0bd6790b1f
Replace the flatMap intermediate array plus two filter passes with one walk over the year bands and the undated bucket. Same counts, no throwaway allocation. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
39 lines
1.4 KiB
TypeScript
39 lines
1.4 KiB
TypeScript
import type { components } from '$lib/generated/api';
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type TimelineDTO = components['schemas']['TimelineDTO'];
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export interface TimelineMeta {
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/** First year band's year, or `null` when there are no bands. */
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firstYear: number | null;
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/** Last year band's year, or `null` when there are no bands. */
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lastYear: number | null;
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/** Every `LETTER` entry across all year bands plus the undated bucket. */
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letterCount: number;
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/** Every `EVENT` entry (derived, curated, and historical) across all bands plus undated. */
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eventCount: number;
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}
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/**
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* Derives the header meta-line figures from a loaded `TimelineDTO` (REQ-002):
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* the year range (first/last band) and the letter/event totals across every
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* year band plus the undated bucket. Pure and the single place these counts
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* live — the route renders them; `TimelineView` never recomputes them.
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*/
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export function timelineMeta(timeline: TimelineDTO): TimelineMeta {
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const years = timeline.years;
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let letterCount = 0;
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let eventCount = 0;
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const tally = (e: TimelineDTO['undated'][number]) => {
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if (e.kind === 'LETTER') letterCount += 1;
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else if (e.kind === 'EVENT') eventCount += 1;
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};
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for (const y of years) for (const e of y.entries) tally(e);
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for (const e of timeline.undated) tally(e);
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return {
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firstYear: years.length ? years[0].year : null,
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lastYear: years.length ? years[years.length - 1].year : null,
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letterCount,
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eventCount
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};
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}
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