# Experimental!
# shogi game core

┌─╴Piece
  ~ {Type Side}
  ┌─╴Type
    |Pawn |PPawn
    |Rook |Dragon
    |Bishop |Horse
    |Lance |PLance
    |Knight |PKnight
    |Silver |PSilver
    |Gold
    |King
  └─╴
  ┌─╴Side
    |Sente |Gote
  └─╴
└─╴

# translates between equivalent board string
# notation and internal structure
┌─╴Representation
  # the standard initial board, in string form
  STARTINGBOARDSTRING ← $  l n s g k g s n l
                        $  . b . . . . . r .
                        $  p p p p p p p p p
                        $  . . . . . . . . .
                        $  . . . . . . . . .
                        $  . . . . . . . . .
                        $  P P P P P P P P P
                        $  . R . . . . . B .
                        $  L N S G K G S N L

  # OptionalPiece ? PieceString
  FromString ↚ (
    # order matters!
    Notation ↚ [" P" "+P" " R" "+R" " B" "+B" " L" "+L" " N" "+N" " S" "+S" " G" " K"]
    ∊Notation⊸⌵
    ⨬(⋅[] # empty tile
    | Piece ⊃(
        ⊗Notation⌵
        ⨬(Piece.Type.Pawn | Piece.Type.PPawn
        | Piece.Type.Rook | Piece.Type.Dragon
        | Piece.Type.Bishop | Piece.Type.Horse
        | Piece.Type.Lance | Piece.Type.PLance
        | Piece.Type.Knight | Piece.Type.PKnight
        | Piece.Type.Silver | Piece.Type.PSilver
        | Piece.Type.Gold
        | Piece.Type.King
        )
      | ⨬(Piece.Side.Gote|Piece.Side.Sente)≍⊸⌵
      )
    )
  )

  # PieceString ? Piece
  ToString ↚ (
    ≠0⊸⧻
    ⨬(⋅" ."
    | °Piece
      ⍡(" P" ⍩°Piece.Type.Pawn | "+P" ⍩°Piece.Type.PPawn
      | " R" ⍩°Piece.Type.Rook | "+R" ⍩°Piece.Type.Dragon
      | " B" ⍩°Piece.Type.Bishop | "+B" ⍩°Piece.Type.Horse
      | " L" ⍩°Piece.Type.Lance | "+L" ⍩°Piece.Type.PLance
      | " N" ⍩°Piece.Type.Knight | "+N" ⍩°Piece.Type.PKnight
      | " S" ⍩°Piece.Type.Silver | "+S" ⍩°Piece.Type.PSilver
      | " G" ⍩°Piece.Type.Gold
      | " K" ⍩°Piece.Type.King
      )
      ˜⍥¯
    )
  )

  PieceString ← ⌅(ToString|FromString)
  ArrayString ← ⌅(≡₀◇ToString|⍚₁FromString)
  BoardString ← ⌅(
    ArrayString
    /$"_\n_" ≡/⊂
  | ⊜(⬚@ ↯∞_2)⊸≠@\n
    °ArrayString
  )
  PrintBoardString ← (
    &p" 9 8 7 6 5 4 3 2 1|"
    &p"------------------+--"
    ⊜∘⊸≠@\n
    ≡⊂@|⍉¤"一二三四五六七八九"
    ≡&p˜≡⊂
  )
└─╴

Representation!(
  STARTINGBOARDSTRING
  ⍜°BoardString(∘)
  PrintBoardString
)