import type { DB } from '../db/client.js';
export interface UsageCounterOptions {
    db: DB;
}
export declare class UsageCounter {
    readonly db: DB;
    constructor({ db }: UsageCounterOptions);
    /**
     * Record a usage event. `key` is an optional content identifier (e.g. the
     * verse you generated an image for) — useful for analytics and dedup.
     */
    record(whatsapp: string, feature: string, key?: string | null): Promise<boolean>;
    getDailyCount(whatsapp: string, feature: string): Promise<number>;
    getLifetimeCount(whatsapp: string, feature: string): Promise<number>;
    /**
     * Atomic check-and-record: if the user is under `dailyMax` for this feature,
     * record a usage event and return true. Otherwise return false.
     *
     * This is best-effort (D1 doesn't support row-level locks); two concurrent
     * calls could race past the cap by 1. For most chat apps that's acceptable.
     */
    tryRecordWithCap(whatsapp: string, feature: string, dailyMax: number, key?: string | null): Promise<boolean>;
    /**
     * @returns count of distinct users who used `feature` since `sinceHoursAgo` ago (default 24h).
     */
    distinctUsersSince(feature: string, { sinceHoursAgo }?: {
        sinceHoursAgo?: number;
    }): Promise<number>;
}
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