/**
 * useNavigation Hook
 * 
 * Fetches the navigation structure from the new Navigation API.
 * The backend provides a blocks-based structure with static and dynamic blocks.
 * 
 * API: GET /api/navigation?language=de
 * 
 * Response structure (gemäss Navigation-API-Konzept):
 * {
 *   "language": "de",
 *   "blocks": [
 *     { "type": "static", "id": "system", "title": "SYSTEM", "order": 10, "items": [...] },
 *     { "type": "dynamic", "id": "features", "title": "MEINE FEATURES", "order": 15, "mandates": [...] },
 *     ...
 *   ]
 * }
 */

import { useState, useEffect, useCallback } from 'react';
import api from '../api';

// =============================================================================
// TYPES - New Navigation API Structure
// =============================================================================

/** Static block item (system, admin pages) */
export interface NavigationItem {
  uiComponent: string;
  uiLabel: string;
  uiPath: string;
  order: number;
  objectKey: string;
}

/** Subgroup within a static block (for nested navigation) */
export interface NavSubgroup {
  id: string;
  title: string;
  order: number;
  items: NavigationItem[];
}

/** Static navigation block */
export interface StaticBlock {
  type: 'static';
  id: string;
  title: string;
  order: number;
  items: NavigationItem[];
  subgroups?: NavSubgroup[];
}

/** View within a feature instance */
export interface FeatureView {
  uiComponent: string;
  uiLabel: string;
  uiPath: string;
  order: number;
  objectKey: string;
}

/** Feature instance within a mandate */
export interface FeatureInstance {
  id: string;
  uiLabel: string;
  order: number;
  views: FeatureView[];
}

/** Feature within a mandate */
export interface MandateFeature {
  uiComponent: string;
  uiLabel: string;
  order: number;
  instances: FeatureInstance[];
}

/** Mandate in the dynamic block */
export interface NavigationMandate {
  id: string;
  uiLabel: string;
  order: number;
  features: MandateFeature[];
}

/** Dynamic navigation block (features) */
export interface DynamicBlock {
  type: 'dynamic';
  id: string;
  title: string;
  order: number;
  mandates: NavigationMandate[];
}

/** Union type for all block types */
export type NavigationBlock = StaticBlock | DynamicBlock;

/** API Response structure */
export interface NavigationResponse {
  language: string;
  blocks: NavigationBlock[];
}

/** Hook return type */
interface UseNavigationReturn {
  /** All navigation blocks from API */
  blocks: NavigationBlock[];
  /** Static blocks only (for convenience) */
  staticBlocks: StaticBlock[];
  /** Dynamic block (features) if present */
  dynamicBlock: DynamicBlock | null;
  /** Loading state */
  loading: boolean;
  /** Error message if any */
  error: string | null;
  /** Refresh navigation data */
  refresh: () => Promise<void>;
}

// =============================================================================
// HELPER FUNCTIONS
// =============================================================================

function isStaticBlock(block: NavigationBlock): block is StaticBlock {
  return block.type === 'static';
}

function isDynamicBlock(block: NavigationBlock): block is DynamicBlock {
  return block.type === 'dynamic';
}

// =============================================================================
// HOOK
// =============================================================================

export function useNavigation(language: string = 'de'): UseNavigationReturn {
  const [blocks, setBlocks] = useState<NavigationBlock[]>([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);

  const fetchNavigation = useCallback(async () => {
    setLoading(true);
    setError(null);
    
    try {
      // New API endpoint: /api/navigation (without /system prefix)
      const response = await api.get<NavigationResponse>(
        `/api/navigation?language=${language}`
      );
      
      // Blocks are already sorted by order from backend
      setBlocks(response.data.blocks || []);
      
    } catch (err: unknown) {
      const errorMsg = err instanceof Error 
        ? err.message 
        : (err as { response?: { data?: { detail?: string } } })?.response?.data?.detail 
          || 'Fehler beim Laden der Navigation';
      setError(errorMsg);
      setBlocks([]);
    } finally {
      setLoading(false);
    }
  }, [language]);

  useEffect(() => {
    fetchNavigation();
  }, [fetchNavigation]);

  useEffect(() => {
    const onFeaturesChanged = () => {
      fetchNavigation();
    };
    window.addEventListener('features-changed', onFeaturesChanged);
    return () => window.removeEventListener('features-changed', onFeaturesChanged);
  }, [fetchNavigation]);

  // Derive static and dynamic blocks
  const staticBlocks = blocks.filter(isStaticBlock);
  const dynamicBlock = blocks.find(isDynamicBlock) || null;

  return {
    blocks,
    staticBlocks,
    dynamicBlock,
    loading,
    error,
    refresh: fetchNavigation,
  };
}

export default useNavigation;