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⚡ Bolt: Add O(1) caching for station lookups #131

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⚡ Bolt: Add O(1) caching for station lookups #131

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3 changes: 3 additions & 0 deletions .jules/bolt.md
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Expand Up @@ -5,3 +5,6 @@
## 2024-04-15 - [Avoid O(N log N) Sorting on Massive Geographical Collections]
**Learning:** In spatial queries like `findNearbyStations` where we scan `railwayData` containing thousands of stations to find the top K nearest points, allocating all elements to an array and running `Array.prototype.sort()` results in massive temporary object allocation and $O(N \log N)$ execution time (taking ~8.5ms in benchmarks).
**Action:** Replace full array sorts with a bounded Top-K array using a simple $O(K)$ insertion sort during the $O(N)$ iteration phase. This brings the time complexity effectively down to $O(N)$, speeding up operations by ~36x (taking ~0.24ms). Remember to apply a final sort if total elements found are less than $K$.
## 2024-05-18 - [O(1) Dictionary Lookup for Arrays]
**Learning:** In highly nested arrays and components, running `Object.values(railwayData).forEach()` multiple times to scan through `line.stations.find()` just to lookup a single ID results in $O(N \times M)$ overhead, blocking UI threads.
**Action:** Implemented a one-time cached `Map` in `src/core/railwayRouting.ts` (`stationIdIndexCache`) to index stations by their IDs for O(1) instantaneous lookups. The cache safely invalidates by comparing the reference identity of the underlying global immutable data.
13 changes: 7 additions & 6 deletions src/RailRound.jsx
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Expand Up @@ -34,6 +34,7 @@ const { meta } = changelog;
import { useStore } from './store';
import toast from 'react-hot-toast';
import { ESLint } from 'eslint';
import { getStationById } from './core/railwayRouting';

const CURRENT_VERSION = meta["currentVersion"];
const LAST_MODIFIED = manifest.lastModified
Expand Down Expand Up @@ -1267,12 +1268,10 @@ const RecordsView = ({ trips, railwayData, setTrips, onEdit, onDelete, onAdd, se
if (isWalk) {
let startName = t.fromId || '';
let endName = t.toId || '';
Object.values(railwayData).forEach(line => {
const s = line.stations.find(st => st.id === t.fromId);
const s = getStationById(railwayData, t.fromId);
if (s) startName = s.name_ja;
const e = line.stations.find(st => st.id === t.toId);
const e = getStationById(railwayData, t.toId);
if (e) endName = e.name_ja;
});

const isTree = t.walkType === 'tree';
const cls = {
Expand Down Expand Up @@ -1462,9 +1461,11 @@ const StatsView = ({ trips, railwayData, geoData, user, userProfile, segmentGeom
let count = 0;
if (railwayData) {
const uniqueStations = new Set();
Object.values(railwayData).forEach(line => {
for (const lineKey in railwayData) {
if (!Object.prototype.hasOwnProperty.call(railwayData, lineKey)) continue;
const line = railwayData[lineKey];
if (line.stations) line.stations.forEach(s => uniqueStations.add(s.id));
});
}
count = uniqueStations.size;
}
return count;
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21 changes: 9 additions & 12 deletions src/components/modals/WalkTripEditor.tsx
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Expand Up @@ -6,6 +6,7 @@ import { useUserData } from '../../hooks/useUserData';
import * as turf from '@turf/turf';
import { useTranslation } from 'react-i18next';
import { showAlert, showConfirm } from '../../utils/alerts';
import { getStationById } from '../../core/railwayRouting';

export const WalkTripEditor: React.FC = () => {
const { t } = useTranslation();
Expand Down Expand Up @@ -82,12 +83,10 @@ export const WalkTripEditor: React.FC = () => {
// Find coordinates for the Bezier curve
let startCoords = null;
let endCoords = null;
Object.values(railwayData).forEach(line => {
const s = line.stations.find(st => st.id === form.fromId);
if (s) startCoords = [s.lng, s.lat];
const e = line.stations.find(st => st.id === form.toId);
if (e) endCoords = [e.lng, e.lat];
});
const s = getStationById(railwayData, form.fromId);
if (s) startCoords = [s.lng, s.lat];
const e = getStationById(railwayData, form.toId);
if (e) endCoords = [e.lng, e.lat];

if (startCoords && endCoords) {
walkPath = generateBezierPath(startCoords as [number, number], endCoords as [number, number]);
Expand Down Expand Up @@ -130,12 +129,10 @@ export const WalkTripEditor: React.FC = () => {
// Resolving station names for read-only display
let startName = t('walk.unknownStart', "未知起点");
let endName = t('walk.unknownEnd', "未知终点");
Object.values(railwayData).forEach(line => {
const s = line.stations.find(st => st.id === form.fromId);
if (s) startName = s.name_ja;
const e = line.stations.find(st => st.id === form.toId);
if (e) endName = e.name_ja;
});
const s = getStationById(railwayData, form.fromId);
if (s) startName = s.name_ja;
const e = getStationById(railwayData, form.toId);
if (e) endName = e.name_ja;

const isTree = form.walkType === 'tree';

Expand Down
35 changes: 28 additions & 7 deletions src/core/railwayRouting.ts
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Expand Up @@ -3,6 +3,7 @@ import { calcDist } from '../core/tripCalculator'; // Ensure calcDist is exporte

// 预构建的换乘站索引缓存
let stationNameIndexCache: Map<string, {lineKey: string, stationIndex: number}[]> | null = null;
let stationIdIndexCache: Map<string, {lineKey: string, stationIndex: number}> | null = null;
let lastRailwayDataRef: RailwayMap | null = null;

export const isCompanyCompatible = (meta1: CompanyMeta | undefined, meta2: CompanyMeta | undefined) => {
Expand All @@ -13,25 +14,45 @@ export const isCompanyCompatible = (meta1: CompanyMeta | undefined, meta2: Compa
};

export const buildStationIndex = (railwayData: RailwayMap) => {
if (stationNameIndexCache && lastRailwayDataRef === railwayData) {
if (stationNameIndexCache && stationIdIndexCache && lastRailwayDataRef === railwayData) {
return stationNameIndexCache;
}

const index = new Map<string, {lineKey: string, stationIndex: number}[]>();
const nameIndex = new Map<string, {lineKey: string, stationIndex: number}[]>();
const idIndex = new Map<string, {lineKey: string, stationIndex: number}>();

for (const lineKey in railwayData) {
if (!Object.prototype.hasOwnProperty.call(railwayData, lineKey)) continue;
const line = railwayData[lineKey];
line.stations.forEach((st, idx) => {
if (!index.has(st.name_ja)) {
index.set(st.name_ja, []);
if (!nameIndex.has(st.name_ja)) {
nameIndex.set(st.name_ja, []);
}
nameIndex.get(st.name_ja)!.push({ lineKey, stationIndex: idx });

if (st.id) {
idIndex.set(st.id, { lineKey, stationIndex: idx });
}
index.get(st.name_ja)!.push({ lineKey, stationIndex: idx });
});
}

stationNameIndexCache = index;
stationNameIndexCache = nameIndex;
stationIdIndexCache = idIndex;
lastRailwayDataRef = railwayData;
return index;
return nameIndex;
};

export const getStationById = (railwayData: RailwayMap, stationId: string): Station | undefined => {
if (!stationId) return undefined;

// Ensure caches are built
buildStationIndex(railwayData);

if (stationIdIndexCache && stationIdIndexCache.has(stationId)) {
const info = stationIdIndexCache.get(stationId)!;
return railwayData[info.lineKey]?.stations[info.stationIndex];
}
return undefined;
};

export const getTransferableLines = (station: Station | undefined, currentLineKey: string, railwayData: RailwayMap, strictMode = true) => {
Expand Down
11 changes: 5 additions & 6 deletions src/pages/TripsPage.tsx
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Expand Up @@ -172,12 +172,10 @@ export const TripsPage: React.FC = () => {
if (isWalk) {
let startName = trip.fromId || '';
let endName = trip.toId || '';
Object.values(railwayData).forEach(line => {
const s = line.stations.find(st => st.id === trip.fromId);
if (s) startName = s.name_ja;
const e = line.stations.find(st => st.id === trip.toId);
if (e) endName = e.name_ja;
});
const s = getStationById(railwayData, trip.fromId);
if (s) startName = s.name_ja;
const e = getStationById(railwayData, trip.toId);
if (e) endName = e.name_ja;

const isTree = trip.walkType === 'tree';
const cls = {
Expand Down Expand Up @@ -288,6 +286,7 @@ export const TripsPage: React.FC = () => {
};

import { ArrowUp, ArrowDown } from 'lucide-react';
import { getStationById } from '../core/railwayRouting';

export const FloatingActionButtons: React.FC<{
fileInputRef: React.RefObject<HTMLInputElement>,
Expand Down