index.ts

import { EventEmitter } from 'node:events';
import { promises as fs } from 'node:fs';
import * as os from 'node:os';
import * as path from 'node:path';

/**
 * Interval of file system polling, in milliseconds.
 */
const PollingInterval = 100;

/**
 * GPIO パス
 */
const SysfsGPIOPath = '/sys/class/gpio';

/**
 * GPIO ポートマップサイズ
 */
const GPIOPortMapSizeMax = 1024;

/**
 * Uint16 Max サイズ
 */
const Uint16Max = 65535;

/**
 *
 * Uint16型変換処理
 * @param parseString 変換文字列
 * @return Uint16型変換値
 */
function parseUint16(parseString: string) {
  const n = Number.parseInt(parseString, 10);
  if (0 <= n && n <= Uint16Max) return n;
  // biome-ignore lint/style/noUselessElse:
  else throw new RangeError(`Must be between 0 and ${Uint16Max}.`);
}

/**
 * GPIO0 オフセット
 * @see {@link https://github.com/raspberrypi/linux/issues/6037}
 */
const GpioOffset =
  process.platform === 'linux' && 6.6 <= Number(os.release().match(/\d+\.\d+/))
    ? 512
    : 0;

/** ポート番号 */
type PortNumber = number;
/** ポート名 */
type PortName = string;
/** ピン名 */
type PinName = string;

/** 入出力方向 */
type DirectionMode = 'in' | 'out';

/** GPIO 値 0: LOW / 1: HIGH */
type GPIOValue = 0 | 1;

/**
 * GPIO チェンジイベント
 */
interface GPIOChangeEvent {
  /** 入出力値 */
  readonly value: GPIOValue;
  /** ポート */
  readonly port: GPIOPort;
}

/**
 * GPIO チェンジイベントハンドラ
 */
interface GPIOChangeEventHandler {
  /** イベント */
  // biome-ignore lint/style/useShorthandFunctionType:
  (event: GPIOChangeEvent): void;
}

/**
 * GPIO
 */
export class GPIOAccess extends EventEmitter {
  /** ポート */
  private readonly _ports: GPIOPortMap;
  /** GPIO チェンジイベントハンドラ */
  onchange: GPIOChangeEventHandler | undefined;

  /**
   * Creates an instance of GPIOAccess.
   * @param ports ポート番号
   */
  constructor(ports?: GPIOPortMap) {
    super();

    this._ports = ports == null ? new GPIOPortMap() : ports;
    // biome-ignore lint/complexity/noForEach:
    this._ports.forEach((port) =>
      port.on('change', (event) => {
        this.emit('change', event);
      }),
    );

    this.on('change', (event: GPIOChangeEvent): void => {
      if (this.onchange !== undefined) this.onchange(event);
    });
  }

  /**
   * ポート情報取得処理
   * @return 現在のポート情報
   */
  get ports(): GPIOPortMap {
    return this._ports;
  }

  /**
   * Unexport all exported GPIO ports.
   * 全てのポート開放をする
   * @return ポート開放結果
   */
  async unexportAll(): Promise<void> {
    await Promise.all(
      [...this.ports.values()].map((port) =>
        port.exported ? port.unexport() : undefined,
      ),
    );
  }
}

/**
 * Different from Web GPIO API specification.
 */
export class GPIOPortMap extends Map<PortNumber, GPIOPort> {}

/**
 * GPIO ポート
 */
export class GPIOPort extends EventEmitter {
  /** ポート番号 */
  private readonly _portNumber: PortNumber;
  /** ポーリング間隔 */
  private readonly _pollingInterval: number;
  /** 入出力方向 */
  private _direction: DirectionMode | OperationError;
  /** エクスポート */
  private _exported: boolean | OperationError;
  /** エクスポートリトライ回数 */
  private _exportRetry: number;
  /** 入出力値 */
  private _value: GPIOValue | undefined;
  /** タイムアウト値 */
  private _timeout: ReturnType<typeof setInterval> | undefined;
  /** GPIO チェンジイベントハンドラ */
  onchange: GPIOChangeEventHandler | undefined;

  /**
   * Creates an instance of GPIOPort.
   * @param portNumber ポート番号
   */
  constructor(portNumber: PortNumber) {
    super();

    this._portNumber = parseUint16(portNumber.toString()) + GpioOffset;
    this._pollingInterval = PollingInterval;
    this._direction = new OperationError('Unknown direction.');
    this._exported = new OperationError('Unknown export.');
    this._exportRetry = 0;

    this.on('change', (event: GPIOChangeEvent): void => {
      if (this.onchange !== undefined) this.onchange(event);
    });
  }

  /**
   * ポート番号取得処理
   * @return 現在のポート番号
   */
  get portNumber(): PortNumber {
    return this._portNumber;
  }

  /**
   * ポート名取得処理
   * @return 現在のポート名
   */
  get portName(): PortName {
    return `gpio${this.portNumber}`;
  }

  /**
   * ピン名取得処理
   * @return 現在のピン名
   */
  get pinName(): PinName {
    // NOTE: Unknown pinName.
    return '';
  }

  /**
   * GPIO 入出力方向 getter
   * @return 現在のGPIO 入出力方向
   */
  get direction(): DirectionMode {
    if (this._direction instanceof OperationError) throw this._direction;
    return this._direction;
  }

  /**
   * GPIO export の有無 getter
   * @return 現在のGPIO 出力
   */
  get exported(): boolean {
    if (this._exported instanceof OperationError) throw this._exported;
    return this._exported;
  }

  /**
   * GPIO 出力処理
   * @param direction GPIO 入出力方向
   * @return export 処理の完了
   */
  async export(direction: DirectionMode): Promise<void> {
    if (!/^(in|out)$/.test(direction)) {
      throw new InvalidAccessError(`Must be "in" or "out".`);
    }

    try {
      await fs.access(path.join(SysfsGPIOPath, this.portName));
      this._exported = true;
    } catch {
      this._exported = false;
    }

    try {
      clearInterval(this._timeout as ReturnType<typeof setInterval>);
      if (!this.exported) {
        await fs.writeFile(
          path.join(SysfsGPIOPath, 'export'),
          String(this.portNumber),
        );
      }
      await fs.writeFile(
        path.join(SysfsGPIOPath, this.portName, 'direction'),
        direction,
      );
      if (direction === 'in') {
        this._timeout = setInterval(
          // eslint-disable-next-line
          this.read.bind(this),
          this._pollingInterval,
        );
      }
      // biome-ignore lint/suspicious/noExplicitAny:
    } catch (error: any) {
      if (this._exportRetry < 10) {
        await sleep(100);
        console.warn('May be the first time port access. Retry..');
        ++this._exportRetry;
        await this.export(direction);
      } else {
        throw new OperationError(error);
      }
    }

    this._direction = direction;
    this._exported = true;
  }

  /**
   * Unexport exported GPIO ports.
   * ポート開放をする
   * @return ポート開放処理の完了
   */
  async unexport(): Promise<void> {
    clearInterval(this._timeout as ReturnType<typeof setInterval>);

    try {
      await fs.writeFile(
        path.join(SysfsGPIOPath, 'unexport'),
        String(this.portNumber),
      );
      // biome-ignore lint/suspicious/noExplicitAny:
    } catch (error: any) {
      throw new OperationError(error);
    }

    this._exported = false;
  }

  /**
   * 入力値読み取り処理
   * @return 読み取り処理の完了
   */
  async read(): Promise<GPIOValue> {
    if (!(this.exported && this.direction === 'in')) {
      throw new InvalidAccessError(
        `The exported must be true and value of direction must be "in".`,
      );
    }

    try {
      const buffer = await fs.readFile(
        path.join(SysfsGPIOPath, this.portName, 'value'),
      );

      const value = parseUint16(buffer.toString()) as GPIOValue;

      if (this._value !== value) {
        this._value = value;
        this.emit('change', { value, port: this });
      }

      return value;
      // biome-ignore lint/suspicious/noExplicitAny:
    } catch (error: any) {
      throw new OperationError(error);
    }
  }

  /**
   * 出力値書き込み処理
   * @return 読み取り処理の完了
   */
  async write(value: GPIOValue): Promise<void> {
    if (!(this.exported && this.direction === 'out')) {
      throw new InvalidAccessError(
        `The exported must be true and value of direction must be "out".`,
      );
    }

    try {
      await fs.writeFile(
        path.join(SysfsGPIOPath, this.portName, 'value'),
        parseUint16(value.toString()).toString(),
      );
      // biome-ignore lint/suspicious/noExplicitAny:
    } catch (error: any) {
      throw new OperationError(error);
    }
  }
}

/**
 * 無効なアクセスエラー
 */
export class InvalidAccessError extends Error {
  /**
   * Creates an instance of InvalidAccessError.
   * @param message エラーメッセージ
   */
  constructor(message: string) {
    super(message);
    this.name = this.constructor.name;
  }
}

/**
 * 操作エラー
 */
export class OperationError extends Error {
  /**
   * Creates an instance of OperationError.
   * @param message エラーメッセージ
   */
  constructor(message: string) {
    super(message);
    this.name = this.constructor.name;
  }
}

// Web GPIOの仕様に基づく意図的なasync関数の使用なので、ルールを無効化
// eslint-disable-next-line
export async function requestGPIOAccess(): Promise<GPIOAccess> {
  const ports = new GPIOPortMap(
    [...Array(GPIOPortMapSizeMax).keys()].map((portNumber) => [
      portNumber,
      new GPIOPort(portNumber),
    ]),
  );

  return new GPIOAccess(ports);
}

/**
 * 待機 関数
 * @param ms スリープ時間（ミリ秒）
 * @return 待機完了
 */
function sleep(ms: number) {
  return new Promise((resolve) => {
    return setTimeout(resolve, ms);
  });
}