fluxer/fluxer_api/src/api/middleware/ProfileSubstringBlocklistCache.ts

// SPDX-License-Identifier: AGPL-3.0-or-later

import type {IKVProvider, IKVSubscription} from '@pkgs/kv_client/src/IKVProvider';
import {AdminRepository} from '../admin/AdminRepository';
import {BANNED_PROFILE_SUBSTRINGS_REFRESH_CHANNEL} from '../constants/ContentModeration';
import type {BannedProfileSubstringScope} from '../database/types/AdminArchiveTypes';
import {Logger} from '../Logger';
import {buildPhraseMatchForms, canonicalizeStoredPhrase} from '../utils/PhraseBlocklistNormalization';

type ProfileScope = BannedProfileSubstringScope;

const PROFILE_SCOPES: ReadonlyArray<ProfileScope> = ['username', 'global_name', 'nickname', 'bio', 'pronouns'];
const PROFILE_NAME_SCOPES = new Set<ProfileScope>(['username', 'global_name', 'nickname']);

interface ScopeMatchers {
	raw: Array<string>;
	words: Array<string>;
	compact: Array<string>;
	asciiWords: Array<string>;
	asciiCompact: Array<string>;
	rawSet: Set<string>;
}

function emptyMatchers(): ScopeMatchers {
	return {raw: [], words: [], compact: [], asciiWords: [], asciiCompact: [], rawSet: new Set()};
}

export class ProfileSubstringBlocklistCache {
	private byScope: Map<ProfileScope, ScopeMatchers> = new Map();
	private isInitialized = false;
	private adminRepository = new AdminRepository();
	private kvClient: IKVProvider | null = null;
	private kvSubscription: IKVSubscription | null = null;
	private subscriberInitialized = false;
	private messageHandler: ((channel: string) => void) | null = null;
	private consecutiveFailures = 0;
	private readonly maxConsecutiveFailures = 5;

	setRefreshSubscriber(kvClient: IKVProvider | null): void {
		this.kvClient = kvClient;
	}

	async initialize(): Promise<void> {
		if (this.isInitialized) return;
		await this.refresh();
		this.isInitialized = true;
		this.setupSubscriber();
	}

	private setupSubscriber(): void {
		if (this.subscriberInitialized || !this.kvClient) return;
		const subscription = this.kvClient.duplicate();
		this.kvSubscription = subscription;
		this.messageHandler = (channel: string) => {
			if (channel === BANNED_PROFILE_SUBSTRINGS_REFRESH_CHANNEL) {
				this.refresh().catch((err) => {
					this.consecutiveFailures++;
					const message = err instanceof Error ? err.message : String(err);
					if (this.consecutiveFailures >= this.maxConsecutiveFailures) {
						Logger.error({error: message}, 'Failed to refresh profile-substring blocklist cache after notification');
					} else {
						Logger.warn({error: message}, 'Failed to refresh profile-substring blocklist cache after notification');
					}
				});
			}
		};
		subscription
			.connect()
			.then(() => subscription.subscribe(BANNED_PROFILE_SUBSTRINGS_REFRESH_CHANNEL))
			.then(() => {
				if (this.messageHandler) {
					subscription.on('message', this.messageHandler);
				}
			})
			.catch((error) => {
				Logger.error({error}, 'Failed to subscribe to profile-substring blocklist refresh channel');
			});
		this.subscriberInitialized = true;
	}

	async refresh(): Promise<void> {
		const rows = await this.adminRepository.loadAllBannedProfileSubstrings();
		const next = new Map<ProfileScope, ScopeMatchers>();
		for (const scope of PROFILE_SCOPES) {
			next.set(scope, emptyMatchers());
		}
		for (const row of rows) {
			const scope = row.scope as ProfileScope;
			const matchers = next.get(scope);
			if (!matchers) continue;
			this.addToMatchers(matchers, row.substring);
		}
		this.byScope = next;
		this.consecutiveFailures = 0;
		Logger.debug(
			{counts: Object.fromEntries(Array.from(next.entries()).map(([k, v]) => [k, v.raw.length]))},
			'Profile-substring blocklist cache refreshed',
		);
	}

	private addToMatchers(matchers: ScopeMatchers, value: string): void {
		const canonical = canonicalizeStoredPhrase(value);
		if (!canonical || matchers.rawSet.has(canonical)) return;
		const forms = buildPhraseMatchForms(canonical);
		matchers.rawSet.add(forms.raw);
		matchers.raw.push(forms.raw);
		if (forms.words) matchers.words.push(forms.words);
		if (forms.compact) matchers.compact.push(forms.compact);
		if (forms.asciiWords) matchers.asciiWords.push(forms.asciiWords);
		if (forms.asciiCompact) matchers.asciiCompact.push(forms.asciiCompact);
	}

	containsBannedSubstring(scope: ProfileScope, text: string): boolean {
		if (!text) return false;
		const forms = buildPhraseMatchForms(text);
		const scopeMatchers = this.getMatchersForCheck(scope);
		return (
			this.matchAnyMatcher(forms.raw, scopeMatchers, (matchers) => matchers.raw) ||
			this.matchAnyMatcher(forms.words, scopeMatchers, (matchers) => matchers.words) ||
			this.matchAnyMatcher(forms.compact, scopeMatchers, (matchers) => matchers.compact) ||
			this.matchAnyMatcher(forms.asciiWords, scopeMatchers, (matchers) => matchers.asciiWords) ||
			this.matchAnyMatcher(forms.asciiCompact, scopeMatchers, (matchers) => matchers.asciiCompact)
		);
	}

	private getMatchersForCheck(scope: ProfileScope): Array<ScopeMatchers> {
		if (PROFILE_NAME_SCOPES.has(scope)) {
			return Array.from(PROFILE_NAME_SCOPES)
				.map((nameScope) => this.byScope.get(nameScope))
				.filter((matchers): matchers is ScopeMatchers => !!matchers && matchers.raw.length > 0);
		}
		const matchers = this.byScope.get(scope);
		return matchers && matchers.raw.length > 0 ? [matchers] : [];
	}

	private matchAnyMatcher(
		text: string,
		matchers: Array<ScopeMatchers>,
		getPhrases: (matchers: ScopeMatchers) => Array<string>,
	): boolean {
		if (!text || matchers.length === 0) return false;
		for (const matcher of matchers) {
			if (this.matchAny(text, getPhrases(matcher))) return true;
		}
		return false;
	}

	private matchAny(text: string, phrases: Array<string>): boolean {
		if (!text || phrases.length === 0) return false;
		for (const phrase of phrases) {
			if (text.includes(phrase)) return true;
		}
		return false;
	}

	add(scope: ProfileScope, substring: string): void {
		let matchers = this.byScope.get(scope);
		if (!matchers) {
			matchers = emptyMatchers();
			this.byScope.set(scope, matchers);
		}
		this.addToMatchers(matchers, substring);
	}

	remove(scope: ProfileScope, substring: string): void {
		const matchers = this.byScope.get(scope);
		if (!matchers) return;
		const canonical = canonicalizeStoredPhrase(substring);
		if (!canonical || !matchers.rawSet.has(canonical)) return;
		matchers.rawSet.delete(canonical);
		const rebuilt = emptyMatchers();
		for (const phrase of matchers.rawSet) {
			this.addToMatchers(rebuilt, phrase);
		}
		this.byScope.set(scope, rebuilt);
	}

	isSubstringBanned(scope: ProfileScope, substring: string): boolean {
		const canonical = canonicalizeStoredPhrase(substring);
		return !!canonical && this.getMatchersForCheck(scope).some((matchers) => matchers.rawSet.has(canonical));
	}

	resetForTesting(): void {
		this.shutdown();
		this.byScope = new Map();
		this.kvClient = null;
		this.subscriberInitialized = false;
		this.consecutiveFailures = 0;
		this.isInitialized = false;
	}

	shutdown(): void {
		if (this.kvSubscription && this.messageHandler) {
			this.kvSubscription.off('message', this.messageHandler);
		}
		if (this.kvSubscription) {
			this.kvSubscription.disconnect();
			this.kvSubscription = null;
		}
		this.messageHandler = null;
	}
}

export const profileSubstringBlocklistCache = new ProfileSubstringBlocklistCache();