nodered_function.js

// This is a modified version of wivaku's script located at https://gist.github.com/wivaku/2d0dde069b4575a85e2d0c8f90342043
// Updated version of the very useful post: https://sixtymeters.com/automations/exporting-apple-health-data-to-home-assistant/

// preferred key names
const fieldKeyLookup = {
    qty: 'value',
    Avg: 'avg',
    Min: 'min',
    Max: 'max',
};

// Convert an ISO date string with timezone to UTC timestamp in nanoseconds.
function isoToUTCUnixNanos(dateStr) {
    const date = new Date(dateStr);
    if (isNaN(date.getTime())) {
        console.error(`Invalid date detected: ${dateStr}`);
        return null;
    }
    // Convert to milliseconds and then to nanoseconds for InfluxDB 1.x
    const unixNanos = date.getTime() * 1e6; 
    console.log(`Converted Date to UTC Unix Nanoseconds: ${unixNanos} for Original Date: ${dateStr}`);
    return unixNanos;
}

msg.payload = msg.payload.data.metrics.map(metric => {
    return metric.data.map(measurement => {
        const timestamp = isoToUTCUnixNanos(measurement.date);
        if (!timestamp) {
            console.error('Skipping measurement due to invalid timestamp.');
            return null;
        }

        delete measurement.date;
        var fields = {};
        Object.keys(measurement).forEach(key => {
            if (typeof measurement[key] !== 'object') fields[fieldKeyLookup[key] || key] = measurement[key];
        });

        if (fields.min && fields.max && fields.min === fields.max) {
            delete fields.min;
            delete fields.max;
        }

        return {
            measurement: metric.name, // active_energy
            fields: fields, // {value: 5} or {systolic:120, diastolic: 70}, etc
            tags: {
                unit: metric.units // e.g., kJ
            },
            timestamp: timestamp //2021-03-16 00:00:00 +0100
        };
    });
// we've created array for each metric consisting of array of measurements
// just in case, only return entries with fields
}).flat().filter(entry => entry !== null && Object.keys(entry.fields).length); 

return msg;