using MediatR;
using Microsoft.Extensions.Logging;
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;

namespace TakeoutSaaS.Application.App.Tenants.Handlers;

/// <summary>
/// 租户注册处理器。
/// </summary>
public sealed class RegisterTenantCommandHandler(
    ITenantRepository tenantRepository,
    IIdGenerator idGenerator,
    ILogger<RegisterTenantCommandHandler> logger)
    : IRequestHandler<RegisterTenantCommand, TenantDto>
{
    /// <inheritdoc />
    public async Task<TenantDto> Handle(RegisterTenantCommand request, CancellationToken cancellationToken)
    {
        // 1. 校验订阅时长
        if (request.DurationMonths <= 0)
        {
            throw new BusinessException(ErrorCodes.BadRequest, "订阅时长必须大于 0");
        }

        // 2. 检查租户编码唯一性
        if (await tenantRepository.ExistsByCodeAsync(request.Code, cancellationToken))
        {
            throw new BusinessException(ErrorCodes.Conflict, $"租户编码 {request.Code} 已存在");
        }

        // 3. 计算生效时间
        var now = DateTime.UtcNow;
        var effectiveFrom = request.EffectiveFrom ?? now;
        var effectiveTo = effectiveFrom.AddMonths(request.DurationMonths);

        // 4. 构建租户实体
        var tenant = new Tenant
        {
            Id = idGenerator.NextId(),
            Code = request.Code.Trim(),
            Name = request.Name,
            ShortName = request.ShortName,
            Industry = request.Industry,
            ContactName = request.ContactName,
            ContactPhone = request.ContactPhone,
            ContactEmail = request.ContactEmail,
            Status = TenantStatus.PendingReview,
            EffectiveFrom = effectiveFrom,
            EffectiveTo = effectiveTo
        };

        // 5. 构建订阅实体
        var subscription = new TenantSubscription
        {
            Id = idGenerator.NextId(),
            TenantId = tenant.Id,
            TenantPackageId = request.TenantPackageId,
            EffectiveFrom = effectiveFrom,
            EffectiveTo = effectiveTo,
            NextBillingDate = effectiveTo,
            Status = SubscriptionStatus.Pending,
            AutoRenew = request.AutoRenew,
            Notes = "Init subscription"
        };

        // 6. 持久化租户、订阅和审计日志
        await tenantRepository.AddTenantAsync(tenant, cancellationToken);
        await tenantRepository.AddSubscriptionAsync(subscription, cancellationToken);
        await tenantRepository.AddAuditLogAsync(new TenantAuditLog
        {
            TenantId = tenant.Id,
            Action = TenantAuditAction.RegistrationSubmitted,
            Title = "租户注册",
            Description = $"提交套餐 {request.TenantPackageId}，时长 {request.DurationMonths} 月"
        }, cancellationToken);

        await tenantRepository.SaveChangesAsync(cancellationToken);

        // 7. 记录日志
        logger.LogInformation("已注册租户 {TenantCode}", tenant.Code);

        // 8. 返回 DTO
        return TenantMapping.ToDto(tenant, subscription, null);
    }
}