// Local-device identity helpers for the chirp-sync architecture.
//
// `deviceId` is a stable UUID v4 generated on first call and persisted in
// `chrome.storage.sync` so it roams across browser-profile reinstalls.
//
// `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 { deriveSyncIdentityKeypair, pubkeyToHex } from "../shared/sync-identity";
import type { DeviceType } from "../shared/sync-types";

const DEVICE_ID_KEY = "peach_chirp_device_id";
const DEVICE_NAME_KEY = "peach_chirp_device_name";

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

export async function getOrCreateDeviceId(): Promise<string> {
  const result = await chrome.storage.sync.get(DEVICE_ID_KEY);
  const current = (result as Record<string, unknown>)[DEVICE_ID_KEY];
  if (typeof current === "string" && current.length > 0) return current;
  const fresh = generateUuidV4();
  await chrome.storage.sync.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 XX sessions) is not
 * exposed by this function — Phase-1 pairing uses ephemeral keys only.
 */
export async function buildLocalIdentity(
  masterKey: Uint8Array,
): Promise<LocalChirpIdentity> {
  const deviceId = await getOrCreateDeviceId();
  const deviceName = await getDeviceName();
  const kp = deriveSyncIdentityKeypair(masterKey, deviceId);
  return {
    deviceId,
    deviceName,
    deviceType: extensionDeviceType(),
    longTermPublicKeyHex: pubkeyToHex(kp.publicKey),
  };
}

/**
 * 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 extensionDeviceType(): DeviceType {
  // The same module ships in both the Chrome extension and the Capacitor
  // mobile build. On Capacitor, Peach acts as an iOS / Android sync host
  // rather than an extension; the `isNativePlatform` check toggles the tag.
  try {
    const native = (globalThis as unknown as { Capacitor?: { isNativePlatform?: () => boolean } }).Capacitor;
    if (native?.isNativePlatform?.()) {
      const platform = (globalThis as unknown as { Capacitor?: { getPlatform?: () => string } }).Capacitor?.getPlatform?.();
      if (platform === "ios") return "ios";
      return "android";
    }
  } catch { /* not on Capacitor */ }
  return "extension";
}

function generateUuidV4(): string {
  // crypto.randomUUID is available in MV3 service workers, popup pages,
  // and modern Capacitor WebView. Falls back to a manual assembly only if
  // a runtime is missing it (effectively unreachable for our targets).
  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)}`;
}