mirror of
https://github.com/MBombeck/HealthLog.git
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Marc-André Bombeck
9445d89b76
A typed apiFetch wrapper owns the envelope unwrap, the ok-check and the error read for every client call — two hundred call sites across the app migrate onto it and a lint rule keeps raw api fetches out for good. The legacy timezone helpers fold into the tz module and test fixtures drop personal names.
77 lines
3.1 KiB
TypeScript
77 lines
3.1 KiB
TypeScript
/**
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* Window-trend helpers for the health-chart `showTrend` overlay.
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*
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* Two complementary deltas:
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*
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* - `weeklyDelta` — first vs last regression-line value, normalised
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* to a per-week rate. Stable for short windows
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* (≤ 90 days) where the user is asking "what is
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* this metric doing this week / month".
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* - `splitHalfDelta` — mean of the second half minus mean of the first
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* half of the visible series. Stays meaningful
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* for long ("All") ranges where the per-week rate
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* rounds to ±0 in the 1-decimal formatter.
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*
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* v1.4.16 Fix A8b — the maintainer reported the chart trend overlay reads
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* "+0.0 kg/Woche" on the All filter, even when their weight clearly
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* shifted across years. Root cause: `weeklyDelta = (last − first) / days
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* × 7` is mathematically correct but visually rounds to zero whenever
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* the slope-per-day is small enough that 7× still falls below the
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* formatter's display precision. The split-half delta side-steps the
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* rounding entirely because it doesn't divide by the window width.
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*
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* Pure & deterministic — pinned by unit test.
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*/
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export interface WindowTrendInput {
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/** Sorted ascending by timestamp. */
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rawValues: number[];
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/** Sorted ascending by timestamp. Must align 1:1 with `rawValues`. */
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trendValues: number[];
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/** Days between the first and last point of the visible series. */
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windowDays: number;
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}
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export interface WindowTrendResult {
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/** Linear-trend per-week delta. Always present when ≥ 2 points. */
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weeklyDelta: number;
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/**
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* First-half-mean vs second-half-mean delta of the raw (not trend)
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* values. Reported as `null` for short windows or when one of the
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* halves is empty (n < 2 split into two halves).
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*/
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splitHalfDelta: number | null;
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}
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/** Default threshold above which the split-half delta is computed. */
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export const SPLIT_HALF_THRESHOLD_DAYS = 90;
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export function computeWindowTrend(
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input: WindowTrendInput,
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splitHalfThresholdDays = SPLIT_HALF_THRESHOLD_DAYS,
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): WindowTrendResult | null {
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if (input.rawValues.length < 2) return null;
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if (input.trendValues.length !== input.rawValues.length) return null;
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if (!Number.isFinite(input.windowDays) || input.windowDays <= 0) return null;
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const firstTrend = input.trendValues[0];
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const lastTrend = input.trendValues[input.trendValues.length - 1];
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const weeklyDelta = ((lastTrend - firstTrend) / input.windowDays) * 7;
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let splitHalfDelta: number | null = null;
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if (input.windowDays >= splitHalfThresholdDays) {
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const mid = Math.floor(input.rawValues.length / 2);
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const firstHalf = input.rawValues.slice(0, mid);
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const secondHalf = input.rawValues.slice(mid);
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if (firstHalf.length > 0 && secondHalf.length > 0) {
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const meanFirst =
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firstHalf.reduce((sum, value) => sum + value, 0) / firstHalf.length;
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const meanSecond =
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secondHalf.reduce((sum, value) => sum + value, 0) / secondHalf.length;
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splitHalfDelta = meanSecond - meanFirst;
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}
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}
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return { weeklyDelta, splitHalfDelta };
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}
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