Generated by XState Viz: https://xstate.js.org/viz

machine.js

const { log } = actions;
const START_CHAR = '-';
const END_CHAR = '-';
const CONTROL_SEQUENCE_COUNT = 3;
const CONTROL_SEQUENCE_TIMEOUT = 200;
const DATA_TIMEOUT = 2000;

const scannerMachine = Machine({
    id: 'scannerMachine',
    initial: 'waitingForChars',
    context: {
        code: '',
        startCharCount: CONTROL_SEQUENCE_COUNT,
        endCharCount: CONTROL_SEQUENCE_COUNT,
    },
    states: {
        waitingForChars: {
            entry: 'resetContext',
            on: {
                KEYPRESS: { target: 'startSeq', cond: 'isStartChar' },
            },
        },
        startSeq: {
            entry: 'decrementStartCharCount',
            on: {
                KEYPRESS: [
                    {
                        target: 'startSeq',
                        cond: 'isStartChar',
                    },
                    { target: 'waitingForChars' },
                ],
                '': { target: 'receiving', cond: 'isStarted' },
            },
            after: {
                [CONTROL_SEQUENCE_TIMEOUT]: 'waitingForChars',
            },
        },
        receiving: {
            entry: 'resetSeqCounters',
            on: {
                KEYPRESS: [
                    {
                        target: 'endSeq',
                        cond: 'isEndChar',
                    },
                    {
                        target: 'receiving',
                        actions: 'appendKeyToCode',
                    },
                ],
            },
            after: {
                [DATA_TIMEOUT]: 'waitingForChars',
            },
        },
        endSeq: {
            entry: 'decrementEndCharCount',
            on: {
                KEYPRESS: [
                    {
                        target: 'endSeq',
                        cond: 'isEndChar',
                    },
                    {
                        target: 'receiving',
                        actions: 'assignEndCharsAndKey',
                    },
                ],
                '': {
                    target: 'received',
                    cond: 'isEnded',
                },
            },
            after: {
                [CONTROL_SEQUENCE_TIMEOUT]: 'waitingForChars',
            },
        },
        received: {
            entry: 'codeReceived',
            on: {
                '': 'waitingForChars',
            },
        },
    },
}, {
    guards: {
        isStartChar: (_, { key }) => key === START_CHAR,
        isEndChar: (_, { key }) => key === END_CHAR,
        isStarted: ({ startCharCount }) => startCharCount === 0,
        isEnded: ({ endCharCount }) => endCharCount === 0,
    },
    actions: {
        codeReceived: log((context, event) => `codeReceived: ${context.code}, event: ${event.type}`),
        assignEndCharsAndKey: assign({
            code: ({ code, endCharCount }, { key }) => code + END_CHAR.repeat(CONTROL_SEQUENCE_COUNT - endCharCount) + key,
        }),
        decrementEndCharCount: assign({
            endCharCount: ({ endCharCount }) => endCharCount - 1,
        }),
        decrementStartCharCount: assign({
            startCharCount: ({ startCharCount }) => startCharCount - 1,
        }),
        appendKeyToCode: assign({
            code: ({ code }, { key }) => code + key,
        }),
        resetSeqCounters: assign({
            startCharCount: CONTROL_SEQUENCE_COUNT,
            endCharCount: CONTROL_SEQUENCE_COUNT,
        }),
        resetContext: assign({
            code: '',
            startCharCount: CONTROL_SEQUENCE_COUNT,
            endCharCount: CONTROL_SEQUENCE_COUNT,
        }),
    },
});