hexchess 2.0.0-alpha.3

# [`@bedard/hexchess`](https://github.com/scottbedard/hexchess.rs)

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A Rust / TypeScript library for [Gliński's hexagonal chess](https://en.wikipedia.org/wiki/Hexagonal_chess#Gli%C5%84ski's_hexagonal_chess), and the brain of [hexchess.club](https://hexchess.club).

<p align="center">
  <a href="https://hexchess.club">
    <img src="assets/hexchess.svg" width="500" />
  </a>
</p>

## Installation

Install this package via NPM.

Depending on your bundler, you may need plugins for [Web Assembly](https://developer.mozilla.org/en-US/docs/WebAssembly) and [top-level await](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await#top_level_await).

```
# npm
npm install @bedard/hexchess

# pnpm
pnpm install @bedard/hexchess

# yarn
yarn add @bedard/hexchess
```

## Basic usage

The `Hexchess` object is a deserialized version of [Forsyth–Edwards Notation](https://en.wikipedia.org/wiki/Forsyth%E2%80%93Edwards_Notation). It contains the board state, current turn, en passant position, and move numbers. Note that since castling is not a part of hexagonal chess, that section is omitted from the notation.

```ts
import { initHexchess } from '@bedard/hexchess'

const hexchess = initHexchess()
```

The board positions coorelate to their position in a FEN string, `null` represents an unoccupied position.

```js
{
  board: [
    'b',  'q',  'b',  'k',  'n',  null, 'b',  null, 'n',  'r',
    null, null, null, null, null, 'r',  'p',  'p',  'p',  'p',
    'p',  'p',  'p',  'p',  'p',  null, null, null, null, null,
    null, null, null, null, null, null, null, null, null, null,
    null, 'P',  null, null, null, null, null, null, null, null,
    null, 'P',  null, 'P',  null, null, null, null, null, null,
    null, 'P',  null, 'B',  null, 'P',  null, null, null, null,
    null, 'P',  null, null, 'B',  null, null, 'P',  null, null,
    null, 'P',  'R',  'N',  'Q',  'B',  'K',  'N',  'R',  'P',
    null
  ],
  turn: 'w',
  ep: null,
  halfmove: 0,
  fullmove: 1
}
```

Below are the available functions to interact with these objects.

#### `applyMove`

Apply `San` object to a `Hexchess` object.

```ts
import { applyMove } from '@bedard/hexchess'

applyMove(hexchess, { from: 53, to: 42, promotion: null })  // { board: [ ... ], ep, turn, fullmove, halfmove }
```

#### `applySequence`

Apply a whitespace separated sequence of move to a `Hexchess` object.

```ts
import { applySequence } from '@bedard/hexchess'

applySequence(hexchess, 'g4g6 f7g6 f5f7 g6f6') // { board: [ ... ], ep, turn, fullmove, halfmove }
```

#### `createHexchess`

Create a blank `Hexchess` object.

```ts
import { createHexchess } from '@bedard/hexchess'

createHexchess() // { board: [ ... ], ep, turn, fullmove, halfmove }
```

#### `currentMoves`

Get current legal moves.

```ts
import { currentMoves } from '@bedard/hexchess'

currentMoves(hexchess) // [{ from, to, promotion }, ...]
```

#### `initHexchess`

Create `Hexchess` object at the initial position.

```ts
import { initHexchess } from '@bedard/hexchess'

initHexchess() // { board: [ ... ], ep, turn, fullmove, halfmove }
```

#### `movesFrom`

Get legal moves from a position index.

```ts
import { movesFrom } from '@bedard/hexchess'

movesFrom(53) // [{ from, to, promotion }, ...]
```

#### `parseHexchess`

Parse `Hexchess` object from [Forsyth–Edwards Notation](https://en.wikipedia.org/wiki/Forsyth%E2%80%93Edwards_Notation).

```ts
import { parseHexchess } from '@bedard/hexchess'

parseHexchess('b/qbk/n1b1n/r5r/ppppppppp/11/5P5/4P1P4/3P1B1P3/2P2B2P2/1PRNQBKNRP1 w - 0 1') // { board, turn, ep, halfmove, fullmove }
```

#### `parseSan`

Parse `San` object from string.

```ts
import { parseSan } from '@bedard/hexchess'

parseSan('g4g5') // { from: 53, to: 42, promotion: null }
```

#### `stringifyHexchess`

Convert `Hexchess` object to string using [Forsyth–Edwards Notation](https://en.wikipedia.org/wiki/Forsyth%E2%80%93Edwards_Notation).

```ts
import { stringifyHexchess } from '@bedard/hexchess'

stringifyHexchess(hexchess) // 'b/qbk/n1b1n/r5r/ppppppppp/11/5P5/4P1P4/3P1B1P3/2P2B2P2/1PRNQBKNRP1 w - 0 1'
```

#### `stringifySan`

Convert `San` object to string.

```ts
import { stringifySan } from '@bedard/hexchess'

stringifySan({ from: 53, to: 42, promotion: null }) // 'g4g5'
```

## License

[MIT](https://github.com/scottbedard/hexchess.rs/blob/main/LICENSE)

Copyright (c) 2024-present, Scott Bedard