rotary encoder for makecode

encoder.ts

// based on https://github.com/PaulStoffregen/Encoder/blob/master/Encoder.h

class Encoder {
    state: number
    position: number
    onChange: (n: number) => void

    constructor(public pinA: DigitalInOutPin, public pinB: DigitalInOutPin) {
        this.state = 0
        this.position = 0
        const updatePins = () => {
            let s = this.state & 3;
            if (this.pinA.digitalRead()) s |= 4;
            if (this.pinB.digitalRead()) s |= 8;

            this.state = (s >> 2);

            switch (s) {
                case 0: case 5: case 10: case 15:
                    return;
                case 1: case 7: case 8: case 14:
                    this.position++; break;
                case 2: case 4: case 11: case 13:
                    this.position--; break;
                case 3: case 12:
                    this.position += 2; break;
                default:
                    this.position -= 2; break;
            }

            if (this.onChange)
                this.onChange(this.position)
        }

        this.pinA.onEvent(PinEvent.Rise, updatePins)
        this.pinB.onEvent(PinEvent.Fall, updatePins)
    }
}