/**
 * @ai-summary Feature tier configuration and utilities
 * @ai-context Defines feature-to-tier mapping for gating premium features
 */

import { SubscriptionTier } from '../../features/user-profile/domain/user-profile.types';

// Tier hierarchy: higher number = higher access level
export const TIER_LEVELS: Record<SubscriptionTier, number> = {
  free: 0,
  pro: 1,
  enterprise: 2,
} as const;

// Feature configuration interface
export interface FeatureConfig {
  minTier: SubscriptionTier;
  name: string;
  upgradePrompt: string;
}

// Feature registry - add new gated features here
export const FEATURE_TIERS: Record<string, FeatureConfig> = {
  'document.scanMaintenanceSchedule': {
    minTier: 'pro',
    name: 'Scan for Maintenance Schedule',
    upgradePrompt: 'Upgrade to Pro to automatically extract maintenance schedules from your vehicle manuals.',
  },
  'vehicle.vinDecode': {
    minTier: 'pro',
    name: 'VIN Decode',
    upgradePrompt: 'Upgrade to Pro to automatically decode VIN and populate vehicle details from the NHTSA database.',
  },
} as const;

/**
 * Get numeric level for a subscription tier
 */
export function getTierLevel(tier: SubscriptionTier): number {
  return TIER_LEVELS[tier] ?? 0;
}

/**
 * Check if a user tier can access a feature
 * Higher tiers inherit access to all lower tier features
 */
export function canAccessFeature(userTier: SubscriptionTier, featureKey: string): boolean {
  const feature = FEATURE_TIERS[featureKey];
  if (!feature) {
    // Unknown features are accessible by all (fail open for unlisted features)
    return true;
  }
  return getTierLevel(userTier) >= getTierLevel(feature.minTier);
}

/**
 * Get the minimum required tier for a feature
 * Returns null if feature is not gated
 */
export function getRequiredTier(featureKey: string): SubscriptionTier | null {
  const feature = FEATURE_TIERS[featureKey];
  return feature?.minTier ?? null;
}

/**
 * Get full feature configuration
 * Returns undefined if feature is not registered
 */
export function getFeatureConfig(featureKey: string): FeatureConfig | undefined {
  return FEATURE_TIERS[featureKey];
}

/**
 * Get all feature configurations (for API endpoint)
 */
export function getAllFeatureConfigs(): Record<string, FeatureConfig> {
  return { ...FEATURE_TIERS };
}

// Vehicle limits per tier
// null indicates unlimited (enterprise tier)
export const VEHICLE_LIMITS: Record<SubscriptionTier, number | null> = {
  free: 2,
  pro: 5,
  enterprise: null,
} as const;

/**
 * Vehicle limits vary by subscription tier and must be queryable
 * at runtime for both backend enforcement and frontend UI state.
 *
 * @param tier - User's subscription tier
 * @returns Maximum vehicles allowed, or null for unlimited (enterprise tier)
 */
export function getVehicleLimit(tier: SubscriptionTier): number | null {
  return VEHICLE_LIMITS[tier] ?? null;
}

/**
 * Check if a user can add another vehicle based on their tier and current count.
 *
 * @param tier - User's subscription tier
 * @param currentCount - Number of vehicles user currently has
 * @returns true if user can add another vehicle, false if at/over limit
 */
export function canAddVehicle(tier: SubscriptionTier, currentCount: number): boolean {
  const limit = getVehicleLimit(tier);
  // null limit means unlimited (enterprise)
  if (limit === null) {
    return true;
  }
  return currentCount < limit;
}

/**
 * Vehicle limit configuration with upgrade prompt.
 * Structure supports additional resource types in the future.
 */
export interface VehicleLimitConfig {
  limit: number | null;
  tier: SubscriptionTier;
  upgradePrompt: string;
}

/**
 * Get vehicle limit configuration with upgrade prompt for a tier.
 *
 * @param tier - User's subscription tier
 * @returns Configuration with limit and upgrade prompt
 */
export function getVehicleLimitConfig(tier: SubscriptionTier): VehicleLimitConfig {
  const limit = getVehicleLimit(tier);

  const defaultPrompt = 'Upgrade to access additional vehicles.';

  let upgradePrompt: string;
  if (tier === 'free') {
    upgradePrompt = 'Free tier is limited to 2 vehicles. Upgrade to Pro for up to 5 vehicles, or Enterprise for unlimited.';
  } else if (tier === 'pro') {
    upgradePrompt = 'Pro tier is limited to 5 vehicles. Upgrade to Enterprise for unlimited vehicles.';
  } else {
    upgradePrompt = defaultPrompt;
  }

  return {
    limit,
    tier,
    upgradePrompt,
  };
}