import apiClient from '@/lib/api/axios-instance';
import { AxiosError } from 'axios';
import { 
  AssetAssignment, 
  AssetAssignmentCreateRequest, 
  AssetAssignmentUpdateRequest,
  validateAssetAssignmentApiResponse 
} from '@/types/asset-management';
import { assetApi } from './assetApi';
import { employeeApi } from './employeeApi';

// Helper to create a safe asset assignment object with default values for null/undefined fields
const createSafeAssetAssignment = (data: any): AssetAssignment => {
  return {
    assignmentID: data.assignmentID || 0,
    assetID: data.assetID || 0,
    employeeID: data.employeeID || 0,
    employeeName: data.employeeName || '',
    assetCode: data.assetCode || '',
    assignedDate: data.assignedDate || new Date().toISOString(),
    returnedDate: data.returnedDate || null,
    remarks: data.remarks || '',
  };
};

// Helper to ensure dates are in ISO 8601 format
const formatDateToISO = (dateString: string): string => {
  if (!dateString) return new Date().toISOString();
  
  // If already in ISO format, return as is
  if (dateString.includes('T') && dateString.includes('Z')) {
    return dateString;
  }
  
  // If it's a date-only string, add time component
  if (dateString.match(/^\d{4}-\d{2}-\d{2}$/)) {
    return `${dateString}T12:00:00.000Z`;
  }
  
  // Try to parse and convert to ISO
  try {
    return new Date(dateString).toISOString();
  } catch (error) {
    console.warn('AssetAssignmentApi: Invalid date format, using current date:', dateString);
    return new Date().toISOString();
  }
};

// Helper to handle API errors with user-friendly messages
const handleApiError = (error: unknown, operation: string): never => {
  console.error(`AssetAssignmentApi: 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 assignment was not found.');
      case 409:
        throw new Error('This assignment conflicts with existing data or the asset is already assigned.');
      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(`AssetAssignmentApi: Retry attempt ${attempt}/${maxRetries} in ${waitTime}ms`);
      await new Promise(resolve => setTimeout(resolve, waitTime));
    }
  }
  
  throw lastError;
};

class AssetAssignmentApi {
  private baseUrl = `/api/AssetAssignments`;

  async getAll(): Promise<AssetAssignment[]> {
    try {
      console.log('AssetAssignmentApi: Fetching all asset assignments from', this.baseUrl);
      const response = await apiClient.get(this.baseUrl);
      
      console.log('AssetAssignmentApi: Response status', response.status);
      
      if (!response.data) {
        console.warn('AssetAssignmentApi: No data in response');
        return [];
      }
      
      if (!Array.isArray(response.data)) {
        console.warn('AssetAssignmentApi: Response is not an array', response.data);
        return [];
      }
      
      console.log(`AssetAssignmentApi: Found ${response.data.length} asset assignments`);
      
      // Map each item to ensure it has all required fields and validate
      return response.data.map(item => {
        try {
          return validateAssetAssignmentApiResponse(item);
        } catch (error) {
          console.warn('AssetAssignmentApi: Invalid asset assignment data, using safe fallback:', error);
          return createSafeAssetAssignment(item);
        }
      });
    } catch (error) {
      console.error('AssetAssignmentApi: Error fetching asset assignments:', error);
      // Return empty array instead of throwing to prevent UI crashes
      return [];
    }
  }

  async getById(id: number): Promise<AssetAssignment | null> {
    try {
      console.log(`AssetAssignmentApi: Fetching asset assignment ${id}`);
      const response = await apiClient.get(`${this.baseUrl}/${id}`);
      
      console.log(`AssetAssignmentApi: Response status for asset assignment ${id}`, response.status);
      
      if (response.data) {
        try {
          return validateAssetAssignmentApiResponse(response.data);
        } catch (error) {
          console.warn(`AssetAssignmentApi: Invalid asset assignment data for ID ${id}, using safe fallback:`, error);
          return createSafeAssetAssignment(response.data);
        }
      }
      return null;
    } catch (error) {
      console.error(`AssetAssignmentApi: Error fetching asset assignment ${id}:`, error);
      return null;
    }
  }

  async getByAssetId(assetId: number): Promise<AssetAssignment[]> {
    try {
      console.log(`AssetAssignmentApi: Fetching asset assignments for asset ${assetId}`);
      const response = await apiClient.get(`${this.baseUrl}/by-asset/${assetId}`);
      
      console.log(`AssetAssignmentApi: Response status for asset ${assetId} assignments`, response.status);
      
      if (!response.data) {
        console.warn(`AssetAssignmentApi: No asset assignments found for asset ${assetId}`);
        return [];
      }
      
      if (!Array.isArray(response.data)) {
        console.warn(`AssetAssignmentApi: Response is not an array for asset ${assetId}`, response.data);
        return [];
      }
      
      console.log(`AssetAssignmentApi: Found ${response.data.length} asset assignments for asset ${assetId}`);
      
      // Map each item to ensure it has all required fields and validate
      return response.data.map(item => {
        try {
          return validateAssetAssignmentApiResponse(item);
        } catch (error) {
          console.warn(`AssetAssignmentApi: Invalid asset assignment data for asset ${assetId}, using safe fallback:`, error);
          return createSafeAssetAssignment(item);
        }
      });
    } catch (error) {
      console.error(`AssetAssignmentApi: Error fetching asset assignments for asset ${assetId}:`, error);
      // Return empty array instead of throwing to prevent UI crashes
      return [];
    }
  }

  async getByEmployeeId(employeeId: number): Promise<AssetAssignment[]> {
    try {
      console.log(`AssetAssignmentApi: Fetching asset assignments for employee ${employeeId}`);
      const response = await apiClient.get(`${this.baseUrl}/by-employee/${employeeId}`);
      
      console.log(`AssetAssignmentApi: Response status for employee ${employeeId} assignments`, response.status);
      
      if (!response.data) {
        console.warn(`AssetAssignmentApi: No asset assignments found for employee ${employeeId}`);
        return [];
      }
      
      if (!Array.isArray(response.data)) {
        console.warn(`AssetAssignmentApi: Response is not an array for employee ${employeeId}`, response.data);
        return [];
      }
      
      console.log(`AssetAssignmentApi: Found ${response.data.length} asset assignments for employee ${employeeId}`);
      
      // Map each item to ensure it has all required fields and validate
      return response.data.map(item => {
        try {
          return validateAssetAssignmentApiResponse(item);
        } catch (error) {
          console.warn(`AssetAssignmentApi: Invalid asset assignment data for employee ${employeeId}, using safe fallback:`, error);
          return createSafeAssetAssignment(item);
        }
      });
    } catch (error) {
      console.error(`AssetAssignmentApi: Error fetching asset assignments for employee ${employeeId}:`, error);
      // Return empty array instead of throwing to prevent UI crashes
      return [];
    }
  }

  async create(assetAssignment: AssetAssignmentCreateRequest): Promise<AssetAssignment> {
    return retryOperation(async () => {
      try {
        // Validate that the referenced asset exists
        const asset = await assetApi.getById(assetAssignment.assetID);
        if (!asset) {
          throw new Error(`Asset with ID ${assetAssignment.assetID} does not exist. Please select a valid asset.`);
        }
        
        // Validate that the referenced employee exists
        const employeeResponse = await employeeApi.getById(assetAssignment.employeeID);
        if (!employeeResponse.success || !employeeResponse.data) {
          throw new Error(`Employee with ID ${assetAssignment.employeeID} does not exist. Please select a valid employee.`);
        }
        
        // Format dates to ISO 8601
        const assetAssignmentData = {
          ...assetAssignment,
          assignedDate: formatDateToISO(assetAssignment.assignedDate),
          returnedDate: assetAssignment.returnedDate ? formatDateToISO(assetAssignment.returnedDate) : null,
        };
        
        console.log('AssetAssignmentApi: Creating asset assignment with data', assetAssignmentData);
        const response = await apiClient.post(this.baseUrl, assetAssignmentData);
        
        console.log('AssetAssignmentApi: Create response status', response.status);
        
        try {
          return validateAssetAssignmentApiResponse(response.data);
        } catch (error) {
          console.warn('AssetAssignmentApi: Invalid response data from create, using safe fallback:', error);
          return createSafeAssetAssignment(response.data);
        }
      } catch (error) {
        handleApiError(error, 'create asset assignment');
      }
    }, 2); // Fewer retries for create operations
  }

  async update(id: number, assetAssignment: AssetAssignmentUpdateRequest): Promise<AssetAssignment> {
    try {
      // Validate that the referenced asset exists
      const asset = await assetApi.getById(assetAssignment.assetID);
      if (!asset) {
        const errorMessage = `Asset with ID ${assetAssignment.assetID} does not exist`;
        console.error('AssetAssignmentApi:', errorMessage);
        throw new Error(errorMessage);
      }
      
      // Validate that the referenced employee exists
      const employeeResponse = await employeeApi.getById(assetAssignment.employeeID);
      if (!employeeResponse.success || !employeeResponse.data) {
        const errorMessage = `Employee with ID ${assetAssignment.employeeID} does not exist`;
        console.error('AssetAssignmentApi:', errorMessage);
        throw new Error(errorMessage);
      }
      
      // Format dates to ISO 8601
      const assetAssignmentData = {
        ...assetAssignment,
        assignedDate: formatDateToISO(assetAssignment.assignedDate),
        returnedDate: assetAssignment.returnedDate ? formatDateToISO(assetAssignment.returnedDate) : null,
      };
      
      console.log(`AssetAssignmentApi: Updating asset assignment ${id} with data`, assetAssignmentData);
      const response = await apiClient.put(`${this.baseUrl}/${id}`, assetAssignmentData);
      
      console.log(`AssetAssignmentApi: Update response status for asset assignment ${id}`, response.status);
      
      try {
        return validateAssetAssignmentApiResponse(response.data);
      } catch (error) {
        console.warn(`AssetAssignmentApi: Invalid response data from update for ID ${id}, using safe fallback:`, error);
        return createSafeAssetAssignment(response.data);
      }
    } catch (error) {
      console.error(`AssetAssignmentApi: Error updating asset assignment ${id}:`, error);
      throw error;
    }
  }

  async delete(id: number): Promise<void> {
    try {
      console.log(`AssetAssignmentApi: Deleting asset assignment ${id}`);
      await apiClient.delete(`${this.baseUrl}/${id}`);
      console.log(`AssetAssignmentApi: Asset assignment ${id} deleted successfully`);
    } catch (error) {
      console.error(`AssetAssignmentApi: Error deleting asset assignment ${id}:`, error);
      throw error;
    }
  }

  async getAssignmentHistory(assetId: number): Promise<{
    success: boolean;
    data: Array<AssetAssignment & {
      assignmentStatus: string;
      assignmentDuration: number | null;
      returnReason: string | null;
      employee: {
        id: number;
        empCode: string;
        firstName: string;
        middleName: string;
        lastName: string;
        email: string;
        mobile: string;
        type: string;
        academics: string;
        financialData: string;
        status: string;
        description: string;
        userId: number;
        passwordHash: string | null;
        roleId: number;
        createdBy: number;
        createdAt: string;
        createdByName: string | null;
        updatedBy: number;
        updatedAt: string;
        updatedByName: string;
      };
    }>;
    totalAssignments: number;
    activeAssignments: number;
    completedAssignments: number;
    totalDaysAssigned: number;
    message: string;
  }> {
    return retryOperation(async () => {
      try {
        console.log(`AssetAssignmentApi: Fetching assignment history for asset ${assetId}`);
        // Use the history by-asset endpoint
        const response = await apiClient.get(`${this.baseUrl}/history/by-asset/${assetId}`);
        
        console.log(`AssetAssignmentApi: Response status for asset ${assetId} assignment history`, response.status);
        
        if (!response.data) {
          console.warn(`AssetAssignmentApi: No assignment history found for asset ${assetId}`);
          return {
            success: false,
            data: [],
            totalAssignments: 0,
            activeAssignments: 0,
            completedAssignments: 0,
            totalDaysAssigned: 0,
            message: `No assignment history found for asset ${assetId}`
          };
        }
        
        // Check if response already has the expected structure (from your curl example)
        if (response.data.success !== undefined && response.data.data !== undefined) {
          console.log(`AssetAssignmentApi: Found assignment history for asset ${assetId}:`, response.data);
          return response.data;
        }
        
        // If it's just an array, transform it to match the expected structure
        const assignments = Array.isArray(response.data) ? response.data : [];
        const activeAssignments = assignments.filter((assignment: any) => !assignment.returnedDate).length;
        const completedAssignments = assignments.filter((assignment: any) => assignment.returnedDate).length;
        
        // Calculate total days assigned for completed assignments
        const totalDaysAssigned = assignments.reduce((total: number, assignment: any) => {
          if (assignment.returnedDate && assignment.assignedDate) {
            const assignedDate = new Date(assignment.assignedDate);
            const returnedDate = new Date(assignment.returnedDate);
            const diffTime = Math.abs(returnedDate.getTime() - assignedDate.getTime());
            const diffDays = Math.ceil(diffTime / (1000 * 60 * 60 * 24));
            return total + diffDays;
          }
          return total;
        }, 0);
        
        console.log(`AssetAssignmentApi: Found ${assignments.length} assignments for asset ${assetId}`);
        
        return {
          success: true,
          data: assignments.map((assignment: any) => ({
            ...assignment,
            assignmentStatus: assignment.returnedDate ? 'Returned' : 'Active',
            assignmentDuration: assignment.returnedDate && assignment.assignedDate 
              ? Math.ceil((new Date(assignment.returnedDate).getTime() - new Date(assignment.assignedDate).getTime()) / (1000 * 60 * 60 * 24))
              : null,
            returnReason: assignment.returnReason || null
          })),
          totalAssignments: assignments.length,
          activeAssignments,
          completedAssignments,
          totalDaysAssigned,
          message: 'Assignment history retrieved successfully'
        };
      } catch (error) {
        if (error instanceof AxiosError && error.response?.status === 404) {
          console.log(`AssetAssignmentApi: No assignment history found for asset ${assetId}`);
          return {
            success: false,
            data: [],
            totalAssignments: 0,
            activeAssignments: 0,
            completedAssignments: 0,
            totalDaysAssigned: 0,
            message: `No assignment history found for asset ${assetId}`
          };
        }
        handleApiError(error, `fetch assignment history for asset ${assetId}`);
      }
    });
  }

  async getActiveAssignments(): Promise<{
    success: boolean;
    data: Array<AssetAssignment & {
      assignmentStatus: string;
      daysSinceAssigned: number;
      employee: {
        id: number;
        empCode: string;
        firstName: string;
        middleName: string;
        lastName: string;
        email: string;
        mobile: string;
        type: string;
        academics: string;
        financialData: string;
        status: string;
        description: string;
        userId: number;
        passwordHash: string | null;
        roleId: number;
        createdBy: number;
        createdAt: string;
        createdByName: string | null;
        updatedBy: number;
        updatedAt: string;
        updatedByName: string;
      };
      asset?: {
        assetID: number;
        assetCode: string;
        assetType: string;
        brandModel: string;
        serialNumber: string;
        assetCondition: string;
      };
    }>;
    totalActiveAssignments: number;
    overdueAssignments: number;
    assignmentsByDepartment: Record<string, number>;
    message: string;
  }> {
    return retryOperation(async () => {
      try {
        console.log('AssetAssignmentApi: Fetching all active assignments');
        const response = await apiClient.get(`${this.baseUrl}/active`);
        
        console.log('AssetAssignmentApi: Response status for active assignments', response.status);
        
        if (!response.data) {
          console.warn('AssetAssignmentApi: No active assignments found');
          return {
            success: false,
            data: [],
            totalActiveAssignments: 0,
            overdueAssignments: 0,
            assignmentsByDepartment: {},
            message: 'No active assignments found'
          };
        }
        
        console.log('AssetAssignmentApi: Found active assignments:', response.data);
        
        // Return the response as-is since it should match the expected structure
        return response.data;
      } catch (error) {
        if (error instanceof AxiosError && error.response?.status === 404) {
          console.log('AssetAssignmentApi: No active assignments found');
          return {
            success: false,
            data: [],
            totalActiveAssignments: 0,
            overdueAssignments: 0,
            assignmentsByDepartment: {},
            message: 'No active assignments found'
          };
        }
        handleApiError(error, 'fetch active assignments');
      }
    });
  }

  async bulkReturn(request: {
    assignmentIds: number[];
    returnedDate: string;
    returnReason?: string;
    remarks?: string;
    performedBy?: {
      employeeID: number;
      name: string;
    };
  }): Promise<{
    success: boolean;
    data: {
      processedAssignments: number;
      successfulReturns: number;
      failedReturns: number;
      results: Array<{
        assignmentID: number;
        status: 'success' | 'failed';
        message: string;
        returnedAssignment?: AssetAssignment;
        error?: string;
      }>;
    };
    summary: {
      totalRequested: number;
      successful: number;
      failed: number;
      assetsReturned: number;
      employeesAffected: number;
    };
    message: string;
  }> {
    return retryOperation(async () => {
      try {
        // Validate input
        if (!Array.isArray(request.assignmentIds) || request.assignmentIds.length === 0) {
          throw new Error('Assignment IDs array is required and cannot be empty');
        }
        
        if (request.assignmentIds.length > 100) {
          throw new Error('Cannot return more than 100 assignments at once');
        }
        
        // Format the request data
        const requestData = {
          assignmentIds: request.assignmentIds,
          returnedDate: formatDateToISO(request.returnedDate),
          returnReason: request.returnReason || 'Bulk return operation',
          remarks: request.remarks || 'Bulk returned via system',
          performedBy: request.performedBy
        };
        
        console.log(`AssetAssignmentApi: Bulk returning ${request.assignmentIds.length} assignments`, requestData);
        const response = await apiClient.post(`${this.baseUrl}/bulk-return`, requestData);
        
        console.log('AssetAssignmentApi: Bulk return response status', response.status);
        console.log('AssetAssignmentApi: Bulk return response data', response.data);
        
        // Validate response structure
        if (!response.data || typeof response.data !== 'object') {
          throw new Error('Invalid response format from bulk return API');
        }
        
        const result = response.data;
        
        // Ensure required fields exist
        if (typeof result.success !== 'boolean') {
          throw new Error('Invalid response: missing success field');
        }
        
        console.log(`AssetAssignmentApi: Bulk return completed - ${result.data?.successfulReturns || 0} successful, ${result.data?.failedReturns || 0} failed`);
        
        return result;
      } catch (error) {
        handleApiError(error, 'bulk return assignments');
      }
    }, 1); // No retries for bulk operations to avoid duplicate operations
  }
}

export const assetAssignmentApi = new AssetAssignmentApi();