/**
 * @ai-summary Standalone tier guard middleware for route-level feature gating
 * @ai-context Returns a Fastify preHandler that checks user subscription tier against feature requirements.
 *   Must be composed AFTER requireAuth in preHandler arrays.
 */

import { FastifyRequest, FastifyReply } from 'fastify';
import { canAccessFeature, getFeatureConfig } from '../config/feature-tiers';
import { logger } from '../logging/logger';

/**
 * Creates a preHandler middleware that enforces subscription tier requirements.
 *
 * Reads the user's tier from request.userContext.subscriptionTier (set by auth middleware).
 * Must be placed AFTER requireAuth in the preHandler chain.
 *
 * Usage:
 *   fastify.post('/premium-route', {
 *     preHandler: [requireAuth, requireTier('fuelLog.receiptScan')],
 *     handler: controller.method
 *   });
 *
 * @param featureKey - Key from FEATURE_TIERS registry (e.g. 'fuelLog.receiptScan')
 * @returns Fastify preHandler function
 */
export function requireTier(featureKey: string) {
  return async (request: FastifyRequest, reply: FastifyReply): Promise<void> => {
    // Validate feature key exists in registry
    const featureConfig = getFeatureConfig(featureKey);
    if (!featureConfig) {
      logger.error('requireTier: unknown feature key', { featureKey });
      return reply.code(500).send({
        error: 'INTERNAL_ERROR',
        message: 'Unknown feature configuration',
      });
    }

    // Get user tier from userContext (populated by auth middleware)
    const currentTier = request.userContext?.subscriptionTier || 'free';

    if (!canAccessFeature(currentTier, featureKey)) {
      logger.warn('requireTier: access denied', {
        userId: request.userContext?.userId?.substring(0, 8) + '...',
        currentTier,
        requiredTier: featureConfig.minTier,
        featureKey,
      });

      return reply.code(403).send({
        error: 'TIER_REQUIRED',
        requiredTier: featureConfig.minTier,
        currentTier,
        featureName: featureConfig.name,
        upgradePrompt: featureConfig.upgradePrompt,
      });
    }

    logger.debug('requireTier: access granted', {
      userId: request.userContext?.userId?.substring(0, 8) + '...',
      currentTier,
      featureKey,
    });
  };
}