// DHCP as Java FILIUS runs it. tools/java-oracle's DhcpRun built each
// scenario's network in Java FILIUS, ran it and wrote what every network card
// saw (<name>.java.json). The engine runs the same network. For each DHCP
// client, the frames that concern it must come in the same order, with the
// same content, at about the same distance from each other (javaRun.ts), and
// every host must end with the same addresses.
//
// Java draws the link-local address with Math.random; it is compared as
// 169.254.1.x. Where several clients start together, which one is first
// varies in Java (the first thread pays for loading the classes); a client is
// therefore compared without the other clients' frames and the answers to
// them.

import { readdirSync, readFileSync } from 'node:fs';
import { dirname, join } from 'node:path';
import { fileURLToPath } from 'node:url';
import { describe, expect, it } from 'vitest';
import { stableMacAddress } from '../src/index.js';
import { expectSameCaptures, GAP_TOLERANCE_MILLISECONDS, javaFrames, watchedEngine, type JavaFrame, type SeenFrame, type JavaTables } from './javaRun.js';
import { type Scenario } from './scenario.js';

const scenarioDirectory = join(dirname(fileURLToPath(import.meta.url)), 'scenarios');

interface JavaRun extends JavaTables {
  frames: Record<string, JavaFrame[]>;
  devices: Record<string, [string, string, string, string]>;
}

const LINK_LOCAL = /169\.254\.1\.\d+/g;

/** The engine's run of the scenario's network, without its steps, for `milliseconds`. */
function runEngine(scenario: Scenario, milliseconds: number) {
  const { engine, frames } = watchedEngine(scenario);
  engine.handle({ type: 'advance', toMilliseconds: milliseconds });
  const devices = Object.fromEntries(
    [...engine.state.topologySnapshot.deviceConfigurations].map(([node, device]) => [
      node,
      [device.ipAddress, device.subnetMask, device.defaultGateway, device.dnsServer],
    ]),
  );
  return { engine, frames: frames(), devices };
}

/** Consecutive frames without the other clients' own: the text, and the time since the one before. */
function steps(frames: readonly SeenFrame[], otherClientMacs: readonly string[]) {
  const theirs = (frame: SeenFrame) =>
    otherClientMacs.some((mac) => frame.text.startsWith(`${mac} >`) || frame.text.includes(`chaddr=${mac}`));
  const own = frames.filter((frame) => !theirs(frame));
  return own.map((frame, index) => ({
    text: frame.text.replace(LINK_LOCAL, '169.254.1.x'),
    gap: index === 0 ? 0 : frame.time - own[index - 1]!.time,
  }));
}

function clientMac(scenario: Scenario, nodeId: string): string {
  const port = scenario.nodes.find((node) => node.id === nodeId)!.ports[0]!;
  return (port.mac ?? stableMacAddress(port.id)).toUpperCase();
}

const runs = readdirSync(scenarioDirectory)
  .filter((name) => name.startsWith('dhcp-') && name.endsWith('.java.json'))
  .map((name) => name.replace('.java.json', ''))
  .sort();

describe('DHCP as Java FILIUS runs it', () => {
  it('has Java runs', () => {
    expect(runs.length).toBeGreaterThan(0);
  });

  for (const name of runs) {
    it(name, () => {
      const scenario = JSON.parse(readFileSync(join(scenarioDirectory, `${name}.scenario.json`), 'utf8')) as Scenario;
      const java = JSON.parse(readFileSync(join(scenarioDirectory, `${name}.java.json`), 'utf8')) as JavaRun;
      const lastJavaFrame = Math.max(...Object.values(java.frames).flatMap((frames) => frames.map((frame) => frame.time)));
      const engine = runEngine(scenario, lastJavaFrame + 10_000);

      const clients = scenario.dhcpClients ?? [];
      for (const client of clients) {
        const others = clients.filter((each) => each !== client).map((each) => clientMac(scenario, each));
        const expected = steps(javaFrames(java.frames), others);
        const actual = steps(engine.frames, others);
        for (let index = 0; index < Math.max(expected.length, actual.length); index += 1) {
          expect(actual[index]?.text, `${client} frame #${index + 1}`).toBe(expected[index]?.text);
          expect(Math.abs(actual[index]!.gap - expected[index]!.gap), `${client} gap before frame #${index + 1}`).toBeLessThanOrEqual(
            GAP_TOLERANCE_MILLISECONDS,
          );
        }
      }
      // Each card's capture, with one client: of two that start together, Java's
      // log loses the DISCOVER of the one that sends second, and which sends
      // first varies (javaRun.ts).
      if (clients.length === 1) expectSameCaptures(engine.engine, scenario, java.frames, { text: (text) => text.replace(LINK_LOCAL, '169.254.1.x'), tables: java });
      const linkLocal = (devices: Record<string, string[]>) =>
        Object.fromEntries(Object.entries(devices).map(([node, device]) => [node, device.map((value) => value.replace(LINK_LOCAL, '169.254.1.x'))]));
      expect(linkLocal(engine.devices)).toEqual(linkLocal(java.devices));
    });
  }

  it('builds the MACs as DhcpRun does', () => {
    expect(stableMacAddress('00000000-0000-0000-0000-000000000112')).toBe('02:00:00:00:01:12');
  });
});