Blog post four - updating the board model

Pentominoes.playground/Contents.swift

@@ -8,23 +8,23 @@ let board = Board(size: .FiveByTwelve)
 
 let tile = Tile(shape: .O)
 
-for boardSquare in board.squares() {
-    if board.canPositionTile(tile, atSquare: boardSquare) {
-        print("Can position at \(boardSquare)")
-    } 
-}
+//tile.rotate(true)
+//print("Rotated")
 
-tile.rotate(true)
-print("Rotated")
+board.positionTile(tile, atSquare: Square(row: 4, column: 6))
+board
 
-for boardSquare in board.squares() {
-    if board.canPositionTile(tile, atSquare: boardSquare) {
-        print("Can position at \(boardSquare)")
+for square in board.squares() {
+    if let tile = board.tileAtSquare(square) {
+        print(square)
     }
 }
 
-
-
-
-
+let tile2 = Tile(shape: .P)
+board.positionTile(tile2, atSquare: Square(row: 4, column: 8))
+board
+let tile3 = Tile(shape: .T)
+board.removeTile(tile3)
+board.removeTile(tile)
+board
 

Pentominoes.playground/Sources/Board.swift

@@ -2,6 +2,19 @@ public class Board: PlayingGrid {
 
     private (set) public var rows: [[Bool]]
 
+    private let emptyBoard: [[Bool]]
+
+    private struct PlacedTile {
+        let square: Square
+        let tile: Tile
+    }
+
+    private var placedTiles = [PlacedTile]() {
+        didSet {
+            updateRows()
+        }
+    }
+
     public struct Size {
         let height: Int
         let width: Int
@@ -23,6 +36,7 @@ public class Board: PlayingGrid {
             rows += [paddingHorizontal + emptyRow + paddingHorizontal]
         }
         rows += fullPaddingVertical
+        emptyBoard = rows
     }
 }
 
@@ -31,7 +45,7 @@ extension Board {
 
         for tileSquare in tile.squares() {
             let boardSquare = tileSquare.offsetBy(atSquare)
-            if !squareWithinBoard(boardSquare) {
+            if !squareWithinGrid(boardSquare) {
                 return false
             }
             if tileSquare.occupied == true && squareOccupied(boardSquare) {
@@ -40,4 +54,48 @@ extension Board {
         }
         return true
     }
+
+    public func positionTile(tile: Tile, atSquare square: Square) -> Bool {
+        if !canPositionTile(tile, atSquare: square) {
+            return false
+        }
+        placedTiles.append(PlacedTile(square: square, tile: tile))
+        return true
+    }
+
+    public func tileAtSquare(square: Square) -> Tile? {
+        for placedTile in placedTiles {
+            let locationInTile = square.offsetBy(-placedTile.square)
+            if placedTile.tile.squareWithinGrid(locationInTile) {
+                let occupiedSquares = placedTile.tile.squares().filter { $0.occupied == true }
+                for tileSquare in occupiedSquares {
+                    if tileSquare == locationInTile {
+                        return placedTile.tile
+                    }
+                }
+            }
+        }
+        return nil
+    }
+
+    public func removeTile(tile: Tile) -> Tile? {
+        if let index = placedTiles.indexOf( { $0.tile === tile } ){
+            placedTiles.removeAtIndex(index)
+            return tile
+        }
+        return nil
+    }
+}
+
+extension Board {
+    private func updateRows() {
+        rows = emptyBoard
+        for placedTile in placedTiles {
+            let occupiedSquares = placedTile.tile.squares().filter { $0.occupied == true }
+            for tileSquare in occupiedSquares {
+                let boardLocation = tileSquare.offsetBy(placedTile.square)
+                rows[boardLocation.row][boardLocation.column] = true
+            }
+        }
+    }
 }

Pentominoes.playground/Sources/PlayingGrid.swift

@@ -37,10 +37,17 @@ public struct Square {
 
     func offsetBy(square: Square) -> Square {
         return Square(row: self.row + square.row, column: self.column + square.column)
-
     }
 }
 
+public prefix func -(square: Square) -> Square {
+    return Square(row: -square.row, column: -square.column)
+}
+
+public func ==(left: Square, right: Square) -> Bool {
+    return left.row == right.row && left.column == right.column
+}
+
 public class GridSquareGenerator: GeneratorType {
     var currentRow: Int = 0
     var currentColumn: Int = -1
@@ -94,8 +101,8 @@ extension PlayingGrid {
         }
     }
 
-    public func squareWithinBoard(square: Square) -> Bool {
-        return square.row < rows.count && square.column < rows[square.row].count
+    public func squareWithinGrid(square: Square) -> Bool {
+        return square.row >= 0 && square.column >= 0 && square.row < rows.count && square.column < rows[square.row].count
     }
 
     public func squareOccupied(square: Square) -> Bool {