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Maurice
4570ace78c
Every element kind and Studio tool gets an op, the auto layout and its templates move from the client to shared with a parity fixture, and a pure design engine turns directives into a finished book with design findings.
46 lines
1.9 KiB
TypeScript
46 lines
1.9 KiB
TypeScript
import { MAX_PATH_POINTS, MAX_PATH_SEGMENTS } from './book.schema';
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/**
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* A journey's tracks, thinned to what a printed line can show.
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*
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* A three-week drive is hundreds of thousands of GPS fixes. At the size a map
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* is printed, a point every fifteen metres and a point every kilometre are the
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* same picture, and only one of them fits in a document that has to be saved,
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* sent over a websocket and parsed on the other side. Moved here from the
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* Studio (client/src/pages/journeyStudio/useJourneyStudio.ts) so the server's
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* design tool draws the same line the editor does.
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*
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* Thinned by taking every nth point rather than by simplifying the geometry:
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* Douglas-Peucker would keep the shape better, and it is a hundred lines of
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* code to gain something nobody can see at 60mm across. The ends of every
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* segment are kept, because a track that stops short of where it ended reads
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* as a bug.
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*/
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/** Points one thinned segment keeps, under the document's own cap. */
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const PER_SEGMENT = Math.min(600, MAX_PATH_POINTS);
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export function bookPath(tracks: readonly { points: readonly (readonly unknown[])[] }[]): [number, number][][] {
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const out: [number, number][][] = [];
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for (const track of tracks.slice(0, MAX_PATH_SEGMENTS)) {
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// Normalised on the way in: the contract types a pair as a tuple, and Zod
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// infers that loosely enough that the pair has to be rebuilt to stay one.
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const pts = track.points
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.map((p): [number, number] => [Number(p[0]), Number(p[1])])
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.filter((p) => Number.isFinite(p[0]) && Number.isFinite(p[1]));
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if (pts.length < 2) continue;
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if (pts.length <= PER_SEGMENT) {
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out.push(pts);
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continue;
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}
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const step = (pts.length - 1) / (PER_SEGMENT - 1);
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const thinned: [number, number][] = [];
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for (let i = 0; i < PER_SEGMENT; i++) {
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const at = pts[Math.round(i * step)];
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if (at) thinned.push(at);
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}
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out.push(thinned);
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}
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return out;
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}
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