// What tools/java-oracle's DhcpRun and TcpRun recorded in Java FILIUS
// (<name>.java.json: every frame each card saw, FILIUS' own packet log), and
// the same view of an engine run: each frame when it first shows on any
// host's card, as a line of text. Shared by dhcpJava.test.ts and
// tcpJava.test.ts.
//
// Not only the frames of one card: FILIUS' log misses the DISCOVER of the
// DHCP client that sends second when two start together (measured in four of
// four runs of dhcp-lan; the server receives it) — a fault of the log, not of
// the network. Java logs no frame identity; the same text within
// DUPLICATE_WINDOW_MILLISECONDS is one frame (measured: a frame reaches the
// last card within some 130 ms; the closest two distinct frames of the same
// text are the DISCOVERs around a DECLINE, some 520 ms apart).
//
// Java runs on threads in real time, at the default speed of 90 % (55 ms a
// cable, a round trip time of 2750 ms). Its gaps match the engine's within a
// few milliseconds; where they do not, it is Java's threads (a sender blocked
// by a busy cable wakes late, up to some 110 ms measured), the log's lost
// DISCOVER above, or a story whose calls the engine makes one after the
// other. A gap may differ by GAP_TOLERANCE_MILLISECONDS; a wrong round trip
// time (250 ms) may not. A cable carries one frame after the other in both
// (engine.test.ts checks that: one cable's delay is below this tolerance).

import { NetworkRuntimeEngine, TCP_FLAG, type EthernetFrame } from '../src/index.js';
import { snapshotOf, type Scenario } from './scenario.js';

export const GAP_TOLERANCE_MILLISECONDS = 120;
const DUPLICATE_WINDOW_MILLISECONDS = 300;

export interface JavaFrame {
  time: number;
  source: string;
  destination: string;
  arp?: number;
  senderIp?: string;
  targetIp?: string;
  sourceIp?: string;
  destinationIp?: string;
  protocol?: number;
  sourcePort?: number;
  destinationPort?: number;
  payload?: string | null;
  icmp?: number;
  tcpFlags?: string;
  sequence?: number;
  acknowledgement?: number;
}

export interface SeenFrame {
  readonly time: number;
  readonly text: string;
}

function javaText(frame: JavaFrame): string {
  const macs = `${frame.source} > ${frame.destination}`.toUpperCase();
  if (frame.arp !== undefined) return `${macs} ARP ${frame.arp === 1 ? 'request' : 'reply'} ${frame.senderIp} > ${frame.targetIp}`;
  if (frame.icmp !== undefined) return `${macs} ICMP ${frame.icmp}`;
  const ends = `${frame.sourceIp}:${frame.sourcePort} > ${frame.destinationIp}:${frame.destinationPort}`;
  if (frame.tcpFlags !== undefined) {
    return `${macs} TCP ${ends} ${frame.tcpFlags || '-'} seq=${frame.sequence} ack=${frame.acknowledgement} length=${(frame.payload ?? '').length}`;
  }
  return `${macs} UDP ${ends} ${frame.payload}`;
}

/** The ICMP type numbers Java logs. */
const ICMP_TYPES: Record<string, number> = {
  echoReply: 0,
  destinationNetworkUnreachable: 3,
  destinationHostUnreachable: 3,
  echoRequest: 8,
  timeExceeded: 11,
};

const FLAG_LETTERS: [number, string][] = [
  [TCP_FLAG.synchronize, 'S'],
  [TCP_FLAG.acknowledgement, 'A'],
  [TCP_FLAG.finish, 'F'],
  [TCP_FLAG.push, 'P'],
  [TCP_FLAG.reset, 'R'],
];

function engineText(frame: EthernetFrame): string {
  const macs = `${frame.sourceMacAddress} > ${frame.destinationMacAddress}`.toUpperCase();
  if (frame.payload.kind === 'arp') {
    const arp = frame.payload.packet;
    return `${macs} ARP ${arp.operation} ${arp.senderIPAddress} > ${arp.targetIPAddress}`;
  }
  const packet = frame.payload.packet;
  if (packet.payload.kind === 'icmp') return `${macs} ICMP ${ICMP_TYPES[packet.payload.message.kind]}`;
  if (packet.payload.kind === 'tcp') {
    const segment = packet.payload.segment;
    const flags = FLAG_LETTERS.filter(([bit]) => (segment.flags & bit) !== 0).map(([, letter]) => letter).join('');
    return `${macs} TCP ${packet.senderIPAddress}:${segment.sourcePort} > ${packet.receiverIPAddress}:${segment.destinationPort} ${flags || '-'} seq=${segment.sequenceNumber} ack=${segment.acknowledgementNumber} length=${segment.payload.length}`;
  }
  const datagram = packet.payload.datagram;
  return `${macs} UDP ${packet.senderIPAddress}:${datagram.sourcePort} > ${packet.receiverIPAddress}:${datagram.destinationPort} ${new TextDecoder().decode(datagram.payload)}`;
}

/** A started engine on the scenario's network whose frames can be read afterwards as FILIUS logs them. */
export function watchedEngine(scenario: Scenario) {
  const engine = new NetworkRuntimeEngine(scenario.seed);
  const framesByIdentity = new Map<number, EthernetFrame>();
  const send = engine.sendEthernetFrame.bind(engine);
  engine.sendEthernetFrame = (fromNodeId, outgoingPortId, frame) => {
    framesByIdentity.set(frame.identity, frame);
    send(fromNodeId, outgoingPortId, frame);
  };
  engine.handle({ type: 'start', snapshot: snapshotOf(scenario), seed: scenario.seed, initialTimeMilliseconds: 0 });

  /** Every frame when it first shows on a host's card (sent, or received). */
  const frames = (): SeenFrame[] => {
    const hosts = new Set(scenario.nodes.filter((node) => node.kind !== 'networkSwitch').map((node) => node.id));
    const firstSeen = new Map<number, SeenFrame>();
    for (const event of engine.state.packetTraces) {
      if (event.layer !== 'physical' || !hosts.has(event.nodeId) || event.frameIdentity === undefined) continue;
      if (!((event.direction === 'outbound' && event.operation === 'sent') || (event.direction === 'inbound' && event.operation === 'received'))) {
        continue;
      }
      if (firstSeen.has(event.frameIdentity)) continue;
      firstSeen.set(event.frameIdentity, { time: event.timeMilliseconds, text: engineText(framesByIdentity.get(event.frameIdentity)!) });
    }
    return [...firstSeen.values()];
  };
  return { engine, frames };
}

/** Java's frames of all cards, each once: the same text within the window is the same frame. */
export function javaFrames(framesByNode: Record<string, JavaFrame[]>): SeenFrame[] {
  const all = Object.values(framesByNode)
    .flat()
    .map((frame) => ({ time: frame.time, text: javaText(frame) }))
    .sort((lhs, rhs) => lhs.time - rhs.time);
  const frames: SeenFrame[] = [];
  for (const frame of all) {
    if (frames.some((each) => each.text === frame.text && frame.time - each.time <= DUPLICATE_WINDOW_MILLISECONDS)) continue;
    frames.push(frame);
  }
  return frames;
}

/** Consecutive frames: the text, and the time since the one before. */
export function gaps(frames: readonly SeenFrame[]) {
  return frames.map((frame, index) => ({ text: frame.text, gap: index === 0 ? 0 : frame.time - frames[index - 1]!.time }));
}