Initial commit - at blog post three

.gitignore

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# Xcode
#
# gitignore contributors: remember to update Global/Xcode.gitignore, Objective-C.gitignore & Swift.gitignore

## Build generated
build/
DerivedData/

## Various settings
*.pbxuser
!default.pbxuser
*.mode1v3
!default.mode1v3
*.mode2v3
!default.mode2v3
*.perspectivev3
!default.perspectivev3
xcuserdata/

## Other
*.moved-aside
*.xcuserstate

## Obj-C/Swift specific
*.hmap
*.ipa
*.dSYM.zip
*.dSYM

## Playgrounds
timeline.xctimeline
playground.xcworkspace

# Swift Package Manager
#
# Add this line if you want to avoid checking in source code from Swift Package Manager dependencies.
# Packages/
.build/

# CocoaPods
#
# We recommend against adding the Pods directory to your .gitignore. However
# you should judge for yourself, the pros and cons are mentioned at:
# https://guides.cocoapods.org/using/using-cocoapods.html#should-i-check-the-pods-directory-into-source-control
#
# Pods/

# Carthage
#
# Add this line if you want to avoid checking in source code from Carthage dependencies.
# Carthage/Checkouts

Carthage/Build

# fastlane
#
# It is recommended to not store the screenshots in the git repo. Instead, use fastlane to re-generate the
# screenshots whenever they are needed.
# For more information about the recommended setup visit:
# https://github.com/fastlane/fastlane/blob/master/fastlane/docs/Gitignore.md

fastlane/report.xml
fastlane/Preview.html
fastlane/screenshots
fastlane/test_output

Pentominoes.playground/Contents.swift

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//: Playground - noun: a place where people can play

import UIKit



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")

for boardSquare in board.squares() {
    if board.canPositionTile(tile, atSquare: boardSquare) {
        print("Can position at \(boardSquare)")
    }
}

Pentominoes.playground/Sources/Board.swift

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public class Board: PlayingGrid {
    
    private (set) public var rows: [[Bool]]
    
    public struct Size {
        let height: Int
        let width: Int
        
        public static let SixByTen = Size(height: 6, width: 10)
        public static let FiveByTwelve = Size(height: 5, width: 12)
        public static let FourByFifteen = Size(height: 4, width: 15)
        public static let ThreeByTwenty = Size(height: 3, width: 20)
    }
    
    public init(size: Size) {
        // Extend by four "occupied" positions in every direction
        let paddingHorizontal = [Bool].init(count: 4, repeatedValue: true)
        let paddingVertical = [Bool].init(count: 8 + size.width, repeatedValue: true)
        let fullPaddingVertical = [[Bool]].init(count: 4, repeatedValue: paddingVertical)
        let emptyRow = [Bool].init(count: size.width, repeatedValue: false)
        rows = fullPaddingVertical
        for _ in 0..<size.height {
            rows += [paddingHorizontal + emptyRow + paddingHorizontal]
        }
        rows += fullPaddingVertical
    }
}

extension Board {
    public func canPositionTile(tile: Tile, atSquare: Square) -> Bool {
        
        for tileSquare in tile.squares() {
            let boardSquare = tileSquare.offsetBy(atSquare)
            if !squareWithinBoard(boardSquare) {
                return false
            }
            if tileSquare.occupied == true && squareOccupied(boardSquare) {
                return false
            }
        }
        return true
    }
}

Pentominoes.playground/Sources/PlayingGrid.swift

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public protocol PlayingGrid : CustomStringConvertible, CustomPlaygroundQuickLookable {
    var rows: [[Bool]] { get }
    subscript(row: Int) -> [Bool] { get }
}

extension Bool {
    var gridCharacter: String {
        return self ? "#" : "_"
    }
}

extension PlayingGrid where Self: protocol<CustomStringConvertible, CustomPlaygroundQuickLookable> {
    public var description: String {
        let descriptions : [String] = rows.map { row in
            row.reduce("") { string, gridValue in
                string + gridValue.gridCharacter
            }
        }
        return descriptions.joinWithSeparator("\n")
    }
    public func customPlaygroundQuickLook() -> PlaygroundQuickLook {
        return PlaygroundQuickLook(reflecting: description)
    }
}


public struct Square {
    let row: Int
    let column: Int
    let occupied: Bool?
    
    public init(row: Int, column: Int, occupied: Bool? = nil) {
        self.row = row
        self.column = column
        self.occupied = occupied
    }
    
    func offsetBy(square: Square) -> Square {
        return Square(row: self.row + square.row, column: self.column + square.column)
        
    }
}

public class GridSquareGenerator: GeneratorType {
    var currentRow: Int = 0
    var currentColumn: Int = -1
    
    let grid: PlayingGrid
    
    public init(grid: PlayingGrid) {
        self.grid = grid
    }
    
    public func next() -> Square? {
        guard currentRow < grid.rows.count else { return nil }
        
        currentColumn += 1
        
        if currentColumn == grid[currentRow].count {
            currentColumn = 0
            currentRow += 1
        }
        if currentRow < grid.rows.count {
            return Square(row: currentRow, column: currentColumn, occupied: grid[currentRow][currentColumn])
        } else {
            return nil
        }
    }
}

public class GridSquareSequence: SequenceType {
    let grid: PlayingGrid
    
    public init(grid: PlayingGrid) {
        self.grid = grid
    }
    
    public func generate() -> GridSquareGenerator {
        return GridSquareGenerator(grid: grid)
    }
}

extension PlayingGrid {
    public func squares() -> GridSquareSequence {
        return GridSquareSequence(grid: self)
    }
}


extension PlayingGrid {
    public subscript(row: Int) -> [Bool] {
        get {
            return rows[row]
        }
    }
    
    public func squareWithinBoard(square: Square) -> Bool {
        return square.row < rows.count && square.column < rows[square.row].count
    }
        
    public func squareOccupied(square: Square) -> Bool {
        return self[square.row][square.column]
    }
}