using MediatR;
using TakeoutSaaS.Application.App.Subscriptions.Commands;
using TakeoutSaaS.Application.App.Subscriptions.Dto;
using TakeoutSaaS.Application.App.Subscriptions.Queries;
using TakeoutSaaS.Domain.Tenants.Entities;
using TakeoutSaaS.Domain.Tenants.Enums;
using TakeoutSaaS.Domain.Tenants.Repositories;
using TakeoutSaaS.Shared.Abstractions.Ids;

namespace TakeoutSaaS.Application.App.Subscriptions.Handlers;

/// <summary>
/// 延期订阅命令处理器。
/// </summary>
public sealed class ExtendSubscriptionCommandHandler(
    ISubscriptionRepository subscriptionRepository,
    IIdGenerator idGenerator,
    IMediator mediator)
    : IRequestHandler<ExtendSubscriptionCommand, SubscriptionDetailDto?>
{
    /// <inheritdoc />
    public async Task<SubscriptionDetailDto?> Handle(ExtendSubscriptionCommand request, CancellationToken cancellationToken)
    {
        // 1. 查询订阅
        var subscription = await subscriptionRepository.FindByIdAsync(request.SubscriptionId, cancellationToken);

        if (subscription == null)
        {
            return null;
        }

        // 2. 计算新的到期时间（从当前到期时间延长）
        var originalEffectiveTo = subscription.EffectiveTo;
        subscription.EffectiveTo = subscription.EffectiveTo.AddMonths(request.DurationMonths);

        // 3. 更新备注
        if (!string.IsNullOrWhiteSpace(request.Notes))
        {
            subscription.Notes = request.Notes;
        }

        // 4. 记录变更历史（使用 Renew 类型表示延期）
        var history = new TenantSubscriptionHistory
        {
            Id = idGenerator.NextId(),
            TenantId = subscription.TenantId,
            TenantSubscriptionId = subscription.Id,
            FromPackageId = subscription.TenantPackageId,
            ToPackageId = subscription.TenantPackageId,
            ChangeType = SubscriptionChangeType.Renew,
            EffectiveFrom = originalEffectiveTo,
            EffectiveTo = subscription.EffectiveTo,
            Amount = null,
            Currency = null,
            Notes = request.Notes ?? $"延期 {request.DurationMonths} 个月"
        };

        await subscriptionRepository.AddHistoryAsync(history, cancellationToken);

        // 5. 保存更改
        await subscriptionRepository.UpdateAsync(subscription, cancellationToken);
        await subscriptionRepository.SaveChangesAsync(cancellationToken);

        // 6. 返回更新后的详情
        return await mediator.Send(new GetSubscriptionDetailQuery { SubscriptionId = subscription.Id }, cancellationToken);
    }
}