using BuildFlow.Shared.Domain.Exceptions;
using MediatR;
using BuildFlow.Application.Roles.DTOs;
using BuildFlow.Domain.Entities;
using BuildFlow.Infrastructure.Persistence;
using BuildFlow.Application.Roles.Commands;

namespace BuildFlow.Application.Roles.Handlers;

/// <summary>
/// Assign权限sCommand处理器。执行业务校验后持久化。
/// </summary>
public class AssignPermissionsCommandHandler(RagDbContext db) : IRequestHandler<AssignPermissionsCommand, RoleDto>
{
    public async Task<RoleDto> Handle(AssignPermissionsCommand request, CancellationToken ct)
    {
        var role = await db.Roles.Include(r => r.RolePermissions).ThenInclude(rp => rp.Permission)
            .FirstOrDefaultAsync(r => r.Id == request.RoleId, ct)
            ?? throw new NotFoundException("角色不存在");

        var permissions = await db.Permissions.Where(p => request.PermissionIds.Contains(p.Id)).ToListAsync(ct);
        // 计数校验：查回的数量必须与请求数量一致，否则说明传入含无效 Id，拒绝执行以免权限静默丢失
        if (permissions.Count != request.PermissionIds.Count)
            throw new NotFoundException("部分权限不存在");

        db.RolePermissions.RemoveRange(role.RolePermissions);
        await db.RolePermissions.AddRangeAsync(
            permissions.Select(p => new RolePermission { RoleId = role.Id, PermissionId = p.Id }), ct);
        await db.SaveChangesAsync(ct);

        return new RoleDto(role.Id, role.Name, role.Description, role.CreatedAt,
            permissions.Select(p => p.Code).ToList());
    }
}