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https://github.com/codelynx/ShogibanKit

ShogibanKit is a framework (not yet) for implementing complex Japanese Chess (Shogii) in Swift. No UI, nor AI.
https://github.com/codelynx/ShogibanKit

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ShogibanKit is a framework (not yet) for implementing complex Japanese Chess (Shogii) in Swift. No UI, nor AI.

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# ShogibanKit



![xcode](https://img.shields.io/badge/Xcode-13-blue)

![swift](https://img.shields.io/badge/Swift-5-orange.svg)

![license](https://img.shields.io/badge/License-MIT-yellow.svg)



Shogi, or Japanese Chess, is based on very complex rules, and it is hard to implement all basic rules.  This ShogibanKit aims to implement such complex algorithm to find valid move or action, or to find out whether it is checkmate or not.  I also would like to state that ShogibanKit does not provide:



- Any Graphical User Interface

- Any Artificial Intelligence



Status: Under Development



* Now, Swift 5 ready



## Coding Experiment

It would be controversial for sure, I tried using Japanese for class names, variable names, and others.  It is part of my experiment to see if coding with non English name would work or not, or impact of maintaining the code.  For example, all type of pieces is expressed as follows using Japanese. It would be natural and easier to read code or Shogi player programmers.



```.swift

enum 駒型 : Int8 {

	case 歩, 香, 桂, 銀, 金, 角, 飛, 王

	// ...

}

```



Since there are no Capitalization in Japanese, Swift complains using the same name for type and variables.



```.swift

enum Koma { ... }

var koma = Koma(...) // OK: no problem!



enum 駒 { ... }

var 駒 = 駒(...) // Error: variable name cannot be same as type name

```



So suffix `型` to be added for Japanese type names.



```

enum 駒型 { ... }

var 駒 = 駒型(...) // OK: no problem!

```



## Common classes and types



Here is the list of common classes or types.



|Name|Type|Description|

|:--|:--|:--|

|筋型 |enum |Column (right to left) |

|段型 |enum |Row |

|位置型 |enum |Position (row and column) |

|駒型 |enum |Type of piece (no front/back) |

|駒面型 |enum |Type of piece (cares front/back) |

|持駒型 |struct |Captured pieces |

|先後型 |enum |Which player |

|升型 |enum |State of board position (which players which piece, or empty?) |

|指手型 |enum |Describe the one movement |

|局面型 |class |Snapshot of the state of game-board |



## Describing position



Here are some example of describe the location of the board.  The column order is from right to left, same as Shogi official. Although columns and rows is 1 based index, actual `rawValue` is 0 based index.



```.swift

let col = 筋.４  // Zenkaku (全角)

let row = 段.七  // Zenkaku (全角)

let position1 = 位置.５五  // Zenkaku (全角)

let position2 = 位置(筋: col, 段: row)

```



## Describing Player



I am not sure how to describe 先手, 後手 in English.  Black and White may be OK for Go (碁), but not Shogi.  It does not describe the detail of individual, just describe which player.



```.swift

enum 先後型 {

	case 先手, 後手

}

```



## Describing Pieces



`駒型` and `駒面型` describe the pieces.  `駒型` does not have state of front and back, on the other hand `駒面型` cares about the state of front and back, or promoted or not. 



```.swift

let fu = 駒型.歩

let to = 駒面型.と

```



For the formatting purpose, promoted pieces of `香`, `桂`, `銀` are expressed as `杏`, `圭`, `全` rather than `成香`, `成桂`, `成銀`.  They are not official way to describe it, but commonly used for computer scene.



```.swift

enum 駒面型 {

	case 歩, 香, 桂, 銀, 金, 角, 飛, 王

	case と, 杏, 圭, 全, 馬, 竜

}

```



## Describing Captured Pieces



`持駒型` describe the state of captured pieces. It knows which `駒型` is captured and its number.  By the way, even though promoted pieces are captured, they cannot be used as state of promoted so are managed as `駒型`.



You find number of captured `駒` as follows.



```.swift

let 先手持駒: 持駒型 = ...

let 銀の持ち駒数 = 先手持駒[.銀]

```



## Describing the state of game-borad



`局面型` describes the snapshot of a game-board.  And each cell is described as `升型`.  



```.swift

let 局面 = 局面型(string:

			"▽持駒:なし\r" +

			"|▽香|▽桂|▽銀|▽金|▽王|▽金|▽銀|▽桂|▽香|\r" +

			"|　　|▽飛|　　|　　|　　|　　|　　|▽角|　　|\r" +

			"|▽歩|▽歩|▽歩|▽歩|▽歩|▽歩|▽歩|▽歩|▽歩|\r" +

			"|　　|　　|　　|　　|　　|　　|　　|　　|　　|\r" +

			"|　　|　　|　　|　　|　　|　　|　　|　　|　　|\r" +

			"|　　|　　|　　|　　|　　|　　|　　|　　|　　|\r" +

			"|▲歩|▲歩|▲歩|▲歩|▲歩|▲歩|▲歩|▲歩|▲歩|\r" +

			"|　　|▲角|　　|　　|　　|　　|　　|▲飛|　　|\r" +

			"|▲香|▲桂|▲銀|▲金|▲王|▲金|▲銀|▲桂|▲香|\r" +

			"▲持駒:なし\r",

		手番: .先手)



```



Or you may provide `指手型` to execute to create the next game-borad state.



```.swift

let 前の局面: 局面型  = ...

let 指手 = ...

let 次の局面 = 局面型.指手を実行(指手)

```



You can also `print()` or `.string` property to extract string representation.  And this string can be used for `局面型(_,手番:)`.



```.swift

let ある局面: = ...

print("\(ある局面)")

let stringRepresentaion = ある局面.string

let 手番 = ある局面.手番

let 再現局面 = 局面(stringRepresentaion, 手番: 手番)

```




後手持駒:桂

|▽香|▲龍|　　|　　|　　|　　|　　|　　|▽香|

|　　|　　|▲金|　　|▲龍|　　|　　|　　|　　|

|▽歩|▲全|　　|　　|▽金|　　|▽歩|▽桂|▽歩|

|　　|▽歩|　　|　　|▽王|　　|▽銀|　　|　　|

|　　|　　|　　|▲金|▲角|　　|　　|　　|　　|

|　　|　　|▽香|▲歩|▲歩|▲銀|▲桂|　　|　　|

|▲歩|▲歩|　　|　　|　　|▲歩|▲銀|　　|▲歩|

|　　|　　|　　|▲金|　　|　　|　　|▲歩|　　|

|▲香|　　|　　|▲玉|　　|　　|　　|▽馬|　　|

先手持駒:桂,歩7




## Describing moves and actions



A move can be described with `指手型`. `指手型` three cases. `動` describes a piece move from one place to the other.  `打` describes place captured piece on the game-board at specific location. `投了` describes the checkmate or equivalent.  



```.swift

enum 指手型 {

	case 動(先後: 先後型, 移動前の位置: 位置型, 移動後の位置: 位置型, 移動後の駒面: 駒面型)

	case 打(先後: 先後型, 位置:位置型, 駒:駒型)

	case 終(終局理由: 終局理由型, 勝者: 先後型?)

}

```



You may construct hand written `指手型`, but it has to be legitimate valid move.  Invalid `指手型`  will be rejected by `局面型`'s `指手を実行()` method.



```.swift

var 局面 = 局面(string: 手合割型.平手初期盤面, 手番: .先手)

局面 = 局面.指手を実行(指手型.動(先後: .先手, 移動前の位置: .７七, 移動後の位置: .７六, 移動後の駒面: .歩))

局面 = 局面.指手を実行(指手型.動(先後: .後手, 移動前の位置: .３三, 移動後の位置: .３四, 移動後の駒面: .歩))

```



For professional player, this `投了` state may be sufficient, but for amateur, `王` may be captured by careless mistake.  Therefore, extra end state should be added later on.



`局面型` provides `全可能指手列()` method to find all possible legitimate moves. So you may iterate through each candidate to examine all moves.  You may also call `指手を実行()` for each moves, but it is not suitable for creating millions of instances recursively.



```.swift

let 局面: 局面型 = ...

let 全可能指手 = 局面.全可能指手列()

for 候補指手 in 全可能指手 {

	if let 次の局面 = 局面(候補指手) {

		// find one you like

	} 

}

```



# Some advanced methods and properties



* Iterate all positions in `局面型`



```.swift

let 局面: 局面型 = ...

for 位置 in 局面 {

	let マス = 局面[位置]

	let 駒面 = マス.駒面

}

```



* All positions that a piece at location can make move



```.swift

let 局面: 局面型 = ...

let 位置列 = 局面.指定位置の駒の移動可能位置列(.５五) // only location

let 指手列 = 局面.指定位置の駒の移動可能指手列(.５五)

```



* Find all positions of where specified type of piece are located



```.swift

let 局面: 局面型 = ...

let 先手の桂の位置 = 局面.駒の位置列(.桂, 先後: .先手)

```



* Which pieces on game-board can make move to specified location?



```.swift

let 局面: 局面型 = ...

let 味方の駒の位置列 = 局面.指定位置へ移動可能な全ての駒の位置列(.７六, 先後: .先手)

let 敵味方双方の駒の位置列 = 局面.指定位置へ移動可能な全ての駒の位置列(.７六, 先後: nil)

let 後手の移動指手列 = 局面.指定位置へ移動可能な全ての駒を移動させる指手列(.７六, .後手)

```



* Find all movies that can capture 王 (King).



```.swift

let 局面: 局面型 = ...

let 王手列 = 局面.王手列(.先手)

```



* Checkmate? (needs more test)



```.swift

let 局面: 局面型 = ...

if 局面.詰みか() {

	// checkmate!

}

```



* Find opponent player



```.swift

let 局面: 局面型 = ...

let 手番の敵方 = 局面.手番.敵方

```



* Is 先手's 王 is on the same line of 後手's 角? (English!!)



```.swift

let 局面: 局面型 = ...

let 後手の角の位置 = ...

for (vx, vy) in 駒面.角.移動可能なベクトル {

	var (x, y) = (後手の角の位置.筋 + vx, 後手の角の位置.段 + vy)

	while let x = x, let y = y {

		if let マス = 局面[x, y] where マス.駒面　== .王 && マス.先後 == .先手 {

			// King is on the line

		}

		(x, y) = (x + vx, y + vy)

	}

}

```



## Generating Image



`局面型` provides extension to generate image.



```.swift

extension 局面型 {

	func imageForSize(size: CGSize) -> CGImage

}

```



Here is the code sample of how to generate an image from `局面型`, and a sample image that generated by this feature.



```.swift

let image = 局面.imageForSize(CGSizeMake(300, 300))

```



![image.tiff](https://qiita-image-store.s3.amazonaws.com/0/65634/7fad6b43-01f3-a73f-6433-cf6eba8ad75a.tiff)



## Some Tips



In ShoogibanKit, textual expression for position can be used, and also, positions also can be printed on debug console in textual expression.  If you simply use Menlo, or Hiragino, it would not be a good experiences for programmers after all. 






I recommend `Source Han Code JP` font from Adobe.  It is free to use.  By using this font, Shogi's textual expression will be look like in source code and in debugger log.






You can get the font from following URLs and try.

https://github.com/adobe-fonts/source-han-code-jp



## TO DO's



* Test for Check mate

* 打ち歩詰め and other special cases

* 千日手 and other rules

* 局面 compaction to save and load

* UnitTest - removed because it crashes (not sure may be Xcode issue)

* may be some more



## Other consideration



* String representation of `局面型` does not include `手番`.  If `手番` is included, it is simple to go back and forth between `局面型` and `String`.



## Environment



* Xcode Version 13.3.1

* Apple Swift version 5.6



## Feedback



Please give me your feedback to [email protected].