import * as SecureStore from "expo-secure-store";

import { authStoragePrefix, buildAccountId } from "@/lib/accounts";
import { normalizeSecureStoreKey } from "@/lib/secure-store-keys";

export const GUEST_AUTH_STORAGE_PREFIX = "beenvoice:guest";

const CHUNK_MARKER = "\u0001ba-chunks:";
const AUTH_STORAGE_SUFFIXES = ["_cookie", "_session_data", "_last_login_method"] as const;

function storageKeyForPrefix(prefix: string, suffix: (typeof AUTH_STORAGE_SUFFIXES)[number]) {
  return normalizeSecureStoreKey(`${prefix}${suffix}`);
}

async function copySecureStoreEntry(fromKey: string, toKey: string): Promise<void> {
  const value = await SecureStore.getItemAsync(fromKey);
  if (value == null) return;

  await SecureStore.setItemAsync(toKey, value);

  if (!value.startsWith(CHUNK_MARKER)) return;

  const count = Number(value.slice(CHUNK_MARKER.length));
  if (!Number.isInteger(count) || count < 1) return;

  for (let i = 0; i < count; i += 1) {
    const chunk = await SecureStore.getItemAsync(`${fromKey}.${i}`);
    if (chunk != null) {
      await SecureStore.setItemAsync(`${toKey}.${i}`, chunk);
    }
  }
}

export async function migrateAuthStorage(fromPrefix: string, toPrefix: string): Promise<void> {
  if (fromPrefix === toPrefix) return;

  await Promise.all(
    AUTH_STORAGE_SUFFIXES.map((suffix) =>
      copySecureStoreEntry(storageKeyForPrefix(fromPrefix, suffix), storageKeyForPrefix(toPrefix, suffix)),
    ),
  );
}

export async function clearAuthStorage(prefix: string): Promise<void> {
  await Promise.all(
    AUTH_STORAGE_SUFFIXES.map(async (suffix) => {
      const key = storageKeyForPrefix(prefix, suffix);
      const value = await SecureStore.getItemAsync(key);

      if (value?.startsWith(CHUNK_MARKER)) {
        const count = Number(value.slice(CHUNK_MARKER.length));
        if (Number.isInteger(count) && count > 0) {
          await Promise.all(
            Array.from({ length: count }, (_, index) =>
              SecureStore.deleteItemAsync(`${key}.${index}`),
            ),
          );
        }
      }

      await SecureStore.deleteItemAsync(key);
    }),
  );
}

/** Clears guest auth storage before signing into an additional account. */
export async function prepareForAdditionalSignIn(): Promise<void> {
  await clearAuthStorage(GUEST_AUTH_STORAGE_PREFIX);
}

export async function finalizeAuthenticatedAccount(input: {
  apiUrl: string;
  userId: string;
  email: string;
  name: string;
  activeAccountId: string | null;
  registerAccount: (input: {
    instanceUrl: string;
    userId: string;
    email: string;
    name: string;
  }) => Promise<unknown>;
}): Promise<void> {
  const accountId = buildAccountId(input.apiUrl, input.userId);
  const targetPrefix = authStoragePrefix(accountId);
  const sourcePrefix = input.activeAccountId
    ? authStoragePrefix(input.activeAccountId)
    : GUEST_AUTH_STORAGE_PREFIX;

  await migrateAuthStorage(sourcePrefix, targetPrefix);

  await input.registerAccount({
    instanceUrl: input.apiUrl,
    userId: input.userId,
    email: input.email,
    name: input.name,
  });
}