// Background wiring for code pairing.
//
// Keeps `code-pairing.ts` a PURE, dependency-injected client (so its unit tests
// run without chrome / vault / WebSocket). This module supplies the production
// `CodePairingDeps` and the single-flight SAS/confirm round-trip that bridges
// the blocking `confirm(sas)` callback to the popup via runtime messages:
//
//   PAIR_WITH_CODE    → startCodePairing()            (popup → bg, messages.ts)
//   CODE_PAIR_SAS     ← push when onSasReady fires    (bg → popup)
//   CODE_PAIR_CONFIRM → resolveCodePairingConfirm()   (popup → bg, messages.ts)
//   CODE_PAIR_RESULT  ← push on complete/error        (bg → popup)

import {
  pairWithCode,
  type CodePairingDeps,
  type CodePairingCallbacks,
} from "./code-pairing";
import { openPairingSocket } from "../shared/pairing-dial";
import { upsertPairedDevice, setLastKnownIp } from "./paired-devices";
import { buildLocalIdentity } from "./chirp-identity";
import { computeVaultId } from "../shared/sync-identity";
import { isUnlocked, getRootKeyHex } from "./vault";
import { probeSubnetForPort, wsPortOpen } from "./desktop-pairing-probe";
import { discoverPeachSync } from "./desktop-pairing-mdns";
import { getLocalSubnet } from "../shared/local-network";
import type { LocalIdentity } from "../shared/chirp-handshake";

function hexToBytesLocal(hex: string): Uint8Array {
  const out = new Uint8Array(hex.length / 2);
  for (let i = 0; i < out.length; i++) out[i] = parseInt(hex.slice(i * 2, i * 2 + 2), 16);
  return out;
}

/** Best-effort push to the popup. The popup may be closed — pushes are advisory. */
function push(type: string, payload: unknown): void {
  try {
    const maybe = chrome.runtime.sendMessage({ type, payload }) as unknown;
    if (maybe && typeof (maybe as Promise<unknown>).catch === "function") {
      (maybe as Promise<unknown>).catch(() => undefined);
    }
  } catch {
    // Popup closed / no receiver — fine.
  }
}

/** Production dependency set — real probe, WebSocket, identity, and storage. */
export function productionCodePairingDeps(): CodePairingDeps {
  return {
    async findHost(port) {
      // Localhost first: peach-sync runs on the same machine as the extension.
      // This works in every browser without mDNS or WebRTC, and is the fastest
      // path. The daemon binds 0.0.0.0 so 127.0.0.1 is always reachable.
      if (await wsPortOpen("127.0.0.1", port, 800)) return "127.0.0.1";
      // mDNS next — instant when chrome.mdns is available (Chrome/Chromium).
      const discovered = await discoverPeachSync();
      if (discovered && (await wsPortOpen(discovered.ip, port, 800))) return discovered.ip;
      // Fallback: /24 subnet probe (Firefox, Chrome without mDNS, or a stale hit).
      const subnet = await getLocalSubnet();
      if (!subnet) return null;
      return probeSubnetForPort(subnet, port);
    },
    openSocket: (ip, port) => openPairingSocket(ip, port),
    async getLocalIdentity(): Promise<LocalIdentity> {
      if (!isUnlocked()) throw new Error("vault_locked");
      const masterKeyHex = getRootKeyHex();
      if (!masterKeyHex) throw new Error("vault_locked");
      // SEV-2-B: derive from the stable ROOT key so pairing survives a
      // master-password change. Zero the copy when done.
      const masterKey = hexToBytesLocal(masterKeyHex);
      try {
        const base = await buildLocalIdentity(masterKey);
        const vaultId = await computeVaultId(masterKey);
        return { ...base, vaultId };
      } finally {
        masterKey.fill(0);
      }
    },
    persistDevice: (d) => upsertPairedDevice(d),
    cacheLastKnownIp: (pubkeyHex, ip) => setLastKnownIp(pubkeyHex, ip),
  };
}

// ── Single in-flight pairing per worker ──────────────────────────────────────
// One pairing at a time. The blocking confirm() resolver is parked here while
// the popup shows the SAS; CODE_PAIR_CONFIRM resolves it.
let pendingConfirm: ((confirmed: boolean) => void) | null = null;
let inFlight = false;

function clearPairingState(): void {
  pendingConfirm = null;
  inFlight = false;
}

export function isCodePairingInFlight(): boolean {
  return inFlight;
}

/**
 * Kick off a code pairing. Returns immediately; the SAS and the terminal
 * result are delivered to the popup as CODE_PAIR_SAS / CODE_PAIR_RESULT
 * pushes. `deps` is injectable for tests.
 */
export function startCodePairing(
  code: string,
  deps: CodePairingDeps = productionCodePairingDeps(),
): void {
  inFlight = true;
  const cb: CodePairingCallbacks = {
    onSasReady: (sas) => push("CODE_PAIR_SAS", { sas }),
    onComplete: (device) => {
      push("CODE_PAIR_RESULT", { status: "complete", device });
      clearPairingState();
    },
    onError: (error) => {
      push("CODE_PAIR_RESULT", { status: "error", error });
      clearPairingState();
    },
  };
  // The confirm callback blocks on the popup's CODE_PAIR_CONFIRM reply.
  const confirm = (_sas: string): Promise<boolean> =>
    new Promise<boolean>((resolve) => { pendingConfirm = resolve; });

  void pairWithCode(code, cb, deps, confirm).finally(() => {
    // onComplete/onError already cleared state; this is the backstop for an
    // unexpected throw that skipped the callbacks.
    if (inFlight) clearPairingState();
  });
}

/** Resolve the parked confirm() with the user's decision from the popup. */
export function resolveCodePairingConfirm(confirmed: boolean): void {
  const resolve = pendingConfirm;
  pendingConfirm = null;
  if (resolve) resolve(confirmed);
}