using BuildFlow.Shared.Domain.Errors;
using BuildFlow.Shared.Domain.Exceptions;
using MediatR;
using BuildFlow.Platform.Domain.Entities.Role;
using BuildFlow.Platform.Domain.Entities.User;
using BuildFlow.Platform.Domain.Entities.UserRole;
using BuildFlow.Platform.Infrastructure.Persistence;
using BuildFlow.Platform.Application.Auth.Commands;

namespace BuildFlow.Platform.Application.Auth.Handlers;

/// <summary>
/// 注册Command处理器。执行业务校验后持久化。
/// </summary>
public class RegisterCommandHandler(PlatformDbContext db) : IRequestHandler<RegisterCommand, Unit>
{
    public async Task<Unit> Handle(RegisterCommand request, CancellationToken ct)
    {
        // 用户名与邮箱任一重复即拒绝，保证唯一性约束在业务层先行拦截
        if (await db.Users.AnyAsync<UserEntity>(u => u.Username == request.Username || u.Email == request.Email, ct))
            throw new BusinessException(ErrorCode.AlreadyExists, "用户名或邮箱已存在");

        var user = new UserEntity
        {
            Username = request.Username,
            Email = request.Email,
            // 用 BCrypt 自带盐哈希密码，永不落地明文
            PasswordHash = BCrypt.Net.BCrypt.HashPassword(request.Password)
        };

        // 自助注册一律授予最低权限的 "User" 角色，避免越权
        var userRole = await db.Roles.FirstAsync<RoleEntity>(r => r.Name == "User", ct);
        await db.Users.AddAsync(user, ct);
        await db.UserRoles.AddAsync(new UserRoleEntity { UserId = user.Id, RoleId = userRole.Id }, ct);
        await db.SaveChangesAsync(ct);

        return Unit.Value;
    }
}