import type { TenantId } from "@suaveplan/api-types/tenant";
import { SSE_BUN_CODES, SseBunError } from "../error-codes/error-codes.js";

/**
 * Per-tenant connection counter the engine consults on every handshake.
 *
 * Implementations expose `tryAcquire(tenantId)` (returns `true` and
 * increments on success, throws {@link SSE_BUN_CODES.TENANT_CAP_EXCEEDED}
 * on cap breach) plus `release(tenantId)` called on graceful close.
 */
export interface TenantConnectionCap {
    tryAcquire(tenantId: TenantId): true;
    release(tenantId: TenantId): void;
    count(tenantId: TenantId): number;
    readonly total: number;
}

/**
 * Build a tenant cap with the given per-tenant ceiling.
 */
export function createTenantConnectionCap(
    maxConnectionsPerTenant: number
): TenantConnectionCap {
    const counts = new Map<TenantId, number>();
    let total = 0;
    return {
        tryAcquire(tenantId): true {
            const current = counts.get(tenantId) ?? 0;
            if (current >= maxConnectionsPerTenant) {
                throw new SseBunError(
                    SSE_BUN_CODES.TENANT_CAP_EXCEEDED,
                    "error.sse_bun.tenant_cap_exceeded",
                    {
                        context: {
                            tenantId,
                            limit: maxConnectionsPerTenant,
                            current,
                        },
                    }
                );
            }
            counts.set(tenantId, current + 1);
            total += 1;
            return true;
        },
        release(tenantId): void {
            const current = counts.get(tenantId) ?? 0;
            if (current <= 1) {
                counts.delete(tenantId);
            } else {
                counts.set(tenantId, current - 1);
            }
            total = Math.max(0, total - 1);
        },
        count(tenantId): number {
            return counts.get(tenantId) ?? 0;
        },
        get total() {
            return total;
        },
    };
}