using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using Domain.Entities.Store.ValueObject;

namespace Domain.Entities.Store;

/// <summary>
/// 통합 환불 이력 (취소/반품/교환/환불). Order N:N (한 주문에 여러 환불 가능).
/// 흐름: Requested -> Approved (관리자) -> Completed (실제 처리, Wallet/재고/쿠폰 환원).
/// </summary>
public class OrderRefund
{
    [ForeignKey(nameof(OrderID))]
    public virtual Order? Order { get; private set; }

    /// <summary>
    /// 환불 단위 — 쿠폰 별 후처리(회수/만료) 정책. OrderRefund 1건에 N개의 OrderRefundItem.
    /// 자동 환불(Cancel)이나 옛 환불은 비어있을 수 있음 (Amount 만 사용).
    /// </summary>
    public virtual ICollection<OrderRefundItem> Items { get; private set; } = new List<OrderRefundItem>();

    [Key]
    public int ID { get; private set; }

    public int OrderID { get; private set; }

    public RefundType Type { get; private set; }

    /// <summary>사유 유형. RefundType 과 직교한 표준화 카테고리. 통계·필터링에 사용.</summary>
    public RefundReasonType ReasonType { get; private set; } = RefundReasonType.Other;

    public RefundStatus Status { get; private set; } = RefundStatus.Requested;

    public int Amount { get; private set; }

    /// <summary>사용자가 직접 작성한 상세 사유. ReasonType 외 보조 설명. ReasonType=Other 인 경우 호출자가 필수 처리.</summary>
    public string Reason { get; private set; } = default!;

    public string? AdminMemo { get; private set; }

    /// <summary>처리 관리자 (ASP.NET Identity ApplicationUser.Id). 자동 환불(Cancel)은 null.</summary>
    public string? AdminUserId { get; private set; }

    /// <summary>처리 관리자 Email 스냅샷 (표시용). Member FK 없이 감사 표시 유지.</summary>
    public string? AdminEmail { get; private set; }

    public DateTime RequestedAt { get; private set; } = DateTime.UtcNow;

    public DateTime? ResolvedAt { get; private set; }

    private OrderRefund() { }

    public static OrderRefund Create(int orderID, RefundType type, RefundReasonType reasonType, int amount, string reason)
    {
        if (orderID <= 0)
        {
            throw new ArgumentOutOfRangeException(nameof(orderID));
        }

        if (amount <= 0)
        {
            throw new ArgumentOutOfRangeException(nameof(amount), "Amount must be positive.");
        }

        if (string.IsNullOrWhiteSpace(reason))
        {
            throw new ArgumentException("Reason is required.", nameof(reason));
        }

        if (reason.Length > 500)
        {
            throw new ArgumentOutOfRangeException(nameof(reason));
        }

        return new OrderRefund
        {
            OrderID = orderID,
            Type = type,
            ReasonType = reasonType,
            Amount = amount,
            Reason = reason
        };
    }

    public void Approve(string adminUserId, string? adminEmail, string? adminMemo = null)
    {
        if (Status != RefundStatus.Requested)
        {
            throw new InvalidOperationException($"Cannot approve from status {Status}.");
        }

        if (string.IsNullOrWhiteSpace(adminUserId))
        {
            throw new ArgumentException("AdminUserId is required.", nameof(adminUserId));
        }

        Status = RefundStatus.Approved;
        AdminUserId = adminUserId;
        AdminEmail = adminEmail;
        AdminMemo = adminMemo;
    }

    public void Reject(string adminUserId, string? adminEmail, string adminMemo)
    {
        if (Status != RefundStatus.Requested)
        {
            throw new InvalidOperationException($"Cannot reject from status {Status}.");
        }

        if (string.IsNullOrWhiteSpace(adminUserId))
        {
            throw new ArgumentException("AdminUserId is required.", nameof(adminUserId));
        }

        if (string.IsNullOrWhiteSpace(adminMemo))
        {
            throw new ArgumentException("Rejection requires admin memo.", nameof(adminMemo));
        }

        Status = RefundStatus.Rejected;
        AdminUserId = adminUserId;
        AdminEmail = adminEmail;
        AdminMemo = adminMemo;
        ResolvedAt = DateTime.UtcNow;
    }

    public void Complete()
    {
        if (Status != RefundStatus.Approved)
        {
            throw new InvalidOperationException($"Cannot complete from status {Status}.");
        }

        Status = RefundStatus.Completed;
        ResolvedAt = DateTime.UtcNow;
    }
}