import apiClient from '@/lib/api/axios-instance';
import { AxiosError } from 'axios';
import { 
  AssetRequest,
  AssetRequestCreateRequest,
  AssetRequestApprovalRequest,
  AssetRequestRejectionRequest,
  AssetRequestAssignmentRequest,
  AssetRequestCommentRequest,
  AssetRequestWithAvailability,
  AvailabilityCheck,
  RequestFilters,
  RequestedAssetItem,
  validateAssetRequestApiResponse,
  isValidStatusTransition
} from '@/types/asset-request';
import { assetAssignmentApi } from './assetAssignmentApi';
import { assetApi } from './assetApi';

// Helper to create a safe asset request object with default values for null/undefined fields
const createSafeAssetRequest = (data: any): AssetRequest => {
  return {
    requestID: data.requestID || 0,
    employeeID: data.employeeID || 0,
    employeeName: data.employeeName || '',
    requestedAssets: data.requestedAssets || [],
    justification: data.justification || '',
    status: data.status || 'pending',
    submittedDate: data.submittedDate || new Date().toISOString(),
    reviewedDate: data.reviewedDate || null,
    reviewedBy: data.reviewedBy || null,
    reviewerName: data.reviewerName || null,
    adminComments: data.adminComments || null,
    assignedDate: data.assignedDate || null,
    assignedBy: data.assignedBy || null,
    assignerName: data.assignerName || null,
    acknowledgedDate: data.acknowledgedDate || null,
    acknowledgedBy: data.acknowledgedBy || null,
    acknowledgementComments: data.acknowledgementComments || null,
  };
};

// Helper to handle API errors with user-friendly messages
const handleApiError = (error: unknown, operation: string): never => {
  console.error(`AssetRequestApi: 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 request was not found.');
      case 409:
        throw new Error('This request conflicts with existing data or cannot be processed in its current state.');
      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(`AssetRequestApi: Retry attempt ${attempt}/${maxRetries} in ${waitTime}ms`);
      await new Promise(resolve => setTimeout(resolve, waitTime));
    }
  }
  
  throw lastError;
};

class AssetRequestApi {
  private baseUrl = `/api/AssetRequests`;

  /**
   * Create a new asset request
   * @param request - Asset request creation data
   * @returns Created asset request
   */
  async create(request: AssetRequestCreateRequest): Promise<AssetRequest> {
    return retryOperation(async () => {
      try {
        console.log('AssetRequestApi: Creating asset request with data', request);
        const response = await apiClient.post(this.baseUrl, request);
        
        console.log('AssetRequestApi: Create response status', response.status);
        
        // Handle wrapped response format: { success, message, data }
        const responseData = response.data.data || response.data;
        
        try {
          return validateAssetRequestApiResponse(responseData);
        } catch (error) {
          console.warn('AssetRequestApi: Invalid response data from create, using safe fallback:', error);
          return createSafeAssetRequest(responseData);
        }
      } catch (error) {
        handleApiError(error, 'create asset request');
      }
    }, 2); // Fewer retries for create operations
  }

  /**
   * Get asset request by ID
   * @param id - Request ID
   * @returns Asset request or null if not found
   */
  async getById(id: number): Promise<AssetRequest | null> {
    return retryOperation(async () => {
      try {
        console.log(`AssetRequestApi: Fetching asset request ${id}`);
        const response = await apiClient.get(`${this.baseUrl}/${id}`);
        
        console.log(`AssetRequestApi: Response status for asset request ${id}`, response.status);
        
        if (response.data) {
          // Handle wrapped response format: { success, message, data }
          const responseData = response.data.data || response.data;
          
          try {
            return validateAssetRequestApiResponse(responseData);
          } catch (error) {
            console.warn(`AssetRequestApi: Invalid asset request data for ID ${id}, using safe fallback:`, error);
            return createSafeAssetRequest(responseData);
          }
        }
        return null;
      } catch (error) {
        if (error instanceof AxiosError && error.response?.status === 404) {
          return null; // Request not found is a valid case
        }
        handleApiError(error, `fetch asset request ${id}`);
      }
    });
  }

  /**
   * Get asset requests by employee ID
   * @param employeeId - Employee ID
   * @returns List of asset requests for the employee
   */
  async getByEmployeeId(employeeId: number): Promise<AssetRequest[]> {
    return retryOperation(async () => {
      try {
        console.log(`AssetRequestApi: Fetching asset requests for employee ${employeeId}`);
        const response = await apiClient.get(`${this.baseUrl}/employee/${employeeId}`);
        
        console.log(`AssetRequestApi: Response status for employee ${employeeId} requests`, response.status);
        
        if (!response.data) {
          console.warn(`AssetRequestApi: No asset requests found for employee ${employeeId}`);
          return [];
        }
        
        // Handle wrapped response format: { success, message, data }
        const dataArray = response.data.data || response.data;
        
        if (!Array.isArray(dataArray)) {
          console.warn(`AssetRequestApi: Response is not an array for employee ${employeeId}`, response.data);
          return [];
        }
        
        console.log(`AssetRequestApi: Found ${dataArray.length} asset requests for employee ${employeeId}`);
        
        // Map each item to ensure it has all required fields and validate
        return dataArray.map(item => {
          try {
            return validateAssetRequestApiResponse(item);
          } catch (error) {
            console.warn(`AssetRequestApi: Invalid asset request data for employee ${employeeId}, using safe fallback:`, error);
            return createSafeAssetRequest(item);
          }
        });
      } catch (error) {
        if (error instanceof AxiosError && error.response?.status === 404) {
          return []; // No requests found is a valid case
        }
        handleApiError(error, `fetch asset requests for employee ${employeeId}`);
      }
    });
  }

  /**
   * Get all asset requests with optional filtering
   * @param filters - Optional filters for status, employee, date range
   * @returns List of asset requests
   */
  async getAll(filters?: RequestFilters): Promise<AssetRequest[]> {
    return retryOperation(async () => {
      try {
        console.log('AssetRequestApi: Fetching all asset requests with filters', filters);
        
        // Build query parameters
        const params: any = {};
        if (filters?.status) params.status = filters.status;
        if (filters?.employeeId) params.employeeId = filters.employeeId;
        if (filters?.dateFrom) params.dateFrom = filters.dateFrom;
        if (filters?.dateTo) params.dateTo = filters.dateTo;
        
        const response = await apiClient.get(this.baseUrl, { params });
        
        console.log('AssetRequestApi: Response status', response.status);
        
        if (!response.data) {
          console.warn('AssetRequestApi: No data in response');
          return [];
        }
        
        // Handle wrapped response format: { success, message, data }
        const dataArray = response.data.data || response.data;
        
        if (!Array.isArray(dataArray)) {
          console.warn('AssetRequestApi: Response is not an array', response.data);
          return [];
        }
        
        console.log(`AssetRequestApi: Found ${dataArray.length} asset requests`);
        
        // Map each item to ensure it has all required fields and validate
        return dataArray.map(item => {
          try {
            return validateAssetRequestApiResponse(item);
          } catch (error) {
            console.warn('AssetRequestApi: Invalid asset request data, using safe fallback:', error);
            return createSafeAssetRequest(item);
          }
        });
      } catch (error) {
        console.error('AssetRequestApi: Error fetching asset requests:', error);
        // Return empty array instead of throwing to prevent UI crashes
        return [];
      }
    });
  }

  /**
   * Get request history for an employee
   * @param employeeId - Employee ID
   * @returns List of asset requests for the employee (alias for getByEmployeeId)
   */
  async getRequestHistory(employeeId: number): Promise<AssetRequest[]> {
    return this.getByEmployeeId(employeeId);
  }

  /**
   * Get all pending asset requests with availability information
   * @returns List of pending requests with availability status
   */
  async getPending(): Promise<AssetRequestWithAvailability[]> {
    return retryOperation(async () => {
      try {
        console.log('AssetRequestApi: Fetching pending asset requests with availability');
        const response = await apiClient.get(`${this.baseUrl}/pending`);
        
        console.log('AssetRequestApi: Response status for pending requests', response.status);
        
        if (!response.data) {
          console.warn('AssetRequestApi: No pending requests found');
          return [];
        }
        
        // Handle wrapped response format: { success, message, data }
        const dataArray = response.data.data || response.data;
        
        if (!Array.isArray(dataArray)) {
          console.warn('AssetRequestApi: Response is not an array', response.data);
          return [];
        }
        
        console.log(`AssetRequestApi: Found ${dataArray.length} pending asset requests`);
        
        // Map each item and ensure availability status is present
        return dataArray.map(item => {
          try {
            const baseRequest = validateAssetRequestApiResponse(item);
            return {
              ...baseRequest,
              availabilityStatus: item.availabilityStatus || []
            } as AssetRequestWithAvailability;
          } catch (error) {
            console.warn('AssetRequestApi: Invalid pending request data, using safe fallback:', error);
            const safeRequest = createSafeAssetRequest(item);
            return {
              ...safeRequest,
              availabilityStatus: item.availabilityStatus || []
            } as AssetRequestWithAvailability;
          }
        });
      } catch (error) {
        console.error('AssetRequestApi: Error fetching pending requests:', error);
        // Return empty array instead of throwing to prevent UI crashes
        return [];
      }
    });
  }

  /**
   * Approve an asset request
   * @param id - Request ID
   * @param data - Approval data with admin comments and reviewer ID
   * @returns Updated asset request
   */
  async approve(id: number, data: AssetRequestApprovalRequest): Promise<AssetRequest> {
    return retryOperation(async () => {
      try {
        // First, get the current request to validate status transition
        const currentRequest = await this.getById(id);
        if (!currentRequest) {
          throw new Error(`Asset request with ID ${id} not found`);
        }
        
        // Validate status transition
        if (!isValidStatusTransition(currentRequest.status, 'approved')) {
          throw new Error(
            `Cannot approve request: Request is currently ${currentRequest.status}. ` +
            'Only pending requests can be approved.'
          );
        }
        
        console.log(`AssetRequestApi: Approving asset request ${id} with data`, data);
        const response = await apiClient.put(`${this.baseUrl}/${id}/approve`, data);
        
        console.log(`AssetRequestApi: Approve response status for request ${id}`, response.status);
        
        // Handle wrapped response format: { success, message, data }
        const responseData = response.data.data || response.data;
        
        try {
          return validateAssetRequestApiResponse(responseData);
        } catch (error) {
          console.warn(`AssetRequestApi: Invalid response data from approve for ID ${id}, using safe fallback:`, error);
          return createSafeAssetRequest(responseData);
        }
      } catch (error) {
        handleApiError(error, `approve asset request ${id}`);
      }
    }, 2); // Fewer retries for state-changing operations
  }

  /**
   * Reject an asset request
   * @param id - Request ID
   * @param data - Rejection data with admin comments and reviewer ID
   * @returns Updated asset request
   */
  async reject(id: number, data: AssetRequestRejectionRequest): Promise<AssetRequest> {
    return retryOperation(async () => {
      try {
        // First, get the current request to validate status transition
        const currentRequest = await this.getById(id);
        if (!currentRequest) {
          throw new Error(`Asset request with ID ${id} not found`);
        }
        
        // Validate status transition
        if (!isValidStatusTransition(currentRequest.status, 'rejected')) {
          throw new Error(
            `Cannot reject request: Request is currently ${currentRequest.status}. ` +
            'Only pending requests can be rejected.'
          );
        }
        
        console.log(`AssetRequestApi: Rejecting asset request ${id} with data`, data);
        const response = await apiClient.put(`${this.baseUrl}/${id}/reject`, data);
        
        console.log(`AssetRequestApi: Reject response status for request ${id}`, response.status);
        
        // Handle wrapped response format: { success, message, data }
        const responseData = response.data.data || response.data;
        
        try {
          return validateAssetRequestApiResponse(responseData);
        } catch (error) {
          console.warn(`AssetRequestApi: Invalid response data from reject for ID ${id}, using safe fallback:`, error);
          return createSafeAssetRequest(responseData);
        }
      } catch (error) {
        handleApiError(error, `reject asset request ${id}`);
      }
    }, 2); // Fewer retries for state-changing operations
  }

  /**
   * Assign assets to an approved request
   * @param id - Request ID
   * @param data - Assignment data with asset details and assigner ID
   * @returns Updated asset request
   */
  async assign(id: number, data: AssetRequestAssignmentRequest): Promise<AssetRequest> {
    return retryOperation(async () => {
      const createdAssignments: number[] = []; // Track created assignments for rollback
      
      try {
        // First, get the current request to validate status transition
        const currentRequest = await this.getById(id);
        if (!currentRequest) {
          throw new Error(`Asset request with ID ${id} not found`);
        }
        
        // Validate status transition
        if (!isValidStatusTransition(currentRequest.status, 'assigned')) {
          throw new Error(
            `Cannot assign assets: Request is currently ${currentRequest.status}. ` +
            'Only approved requests can have assets assigned.'
          );
        }
        
        // Validate that we have assets to assign
        if (!data.assignedAssets || data.assignedAssets.length === 0) {
          throw new Error('At least one asset must be assigned');
        }
        
        // Check availability for all requested assets before proceeding
        const availabilityCheck = await this.checkAvailability(currentRequest.requestedAssets);
        if (!availabilityCheck.canFulfill) {
          const shortfalls = availabilityCheck.details
            .filter(d => d.shortfall > 0)
            .map(d => `${d.assetType}: need ${d.requested}, only ${d.available} available`)
            .join('; ');
          throw new Error(`Insufficient inventory to fulfill request: ${shortfalls}`);
        }
        
        // Validate that assigned assets match requested quantities
        const assignedByType = new Map<string, number>();
        data.assignedAssets.forEach(asset => {
          const count = assignedByType.get(asset.assetType) || 0;
          assignedByType.set(asset.assetType, count + 1);
        });
        
        for (const requestedItem of currentRequest.requestedAssets) {
          const assignedCount = assignedByType.get(requestedItem.assetType) || 0;
          if (assignedCount !== requestedItem.quantity) {
            throw new Error(
              `Asset quantity mismatch for ${requestedItem.assetType}: ` +
              `requested ${requestedItem.quantity}, assigning ${assignedCount}`
            );
          }
        }
        
        // Validate that all assets are currently available (not assigned)
        const allAssignments = await assetAssignmentApi.getAll();
        const activeAssignments = allAssignments.filter(a => !a.returnedDate);
        const assignedAssetIds = new Set(activeAssignments.map(a => a.assetID));
        
        for (const assignedAsset of data.assignedAssets) {
          if (assignedAssetIds.has(assignedAsset.assetID)) {
            throw new Error(
              `Asset ${assignedAsset.assetCode} is already assigned to another employee. ` +
              'Please select a different asset.'
            );
          }
        }
        
        console.log(`AssetRequestApi: Assigning assets to request ${id} with data`, data);
        console.log(`AssetRequestApi: Validation passed - proceeding with ${data.assignedAssets.length} assignments`);
        
        // Create asset assignments for each assigned asset
        for (const assignedAsset of data.assignedAssets) {
          try {
            const assignmentData = {
              assetID: assignedAsset.assetID,
              employeeID: currentRequest.employeeID,
              employeeName: currentRequest.employeeName,
              assetCode: assignedAsset.assetCode,
              assignedDate: new Date().toISOString(),
              returnedDate: null,
              remarks: `Assigned via asset request #${id}: ${currentRequest.justification.substring(0, 100)}`
            };
            
            console.log(`AssetRequestApi: Creating assignment for asset ${assignedAsset.assetID}`, assignmentData);
            const assignment = await assetAssignmentApi.create(assignmentData);
            createdAssignments.push(assignment.assignmentID);
            console.log(`AssetRequestApi: Successfully created assignment ${assignment.assignmentID} for asset ${assignedAsset.assetID}`);
          } catch (error) {
            console.error(`AssetRequestApi: Failed to create assignment for asset ${assignedAsset.assetID}:`, error);
            throw new Error(`Failed to assign asset ${assignedAsset.assetCode}: ${error instanceof Error ? error.message : 'Unknown error'}`);
          }
        }
        
        console.log(`AssetRequestApi: Successfully created ${data.assignedAssets.length} asset assignments`);
        
        // Update the request status to assigned
        try {
          const response = await apiClient.put(`${this.baseUrl}/${id}/assign`, data);
          console.log(`AssetRequestApi: Assign response status for request ${id}`, response.status);
          
          // Log audit trail
          console.log(`AssetRequestApi: Audit log - Request ${id} assigned by user ${data.assignedBy} at ${new Date().toISOString()}`);
          console.log(`AssetRequestApi: Audit log - Assets assigned: ${data.assignedAssets.map(a => a.assetCode).join(', ')}`);
          console.log(`AssetRequestApi: Audit log - Employee: ${currentRequest.employeeName} (ID: ${currentRequest.employeeID})`);
          
          // Handle wrapped response format: { success, message, data }
          const responseData = response.data.data || response.data;
          
          try {
            return validateAssetRequestApiResponse(responseData);
          } catch (error) {
            console.warn(`AssetRequestApi: Invalid response data from assign for ID ${id}, using safe fallback:`, error);
            return createSafeAssetRequest(responseData);
          }
        } catch (error) {
          // If updating the request status fails, rollback all created assignments
          console.error(`AssetRequestApi: Failed to update request status, rolling back ${createdAssignments.length} assignments`);
          await this.rollbackAssignments(createdAssignments);
          throw error;
        }
      } catch (error) {
        // If any error occurs, rollback all created assignments
        if (createdAssignments.length > 0) {
          console.error(`AssetRequestApi: Error during assignment, rolling back ${createdAssignments.length} assignments`);
          await this.rollbackAssignments(createdAssignments);
        }
        handleApiError(error, `assign assets to request ${id}`);
      }
    }, 1); // No retries for assignment operations to avoid duplicate assignments
  }

  /**
   * Add admin comments to a request without changing status
   * @param id - Request ID
   * @param data - Comment data with admin comments and commenter ID
   * @returns Updated asset request
   */
  async addComment(id: number, data: AssetRequestCommentRequest): Promise<AssetRequest> {
    return retryOperation(async () => {
      try {
        console.log(`AssetRequestApi: Adding comment to asset request ${id} with data`, data);
        const response = await apiClient.put(`${this.baseUrl}/${id}/comment`, data);
        
        console.log(`AssetRequestApi: Add comment response status for request ${id}`, response.status);
        
        // Handle wrapped response format: { success, message, data }
        const responseData = response.data.data || response.data;
        
        try {
          return validateAssetRequestApiResponse(responseData);
        } catch (error) {
          console.warn(`AssetRequestApi: Invalid response data from addComment for ID ${id}, using safe fallback:`, error);
          return createSafeAssetRequest(responseData);
        }
      } catch (error) {
        handleApiError(error, `add comment to asset request ${id}`);
      }
    }, 2); // Allow retries for comment operations
  }

  /**
   * Rollback created assignments in case of failure
   * @param assignmentIds - Array of assignment IDs to delete
   */
  private async rollbackAssignments(assignmentIds: number[]): Promise<void> {
    console.log(`AssetRequestApi: Starting rollback for ${assignmentIds.length} assignments`);
    
    for (const assignmentId of assignmentIds) {
      try {
        await assetAssignmentApi.delete(assignmentId);
        console.log(`AssetRequestApi: Rolled back assignment ${assignmentId}`);
      } catch (error) {
        console.error(`AssetRequestApi: Failed to rollback assignment ${assignmentId}:`, error);
        // Continue with other rollbacks even if one fails
      }
    }
    
    console.log(`AssetRequestApi: Rollback completed`);
  }

  /**
   * Check availability of requested assets
   * @param requestedAssets - List of requested asset items
   * @returns Availability check result with details for each asset type
   */
  async checkAvailability(requestedAssets: RequestedAssetItem[]): Promise<AvailabilityCheck> {
    return retryOperation(async () => {
      try {
        console.log('AssetRequestApi: Checking availability for requested assets', requestedAssets);
        
        // Get all assets to calculate availability
        const allAssets = await assetApi.getAll();
        
        // Get all active assignments to calculate what's currently assigned
        const allAssignments = await assetAssignmentApi.getAll();
        const activeAssignments = allAssignments.filter(assignment => !assignment.returnedDate);
        
        // Calculate availability for each requested asset type
        const details = requestedAssets.map(requestedItem => {
          // Count total assets of this type
          const totalAssets = allAssets.filter(asset => asset.assetType === requestedItem.assetType).length;
          
          // Count how many are currently assigned
          const assignedCount = activeAssignments.filter(assignment => {
            const asset = allAssets.find(a => a.assetID === assignment.assetID);
            return asset && asset.assetType === requestedItem.assetType;
          }).length;
          
          // Calculate available
          const available = totalAssets - assignedCount;
          const shortfall = Math.max(0, requestedItem.quantity - available);
          
          return {
            assetType: requestedItem.assetType,
            requested: requestedItem.quantity,
            available,
            shortfall
          };
        });
        
        // Check if all requested items can be fulfilled
        const canFulfill = details.every(detail => detail.shortfall === 0);
        
        console.log('AssetRequestApi: Availability check result', { canFulfill, details });
        
        return {
          canFulfill,
          details
        };
      } catch (error) {
        console.error('AssetRequestApi: Error checking availability:', error);
        // Return a conservative result on error
        return {
          canFulfill: false,
          details: requestedAssets.map(item => ({
            assetType: item.assetType,
            requested: item.quantity,
            available: 0,
            shortfall: item.quantity
          }))
        };
      }
    });
  }
}

export const assetRequestApi = new AssetRequestApi();