// Ported from filius-ipad (GPLv2/GPLv3):
//   State/TopologyNetworkRuntimeEngine.swift (packet trace model)
// Java counterpart: filius.rahmenprogramm.nachrichten.Lauscher — here every
// step a frame or packet takes is one trace event; the packet viewer groups them.

import type { Id } from '../ids.js';

export type TraceDirection = 'inbound' | 'outbound' | 'local';

export type TraceLayer = 'application' | 'transport' | 'network' | 'dataLink' | 'physical';

export type TraceOperation =
  | 'created'
  | 'sent'
  | 'received'
  | 'forwarded'
  | 'accepted'
  | 'dropped'
  | 'rewritten'
  | 'retransmitted'
  | 'compatibilityAdapter';

export interface HeaderField {
  readonly name: string;
  readonly value: string;
}

export interface TraceEvent {
  readonly id: number;
  readonly timeMilliseconds: number;
  readonly frameIdentity?: number;
  readonly packetIdentity?: number;
  readonly nodeId: Id;
  readonly interfaceId?: Id;
  readonly direction: TraceDirection;
  readonly layer: TraceLayer;
  readonly operation: TraceOperation;
  readonly beforeHeaders: readonly HeaderField[];
  readonly afterHeaders: readonly HeaderField[];
  readonly detail?: string;
}

/** How many trace events the runtime keeps, and how many it drops at once when full. */
export interface TraceRetentionPolicy {
  readonly maximumEventCount: number;
  readonly evictionBatchSize: number;
}

export function traceRetentionPolicy(maximumEventCount: number, evictionBatchSize: number): TraceRetentionPolicy {
  if (!(maximumEventCount > 0)) throw new RangeError('Packet-trace retention must keep at least one event');
  if (!(evictionBatchSize > 0)) throw new RangeError('Packet-trace eviction must remove at least one event');
  if (evictionBatchSize > maximumEventCount) {
    throw new RangeError('Packet-trace eviction cannot exceed the retention limit');
  }
  return { maximumEventCount, evictionBatchSize };
}

export const PRODUCTION_TRACE_RETENTION = traceRetentionPolicy(10_000, 1_000);