Create search index cache and return more meta

src/reader.js

@@ -1,10 +1,12 @@
 'use strict';
 
 import fs from 'node:fs';
+import path from 'node:path';
 import {decompress as lzmaDecompress} from 'lzma1';
 import {ZstdCodec} from 'zstd-codec';
 import {fuzzyMatch, titleFromUrl} from './utils.js';
 
+const INDEX_VERSION = 1;
 const HEADER_SIZE = 80;
 const NS_CONTENT = 'C';
 const NS_METADATA = 'M';
@@ -32,6 +34,7 @@ export class ZimReader {
 	#header = null;
 	#mimeTypes = [];
 	#hasTitleListing = false;
+	#index;
 
 	get articleCount() { return this.#header?.articleCount ?? 0; }
 
@@ -86,6 +89,13 @@ export class ZimReader {
 		return data.subarray(readPtr(blobNumber), readPtr(blobNumber + 1));
 	}
 
+	async #icon(size = 48) {
+		const page = await this.readPage(`Illustration_${size}x${size}@1`, NS_METADATA)
+			|| await this.readPage('Favicon', NS_METADATA);
+		if (!page) return null;
+		return `data:${page.mimetype};base64,${page.data.toString('base64')}`;
+	}
+
 	async #ptr64(base, index) {
 		return Number((await this.#read(base + index * 8, 8)).readBigUInt64LE(0));
 	}
@@ -172,15 +182,89 @@ export class ZimReader {
 		return dirents;
 	}
 
+	/** Path of the cached word index, kept in an `index/` subdirectory next to the archive. */
+	#indexPath() {
+		return path.join(path.dirname(this.path), 'index', `${path.basename(this.path)}.idx.json`);
+	}
+
+	/** Builds (or loads a cached) word -> entry index, avoiding a re-scan on every search. */
+	async #wordIndex() {
+		if (this.#index) return this.#index;
+		const cachePath = this.#indexPath();
+		const stat = await fs.promises.stat(this.path);
+
+		if (fs.existsSync(cachePath)) {
+			try {
+				const cached = JSON.parse(await fs.promises.readFile(cachePath, 'utf8'));
+				// Rebuild if stale: index predates the archive's current mtime (e.g. a re-download).
+				if (cached.version === INDEX_VERSION && cached.mtimeMs >= stat.mtimeMs) {
+					return (this.#index = cached);
+				}
+			} catch {}
+		}
+
+		// Expensive full scan — only happens once per archive (or after it changes).
+		const dirents = await this.#allDirents();
+		const entries = [];
+		const words = new Map(); // word -> [entryIndex, ...]
+		for (const d of dirents) {
+			if (d.namespace !== NS_CONTENT) continue;
+			const idx = entries.length;
+			entries.push({url: d.url, title: d.title, mimetype: d.mimetype});
+			const text = `${d.title} ${titleFromUrl(d.url)}`.toLowerCase();
+			for (const w of text.split(/\W+/).filter(Boolean)) {
+				if (!words.has(w)) words.set(w, []);
+				words.get(w).push(idx);
+			}
+		}
+
+		const index = {version: INDEX_VERSION, size: stat.size, mtimeMs: stat.mtimeMs, entries, words: Object.fromEntries(words)};
+		await fs.promises.mkdir(path.dirname(cachePath), {recursive: true});
+		await fs.promises.writeFile(cachePath, JSON.stringify(index));
+		return (this.#index = index);
+	}
+
 	async close() {
 		if (this.#fd) await this.#fd.close();
 		this.#fd = null;
 	}
 
+	/** Deletes the zim archive and its cached index (if any). Safe to call on unopened readers. */
+	async delete() {
+		await this.close();
+		this.#index = null;
+		await fs.promises.rm(this.path, {force: true});
+		await fs.promises.rm(this.#indexPath(), {force: true});
+	}
+
 	/** Reads an 'M' namespace metadata value (e.g. Name, Date, Title). Returns null if missing. */
 	async metadata(key) {
-		const page = await this.readPage(key, NS_METADATA);
-		return page ? page.data.toString('utf8') : null;
+		const get = async key => {
+			const page = await this.readPage(key, NS_METADATA);
+			return page ? page.data.toString('utf8') : null;
+		};
+		if(key) return get(key);
+
+		const [title, creator, publisher, date, description, language, name, tags] = await Promise.all(
+			['Title', 'Creator', 'Publisher', 'Date', 'Description', 'Language', 'Name', 'Tags'].map(get)
+		);
+		return {
+			id: name,
+			title,
+			updated: date ? new Date(date) : null,
+			summary: description,
+			language,
+			name,
+			category: tags ? tags.split(';')[0] || '' : '',
+			tags: tags ? tags.split(';') : [],
+			mediaCount: 0,
+			author: creator,
+			publisher,
+			articleCount: this.articleCount,
+			sizeMb: ((await fs.promises.stat(this.path)).size / 1024 / 1024).toFixed(1),
+			href: null,
+			icon: await this.#icon(),
+		};
 	}
 
 	/** Opens the archive and parses its header + mimetype list. */
@@ -219,24 +303,29 @@ export class ZimReader {
 		const termList = String(terms).split(',').map(t => t.trim()).filter(Boolean);
 		if (!termList.length) return [];
 
-		const candidates = (this.#hasTitleListing && this.#header.articleCount > 5000)
-			? await this.#titleIndexCandidates(termList[0])
-			: await this.#allDirents();
+		let candidates;
+		if (this.#hasTitleListing && this.#header.articleCount > 5000) {
+			candidates = await this.#titleIndexCandidates(termList[0]);
+		} else {
+			const {entries, words} = await this.#wordIndex();
+			// Pull candidates from postings of any word that starts with (or contains) the search term.
+			const q = termList[0].toLowerCase();
+			const idxSet = new Set();
+			for (const [word, postings] of Object.entries(words)) {
+				if (word.includes(q) || q.includes(word)) postings.forEach(i => idxSet.add(i));
+			}
+			candidates = [...idxSet].map(i => ({...entries[i], namespace: NS_CONTENT}));
+		}
 
 		const scored = [];
 		for (const dirent of candidates) {
-			if (dirent.namespace !== NS_CONTENT) continue;
 			if (htmlOnly && !(this.#mimeTypes[dirent.mimetype] || '').startsWith('text/html')) continue;
 			const urlTitle = titleFromUrl(dirent.url);
 			const titleScore = fuzzyMatch(dirent.title, ...termList).max;
 			const urlScore = fuzzyMatch(urlTitle, ...termList).max;
-			scored.push({
-				url: dirent.url,
-				title: dirent.title.length > urlTitle.length ? dirent.title : urlTitle,
-				namespace: dirent.namespace,
-				score: Math.max(titleScore, urlScore)
-			});
+			scored.push({url: dirent.url, title: dirent.title.length > urlTitle.length ? dirent.title : urlTitle, namespace: NS_CONTENT, score: Math.max(titleScore, urlScore)});
 		}
-		return scored.filter(a => a.score > 0).toSorted((a, b) => b.score - a.score).slice(0, limit);
+		const {id, summary, mediaCount, articleCount, sizeMb, href, ...meta} = await this.metadata();
+		return scored.filter(a => a.score > 0).toSorted((a, b) => b.score - a.score).slice(0, limit).map(a => ({...meta, ...a}));
 	}
 }