import * as Crypto from "expo-crypto";
import * as SecureStore from "expo-secure-store";
import { storage } from "./mmkv";

const CREDENTIAL_KEY_PREFIX = "credential_";
const MULTI_ACCOUNT_MIGRATED_KEY = "multiAccountMigrated";

/**
 * Security type for saved accounts.
 */
export type AccountSecurityType = "none" | "pin" | "password";

/**
 * Credential stored in secure storage for a specific account.
 */
export interface ServerCredential {
  serverUrl: string;
  serverName: string;
  token: string;
  userId: string;
  username: string;
  savedAt: number;
  securityType: AccountSecurityType;
  pinHash?: string;
}

/**
 * Account summary stored in SavedServer for display in UI.
 */
export interface SavedServerAccount {
  userId: string;
  username: string;
  securityType: AccountSecurityType;
  savedAt: number;
}

/**
 * Local network configuration for automatic URL switching.
 */
export interface LocalNetworkConfig {
  localUrl: string;
  homeWifiSSIDs: string[];
  enabled: boolean;
}

/**
 * Server with multiple saved accounts.
 */
export interface SavedServer {
  address: string;
  name?: string;
  accounts: SavedServerAccount[];
  localNetworkConfig?: LocalNetworkConfig;
}

/**
 * Legacy interface for migration purposes.
 */
interface LegacySavedServer {
  address: string;
  name?: string;
  hasCredentials?: boolean;
  username?: string;
}

/**
 * Legacy credential interface for migration purposes.
 */
interface LegacyServerCredential {
  serverUrl: string;
  serverName: string;
  token: string;
  userId: string;
  username: string;
  savedAt: number;
}

/**
 * Encode server URL to valid secure store key (legacy, for migration).
 */
export function serverUrlToKey(serverUrl: string): string {
  const encoded = btoa(serverUrl).replace(/[^a-zA-Z0-9]/g, "_");
  return `${CREDENTIAL_KEY_PREFIX}${encoded}`;
}

/**
 * Generate credential key for a specific account (serverUrl + userId).
 */
export function credentialKey(serverUrl: string, userId: string): string {
  const combined = `${serverUrl}:${userId}`;
  const encoded = btoa(combined).replace(/[^a-zA-Z0-9]/g, "_");
  return `${CREDENTIAL_KEY_PREFIX}${encoded}`;
}

/**
 * Hash a PIN using SHA256.
 */
export async function hashPIN(pin: string): Promise<string> {
  return await Crypto.digestStringAsync(
    Crypto.CryptoDigestAlgorithm.SHA256,
    pin,
  );
}

/**
 * Verify a PIN against stored hash.
 */
export async function verifyAccountPIN(
  serverUrl: string,
  userId: string,
  pin: string,
): Promise<boolean> {
  const credential = await getAccountCredential(serverUrl, userId);
  if (!credential?.pinHash) return false;
  const inputHash = await hashPIN(pin);
  return inputHash === credential.pinHash;
}

/**
 * Save credential for a specific account.
 */
export async function saveAccountCredential(
  credential: ServerCredential,
): Promise<void> {
  const key = credentialKey(credential.serverUrl, credential.userId);
  await SecureStore.setItemAsync(key, JSON.stringify(credential));

  // Update previousServers to include this account
  addAccountToServer(credential.serverUrl, credential.serverName, {
    userId: credential.userId,
    username: credential.username,
    securityType: credential.securityType,
    savedAt: credential.savedAt,
  });
}

/**
 * Retrieve credential for a specific account.
 */
export async function getAccountCredential(
  serverUrl: string,
  userId: string,
): Promise<ServerCredential | null> {
  const key = credentialKey(serverUrl, userId);
  const stored = await SecureStore.getItemAsync(key);

  if (stored) {
    try {
      return JSON.parse(stored) as ServerCredential;
    } catch {
      return null;
    }
  }
  return null;
}

/**
 * Delete credential for a specific account.
 */
export async function deleteAccountCredential(
  serverUrl: string,
  userId: string,
): Promise<void> {
  const key = credentialKey(serverUrl, userId);
  await SecureStore.deleteItemAsync(key);

  // Remove account from previousServers
  removeAccountFromServer(serverUrl, userId);
}

/**
 * Get all credentials for a server (by iterating through accounts).
 */
export async function getServerAccounts(
  serverUrl: string,
): Promise<ServerCredential[]> {
  const servers = getPreviousServers();
  const server = servers.find((s) => s.address === serverUrl);
  if (!server) return [];

  const credentials: ServerCredential[] = [];
  for (const account of server.accounts) {
    const credential = await getAccountCredential(serverUrl, account.userId);
    if (credential) {
      credentials.push(credential);
    }
  }
  return credentials;
}

/**
 * Check if credentials exist for a specific account.
 */
export async function hasAccountCredential(
  serverUrl: string,
  userId: string,
): Promise<boolean> {
  const key = credentialKey(serverUrl, userId);
  const stored = await SecureStore.getItemAsync(key);
  return stored !== null;
}

/**
 * Delete all credentials for all accounts on all servers.
 */
export async function clearAllCredentials(): Promise<void> {
  const previousServers = getPreviousServers();

  for (const server of previousServers) {
    for (const account of server.accounts) {
      const key = credentialKey(server.address, account.userId);
      await SecureStore.deleteItemAsync(key);
    }
  }

  // Clear all accounts from servers
  const clearedServers = previousServers.map((server) => ({
    ...server,
    accounts: [],
  }));
  storage.set("previousServers", JSON.stringify(clearedServers));
}

/**
 * Add or update an account in a server's accounts list.
 */
function addAccountToServer(
  serverUrl: string,
  serverName: string,
  account: SavedServerAccount,
): void {
  const previousServers = getPreviousServers();
  let serverFound = false;

  const updatedServers = previousServers.map((server) => {
    if (server.address === serverUrl) {
      serverFound = true;
      // Check if account already exists
      const existingIndex = server.accounts.findIndex(
        (a) => a.userId === account.userId,
      );
      if (existingIndex >= 0) {
        // Update existing account
        const updatedAccounts = [...server.accounts];
        updatedAccounts[existingIndex] = account;
        return {
          ...server,
          name: serverName || server.name,
          accounts: updatedAccounts,
        };
      }
      // Add new account
      return {
        ...server,
        name: serverName || server.name,
        accounts: [...server.accounts, account],
      };
    }
    return server;
  });

  // If server not found, add it
  if (!serverFound) {
    updatedServers.push({
      address: serverUrl,
      name: serverName,
      accounts: [account],
    });
  }

  storage.set("previousServers", JSON.stringify(updatedServers));
}

/**
 * Remove an account from a server's accounts list.
 */
function removeAccountFromServer(serverUrl: string, userId: string): void {
  const previousServers = getPreviousServers();

  const updatedServers = previousServers.map((server) => {
    if (server.address === serverUrl) {
      return {
        ...server,
        accounts: server.accounts.filter((a) => a.userId !== userId),
      };
    }
    return server;
  });

  storage.set("previousServers", JSON.stringify(updatedServers));
}

/**
 * Get previous servers list from MMKV.
 */
export function getPreviousServers(): SavedServer[] {
  const stored = storage.getString("previousServers");
  if (stored) {
    try {
      return JSON.parse(stored) as SavedServer[];
    } catch {
      return [];
    }
  }
  return [];
}

/**
 * Remove a server from the list and delete all its account credentials.
 */
export async function removeServerFromList(serverUrl: string): Promise<void> {
  const servers = getPreviousServers();
  const server = servers.find((s) => s.address === serverUrl);

  // Delete all account credentials for this server
  if (server) {
    for (const account of server.accounts) {
      const key = credentialKey(serverUrl, account.userId);
      await SecureStore.deleteItemAsync(key);
    }
  }

  // Remove server from list
  const filtered = servers.filter((s) => s.address !== serverUrl);
  storage.set("previousServers", JSON.stringify(filtered));
}

/**
 * Add a server to the list without credentials (for server discovery).
 */
export function addServerToList(serverUrl: string, serverName?: string): void {
  const servers = getPreviousServers();
  const existing = servers.find((s) => s.address === serverUrl);

  if (existing) {
    // Update name if provided
    if (serverName) {
      const updated = servers.map((s) =>
        s.address === serverUrl ? { ...s, name: serverName } : s,
      );
      storage.set("previousServers", JSON.stringify(updated));
    }
    return;
  }

  // Add new server with empty accounts
  const newServer: SavedServer = {
    address: serverUrl,
    name: serverName,
    accounts: [],
  };

  // Keep max 10 servers
  const updatedServers = [newServer, ...servers].slice(0, 10);
  storage.set("previousServers", JSON.stringify(updatedServers));
}

/**
 * Update local network configuration for a server.
 */
export function updateServerLocalConfig(
  serverUrl: string,
  config: LocalNetworkConfig | undefined,
): void {
  const servers = getPreviousServers();
  const updatedServers = servers.map((server) => {
    if (server.address === serverUrl) {
      return {
        ...server,
        localNetworkConfig: config,
      };
    }
    return server;
  });
  storage.set("previousServers", JSON.stringify(updatedServers));
}

/**
 * Get local network configuration for a server.
 */
export function getServerLocalConfig(
  serverUrl: string,
): LocalNetworkConfig | undefined {
  const servers = getPreviousServers();
  const server = servers.find((s) => s.address === serverUrl);
  return server?.localNetworkConfig;
}

/**
 * Migrate from legacy single-account format to multi-account format.
 * Should be called on app startup.
 */
export async function migrateToMultiAccount(): Promise<void> {
  // Check if already migrated
  if (storage.getBoolean(MULTI_ACCOUNT_MIGRATED_KEY)) {
    return;
  }

  const stored = storage.getString("previousServers");
  if (!stored) {
    storage.set(MULTI_ACCOUNT_MIGRATED_KEY, true);
    return;
  }

  try {
    const servers = JSON.parse(stored);

    // Check if already in new format (has accounts array)
    if (servers.length > 0 && Array.isArray(servers[0].accounts)) {
      storage.set(MULTI_ACCOUNT_MIGRATED_KEY, true);
      return;
    }

    // Migrate from legacy format
    const migratedServers: SavedServer[] = [];

    for (const legacyServer of servers as LegacySavedServer[]) {
      const newServer: SavedServer = {
        address: legacyServer.address,
        name: legacyServer.name,
        accounts: [],
      };

      // Try to get existing credential using legacy key
      if (legacyServer.hasCredentials) {
        const legacyKey = serverUrlToKey(legacyServer.address);
        const storedCred = await SecureStore.getItemAsync(legacyKey);

        if (storedCred) {
          try {
            const legacyCred = JSON.parse(storedCred) as LegacyServerCredential;

            // Create new credential with security type
            const newCredential: ServerCredential = {
              ...legacyCred,
              securityType: "none", // Existing accounts get no protection (preserve quick-login)
            };

            // Save with new key format
            const newKey = credentialKey(
              legacyServer.address,
              legacyCred.userId,
            );
            await SecureStore.setItemAsync(
              newKey,
              JSON.stringify(newCredential),
            );

            // Delete old key
            await SecureStore.deleteItemAsync(legacyKey);

            // Add account to server
            newServer.accounts.push({
              userId: legacyCred.userId,
              username: legacyCred.username,
              securityType: "none",
              savedAt: legacyCred.savedAt,
            });
          } catch {
            // Skip invalid credentials
          }
        }
      }

      migratedServers.push(newServer);
    }

    storage.set("previousServers", JSON.stringify(migratedServers));
    storage.set(MULTI_ACCOUNT_MIGRATED_KEY, true);
  } catch {
    // If parsing fails, reset to empty array
    storage.set("previousServers", "[]");
    storage.set(MULTI_ACCOUNT_MIGRATED_KEY, true);
  }
}

/**
 * Update account's token after successful login.
 */
export async function updateAccountToken(
  serverUrl: string,
  userId: string,
  newToken: string,
): Promise<void> {
  const credential = await getAccountCredential(serverUrl, userId);
  if (credential) {
    credential.token = newToken;
    credential.savedAt = Date.now();
    const key = credentialKey(serverUrl, userId);
    await SecureStore.setItemAsync(key, JSON.stringify(credential));
  }
}

// Legacy functions for backward compatibility during transition
// These delegate to new functions

/**
 * @deprecated Use saveAccountCredential instead
 */
export async function saveServerCredential(
  credential: ServerCredential,
): Promise<void> {
  return saveAccountCredential(credential);
}

/**
 * @deprecated Use getAccountCredential instead
 */
export async function getServerCredential(
  serverUrl: string,
): Promise<ServerCredential | null> {
  // Try to get first account's credential for backward compatibility
  const servers = getPreviousServers();
  const server = servers.find((s) => s.address === serverUrl);
  if (server && server.accounts.length > 0) {
    return getAccountCredential(serverUrl, server.accounts[0].userId);
  }
  return null;
}

/**
 * @deprecated Use deleteAccountCredential instead
 */
export async function deleteServerCredential(serverUrl: string): Promise<void> {
  // Delete first account for backward compatibility
  const servers = getPreviousServers();
  const server = servers.find((s) => s.address === serverUrl);
  if (server && server.accounts.length > 0) {
    return deleteAccountCredential(serverUrl, server.accounts[0].userId);
  }
}

/**
 * @deprecated Use hasAccountCredential instead
 */
export async function hasServerCredential(serverUrl: string): Promise<boolean> {
  const servers = getPreviousServers();
  const server = servers.find((s) => s.address === serverUrl);
  return server ? server.accounts.length > 0 : false;
}

/**
 * @deprecated Use migrateToMultiAccount instead
 */
export async function migrateServersList(): Promise<void> {
  return migrateToMultiAccount();
}

/**
 * @deprecated Use saveAccountCredential instead
 */
export async function migrateCurrentSessionToSecureStorage(
  serverUrl: string,
  token: string,
  userId: string,
  username: string,
  serverName?: string,
): Promise<void> {
  const existingCredential = await getAccountCredential(serverUrl, userId);

  // Only save if not already saved
  if (!existingCredential) {
    await saveAccountCredential({
      serverUrl,
      serverName: serverName || "",
      token,
      userId,
      username,
      savedAt: Date.now(),
      securityType: "none",
    });
  }
}