import { type Counter, type Histogram, metrics } from "@opentelemetry/api";

/**
 * Bundle of OpenTelemetry instruments emitted by the banking plugin.
 *
 * - `banksTotal{op}` — bank lifecycle transitions. `op ∈
 *   "create" | "soft-delete" | "update"`.
 * - `accountsTotal{op}` — account lifecycle transitions. `op ∈
 *   "create" | "delete" | "update" | "status-change"`.
 * - `transfersTotal{outcome}` — `transferFunds` call counter.
 *   `outcome ∈ "success" | "insufficient_funds" | "error"`.
 * - `transferAmount` — histogram of transfer amounts (units: currency
 *   minor units, treated as a unitless float for genericity).
 * - `fundOperationsTotal{op,outcome}` — `addFunds` / `subtractFunds`.
 *   `op ∈ "add" | "subtract"`, `outcome ∈ "success" | "error" |
 *   "insufficient_funds"`.
 * - `queryDurationMs{op}` — histogram of repository query wall-clock
 *   duration in ms, partitioned by op (`"bank.list"`, `"account.list"`,
 *   `"transfer"`, etc.).
 */
export interface BankingInstruments {
    readonly banksTotal: Counter;
    readonly accountsTotal: Counter;
    readonly transfersTotal: Counter;
    readonly transferAmount: Histogram;
    readonly fundOperationsTotal: Counter;
    readonly queryDurationMs: Histogram;
}

let cached: BankingInstruments | undefined;

/**
 * Lazily build (and cache) the banking instruments bundle against the
 * current global `MeterProvider`. Call {@link resetBankingInstruments}
 * in test setup to force a re-bind against a freshly-installed
 * provider.
 */
export function getBankingInstruments(): BankingInstruments {
    if (cached !== undefined) return cached;
    const meter = metrics.getMeter("@suaveplan/api-plugin-banking");
    cached = {
        banksTotal: meter.createCounter("banking.banks_total", {
            description:
                "Total bank lifecycle transitions, partitioned by op label",
        }),
        accountsTotal: meter.createCounter("banking.accounts_total", {
            description:
                "Total bank-account lifecycle transitions, partitioned by op label",
        }),
        transfersTotal: meter.createCounter("banking.transfers_total", {
            description:
                "Total transferFunds() calls, partitioned by outcome label",
        }),
        transferAmount: meter.createHistogram("banking.transfer_amount", {
            description:
                "Histogram of transfer amounts (unitless float; treat as minor currency units)",
        }),
        fundOperationsTotal: meter.createCounter(
            "banking.fund_operations_total",
            {
                description:
                    "Total addFunds/subtractFunds calls, partitioned by op + outcome",
            }
        ),
        queryDurationMs: meter.createHistogram("banking.query_duration_ms", {
            description:
                "Wall-clock duration of banking repository queries in ms",
            unit: "ms",
        }),
    };
    return cached;
}

/**
 * Drop the cached instrument bundle so the next
 * {@link getBankingInstruments} call rebinds against the global
 * `MeterProvider` in effect at that point. Tests call this after
 * installing a fresh `MeterProvider`.
 */
export function resetBankingInstruments(): void {
    cached = undefined;
}