/**
 * MotorSignal Firebase Configuration and Isolation Guards
 *
 * Enforces strict environment separation between production (motoapp-d22e0)
 * and staging (motorsignal-staging), preventing staging environments from
 * accidentally initializing against production Firebase resources.
 */

export const PRODUCTION_FIREBASE_PROJECT_ID = 'motoapp-d22e0';
export const STAGING_FIREBASE_PROJECT_ID = 'motorsignal-staging';

export interface FirebaseClientOptions {
  apiKey: string;
  authDomain: string;
  projectId: string;
  storageBucket: string;
  messagingSenderId?: string;
  appId?: string;
}

/**
 * Determines whether the current execution context is a staging deployment.
 * Inspects standard environment variables and browser hostname.
 */
export function isStagingEnvironment(): boolean {
  // Check standard environment descriptors
  const motorsignalEnv = (process.env.MOTORSIGNAL_ENV || '').toLowerCase().trim();
  const appEnv = (process.env.APP_ENV || process.env.NEXT_PUBLIC_APP_ENV || '').toLowerCase().trim();

  // If explicitly flagged as production, it is never staging
  if (motorsignalEnv === 'production' || appEnv === 'production') {
    return false;
  }

  // Explicit staging flags
  if (motorsignalEnv === 'staging' || appEnv === 'staging') {
    return true;
  }

  if (process.env.STAGING === 'true' || process.env.NEXT_PUBLIC_STAGING === 'true') {
    return true;
  }

  const nodeEnv = (process.env.NODE_ENV || '').toLowerCase().trim();
  if (nodeEnv === 'staging') {
    return true;
  }

  // Staging API base URL indicator (e.g. https://api-staging.motorsignal.app)
  const apiBaseUrl = (process.env.MOTORSIGNAL_API_BASE_URL || '').toLowerCase();
  if (apiBaseUrl.includes('api-staging.motorsignal.app') || apiBaseUrl.includes('//staging.')) {
    return true;
  }

  // Staging site URL indicator (e.g. https://staging.motorsignal.app)
  const siteUrl = (process.env.NEXT_PUBLIC_SITE_URL || '').toLowerCase();
  if (siteUrl.includes('staging.motorsignal.app')) {
    return true;
  }

  // Browser hostname inspection
  if (typeof window !== 'undefined' && window.location?.hostname) {
    const hostname = window.location.hostname.toLowerCase();
    if (hostname === 'staging.motorsignal.app') {
      return true;
    }
  }

  return false;
}

/**
 * Staging safety guard: strictly prevents any staging deployment from
 * initializing Firebase against the production project (motoapp-d22e0).
 */
export function assertStagingSafety(projectId: string): void {
  if (isStagingEnvironment() && projectId === PRODUCTION_FIREBASE_PROJECT_ID) {
    throw new Error(
      `Staging safety guard violation: Staging deployment cannot initialize Firebase against production project "${PRODUCTION_FIREBASE_PROJECT_ID}". ` +
      `Expected staging project "${STAGING_FIREBASE_PROJECT_ID}".`
    );
  }
}

/**
 * Validates that server-side and browser-side Firebase project IDs agree.
 * Throws if both are provided but do not match.
 */
export function assertProjectIdsMatch(clientProjectId?: string, serverProjectId?: string): void {
  if (clientProjectId && serverProjectId && clientProjectId !== serverProjectId) {
    throw new Error(
      `Firebase project ID mismatch: Client project ID "${clientProjectId}" ` +
      `does not match server project ID "${serverProjectId}".`
    );
  }
}

/**
 * Validates and retrieves the client-side Firebase configuration options
 * from environment variables.
 *
 * Throws if required configuration is missing or if the staging safety guard is violated.
 */
export function getFirebaseClientConfig(): FirebaseClientOptions {
  const apiKey = process.env.NEXT_PUBLIC_FIREBASE_API_KEY;
  const authDomain = process.env.NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN;
  const projectId = process.env.NEXT_PUBLIC_FIREBASE_PROJECT_ID;
  const storageBucket = process.env.NEXT_PUBLIC_FIREBASE_STORAGE_BUCKET;
  const messagingSenderId = process.env.NEXT_PUBLIC_FIREBASE_MESSAGING_SENDER_ID;
  const appId = process.env.NEXT_PUBLIC_FIREBASE_APP_ID;

  if (!projectId || !apiKey) {
    throw new Error(
      'Missing required Firebase client configuration: NEXT_PUBLIC_FIREBASE_PROJECT_ID ' +
      'and NEXT_PUBLIC_FIREBASE_API_KEY must be set.'
    );
  }

  // Enforce staging safety guard
  assertStagingSafety(projectId);

  // Enforce client/server project ID consistency if server env var is visible
  if (process.env.FIREBASE_PROJECT_ID) {
    assertProjectIdsMatch(projectId, process.env.FIREBASE_PROJECT_ID);
  }

  return {
    apiKey,
    authDomain: authDomain || `${projectId}.firebaseapp.com`,
    projectId,
    storageBucket: storageBucket || `${projectId}.firebasestorage.app`,
    ...(messagingSenderId ? { messagingSenderId } : {}),
    ...(appId ? { appId } : {}),
  };
}

/**
 * Validates and retrieves the server-side Firebase project ID.
 * Requires explicit FIREBASE_PROJECT_ID; fails closed without falling back to production.
 */
export function getServerFirebaseProjectId(): string {
  const projectId = process.env.FIREBASE_PROJECT_ID;
  if (!projectId) {
    throw new Error('FIREBASE_PROJECT_ID is required for Firebase Admin SDK initialization.');
  }

  // Enforce staging safety guard
  assertStagingSafety(projectId);

  // Enforce client/server project ID consistency if client env var is set
  if (process.env.NEXT_PUBLIC_FIREBASE_PROJECT_ID) {
    assertProjectIdsMatch(process.env.NEXT_PUBLIC_FIREBASE_PROJECT_ID, projectId);
  }

  return projectId;
}