mirror of
https://github.com/orangecoding/fredy.git
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d43c5b3f97
* init map view * switching off 3d buildings when sattelite view is on * rename menu items * upgrading dependencies, adding provider to popups * adding screenshot for map view * fixing readme * next release version
100 lines
3.5 KiB
JavaScript
100 lines
3.5 KiB
JavaScript
/*
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* Copyright (c) 2026 by Christian Kellner.
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* Licensed under Apache-2.0 with Commons Clause and Attribution/Naming Clause
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*/
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/**
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* Similarity cache
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*
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* Maintains an in-memory Set of content hashes to detect whether a listing
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* (identified by a tuple of title, price and address) has been seen before.
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*
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* Design notes:
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* - The cache is refreshed periodically from persistent storage. To avoid
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* modification-during-iteration issues, the refresh builds a new Set and
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* atomically swaps the reference instead of mutating in place.
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* - Hashing ignores null/undefined values but preserves falsy-yet-valid values
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* like 0. Non-string values are coerced to strings before hashing.
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*
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* This module has no persistence of its own; it relies on
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* getAllEntriesFromListings() for data hydration.
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* @module similarityCache
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*/
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import crypto from 'crypto';
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import { getAllEntriesFromListings } from '../storage/listingsStorage.js';
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/** @type {number} Refresh interval in milliseconds (defaults to one hour). */
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const reloadCycle = 60 * 60 * 1000; // every hour, refresh
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/**
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* Internal cache of content hashes for known listings.
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*
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* Each entry is an SHA-256 hex digest produced by toHash(title, price, address).
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* @type {Set<string>}
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*/
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let cache = new Set();
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export const startSimilarityCacheReloader = () => {
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// Periodically refresh the cache from storage
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setInterval(() => {
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initSimilarityCache();
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}, reloadCycle);
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};
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/**
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* Initialize or refresh the similarity cache from persistent storage.
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*
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* Reads all stored listings via getAllEntriesFromListings(), computes a hash for
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* each, and swaps the in-memory Set atomically to avoid in-place mutations that
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* could interfere with concurrent iteration.
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*
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* This function is idempotent and safe to call at any time.
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* @returns {void}
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*/
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export const initSimilarityCache = () => {
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const allEntries = getAllEntriesFromListings();
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const newCache = new Set();
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for (const entry of allEntries) {
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newCache.add(toHash(entry?.title, entry?.price, entry?.address));
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}
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// Atomic swap to avoid mutating the cache while it may be iterated elsewhere
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cache = newCache;
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};
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/**
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* Check if a listing is already known and add it to the cache if not.
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*
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* The listing is identified by the combination of its title, price and
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* address. Null/undefined fields are ignored during hashing. Falsy-but-valid
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* values (e.g., price 0) are preserved.
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*
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* @param {Object} params - Listing fields
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* @param {string|undefined|null} params.title - The listing title
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* @param {string|undefined|null} params.address - The listing address
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* @param {number|string|undefined|null} params.price - The listing price
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* @returns {boolean} true if the entry already existed in the cache (duplicate), otherwise false
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*/
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export const checkAndAddEntry = ({ title, address, price }) => {
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const hash = toHash(title, price, address);
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if (cache.has(hash)) {
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return true;
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}
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cache.add(hash);
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return false;
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};
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/**
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* Generate an SHA-256 hash from a list of input values.
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* Null or undefined values are ignored. Falsy but valid values like 0 are preserved.
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* Non-string values are coerced to strings prior to hashing.
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*
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* @param {...(string|number|null|undefined)} strings - Input values to hash
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* @returns {string} Hexadecimal hash
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*/
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function toHash(...strings) {
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const normalized = strings
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.filter((v) => v !== null && v !== undefined)
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.map((v) => (typeof v === 'string' ? v : String(v)));
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return crypto.createHash('sha256').update(normalized.join('|')).digest('hex');
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}
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