// Local-device identity helpers for the sync architecture.
//
// `deviceId` is a stable UUID v4 generated on first call and persisted in
// `chrome.storage.local`. It is deliberately device-local and must NOT roam:
// it is the only symmetry-breaker in the sync-identity HKDF (see PCH-01-004),
// so a shared id across profiles would collide derived sync keys.
//
// `deviceName` defaults to a short, friendly browser+OS description and
// can be overridden by the user from Settings → Sync.
//
// The local sync identity itself is derived deterministically from the
// vault master key (`deriveSyncIdentityKeypair`); the function below is a
// thin coordinator that pulls the master key out of `vault.ts` and exposes
// only the public half to callers that don't need to sign.

import {
  computeVaultId,
  deriveSyncIdentityKeypair,
  deriveSyncSigningKeypair,
  pubkeyToHex,
} from "../shared/sync-identity";
import type { LocalIdentity } from "../shared/pairing-handshake";
import type { DeviceType } from "../shared/sync-types";
import { getRootKeyHex, isUnlocked } from "./vault";

const DEVICE_ID_KEY = "peach_device_id";
const DEVICE_NAME_KEY = "peach_device_name";

export interface LocalDeviceIdentity {
  deviceId: string;
  deviceName: string;
  deviceType: DeviceType;
  longTermPublicKeyHex: string;
  signingPublicKeyHex: string;
}

export async function getOrCreateDeviceId(): Promise<string> {
  // PCH-01-004: deviceId is the ONLY symmetry-breaker in the sync-identity HKDF
  // (sync-identity.ts:54). It must NOT roam across profiles via chrome.storage.sync,
  // or two profiles on the same browser account sharing a vault derive identical
  // static + signing keys and collide in the device graph. Keep it device-local.
  const local = await chrome.storage.local.get(DEVICE_ID_KEY);
  const localId = (local as Record<string, unknown>)[DEVICE_ID_KEY];
  if (typeof localId === "string" && localId.length > 0) return localId;

  const fresh = generateUuidV4();
  await chrome.storage.local.set({ [DEVICE_ID_KEY]: fresh });
  return fresh;
}

/** Replace a copied profile identity after an authenticated peer detects a collision. */
export async function rotateDeviceId(): Promise<string> {
  const fresh = generateUuidV4();
  await chrome.storage.local.set({ [DEVICE_ID_KEY]: fresh });
  return fresh;
}

export async function getDeviceName(): Promise<string> {
  const result = await chrome.storage.sync.get(DEVICE_NAME_KEY);
  const stored = (result as Record<string, unknown>)[DEVICE_NAME_KEY];
  if (typeof stored === "string" && stored.length > 0) return stored;
  return defaultDeviceName();
}

export async function setDeviceName(name: string): Promise<void> {
  const trimmed = name.trim();
  if (!trimmed) throw new Error("device name must not be empty");
  if (trimmed.length > 64) throw new Error("device name must be 64 chars or fewer");
  await chrome.storage.sync.set({ [DEVICE_NAME_KEY]: trimmed });
}

/**
 * Build the public-facing identity record for the local extension. The
 * private key half (used only for ongoing Noise KK sessions) is not
 * exposed by this function — Phase-1 pairing uses ephemeral keys only.
 */
export async function buildLocalIdentity(
  masterKey: Uint8Array,
): Promise<LocalDeviceIdentity> {
  const deviceId = await getOrCreateDeviceId();
  const deviceName = await getDeviceName();
  const kp = deriveSyncIdentityKeypair(masterKey, deviceId);
  const signing = await deriveSyncSigningKeypair(masterKey, deviceId);
  return {
    deviceId,
    deviceName,
    deviceType: "extension",
    longTermPublicKeyHex: pubkeyToHex(kp.publicKey),
    signingPublicKeyHex: pubkeyToHex(signing.publicKeyRaw),
  };
}

/**
 * Return the local sync identity keypair (public and private). Reserved
 * for the Phase-2 WebSocket sync coordinator that runs in the background.
 * Never surface the private key over a message handler.
 */
export function deriveLocalSyncKeypair(masterKey: Uint8Array, deviceId: string) {
  return deriveSyncIdentityKeypair(masterKey, deviceId);
}

function defaultDeviceName(): string {
  // Best-effort browser + platform string. Avoids userAgent parsing — the
  // user can rename via Settings.
  const ua = (typeof navigator !== "undefined" ? navigator.userAgent : "") || "";
  if (/Firefox/i.test(ua)) return "Firefox";
  if (/Edg\//i.test(ua)) return "Edge";
  if (/Chrome/i.test(ua)) return "Chrome";
  if (/Safari/i.test(ua)) return "Safari";
  return "Browser";
}

function generateUuidV4(): string {
  // crypto.randomUUID is available in MV3 service workers and popup pages.
  // Falls back to manual assembly only if a runtime is missing it.
  if (typeof crypto !== "undefined" && typeof crypto.randomUUID === "function") {
    return crypto.randomUUID();
  }
  const bytes = new Uint8Array(16);
  crypto.getRandomValues(bytes as Uint8Array<ArrayBuffer>);
  bytes[6] = (bytes[6] & 0x0f) | 0x40;
  bytes[8] = (bytes[8] & 0x3f) | 0x80;
  const hex = Array.from(bytes, (b) => b.toString(16).padStart(2, "0")).join("");
  return `${hex.slice(0, 8)}-${hex.slice(8, 12)}-${hex.slice(12, 16)}-${hex.slice(16, 20)}-${hex.slice(20)}`;
}

/**
 * The full local pairing identity plus its sync keypair, derived from the
 * stable ROOT key so pairing survives a master-password change. Callers own
 * the returned key material and must zero it.
 *
 * Lived in `code-pairing-bg.ts` until LAN code pairing was retired
 * (docs/sync-lan-retirement.md); it was never LAN-specific.
 */
export async function getLocalPairingIdentity(): Promise<{
  identity: LocalIdentity;
  privateKey: Uint8Array;
  publicKey: Uint8Array;
}> {
  if (!isUnlocked()) throw new Error("vault_locked");
  const masterKeyHex = getRootKeyHex();
  if (!masterKeyHex) throw new Error("vault_locked");
  const masterKey = new Uint8Array(masterKeyHex.length / 2);
  for (let i = 0; i < masterKey.length; i++) {
    masterKey[i] = parseInt(masterKeyHex.slice(i * 2, i * 2 + 2), 16);
  }
  try {
    const base = await buildLocalIdentity(masterKey);
    const vaultId = await computeVaultId(masterKey);
    const keys = deriveSyncIdentityKeypair(masterKey, base.deviceId);
    return {
      identity: { ...base, vaultId },
      privateKey: keys.secretKey,
      publicKey: keys.publicKey,
    };
  } finally {
    masterKey.fill(0);
  }
}