using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using rgbc_sds.dal.DB;

namespace rgbc_sds.services.Services
{
    /// <summary>
    /// Service interface for handling shipment import operations
    /// </summary>
    public interface IImportService
    {
        /// <summary>
        /// Creates a new import session and validates the uploaded file
        /// </summary>
        /// <param name="fileStream">Excel file stream</param>
        /// <param name="fileName">Original filename</param>
        /// <param name="fileSize">File size in bytes</param>
        /// <param name="importMode">Import strategy to use</param>
        /// <param name="createdBy">User initiating the import</param>
        /// <returns>Import session with validation results</returns>
        Task<ImportSession> CreateImportSessionAsync(
            Stream fileStream, 
            string fileName, 
            long fileSize, 
            string importMode, 
            string createdBy);

        /// <summary>
        /// Gets a summary of the import session
        /// </summary>
        /// <param name="sessionId">Import session ID</param>
        /// <returns>Import session summary</returns>
        Task<ImportSession> GetImportSessionAsync(Guid sessionId);

        /// <summary>
        /// Gets staging data for preview before import
        /// </summary>
        /// <param name="sessionId">Import session ID</param>
        /// <param name="pageNumber">Page number for pagination</param>
        /// <param name="pageSize">Number of records per page</param>
        /// <returns>Paged staging data</returns>
        Task<(List<StagingShipment> Data, int TotalCount)> GetStagingDataForPreviewAsync(
            Guid sessionId, 
            int pageNumber = 1, 
            int pageSize = 50);

        /// <summary>
        /// Gets validation errors for the import session
        /// </summary>
        /// <param name="sessionId">Import session ID</param>
        /// <returns>List of validation errors</returns>
        Task<List<ImportErrorLog>> GetValidationErrorsAsync(Guid sessionId);

        /// <summary>
        /// Executes the import process for validated data
        /// </summary>
        /// <param name="sessionId">Import session ID</param>
        /// <param name="progressCallback">Optional progress callback for real-time updates</param>
        /// <returns>Import result with success/failure details</returns>
        Task<ImportResult> ExecuteImportAsync(
            Guid sessionId, 
            IProgress<ImportProgress>? progressCallback = null);

        /// <summary>
        /// Cancels an import session
        /// </summary>
        /// <param name="sessionId">Import session ID</param>
        /// <param name="cancelledBy">User cancelling the import</param>
        /// <returns>Success status</returns>
        Task<bool> CancelImportSessionAsync(Guid sessionId, string cancelledBy);

        /// <summary>
        /// Gets recent import sessions for the current user
        /// </summary>
        /// <param name="createdBy">User to get sessions for</param>
        /// <param name="maxResults">Maximum number of results</param>
        /// <returns>List of recent import sessions</returns>
        Task<List<ImportSession>> GetRecentImportSessionsAsync(string createdBy, int maxResults = 10);

        /// <summary>
        /// Cleans up old import sessions and staging data
        /// </summary>
        /// <param name="daysToKeep">Number of days to keep data</param>
        /// <returns>Number of records cleaned up</returns>
        Task<int> CleanupOldImportSessionsAsync(int daysToKeep = 30);
    }

    /// <summary>
    /// Result of an import operation
    /// </summary>
    public class ImportResult
    {
        public bool IsSuccess { get; set; }
        public string Message { get; set; } = string.Empty;
        public int RecordsProcessed { get; set; }
        public int RecordsSkipped { get; set; }
        public int RecordsFailed { get; set; }
        public List<string> Errors { get; set; } = new List<string>();
        public TimeSpan ProcessingTime { get; set; }
    }

    /// <summary>
    /// Progress information during import processing
    /// </summary>
    public class ImportProgress
    {
        public int CurrentRecord { get; set; }
        public int TotalRecords { get; set; }
        public string CurrentOperation { get; set; } = string.Empty;
        public decimal PercentageComplete => TotalRecords > 0 ? (decimal)CurrentRecord / TotalRecords * 100 : 0;
    }
}