# ChessLogic

## Description

This package contains logic to play the game of chess. 
Functional Chess validator written in Elixir. 

It includes [fcardinaux/chessfold](https://github.com/fcardinaux/chessfold/blob/master/erl/chessfold.erl) source files, as hex does not permit non hex dependencies.

It uses leex to parse pgn files, and chessfold to implement chess logic. Both in Erlang.

It understands following rules:

* draw by 3 times the same position
* draw by 50 moves rule
* mat
* pat
* check
* taken
* en passant
* castling

But it does not understand draw by not enough material rule! It is not meant to be an AI of some sort, just a simple chess move validator (and generator), to be used in a larger project.

It also supports importing/exporting pgn files.

## Installation

The package can be installed by adding `chess_logic` to your list of dependencies in `mix.exs`:

```elixir
def deps do
  [{:chess_logic, "~> 0.1.0"}]
end
```

[Available in Hex](https://hex.pm/packages/chess_logic).

Documentation can be found at [https://hexdocs.pm/chess_logic](https://hexdocs.pm/chess_logic).

## Erlang and dialyxir configuration

Because of some warnings detected in Erlang outside code (chessfold, leex), it is nice to configure dialyxir to avoid them... It is also important to specify chessfold dependency path in erlc_paths.

Update mix.exs

      erlc_paths: ["deps/chessfold/erl", "src"],
      dialyzer: [
        ignore_warnings: "dialyzer.ignore-warnings"
      ],

Add file ./dialyzer.ignore-warnings

```elixir
Unknown function chessfold
Guard test RowId::0
The variable _ can never match since previous clauses completely covered the type
Function yyrev/2 will never be called
```

## Sample usage

More sample usage in the test folder.

 ```elixir
iex(1)> g = ChessLogic.Game.new
%ChessLogic.Game{
  current_position: %ChessLogic.Position{
    fen: "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1",
    position: [
      ["r", "n", "b", "q", "k", "b", "n", "r"],
      ["p", "p", "p", "p", "p", "p", "p", "p"],
      [" ", " ", " ", " ", " ", " ", " ", " "],
      [" ", " ", " ", " ", " ", " ", " ", " "],
      [" ", " ", " ", " ", " ", " ", " ", " "],
      [" ", " ", " ", " ", " ", " ", " ", " "],
      ["P", "P", "P", "P", "P", "P", "P", "P"],
      ["R", "N", "B", "Q", "K", "B", "N", "R"]
    ]
  },
  history: [],
  result: nil,
  status: :started,
  winner: nil
}
iex(2)> {:ok, g} = ChessLogic.Game.play(g, "e2e4")
{:ok,
 %ChessLogic.Game{
   current_position: %ChessLogic.Position{
     fen: "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1",
     position: [
       ["r", "n", "b", "q", "k", "b", "n", "r"],
       ["p", "p", "p", "p", "p", "p", "p", "p"],
       [" ", " ", " ", " ", " ", " ", " ", " "],
       [" ", " ", " ", " ", " ", " ", " ", " "], 
       [" ", " ", " ", " ", "P", " ", " ", " "],
       [" ", " ", " ", " ", " ", " ", " ", " "],
       ["P", "P", "P", "P", " ", "P", "P", "P"],
       ["R", "N", "B", "Q", "K", "B", "N", "R"]
     ]
   },
   history: [
     %{
       fen: "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1",
       move: "e2e4",
       san: "e4"
     }
   ],
   result: nil,
   status: :playing,
   winner: nil
 }}
iex(3)> {:ok, g} = ChessLogic.Game.play(g, "g8f6")
{:ok,
 %ChessLogic.Game{
   current_position: %ChessLogic.Position{
     fen: "rnbqkb1r/pppppppp/5n2/8/4P3/8/PPPP1PPP/RNBQKBNR w KQkq - 1 2",
     position: [
       ["r", "n", "b", "q", "k", "b", " ", "r"],
       ["p", "p", "p", "p", "p", "p", "p", "p"],
       [" ", " ", " ", " ", " ", "n", " ", " "],
       [" ", " ", " ", " ", " ", " ", " ", " "],
       [" ", " ", " ", " ", "P", " ", " ", " "],
       [" ", " ", " ", " ", " ", " ", " ", " "],
       ["P", "P", "P", "P", " ", "P", "P", "P"],
       ["R", "N", "B", "Q", "K", "B", "N", "R"]
     ]
   },
   history: [
     %{
       fen: "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1",
       move: "g8f6",
       san: "Nf6"
     },
     %{
       fen: "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1",
       move: "e2e4",
       san: "e4"
     }
   ],
   result: nil,
   status: :playing,
   winner: nil
 }}
iex(4)> g |> ChessLogic.Game.to_pgn()
"1. e4 Nf6"
```