using System;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace rgbc_sds.dal.DB
{
    /// <summary>
    /// Entity representing an import session for shipment data
    /// Maps to sdsImportSessions table
    /// </summary>
    [Table("sdsImportSessions")]
    public class ImportSession
    {
        /// <summary>
        /// Unique identifier for the import session
        /// </summary>
        [Key]
        [Required]
        public Guid Id { get; set; }

        /// <summary>
        /// User who initiated the import
        /// </summary>
        [Required]
        [StringLength(100)]
        public string CreatedBy { get; set; } = string.Empty;

        /// <summary>
        /// When the import session was created
        /// </summary>
        [Required]
        public DateTime CreatedAt { get; set; }

        /// <summary>
        /// Current status of the import session
        /// </summary>
        [Required]
        [StringLength(20)]
        public string Status { get; set; } = "Pending";

        /// <summary>
        /// Total number of rows in the import file
        /// </summary>
        [Required]
        [Range(0, int.MaxValue)]
        public int TotalRows { get; set; } = 0;

        /// <summary>
        /// Number of rows that passed validation
        /// </summary>
        [Required]
        [Range(0, int.MaxValue)]
        public int ValidRows { get; set; } = 0;

        /// <summary>
        /// Number of rows with validation errors
        /// </summary>
        [Required]
        [Range(0, int.MaxValue)]
        public int ErrorRows { get; set; } = 0;

        /// <summary>
        /// Processing time in milliseconds
        /// </summary>
        [Range(0, int.MaxValue)]
        public int? ProcessingTime { get; set; }

        /// <summary>
        /// Original filename that was imported
        /// </summary>
        [StringLength(255)]
        public string? FileName { get; set; }

        /// <summary>
        /// Size of the imported file in bytes
        /// </summary>
        [Range(0, long.MaxValue)]
        public long? FileSize { get; set; }

        /// <summary>
        /// Import strategy: UpdateExisting or AddNewOnly
        /// </summary>
        [StringLength(20)]
        public string? ImportMode { get; set; }

        /// <summary>
        /// Additional notes about the import session
        /// </summary>
        [StringLength(500)]
        public string? Notes { get; set; }

        /// <summary>
        /// When the import session was completed
        /// </summary>
        public DateTime? CompletedAt { get; set; }

        // Navigation Properties
        /// <summary>
        /// Collection of staging shipments for this session
        /// </summary>
        public virtual ICollection<StagingShipment> StagingShipments { get; set; } = new List<StagingShipment>();

        /// <summary>
        /// Collection of error logs for this session
        /// </summary>
        public virtual ICollection<ImportErrorLog> ImportErrorLogs { get; set; } = new List<ImportErrorLog>();

        // Computed Properties
        /// <summary>
        /// Success rate as a percentage
        /// </summary>
        [NotMapped]
        public decimal SuccessRate => TotalRows > 0 ? (decimal)ValidRows / TotalRows * 100 : 0;

        /// <summary>
        /// Whether the session is currently active
        /// </summary>
        [NotMapped]
        public bool IsActive => Status == "Pending" || Status == "Processing";

        /// <summary>
        /// Whether the session has completed (successfully or with errors)
        /// </summary>
        [NotMapped]
        public bool IsCompleted => Status == "Completed" || Status == "Failed";

        // Constructor
        public ImportSession()
        {
            Id = Guid.NewGuid();
            CreatedAt = DateTime.UtcNow;
            Status = "Pending";
            TotalRows = 0;
            ValidRows = 0;
            ErrorRows = 0;
        }

        // Business Methods
        /// <summary>
        /// Start processing the import session
        /// </summary>
        public void StartProcessing()
        {
            if (Status != "Pending")
                throw new InvalidOperationException("Can only start processing from Pending status");
            
            Status = "Processing";
        }

        /// <summary>
        /// Complete the import session
        /// </summary>
        /// <param name="success">Whether the import was successful</param>
        public void Complete(bool success)
        {
            if (Status != "Processing")
                throw new InvalidOperationException("Can only complete from Processing status");
            
            Status = success ? "Completed" : "Failed";
            CompletedAt = DateTime.UtcNow;
        }

        /// <summary>
        /// Update row counts during processing
        /// </summary>
        /// <param name="validCount">Number of valid rows</param>
        /// <param name="errorCount">Number of error rows</param>
        public void UpdateRowCounts(int validCount, int errorCount)
        {
            ValidRows = validCount;
            ErrorRows = errorCount;
            
            if (ValidRows + ErrorRows > TotalRows)
                throw new InvalidOperationException("Row counts exceed total rows");
        }
    }
}