import { getDbInstance } from "./core.ts";
import type { SqliteAdapter } from "./adapters/types.ts";

/**
 * Total input+output tokens for the current calendar month, across BOTH storage legs:
 *
 * 1. `daily_usage_summary` — the rolled-up aggregate (filled only by the retention
 *    cleanup path rolling up rows OLDER than `retention.usageHistory`, default 365 days),
 *    so the current month's rows never appear here until ~a year later (or the operator
 *    lowers retention).
 * 2. `usage_history` — the live per-request rows (written by `saveRequestUsage` with
 *    `tokens_input`/`tokens_output` and an ISO `timestamp`), which hold the current month's
 *    actual usage.
 *
 * #10381: reading only leg 1 always returned ~0 for the current month. No double-count:
 * a row is rolled into `daily_usage_summary` only immediately before being deleted from
 * `usage_history` by the same cleanup step. The analytics layer uses the same
 * reconciliation in `buildUnifiedSource`.
 */
export function sumUsageTokensThisMonth(db: SqliteAdapter = getDbInstance()): number {
  try {
    const row = db
      .prepare(
        `SELECT
           COALESCE((
             SELECT SUM(tokens_input + tokens_output)
             FROM usage_history
             WHERE timestamp >= strftime('%Y-%m-01T00:00:00.000Z','now')
               AND timestamp < strftime('%Y-%m-01T00:00:00.000Z','now','+1 month')
           ), 0) +
           COALESCE((
             SELECT SUM(total_input_tokens + total_output_tokens)
             FROM daily_usage_summary
             WHERE date >= strftime('%Y-%m-01', 'now')
           ), 0) AS used`
      )
      .get() as { used: number } | undefined;
    return row?.used ?? 0;
  } catch {
    return 0; // table may not exist yet on a fresh install — treat as 0 used
  }
}