/**
 * Google Drive OAuth Adapter - PKCE Loopback Flow
 * 
 * Uses Authorization Code Grant with PKCE (RFC 7636) and loopback redirect.
 * Data is stored in appDataFolder (hidden, app-specific folder).
 * 
 * Flow:
 * 1. Generate PKCE challenge
 * 2. Open browser with auth URL
 * 3. User authorizes, redirected to loopback
 * 4. Exchange code for tokens
 * 5. Use Drive API to manage sync file
 */

import {
  SYNC_CONSTANTS,
  type OAuthTokens,
  type ProviderAccount,
  type SyncedFile,
  type PKCEChallenge,
} from '../../../domain/sync';
import { arrayBufferToBase64, generateRandomBytes } from '../EncryptionService';
import { netcattyBridge } from '../netcattyBridge';

// ============================================================================
// Types
// ============================================================================

export interface GoogleUserInfo {
  id: string;
  email: string;
  name: string;
  picture: string;
}

export interface DriveFile {
  id: string;
  name: string;
  modifiedTime: string;
  size?: string;
}

// ============================================================================
// PKCE Utilities
// ============================================================================

/**
 * Generate a cryptographically random code verifier
 */
const generateCodeVerifier = (): string => {
  const bytes = generateRandomBytes(32);
  return base64UrlEncode(bytes);
};

/**
 * Generate code challenge from verifier (S256)
 */
const generateCodeChallenge = async (verifier: string): Promise<string> => {
  const encoder = new TextEncoder();
  const data = encoder.encode(verifier);
  const digest = await crypto.subtle.digest('SHA-256', data);
  return base64UrlEncode(new Uint8Array(digest));
};

/**
 * Base64 URL encoding (no padding, URL-safe chars)
 */
const base64UrlEncode = (bytes: Uint8Array): string => {
  const base64 = arrayBufferToBase64(bytes);
  return base64
    .replace(/\+/g, '-')
    .replace(/\//g, '_')
    .replace(/=+$/, '');
};

/**
 * Generate PKCE challenge
 */
export const generatePKCEChallenge = async (): Promise<PKCEChallenge> => {
  const codeVerifier = generateCodeVerifier();
  const codeChallenge = await generateCodeChallenge(codeVerifier);
  const state = base64UrlEncode(generateRandomBytes(16));

  return {
    codeVerifier,
    codeChallenge,
    state,
  };
};

// ============================================================================
// OAuth Flow
// ============================================================================

/**
 * Build authorization URL for Google OAuth
 */
export const buildAuthUrl = async (
  redirectUri: string
): Promise<{ url: string; pkce: PKCEChallenge }> => {
  const pkce = await generatePKCEChallenge();

  const params = new URLSearchParams({
    client_id: SYNC_CONSTANTS.GOOGLE_CLIENT_ID,
    redirect_uri: redirectUri,
    response_type: 'code',
    scope: 'https://www.googleapis.com/auth/drive.appdata https://www.googleapis.com/auth/userinfo.profile https://www.googleapis.com/auth/userinfo.email',
    code_challenge: pkce.codeChallenge,
    code_challenge_method: 'S256',
    state: pkce.state,
    access_type: 'offline',
    prompt: 'consent',
  });

  return {
    url: `${SYNC_CONSTANTS.GOOGLE_AUTH_URL}?${params.toString()}`,
    pkce,
  };
};

/**
 * Exchange authorization code for tokens
 */
export const exchangeCodeForTokens = async (
  code: string,
  codeVerifier: string,
  redirectUri: string
): Promise<OAuthTokens> => {
  const bridge = netcattyBridge.get();
  const exchangeViaMain = bridge?.googleExchangeCodeForTokens;
  if (!exchangeViaMain) {
    throw new Error(
      'Google OAuth bridge unavailable (token exchange is blocked by CORS in renderer). Please restart Netcatty.'
    );
  }

  return await exchangeViaMain({
    clientId: SYNC_CONSTANTS.GOOGLE_CLIENT_ID,
    clientSecret: SYNC_CONSTANTS.GOOGLE_CLIENT_SECRET,
    code,
    codeVerifier,
    redirectUri,
  });
};

/**
 * Refresh access token
 */
export const refreshAccessToken = async (refreshToken: string): Promise<OAuthTokens> => {
  const bridge = netcattyBridge.get();
  const refreshViaMain = bridge?.googleRefreshAccessToken;
  if (!refreshViaMain) {
    throw new Error(
      'Google OAuth bridge unavailable (token refresh is blocked by CORS in renderer). Please restart Netcatty.'
    );
  }

  return await refreshViaMain({
    clientId: SYNC_CONSTANTS.GOOGLE_CLIENT_ID,
    clientSecret: SYNC_CONSTANTS.GOOGLE_CLIENT_SECRET,
    refreshToken,
  });
};

// ============================================================================
// User Info
// ============================================================================

/**
 * Get authenticated user info
 */
export const getUserInfo = async (accessToken: string): Promise<ProviderAccount> => {
  const bridge = netcattyBridge.get();
  const userInfoViaMain = bridge?.googleGetUserInfo;
  if (userInfoViaMain) {
    const user = await userInfoViaMain({ accessToken });
    return {
      id: user.id,
      email: user.email,
      name: user.name,
      avatarUrl: user.picture,
    };
  }

  const response = await fetch('https://www.googleapis.com/oauth2/v2/userinfo', {
    headers: {
      'Authorization': `Bearer ${accessToken}`,
    },
  });

  if (!response.ok) {
    throw new Error('Failed to get user info');
  }

  const user: GoogleUserInfo = await response.json();

  return {
    id: user.id,
    email: user.email,
    name: user.name,
    avatarUrl: user.picture,
  };
};

/**
 * Validate access token
 */
export const validateToken = async (accessToken: string): Promise<boolean> => {
  try {
    const bridge = netcattyBridge.get();
    const userInfoViaMain = bridge?.googleGetUserInfo;
    if (userInfoViaMain) {
      await userInfoViaMain({ accessToken });
      return true;
    }

    const response = await fetch('https://www.googleapis.com/oauth2/v2/userinfo', {
      headers: { 'Authorization': `Bearer ${accessToken}` },
    });
    return response.ok;
  } catch {
    return false;
  }
};

// ============================================================================
// Drive Operations (appDataFolder)
// ============================================================================

/**
 * Find sync file in appDataFolder
 */
export const findSyncFile = async (accessToken: string): Promise<string | null> => {
  const bridge = netcattyBridge.get();
  const findViaMain = bridge?.googleDriveFindSyncFile;
  if (findViaMain) {
    const { fileId } = await findViaMain({
      accessToken,
      fileName: SYNC_CONSTANTS.SYNC_FILE_NAME,
    });
    return fileId || null;
  }

  const params = new URLSearchParams({
    spaces: 'appDataFolder',
    q: `name = '${SYNC_CONSTANTS.SYNC_FILE_NAME}'`,
    fields: 'files(id, name, modifiedTime)',
  });

  const url = `${SYNC_CONSTANTS.GOOGLE_DRIVE_API}/files?${params.toString()}`;
  console.log('[GoogleDrive] Searching for sync file:', url);

  let response: Response;
  try {
    response = await fetch(url, {
      headers: {
        'Authorization': `Bearer ${accessToken}`,
      },
    });
  } catch (fetchError) {
    console.error('[GoogleDrive] Network error:', fetchError);
    throw new Error(`Network error: ${fetchError instanceof Error ? fetchError.message : 'Failed to fetch'}`);
  }

  if (!response.ok) {
    const errorData = await response.json().catch(() => ({}));
    console.error('[GoogleDrive] API error:', response.status, errorData);
    
    if (response.status === 403) {
      throw new Error('Google Drive API not enabled. Please enable it in Google Cloud Console.');
    }
    if (response.status === 401) {
      throw new Error('Token expired or invalid. Please reconnect.');
    }
    
    throw new Error(`Drive API error: ${errorData.error?.message || response.status}`);
  }

  const data = await response.json();
  console.log('[GoogleDrive] Found files:', data.files?.length || 0);
  return data.files?.[0]?.id || null;
};

/**
 * Create sync file in appDataFolder
 */
export const createSyncFile = async (
  accessToken: string,
  syncedFile: SyncedFile
): Promise<string> => {
  const bridge = netcattyBridge.get();
  const createViaMain = bridge?.googleDriveCreateSyncFile;
  if (createViaMain) {
    const { fileId } = await createViaMain({
      accessToken,
      fileName: SYNC_CONSTANTS.SYNC_FILE_NAME,
      syncedFile,
    });
    return fileId;
  }

  const metadata = {
    name: SYNC_CONSTANTS.SYNC_FILE_NAME,
    parents: ['appDataFolder'],
  };

  const form = new FormData();
  form.append(
    'metadata',
    new Blob([JSON.stringify(metadata)], { type: 'application/json' })
  );
  form.append(
    'file',
    new Blob([JSON.stringify(syncedFile, null, 2)], { type: 'application/json' })
  );

  let response: Response;
  try {
    response = await fetch(
      `${SYNC_CONSTANTS.GOOGLE_DRIVE_API.replace('/v3', '/upload/v3')}/files?uploadType=multipart`,
      {
        method: 'POST',
        headers: {
          'Authorization': `Bearer ${accessToken}`,
        },
        body: form,
      }
    );
  } catch (fetchError) {
    console.error('[GoogleDrive] Network error:', fetchError);
    throw new Error(`Network error: ${fetchError instanceof Error ? fetchError.message : 'Failed to fetch'}`);
  }

  if (!response.ok) {
    const errorData = await response.json().catch(() => ({}));
    if (response.status === 403) {
      throw new Error('Google Drive API not enabled. Please enable it in Google Cloud Console.');
    }
    if (response.status === 401) {
      throw new Error('Token expired or invalid. Please reconnect.');
    }
    throw new Error(`Failed to create file: ${errorData.error?.message || response.status}`);
  }

  const data = await response.json();
  return data.id;
};

/**
 * Update sync file
 */
export const updateSyncFile = async (
  accessToken: string,
  fileId: string,
  syncedFile: SyncedFile
): Promise<void> => {
  const bridge = netcattyBridge.get();
  const updateViaMain = bridge?.googleDriveUpdateSyncFile;
  if (updateViaMain) {
    await updateViaMain({ accessToken, fileId, syncedFile });
    return;
  }

  let response: Response;
  try {
    response = await fetch(
      `${SYNC_CONSTANTS.GOOGLE_DRIVE_API.replace('/v3', '/upload/v3')}/files/${fileId}?uploadType=media`,
      {
        method: 'PATCH',
        headers: {
          'Authorization': `Bearer ${accessToken}`,
          'Content-Type': 'application/json',
        },
        body: JSON.stringify(syncedFile, null, 2),
      }
    );
  } catch (fetchError) {
    console.error('[GoogleDrive] Network error:', fetchError);
    throw new Error(`Network error: ${fetchError instanceof Error ? fetchError.message : 'Failed to fetch'}`);
  }

  if (!response.ok) {
    const errorData = await response.json().catch(() => ({}));
    if (response.status === 403) {
      throw new Error('Google Drive API not enabled. Please enable it in Google Cloud Console.');
    }
    if (response.status === 401) {
      throw new Error('Token expired or invalid. Please reconnect.');
    }
    throw new Error(`Failed to update file: ${errorData.error?.message || response.status}`);
  }
};

/**
 * Download sync file
 */
export const downloadSyncFile = async (
  accessToken: string,
  fileId: string
): Promise<SyncedFile | null> => {
  const bridge = netcattyBridge.get();
  const downloadViaMain = bridge?.googleDriveDownloadSyncFile;
  if (downloadViaMain) {
    const { syncedFile } = await downloadViaMain({ accessToken, fileId });
    return (syncedFile as SyncedFile | null) || null;
  }

  let response: Response;
  try {
    response = await fetch(
      `${SYNC_CONSTANTS.GOOGLE_DRIVE_API}/files/${fileId}?alt=media`,
      {
        headers: {
          'Authorization': `Bearer ${accessToken}`,
        },
      }
    );
  } catch (fetchError) {
    console.error('[GoogleDrive] Network error:', fetchError);
    throw new Error(`Network error: ${fetchError instanceof Error ? fetchError.message : 'Failed to fetch'}`);
  }

  if (!response.ok) {
    if (response.status === 404) {
      return null;
    }
    const errorData = await response.json().catch(() => ({}));
    if (response.status === 403) {
      throw new Error('Google Drive API not enabled. Please enable it in Google Cloud Console.');
    }
    if (response.status === 401) {
      throw new Error('Token expired or invalid. Please reconnect.');
    }
    throw new Error(`Failed to download file: ${errorData.error?.message || response.status}`);
  }

  return response.json();
};

/**
 * Delete sync file
 */
export const deleteSyncFile = async (
  accessToken: string,
  fileId: string
): Promise<void> => {
  const bridge = netcattyBridge.get();
  const deleteViaMain = bridge?.googleDriveDeleteSyncFile;
  if (deleteViaMain) {
    await deleteViaMain({ accessToken, fileId });
    return;
  }

  let response: Response;
  try {
    response = await fetch(`${SYNC_CONSTANTS.GOOGLE_DRIVE_API}/files/${fileId}`, {
      method: 'DELETE',
      headers: {
        'Authorization': `Bearer ${accessToken}`,
      },
    });
  } catch (fetchError) {
    console.error('[GoogleDrive] Network error:', fetchError);
    throw new Error(`Network error: ${fetchError instanceof Error ? fetchError.message : 'Failed to fetch'}`);
  }

  if (!response.ok && response.status !== 404) {
    const errorData = await response.json().catch(() => ({}));
    if (response.status === 403) {
      throw new Error('Google Drive API not enabled. Please enable it in Google Cloud Console.');
    }
    if (response.status === 401) {
      throw new Error('Token expired or invalid. Please reconnect.');
    }
    throw new Error(`Failed to delete file: ${errorData.error?.message || response.status}`);
  }
};

// ============================================================================
// Google Drive Adapter Class
// ============================================================================

export class GoogleDriveAdapter {
  private tokens: OAuthTokens | null = null;
  private fileId: string | null = null;
  private account: ProviderAccount | null = null;
  private pkceChallenge: PKCEChallenge | null = null;
  /**
   * Invoked whenever the access token is silently refreshed. Lets the owner
   * (CloudSyncManager) persist the rotated tokens so the next launch doesn't
   * load a stale access token and force a reconnect. Mirrors the OneDrive fix
   * (#1189 / #1208); Google differs in that its refresh response usually omits a
   * new refresh token, so refreshTokens() carries the previous one forward.
   */
  private onTokensRefreshed: ((tokens: OAuthTokens) => void) | null = null;

  constructor(tokens?: OAuthTokens, fileId?: string) {
    if (tokens) {
      this.tokens = tokens;
    }
    this.fileId = fileId || null;
  }

  /**
   * Register a callback that receives refreshed tokens so the caller can
   * persist them. Passing null removes the callback.
   */
  setOnTokensRefreshed(callback: ((tokens: OAuthTokens) => void) | null): void {
    this.onTokensRefreshed = callback;
  }

  /**
   * Refresh the access token using the supplied refresh token, store the
   * rotated tokens in-memory, and notify the persistence callback. Google
   * typically returns the same (or no) refresh token on refresh, so the prior
   * refresh token is preserved when the response omits one — otherwise the
   * persisted credentials would lose the ability to refresh again and force a
   * reconnect on the next launch.
   */
  private async refreshTokens(refreshToken: string): Promise<OAuthTokens> {
    const refreshed = await refreshAccessToken(refreshToken);
    // Google's refresh response frequently omits refresh_token (it does not
    // rotate on every refresh). Never let a missing value clobber the working
    // refresh token, or the persisted connection becomes unrefreshable.
    const merged: OAuthTokens = {
      ...refreshed,
      refreshToken: refreshed.refreshToken || refreshToken,
    };
    this.tokens = merged;
    try {
      this.onTokensRefreshed?.(merged);
    } catch {
      // Persistence is best-effort; a failed save must not abort the sync that
      // triggered the refresh — the fresh tokens still work for this session.
    }
    return merged;
  }

  get isAuthenticated(): boolean {
    return !!this.tokens?.accessToken;
  }

  get accountInfo(): ProviderAccount | null {
    return this.account;
  }

  get resourceId(): string | null {
    return this.fileId;
  }

  /**
   * Start OAuth flow - returns URL to open in browser
   */
  async startAuth(redirectUri: string): Promise<string> {
    const { url, pkce } = await buildAuthUrl(redirectUri);
    this.pkceChallenge = pkce;
    return url;
  }

  /**
   * Get PKCE state for verification
   */
  getPKCEState(): string | null {
    return this.pkceChallenge?.state || null;
  }

  /**
   * Complete authentication with authorization code
   */
  async completeAuth(code: string, redirectUri: string): Promise<OAuthTokens> {
    if (!this.pkceChallenge) {
      throw new Error('No PKCE challenge - start auth first');
    }

    this.tokens = await exchangeCodeForTokens(
      code,
      this.pkceChallenge.codeVerifier,
      redirectUri
    );
    this.pkceChallenge = null;

    this.account = await getUserInfo(this.tokens.accessToken);

    return this.tokens;
  }

  /**
   * Set tokens from storage
   */
  async setTokens(tokens: OAuthTokens): Promise<void> {
    this.tokens = tokens;

    // Refresh if expired
    if (tokens.expiresAt && Date.now() > tokens.expiresAt - 60000) {
      if (tokens.refreshToken) {
        this.tokens = await this.refreshTokens(tokens.refreshToken);
      } else {
        throw new Error('Token expired and no refresh token');
      }
    }

    if (await validateToken(this.tokens.accessToken)) {
      this.account = await getUserInfo(this.tokens.accessToken);
    } else {
      throw new Error('Token is invalid');
    }
  }

  /**
   * Ensure token is fresh
   */
  private async ensureValidToken(): Promise<string> {
    if (!this.tokens) {
      throw new Error('Not authenticated');
    }

    if (this.tokens.expiresAt && Date.now() > this.tokens.expiresAt - 60000) {
      if (this.tokens.refreshToken) {
        this.tokens = await this.refreshTokens(this.tokens.refreshToken);
      } else {
        throw new Error('Token expired');
      }
    }

    return this.tokens.accessToken;
  }

  /**
   * Sign out
   */
  signOut(): void {
    this.tokens = null;
    this.fileId = null;
    this.account = null;
    this.pkceChallenge = null;
    this.onTokensRefreshed = null;
  }

  /**
   * Initialize or find sync file
   */
  async initializeSync(): Promise<string | null> {
    const accessToken = await this.ensureValidToken();
    this.fileId = await findSyncFile(accessToken);
    return this.fileId;
  }

  /**
   * Upload sync file
   */
  async upload(syncedFile: SyncedFile): Promise<string> {
    const accessToken = await this.ensureValidToken();

    if (this.fileId) {
      await updateSyncFile(accessToken, this.fileId, syncedFile);
      return this.fileId;
    } else {
      this.fileId = await createSyncFile(accessToken, syncedFile);
      return this.fileId;
    }
  }

  /**
   * Download sync file
   */
  async download(): Promise<SyncedFile | null> {
    const accessToken = await this.ensureValidToken();

    if (!this.fileId) {
      this.fileId = await findSyncFile(accessToken);
    }

    if (!this.fileId) {
      return null;
    }

    return downloadSyncFile(accessToken, this.fileId);
  }

  /**
   * Delete sync data
   */
  async deleteSync(): Promise<void> {
    if (!this.tokens || !this.fileId) {
      return;
    }

    const accessToken = await this.ensureValidToken();
    await deleteSyncFile(accessToken, this.fileId);
    this.fileId = null;
  }

  /**
   * Get tokens for storage
   */
  getTokens(): OAuthTokens | null {
    return this.tokens;
  }
}

export default GoogleDriveAdapter;