// - Parameter newValue: The new value
+    mutating func move(from: Self.Index, to: Self.Index, with newValue: T.Value) {
+        guard isIndexValid(from) && isIndexValid(to) else {
+            // TODO: Throw an error?
+            return
+        }
+        
+        guard var source = self[from] else {
+            return
+        }
+        
+        source.number = newValue
+        
+        matrix[to.1][to.0] = source
+        matrix[from.1][from.0] = nil
+    }
+    
+    /// Place a block to specific location.
+    /// - Parameter block: The block to place
+    /// - Parameter to: Destination location
+    mutating func place(_ block: T?, to: Self.Index) {
+        matrix[to.1][to.0] = block
+    }
+    
+    fileprivate func isIndexValid(_ index: Self.Index) -> Bool {
+        guard index.0 >= 0 && index.0 < 4 else {
+            return false
+        }
+        
+        guard index.1 >= 0 && index.1 < 4 else {
+            return false
+        }
+        
+        return true
+    }
+    
+}