import type { HeatZone } from '../types/index.js';
import { formatDuration } from './format-units.js';
/**
* Heat zone definitions based on Heat Strain Index (HSI).
* Zones are derived from the Heat Strain Index metric.
*/
const HEAT_ZONE_DEFINITIONS = [
{
name: 'Zone 1: No Heat Strain',
low: 0,
high: 1,
},
{
name: 'Zone 2: Moderate Heat Strain',
low: 1,
high: 3,
},
{
name: 'Zone 3: High Heat Strain',
low: 3,
high: 7,
},
{
name: 'Zone 4: Extremely High Heat Strain',
low: 7,
high: null, // Unbounded
},
];
/**
* Stream data response from Intervals.icu API for heat strain index.
*/
interface StreamDataPoint {
type: string;
data: number[];
}
/**
* Heat metrics calculated from stream data
*/
export interface HeatMetrics {
zones: HeatZone[];
max_heat_strain_index: number;
median_heat_strain_index: number;
}
/**
* Calculate time in each heat zone from activity stream data.
*
* @param timeData - Array of time values in seconds
* @param heatStrainData - Array of heat strain index values (aligned with timeData)
* @returns Array of HeatZone objects with time_in_zone calculated
*/
export function calculateHeatZones(
timeData: number[],
heatStrainData: number[]
): HeatZone[] {
if (timeData.length !== heatStrainData.length) {
throw new Error('Time and heat strain data arrays must have the same length');
}
// Initialize time counters for each zone
const zoneTimes = new Array(HEAT_ZONE_DEFINITIONS.length).fill(0);
// For each data point (each second), determine which zone it belongs to
for (let i = 0; i < heatStrainData.length; i++) {
const hsi = heatStrainData[i];
// Find the appropriate zone for this HSI value
for (let zoneIndex = 0; zoneIndex < HEAT_ZONE_DEFINITIONS.length; zoneIndex++) {
const zone = HEAT_ZONE_DEFINITIONS[zoneIndex];
const inZone = hsi >= zone.low && (zone.high === null || hsi < zone.high);
if (inZone) {
// Calculate time spent at this data point
// Time is the difference to the next point (or 1 second for the last point)
const timeSpent = i < timeData.length - 1
? timeData[i + 1] - timeData[i]
: 1;
zoneTimes[zoneIndex] += timeSpent;
break;
}
}
}
// Build the result array with formatted durations
return HEAT_ZONE_DEFINITIONS.map((zone, index) => ({
name: zone.name,
low_heat_strain_index: zone.low,
high_heat_strain_index: zone.high,
time_in_zone: formatDuration(zoneTimes[index]),
}));
}
/**
* Calculate comprehensive heat metrics from activity stream data.
*
* @param timeData - Array of time values in seconds
* @param heatStrainData - Array of heat strain index values (aligned with timeData)
* @returns Heat metrics including zones, max, avg, and heat training load
*/
export function calculateHeatMetrics(
timeData: number[],
heatStrainData: number[]
): HeatMetrics {
const zones = calculateHeatZones(timeData, heatStrainData);
// Calculate max HSI
const maxHSI = heatStrainData.length > 0 ? Math.max(...heatStrainData) : 0;
// Calculate median HSI
let medianHSI = 0;
if (heatStrainData.length > 0) {
const sorted = [...heatStrainData].sort((a, b) => a - b);
const mid = Math.floor(sorted.length / 2);
medianHSI = sorted.length % 2 === 0
? (sorted[mid - 1] + sorted[mid]) / 2
: sorted[mid];
}
return {
zones,
max_heat_strain_index: Math.round(maxHSI * 10) / 10, // Round to 1 decimal
median_heat_strain_index: Math.round(medianHSI * 10) / 10, // Round to 1 decimal
};
}
/**
* Parse stream data response from Intervals.icu API.
*
* @param streams - Array of stream data from the API
* @returns Object with time and heat_strain_index arrays, or null if heat strain data not available
*/
export function parseHeatStrainStreams(
streams: StreamDataPoint[]
): { time: number[]; heat_strain_index: number[] } | null {
const timeStream = streams.find((s) => s.type === 'time');
const heatStrainStream = streams.find((s) => s.type === 'heat_strain_index');
if (!timeStream || !heatStrainStream) {
return null;
}
return {
time: timeStream.data,
heat_strain_index: heatStrainStream.data,
};
}
