// Package service 持有业务逻辑,只依赖 repository 接口,不直接碰 GORM。
//
// 计算类逻辑(如油价/油耗/成本)放这里,不放在 handler,便于单测。
package service

import (
	"context"
	"strings"

	"gorm.io/gorm"

	"github.com/kennethcheng/fuellog-api/internal/dto"
	"github.com/kennethcheng/fuellog-api/internal/model"
	"github.com/kennethcheng/fuellog-api/internal/repository"
	"github.com/kennethcheng/fuellog-api/pkg/apperror"
)

// VehicleService 车辆业务逻辑。
type VehicleService interface {
	Create(ctx context.Context, in *dto.VehicleCreate) (*model.Vehicle, error)
	Get(ctx context.Context, id uint64) (*model.Vehicle, error)
	List(ctx context.Context) ([]model.Vehicle, error)
	Update(ctx context.Context, id uint64, in *dto.VehicleUpdate) (*model.Vehicle, error)
	Delete(ctx context.Context, id uint64) error
	SetDefault(ctx context.Context, id uint64) (*model.Vehicle, error)
}

func NewVehicleService(repo repository.VehicleRepository, db *gorm.DB) VehicleService {
	return &vehicleService{repo: repo, db: db}
}

type vehicleService struct {
	repo repository.VehicleRepository
	db   *gorm.DB
}

func (s *vehicleService) Create(ctx context.Context, in *dto.VehicleCreate) (*model.Vehicle, error) {
	v := &model.Vehicle{
		Name:            strings.TrimSpace(in.Name),
		Brand:           strings.TrimSpace(in.Brand),
		Model:           strings.TrimSpace(in.Model),
		PlateNumber:     strings.TrimSpace(in.PlateNumber),
		FuelType:        strings.TrimSpace(in.FuelType),
		TankCapacity:    in.TankCapacity,
		CurrentOdometer: in.CurrentOdometer,
		DefaultVehicle:  in.DefaultVehicle,
	}
	if v.Name == "" {
		return nil, apperror.New(apperror.CodeInvalidArg, "车辆名称不能为空")
	}
	if v.FuelType == "" {
		return nil, apperror.New(apperror.CodeInvalidArg, "能源类型不能为空")
	}

	// 任何显式设为默认的车辆,都要先清掉其它默认(在事务里完成)
	if v.DefaultVehicle {
		err := s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
			if err := s.repo.ClearDefault(ctx, tx); err != nil {
				return err
			}
			if err := tx.WithContext(ctx).Create(v).Error; err != nil {
				return apperror.Wrap(apperror.CodeInternal, "创建车辆失败", err)
			}
			return nil
		})
		if err != nil {
			if appErr, ok := apperror.As(err); ok {
				return nil, appErr
			}
			return nil, err
		}
		return v, nil
	}

	if err := s.repo.Create(ctx, v); err != nil {
		return nil, err
	}
	return v, nil
}

func (s *vehicleService) Get(ctx context.Context, id uint64) (*model.Vehicle, error) {
	return s.repo.Get(ctx, id)
}

func (s *vehicleService) List(ctx context.Context) ([]model.Vehicle, error) {
	return s.repo.List(ctx)
}

func (s *vehicleService) Update(ctx context.Context, id uint64, in *dto.VehicleUpdate) (*model.Vehicle, error) {
	v, err := s.repo.Get(ctx, id)
	if err != nil {
		return nil, err
	}
	if in.Name != nil {
		v.Name = strings.TrimSpace(*in.Name)
	}
	if in.Brand != nil {
		v.Brand = strings.TrimSpace(*in.Brand)
	}
	if in.Model != nil {
		v.Model = strings.TrimSpace(*in.Model)
	}
	if in.PlateNumber != nil {
		v.PlateNumber = strings.TrimSpace(*in.PlateNumber)
	}
	if in.FuelType != nil {
		v.FuelType = strings.TrimSpace(*in.FuelType)
	}
	if in.TankCapacity != nil {
		v.TankCapacity = *in.TankCapacity
	}
	if in.CurrentOdometer != nil {
		v.CurrentOdometer = *in.CurrentOdometer
	}
	if v.Name == "" {
		return nil, apperror.New(apperror.CodeInvalidArg, "车辆名称不能为空")
	}
	if v.FuelType == "" {
		return nil, apperror.New(apperror.CodeInvalidArg, "能源类型不能为空")
	}

	// 切换默认车辆同样要在事务里:先清默认,再置新默认
	if in.DefaultVehicle != nil && *in.DefaultVehicle && !v.DefaultVehicle {
		err := s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
			if err := s.repo.ClearDefault(ctx, tx); err != nil {
				return err
			}
			v.DefaultVehicle = true
			if err := tx.WithContext(ctx).Save(v).Error; err != nil {
				return apperror.Wrap(apperror.CodeInternal, "更新车辆失败", err)
			}
			return nil
		})
		if err != nil {
			if appErr, ok := apperror.As(err); ok {
				return nil, appErr
			}
			return nil, err
		}
		return v, nil
	}

	if err := s.repo.Update(ctx, v); err != nil {
		return nil, err
	}
	return v, nil
}

func (s *vehicleService) Delete(ctx context.Context, id uint64) error {
	return s.repo.Delete(ctx, id)
}

func (s *vehicleService) SetDefault(ctx context.Context, id uint64) (*model.Vehicle, error) {
	// 校验存在
	if _, err := s.repo.Get(ctx, id); err != nil {
		return nil, err
	}
	err := s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		if err := s.repo.ClearDefault(ctx, tx); err != nil {
			return err
		}
		return s.repo.SetDefault(ctx, tx, id)
	})
	if err != nil {
		if appErr, ok := apperror.As(err); ok {
			return nil, appErr
		}
		return nil, err
	}
	return s.repo.Get(ctx, id)
}