using MediatR;
using TakeoutSaaS.Application.App.Tenants.Commands;
using TakeoutSaaS.Application.App.Tenants.Dto;
using TakeoutSaaS.Domain.Tenants.Entities;
using TakeoutSaaS.Domain.Tenants.Enums;
using TakeoutSaaS.Domain.Tenants.Repositories;
using TakeoutSaaS.Shared.Abstractions.Constants;
using TakeoutSaaS.Shared.Abstractions.Exceptions;
using TakeoutSaaS.Shared.Abstractions.Ids;
using TakeoutSaaS.Shared.Abstractions.Security;

namespace TakeoutSaaS.Application.App.Tenants.Handlers;

/// <summary>
/// 延期/赠送订阅处理器（按当前订阅套餐续费）。
/// </summary>
public sealed class ExtendTenantSubscriptionCommandHandler(
    ITenantRepository tenantRepository,
    IIdGenerator idGenerator,
    ICurrentUserAccessor currentUserAccessor)
    : IRequestHandler<ExtendTenantSubscriptionCommand, TenantSubscriptionDto>
{
    /// <inheritdoc />
    public async Task<TenantSubscriptionDto> Handle(ExtendTenantSubscriptionCommand request, CancellationToken cancellationToken)
    {
        // 1. 校验时长
        if (request.DurationMonths <= 0)
        {
            throw new BusinessException(ErrorCodes.BadRequest, "延期/赠送时长必须大于 0");
        }

        // 2. 获取租户与当前订阅
        var tenant = await tenantRepository.FindByIdAsync(request.TenantId, cancellationToken)
            ?? throw new BusinessException(ErrorCodes.NotFound, "租户不存在");

        var current = await tenantRepository.GetActiveSubscriptionAsync(request.TenantId, cancellationToken)
            ?? throw new BusinessException(ErrorCodes.BadRequest, "订阅不存在，无法延期/赠送");

        var now = DateTime.UtcNow;
        var effectiveFrom = current.EffectiveTo > now ? current.EffectiveTo : now;
        var effectiveTo = effectiveFrom.AddMonths(request.DurationMonths);

        var previousStatus = tenant.Status;
        var actorName = currentUserAccessor.IsAuthenticated
            ? $"user:{currentUserAccessor.UserId}"
            : "system";

        // 3. 创建续费订阅
        var subscription = new TenantSubscription
        {
            Id = idGenerator.NextId(),
            TenantId = tenant.Id,
            TenantPackageId = current.TenantPackageId,
            EffectiveFrom = effectiveFrom,
            EffectiveTo = effectiveTo,
            NextBillingDate = effectiveTo,
            Status = SubscriptionStatus.Active,
            AutoRenew = current.AutoRenew,
            Notes = request.Notes
        };

        await tenantRepository.AddSubscriptionAsync(subscription, cancellationToken);
        await tenantRepository.AddSubscriptionHistoryAsync(new TenantSubscriptionHistory
        {
            Id = idGenerator.NextId(),
            TenantId = tenant.Id,
            TenantSubscriptionId = subscription.Id,
            FromPackageId = current.TenantPackageId,
            ToPackageId = current.TenantPackageId,
            ChangeType = SubscriptionChangeType.Renew,
            EffectiveFrom = effectiveFrom,
            EffectiveTo = effectiveTo,
            Amount = null,
            Currency = null,
            Notes = request.Notes
        }, cancellationToken);

        // 4. 若租户处于到期状态则恢复为正常（冻结状态需先解冻）
        if (tenant.Status == TenantStatus.Expired)
        {
            tenant.Status = TenantStatus.Active;
        }

        tenant.EffectiveFrom = subscription.EffectiveFrom;
        tenant.EffectiveTo = subscription.EffectiveTo;

        await tenantRepository.UpdateTenantAsync(tenant, cancellationToken);

        // 5. 记录审计
        await tenantRepository.AddAuditLogAsync(new TenantAuditLog
        {
            TenantId = tenant.Id,
            Action = TenantAuditAction.SubscriptionUpdated,
            Title = "延期/赠送时长",
            Description = $"续费 {request.DurationMonths} 月，到期时间：{current.EffectiveTo:yyyy-MM-dd HH:mm:ss} -> {subscription.EffectiveTo:yyyy-MM-dd HH:mm:ss}",
            OperatorId = currentUserAccessor.UserId == 0 ? null : currentUserAccessor.UserId,
            OperatorName = actorName,
            PreviousStatus = previousStatus,
            CurrentStatus = tenant.Status
        }, cancellationToken);

        // 6. 保存并返回
        await tenantRepository.SaveChangesAsync(cancellationToken);
        return subscription.ToSubscriptionDto()
               ?? throw new BusinessException(ErrorCodes.InternalServerError, "订阅生成失败");
    }
}