package service

import (
	"encoding/json"
	"fmt"
	"strconv"
	"strings"

	"github.com/wmms/wmms/internal/model"
	"github.com/wmms/wmms/internal/repository"
)

type MaterialLogService struct {
	logRepo *repository.MaterialLogRepo
}

func NewMaterialLogService() *MaterialLogService {
	return &MaterialLogService{
		logRepo: repository.NewMaterialLogRepo(),
	}
}

func (s *MaterialLogService) LogCreate(material *model.Material, operator string) error {
	newValue, _ := json.Marshal(material)
	log := &model.MaterialLog{
		OperationType: "CREATE",
		MaterialID:    material.ID,
		NewValue:      string(newValue),
		Operator:      operator,
		Description:   fmt.Sprintf("新增物料：%s", material.Name),
	}
	return s.logRepo.Create(log)
}

func (s *MaterialLogService) LogUpdate(material *model.Material, oldMaterial *model.Material, operator string) error {
	// 上层取「修改后」的物料失败时仍会走到这里，material 为 nil，取字段会 panic
	if material == nil {
		return nil
	}
	oldValue, _ := json.Marshal(oldMaterial)
	newValue, _ := json.Marshal(material)
	log := &model.MaterialLog{
		OperationType: "UPDATE",
		MaterialID:    material.ID,
		OldValue:      string(oldValue),
		NewValue:      string(newValue),
		Operator:      operator,
		Description:   updateDescription(material, oldMaterial),
	}
	return s.logRepo.Create(log)
}

// updateDescription 让日志详情直接说明改了什么，用户不必去比对 old_value/new_value 里的整段 JSON。
// 比对不出任何变化时退回只带物料名的简版。
func updateDescription(material, oldMaterial *model.Material) string {
	description := fmt.Sprintf("修改物料：%s", material.Name)
	if oldMaterial == nil {
		return description
	}
	changes := materialChanges(oldMaterial, material)
	if len(changes) == 0 {
		return description
	}
	return fmt.Sprintf("%s（%s）", description, strings.Join(changes, "；"))
}

// materialChanges 逐字段比对，返回「字段名：旧值 → 新值」形式的变更列表，顺序即展示顺序。
// 分类和基本单位在服务层拿不到名称，如实显示 ID；物料图片只报「已更新」，
// 图片 URL 往往很长，整条塞进描述会把别的变更挤没。
func materialChanges(oldMaterial, newMaterial *model.Material) []string {
	fields := []struct {
		label    string
		oldValue string
		newValue string
	}{
		{"物料编码", oldMaterial.MaterialCode, newMaterial.MaterialCode},
		{"名称", oldMaterial.Name, newMaterial.Name},
		{"规格", oldMaterial.Spec, newMaterial.Spec},
		{"厂商型号", derefString(oldMaterial.ManufacturerModel), derefString(newMaterial.ManufacturerModel)},
		{"分类", derefID(oldMaterial.CategoryID), derefID(newMaterial.CategoryID)},
		{"基本单位", derefID(oldMaterial.BaseUnitID), derefID(newMaterial.BaseUnitID)},
		{"单位", oldMaterial.Unit, newMaterial.Unit},
		// 作废和恢复也是走这里的：状态一变，日志就写明「状态：启用 → 作废」
		{"状态", materialStatusLabel(oldMaterial.Status), materialStatusLabel(newMaterial.Status)},
	}

	var changes []string
	for _, field := range fields {
		if field.oldValue != field.newValue {
			changes = append(changes, fmt.Sprintf("%s：%s → %s",
				field.label, orEmptyValue(field.oldValue), orEmptyValue(field.newValue)))
		}
	}
	if derefString(oldMaterial.MaterialImage) != derefString(newMaterial.MaterialImage) {
		changes = append(changes, "物料图片：已更新")
	}
	return changes
}

func derefString(value *string) string {
	if value == nil {
		return ""
	}
	return *value
}

func derefID(value *int64) string {
	if value == nil {
		return ""
	}
	return strconv.FormatInt(*value, 10)
}

// orEmptyValue 把空值显示成「空」，否则会写出「规格： → 6205」这种读不出是新增还是清空的描述。
func orEmptyValue(value string) string {
	if value == "" {
		return "空"
	}
	return value
}

// materialStatusLabel 把状态值转成界面用语，日志里直接写 active/obsolete 对用户没有意义。
func materialStatusLabel(status string) string {
	switch status {
	case "active":
		return "启用"
	case "obsolete":
		return "作废"
	default:
		return status
	}
}

func (s *MaterialLogService) LogDelete(material *model.Material, operator string) error {
	oldValue, _ := json.Marshal(material)
	log := &model.MaterialLog{
		OperationType: "DELETE",
		MaterialID:    material.ID,
		OldValue:      string(oldValue),
		Operator:      operator,
		Description:   fmt.Sprintf("删除物料：%s", material.Name),
	}
	return s.logRepo.Create(log)
}

func (s *MaterialLogService) List(operationType, materialId, startDate, endDate string, limit, offset int) ([]model.MaterialLog, int64, error) {
	return s.logRepo.List(operationType, materialId, startDate, endDate, limit, offset)
}

func (s *MaterialLogService) GetByMaterialID(materialID int64) ([]model.MaterialLog, error) {
	return s.logRepo.GetByMaterialID(materialID)
}