import apiClient from '@/lib/api/axios-instance';
import { AxiosError } from 'axios';
import { 
  Asset, 
  AssetCreateRequest, 
  AssetUpdateRequest,
  BulkImportResponse,
  validateAssetApiResponse 
} from '@/types/asset-management';

// Helper to create a safe asset object with default values for null/undefined fields
const createSafeAsset = (data: any): Asset => {
  return {
    assetID: data.assetID || 0,
    assetType: data.assetType || '',
    brandModel: data.brandModel || '',
    serialNumber: data.serialNumber || '',
    assetCondition: data.assetCondition || 'Good',
  };
};

// Helper to handle API errors with user-friendly messages
const handleApiError = (error: unknown, operation: string): never => {
  console.error(`AssetApi: Error during ${operation}:`, error);
  
  if (error instanceof AxiosError) {
    const status = error.response?.status;
    const message = error.response?.data?.message || error.message;
    
    switch (status) {
      case 400:
        throw new Error(`Invalid request: ${message}`);
      case 401:
        throw new Error('You are not authorized to perform this action. Please log in again.');
      case 403:
        throw new Error('You do not have permission to perform this action.');
      case 404:
        throw new Error('The requested asset was not found.');
      case 409:
        throw new Error('This asset already exists or conflicts with existing data.');
      case 422:
        throw new Error(`Validation failed: ${message}`);
      case 500:
        throw new Error('Server error occurred. Please try again later.');
      case 503:
        throw new Error('Service is temporarily unavailable. Please try again later.');
      default:
        throw new Error(`${operation} failed: ${message}`);
    }
  }
  
  if (error instanceof Error) {
    throw new Error(`${operation} failed: ${error.message}`);
  }
  
  throw new Error(`${operation} failed: Unknown error occurred`);
};

// Helper for retry logic
const retryOperation = async <T>(
  operation: () => Promise<T>,
  maxRetries: number = 3,
  delay: number = 1000
): Promise<T> => {
  let lastError: unknown;
  
  for (let attempt = 1; attempt <= maxRetries; attempt++) {
    try {
      return await operation();
    } catch (error) {
      lastError = error;
      
      // Don't retry on client errors (4xx) except for 408 (timeout) and 429 (rate limit)
      if (error instanceof AxiosError) {
        const status = error.response?.status;
        if (status && status >= 400 && status < 500 && status !== 408 && status !== 429) {
          throw error;
        }
      }
      
      if (attempt === maxRetries) {
        throw lastError;
      }
      
      // Exponential backoff
      const waitTime = delay * Math.pow(2, attempt - 1);
      console.log(`AssetApi: Retry attempt ${attempt}/${maxRetries} in ${waitTime}ms`);
      await new Promise(resolve => setTimeout(resolve, waitTime));
    }
  }
  
  throw lastError;
};

class AssetApi {
  private baseUrl = `/api/Assets`;

  async getAll(): Promise<Asset[]> {
    return retryOperation(async () => {
      try {
        console.log('AssetApi: Fetching all assets from', this.baseUrl);
        const response = await apiClient.get(this.baseUrl);
        
        console.log('AssetApi: Response status', response.status);
        
        if (!response.data) {
          console.warn('AssetApi: No data in response');
          return [];
        }
        
        if (!Array.isArray(response.data)) {
          console.warn('AssetApi: Response is not an array', response.data);
          return [];
        }
        
        console.log(`AssetApi: Found ${response.data.length} assets`);
        
        // Map each item to ensure it has all required fields and validate
        return response.data.map(item => {
          try {
            return validateAssetApiResponse(item);
          } catch (error) {
            console.warn('AssetApi: Invalid asset data, using safe fallback:', error);
            return createSafeAsset(item);
          }
        });
      } catch (error) {
        handleApiError(error, 'fetch assets');
      }
    });
  }

  async getById(id: number): Promise<Asset | null> {
    return retryOperation(async () => {
      try {
        console.log(`AssetApi: Fetching asset ${id}`);
        const response = await apiClient.get(`${this.baseUrl}/${id}`);
        
        console.log(`AssetApi: Response status for asset ${id}`, response.status);
        
        if (response.data) {
          try {
            return validateAssetApiResponse(response.data);
          } catch (error) {
            console.warn(`AssetApi: Invalid asset data for ID ${id}, using safe fallback:`, error);
            return createSafeAsset(response.data);
          }
        }
        return null;
      } catch (error) {
        if (error instanceof AxiosError && error.response?.status === 404) {
          return null; // Asset not found is a valid case
        }
        handleApiError(error, `fetch asset ${id}`);
      }
    });
  }

  async create(asset: AssetCreateRequest): Promise<Asset> {
    return retryOperation(async () => {
      try {
        // Validate and normalize the input data structure
        const assetData = { 
          ...asset,
          // Ensure serialNumber is always a string
          serialNumber: String(asset.serialNumber || '').trim()
        };
        
        console.log('AssetApi: Creating asset with data', assetData);
        const response = await apiClient.post(this.baseUrl, assetData);
        
        console.log('AssetApi: Create response status', response.status);
        
        try {
          return validateAssetApiResponse(response.data);
        } catch (error) {
          console.warn('AssetApi: Invalid response data from create, using safe fallback:', error);
          return createSafeAsset(response.data);
        }
      } catch (error) {
        handleApiError(error, 'create asset');
      }
    }, 2); // Fewer retries for create operations
  }

  async update(id: number, asset: AssetUpdateRequest): Promise<Asset> {
    return retryOperation(async () => {
      try {
        const assetData = { 
          ...asset,
          // Ensure serialNumber is always a string
          serialNumber: String(asset.serialNumber || '').trim()
        };
        
        console.log(`AssetApi: Updating asset ${id} with data`, assetData);
        const response = await apiClient.put(`${this.baseUrl}/${id}`, assetData);
        
        console.log(`AssetApi: Update response status for asset ${id}`, response.status);
        
        try {
          return validateAssetApiResponse(response.data);
        } catch (error) {
          console.warn(`AssetApi: Invalid response data from update for ID ${id}, using safe fallback:`, error);
          return createSafeAsset(response.data);
        }
      } catch (error) {
        handleApiError(error, `update asset ${id}`);
      }
    }, 2); // Fewer retries for update operations
  }

  async delete(id: number): Promise<void> {
    return retryOperation(async () => {
      try {
        console.log(`AssetApi: Deleting asset ${id}`);
        
        // Check for referential integrity - prevent deletion if asset has active assignments
        try {
          const response = await apiClient.get(`/api/AssetAssignments/by-asset/${id}`);
          const assignments = response.data || [];
          
          // Check if there are any active assignments (no returned date)
          const activeAssignments = assignments.filter((assignment: any) => !assignment.returnedDate);
          if (activeAssignments.length > 0) {
            throw new Error(
              `Cannot delete asset: Asset is currently assigned to ${activeAssignments.length} employee(s). ` +
              'Please return all active assignments before deleting this asset.'
            );
          }
          
          // Check if there are any assignments at all (for user confirmation)
          if (assignments.length > 0) {
            console.warn(`AssetApi: Asset ${id} has ${assignments.length} historical assignment(s) that will be deleted`);
          }
        } catch (checkError) {
          // If the check fails due to network issues, we still allow deletion
          // but if it's a referential integrity error, we throw it
          if (checkError instanceof Error && checkError.message.includes('Cannot delete asset')) {
            throw checkError;
          }
          console.warn(`AssetApi: Could not check assignments for asset ${id}, proceeding with deletion:`, checkError);
        }
        
        await apiClient.delete(`${this.baseUrl}/${id}`);
        console.log(`AssetApi: Asset ${id} deleted successfully`);
      } catch (error) {
        handleApiError(error, `delete asset ${id}`);
      }
    }, 2); // Fewer retries for delete operations
  }

  async bulkImport(assets: AssetCreateRequest[]): Promise<BulkImportResponse> {
    return retryOperation(async () => {
      try {
        console.log(`AssetApi: Bulk importing ${assets.length} assets`);
        
        // Validate input
        if (!Array.isArray(assets) || assets.length === 0) {
          throw new Error('Assets array is required and cannot be empty');
        }
        
        if (assets.length > 1000) {
          throw new Error('Cannot import more than 1000 assets at once');
        }
        
        // Normalize all assets to ensure serialNumber is a string
        const normalizedAssets = assets.map(asset => ({
          ...asset,
          // Ensure serialNumber is always a string, handle numbers, nulls, etc.
          serialNumber: String(asset.serialNumber || '').trim(),
          // Also normalize other string fields that might come as numbers
          assetType: String(asset.assetType || '').trim(),
          brandModel: String(asset.brandModel || '').trim(),
          assetCondition: String(asset.assetCondition || '').trim(),
          location: asset.location ? String(asset.location).trim() : undefined,
          notes: asset.notes ? String(asset.notes).trim() : undefined,
          purchaseDate: asset.purchaseDate ? String(asset.purchaseDate).trim() : undefined,
          warrantyExpiry: asset.warrantyExpiry ? String(asset.warrantyExpiry).trim() : undefined
        }));
        
        const requestData = { assets: normalizedAssets };
        console.log('AssetApi: Bulk import request data', requestData);
        
        const response = await apiClient.post(`${this.baseUrl}/bulk-import`, requestData);
        
        console.log('AssetApi: Bulk import response status', response.status);
        console.log('AssetApi: Bulk import response data', response.data);
        
        // Validate response structure
        if (!response.data || typeof response.data !== 'object') {
          throw new Error('Invalid response format from bulk import API');
        }
        
        const result = response.data as BulkImportResponse;
        
        // Ensure required fields exist
        if (typeof result.success !== 'boolean') {
          throw new Error('Invalid response: missing success field');
        }
        
        if (!result.results || typeof result.results !== 'object') {
          throw new Error('Invalid response: missing results field');
        }
        
        // Validate and sanitize created assets
        if (result.results.createdAssets && Array.isArray(result.results.createdAssets)) {
          result.results.createdAssets = result.results.createdAssets.map(asset => {
            try {
              return validateAssetApiResponse(asset);
            } catch (error) {
              console.warn('AssetApi: Invalid asset in bulk import response, using safe fallback:', error);
              return createSafeAsset(asset);
            }
          });
        }
        
        console.log(`AssetApi: Bulk import completed - ${result.results.successful} successful, ${result.results.failed} failed`);
        
        return result;
      } catch (error) {
        handleApiError(error, 'bulk import assets');
      }
    }, 1); // No retries for bulk operations to avoid duplicate imports
  }
}

export const assetApi = new AssetApi();