// The settings of a node's system software that the topology needs, read as
// Java FILIUS holds them after loading: a switch's SSID and learning time, a
// host's wireless SSID, a router's RIP switch, the manual routes, and the
// firewall of a router or home router.
// Java counterparts: filius.software.system.SwitchFirmware, Betriebssystem,
// VermittlungsrechnerBetriebssystem, GatewayFirmware, InternetKnotenBetriebssystem,
// filius.software.vermittlungsschicht.Weiterleitungstabelle,
// filius.software.firewall.Firewall and FirewallRule.
//
// Also DHCP (client switch and server settings), a home router's static NAT
// table (port forwarding) and a modem's connection settings.
// Java counterparts as well: filius.software.dhcp.DHCPServer, ModemFirmware.
//
// Checked against Java (corpus.java.json, `system`). File systems and
// applications are later layers.
//
// A router's firewall is one object its constructor makes and hangs in two
// places: the installed applications and the configuration plug-ins of its
// web server. XMLEncoder writes its settings wherever it meets it first —
// in the corpus, under the web server's `konfig` plug-in. The decoder does
// not know Java's constructors and sees a placeholder per path; they are
// merged here.

import { isJavaObject, isUnresolved, listItems, mapEntries, type JavaObject, type JavaValue } from './javabeans.js';
import type { FlsNodeClass } from './topology.js';

export interface FlsFirewallRule {
  srcIP: string | null;
  srcMask: string | null;
  destIP: string | null;
  destMask: string | null;
  /** A port, or -1 for all. */
  port: number;
  /** -1 all, 1 ICMP, 6 TCP, 17 UDP. */
  protocol: number;
  /** 0 drop, 1 accept. */
  action: number;
}

export interface FlsFirewall {
  activated: boolean;
  /** 0 drop, 1 accept. */
  defaultPolicy: number;
  dropICMP: boolean;
  filterSYNSegmentsOnly: boolean;
  filterUdp: boolean;
  rules: FlsFirewallRule[];
}

/** The settings of Java's DHCPServer under English names (Java's own: javaDhcpServer in the topology test). */
export interface FlsDhcpServer {
  isActive: boolean;
  lowerBound: string | null;
  upperBound: string | null;
  gateway: string | null;
  dnsServer: string | null;
  useOwnSettings: boolean;
  /** As Java keeps them after setStaticAssignedAddresses: MAC and IP of each entry. */
  staticAssignedAddresses: { mac: string; ip: string }[];
}

export interface FlsModem {
  /** 1 server, 2 client. */
  mode: number;
  port: number;
  /** Java's ipAdresse: the host a client modem connects to. */
  ipAddress: string | null;
}

export interface FlsSystemSoftware {
  /**
   * Switch: its SSID, undefined when the file has none (Java rolls one).
   * Rechner, Notebook: the wireless network it joins, null for none.
   */
  ssid?: string | null | undefined;
  /** Switch: how long it keeps a learned MAC address, in milliseconds. */
  retentionTime?: number;
  /** Vermittlungsrechner. */
  ripEnabled?: boolean;
  /** Every node with an IP stack: rows of destination, mask, gateway, interface address — as the file has them. */
  manualRoutes?: (string | null)[][];
  /** Vermittlungsrechner, Gateway. */
  firewall?: FlsFirewall;
  /** Every node with an IP stack: whether it asks a DHCP server for its address. */
  dhcpClient?: boolean;
  /** Every node with an IP stack. */
  dhcpServer?: FlsDhcpServer;
  /** Gateway: rows of protocol, public port, LAN address, LAN port — as the file has them. */
  staticNAT?: (string | null)[][];
  /** Modem. */
  modem?: FlsModem;
}

type Warn = (message: string) => void;

const FIREWALL_CLASS = 'filius.software.firewall.Firewall';
const WEB_SERVER_CLASS = 'filius.software.www.WebServer';

export function readSystemSoftware(device: JavaObject, javaClass: FlsNodeClass, warn: Warn): FlsSystemSoftware {
  const system = device.properties.get('systemSoftware');
  const software = isJavaObject(system) ? system : undefined;
  const value = (property: string) => software?.properties.get(property);
  const result: FlsSystemSoftware = {};

  switch (javaClass) {
    case 'Switch':
      result.ssid = optionalString(value('SSID'), 'SSID', warn);
      result.retentionTime = integer(value('retentionTime'), 300_000, 'retentionTime', warn);
      break;
    case 'Rechner':
    case 'Notebook':
      result.ssid = optionalString(value('ssid'), 'ssid', warn) ?? null;
      break;
    case 'Vermittlungsrechner':
      result.ripEnabled = boolean(value('ripEnabled'), false, 'ripEnabled', warn);
      break;
    case 'Gateway':
    case 'Modem':
      break;
  }
  if (javaClass !== 'Switch' && javaClass !== 'Modem') {
    result.manualRoutes = manualRoutes(value('weiterleitungstabelle'), warn);
    result.dhcpClient = boolean(value('DHCPKonfiguration'), false, 'DHCPKonfiguration', warn);
    result.dhcpServer = dhcpServer(value('DHCPServer'), warn);
  }
  if (javaClass === 'Gateway') result.staticNAT = rowsOfStrings(value('staticNAT'));
  if (javaClass === 'Modem') {
    result.modem = {
      mode: integer(value('mode'), 2, 'modem mode', warn),
      port: integer(value('port'), 12_345, 'modem port', warn),
      ipAddress: modemAddress(optionalString(value('ipAdresse'), 'modem ipAdresse', warn)),
    };
  }
  if (javaClass === 'Vermittlungsrechner' || javaClass === 'Gateway') {
    result.firewall = firewall(software, warn);
  }
  return result;
}

function manualRoutes(table: JavaValue | undefined, warn: Warn): (string | null)[][] {
  if (table === undefined || table === null) return [];
  if (!isJavaObject(table)) {
    warn(`weiterleitungstabelle is ${describe(table)}, ignored`);
    return [];
  }
  return rowsOfStrings(table.properties.get('manuelleTabelle'));
}

function modemAddress(value: string | null | undefined): string | null {
  return value === undefined ? 'localhost' : value;
}

/** A list of String arrays (routes, static NAT); anything but a string is null. */
function rowsOfStrings(list: JavaValue | undefined): (string | null)[][] {
  return listItems(list).map((row) => listItems(row).map((cell) => (typeof cell === 'string' ? cell : null)));
}

/** The DHCP server every IP stack's constructor makes: off, all addresses 0.0.0.0. */
function dhcpServer(server: JavaValue | undefined, warn: Warn): FlsDhcpServer {
  const at = (property: string) => (isJavaObject(server) ? server.properties.get(property) : undefined);
  const address = (property: string) => {
    const value = optionalString(at(property), `DHCPServer ${property}`, warn);
    return value === undefined ? '0.0.0.0' : value;
  };
  return {
    isActive: boolean(at('aktiv'), false, 'DHCPServer aktiv', warn),
    lowerBound: address('untergrenze'),
    upperBound: address('obergrenze'),
    gateway: address('gatewayip'),
    dnsServer: address('dnsserverip'),
    useOwnSettings: boolean(at('ownSettings'), false, 'DHCPServer ownSettings', warn),
    staticAssignedAddresses: staticAssignments(at('staticAssignedAddresses'), warn),
  };
}

/**
 * setStaticAssignedAddresses: each entry split at whitespace (StringUtils.split),
 * MAC and IP from the first two parts. An entry with fewer throws inside the
 * loop — XMLDecoder swallows it, and the entries after it are lost.
 */
function staticAssignments(list: JavaValue | undefined, warn: Warn): { mac: string; ip: string }[] {
  const result: { mac: string; ip: string }[] = [];
  for (const entry of listItems(list)) {
    const parts = typeof entry === 'string' ? javaWhitespaceSplit(entry) : [];
    if (parts.length < 2) {
      warn(`DHCPServer: static assignment ${describe(entry)} has no MAC and IP; Java stops reading here`);
      break;
    }
    result.push({ mac: parts[0]!, ip: parts[1]! });
  }
  return result;
}

/**
 * Character.isWhitespace: space, line and paragraph separators except the
 * no-break ones (U+00A0, U+2007, U+202F), and the controls TAB, LF, VT, FF,
 * CR, FS, GS, RS, US.
 */
const JAVA_WHITESPACE = /(?:(?![\u00A0\u2007\u202F])[\p{Zs}\p{Zl}\p{Zp}]|[\t\n\u000B\f\r\u001C-\u001F])+/u;

function javaWhitespaceSplit(text: string): string[] {
  return text.split(JAVA_WHITESPACE).filter((part) => part !== '');
}

/** Every object the file reaches the router's one firewall by. */
function firewallObjects(software: JavaObject | undefined): JavaObject[] {
  const found: JavaObject[] = [];
  const applications = new Map(mapEntries(software?.properties.get('installierteAnwendungen')));
  const installed = applications.get(FIREWALL_CLASS);
  if (isJavaObject(installed)) found.push(installed);
  const webServer = applications.get(WEB_SERVER_CLASS);
  if (isJavaObject(webServer)) {
    for (const [, plugin] of mapEntries(webServer.properties.get('plugins'))) {
      const pluginFirewall = isJavaObject(plugin) ? plugin.properties.get('firewall') : undefined;
      if (isJavaObject(pluginFirewall) && !found.includes(pluginFirewall)) found.push(pluginFirewall);
    }
  }
  return found;
}

/** The firewall as the router's constructor leaves it (off, drop), then the file's settings. */
function firewall(software: JavaObject | undefined, warn: Warn): FlsFirewall {
  const properties = new Map<string, JavaValue>();
  for (const object of firewallObjects(software)) {
    for (const [property, value] of object.properties) {
      if (properties.has(property) && properties.get(property) !== value) {
        warn(`firewall: ${property} is set in two places, the later one is used`);
      }
      properties.set(property, value);
    }
  }
  const at = (property: string) => properties.get(property);
  // setAllowRelatedPackets is the old name of setFilterSYNSegmentsOnly.
  const filterSyn = at('filterSYNSegmentsOnly') ?? at('allowRelatedPackets');
  return {
    activated: boolean(at('activated'), false, 'firewall activated', warn),
    defaultPolicy: integer(at('defaultPolicy'), 0, 'firewall defaultPolicy', warn),
    dropICMP: boolean(at('dropICMP'), false, 'firewall dropICMP', warn),
    filterSYNSegmentsOnly: boolean(filterSyn, true, 'firewall filterSYNSegmentsOnly', warn),
    filterUdp: boolean(at('filterUdp'), true, 'firewall filterUdp', warn),
    rules: listItems(at('ruleset')).flatMap((rule) => (isJavaObject(rule) ? [firewallRule(rule, warn)] : [])),
  };
}

/**
 * FirewallRule: public fields set one by one (`getField(name).set`), or the
 * seven-argument constructor. Defaults: all addresses empty, all ports, TCP,
 * drop.
 */
function firewallRule(rule: JavaObject, warn: Warn): FlsFirewallRule {
  const [srcIP, srcMask, destIP, destMask, port, protocol, action] = rule.args.length === 7 ? rule.args : [];
  const field = (name: string, fromConstructor: JavaValue | undefined) => rule.properties.get(name) ?? fromConstructor;
  const text = (name: string, fromConstructor: JavaValue | undefined) => {
    const value = field(name, fromConstructor) ?? '';
    if (typeof value === 'string' || value === null) return value;
    warn(`firewall rule: ${name} is ${describe(value)}, used ""`);
    return '';
  };
  return {
    srcIP: text('srcIP', srcIP),
    srcMask: text('srcMask', srcMask),
    destIP: text('destIP', destIP),
    destMask: text('destMask', destMask),
    port: integer(field('port', port), -1, 'firewall rule port', warn),
    protocol: integer(field('protocol', protocol), 6, 'firewall rule protocol', warn),
    action: integer(field('action', action), 0, 'firewall rule action', warn),
  };
}

function optionalString(value: JavaValue | undefined, name: string, warn: Warn): string | null | undefined {
  if (value === undefined || value === null || typeof value === 'string') return value;
  warn(`${name} is ${describe(value)}, ignored`);
  return undefined;
}

function boolean(value: JavaValue | undefined, fallback: boolean, name: string, warn: Warn): boolean {
  if (value === undefined) return fallback;
  if (typeof value === 'boolean') return value;
  warn(`${name} is ${describe(value)}, used ${fallback}`);
  return fallback;
}

function integer(value: JavaValue | undefined, fallback: number, name: string, warn: Warn): number {
  if (value === undefined) return fallback;
  if (typeof value === 'number' && Number.isInteger(value)) return value;
  warn(`${name} is ${describe(value)}, used ${fallback}`);
  return fallback;
}

function describe(value: JavaValue): string {
  if (isUnresolved(value)) return `unresolved (${value.reason})`;
  if (isJavaObject(value)) return `an object of ${value.className}`;
  return typeof value === 'bigint' ? `${value}` : JSON.stringify(value);
}