package services

import (
	"encoding/base64"
	"errors"
	"fmt"
	"os"
	"strings"
	"sync"
	"time"

	"github.com/google/uuid"
	qr "github.com/yeqown/go-qrcode/v2"
	"github.com/yeqown/go-qrcode/writer/standard"

	"git.beifan.cn/trace-system/backend-go/database"
	"git.beifan.cn/trace-system/backend-go/models"
)

// AftersalesService 售后工单服务
type AftersalesService struct{}

// 工单状态常量
const (
	WorkOrderStatusCreated             = "created"
	WorkOrderStatusPendingConfirmation = "pending_confirmation"
	WorkOrderStatusClosed              = "closed"
	WorkOrderStatusRejected            = "rejected"

	AuthorizationStatusPending      = "pending"
	AuthorizationStatusAuthorized   = "authorized"
	AuthorizationStatusUnauthorized = "unauthorized"

	aftersalesSerialPrefix = "zjbf-sh-"

	// 签名 base64 解码后的大小限制
	signatureMinBytes = 200
	signatureMaxBytes = 500 * 1024
)

// validateSignature 校验客户签名 dataURL 是否合法
// 接受 data:image/png;base64,... 或 data:image/jpeg;base64,... 形式
func validateSignature(s string) error {
	s = strings.TrimSpace(s)
	if s == "" {
		return errors.New("签名不能为空")
	}
	var payload string
	switch {
	case strings.HasPrefix(s, "data:image/png;base64,"):
		payload = strings.TrimPrefix(s, "data:image/png;base64,")
	case strings.HasPrefix(s, "data:image/jpeg;base64,"):
		payload = strings.TrimPrefix(s, "data:image/jpeg;base64,")
	default:
		return errors.New("签名格式不合法")
	}
	decoded, err := base64.StdEncoding.DecodeString(payload)
	if err != nil {
		return errors.New("签名内容解码失败")
	}
	if len(decoded) < signatureMinBytes {
		return errors.New("签名内容过短，请重新签名")
	}
	if len(decoded) > signatureMaxBytes {
		return errors.New("签名内容过大，请精简后重试")
	}
	return nil
}

// 客户确认接口频率限制：每分钟同一工单最多 5 次尝试
var confirmRateLimiter = struct {
	sync.Mutex
	attempts map[string][]time.Time
}{attempts: map[string][]time.Time{}}

// ResetConfirmRateLimit 清空确认限流器（仅用于测试）
func ResetConfirmRateLimit() {
	confirmRateLimiter.Lock()
	defer confirmRateLimiter.Unlock()
	confirmRateLimiter.attempts = map[string][]time.Time{}
}

func checkConfirmRateLimit(serialNumber string) bool {
	confirmRateLimiter.Lock()
	defer confirmRateLimiter.Unlock()

	now := time.Now()
	windowStart := now.Add(-time.Minute)

	attempts := confirmRateLimiter.attempts[serialNumber]
	filtered := attempts[:0]
	for _, t := range attempts {
		if t.After(windowStart) {
			filtered = append(filtered, t)
		}
	}
	if len(filtered) >= 5 {
		confirmRateLimiter.attempts[serialNumber] = filtered
		return false
	}
	filtered = append(filtered, now)
	confirmRateLimiter.attempts[serialNumber] = filtered
	return true
}

func normalizeAftersalesSerial(sn string) string {
	return strings.ToLower(strings.TrimSpace(sn))
}

// generateUniqueSerial 生成唯一的售后工单序列号
// 格式：zjbf-sh-YYMMDDNN，YY=年份后两位，MM=月份，DD=日期，NN=当天第几单（至少 2 位，溢出自然加宽）
func (s *AftersalesService) generateUniqueSerial() (string, error) {
	now := time.Now()
	yy := now.Year() % 100
	mm := int(now.Month())
	dd := now.Day()

	dayStart := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
	nextDay := dayStart.AddDate(0, 0, 1)

	// 统计当天已创建工单数（含软删除，避免编号回收）
	var count int64
	if err := database.DB.Unscoped().Model(&models.AftersalesOrder{}).
		Where("created_at >= ? AND created_at < ?", dayStart, nextDay).
		Count(&count).Error; err != nil {
		return "", fmt.Errorf("统计当日工单数失败: %w", err)
	}

	seq := int(count) + 1
	for attempt := 0; attempt < 100; attempt++ {
		candidate := fmt.Sprintf("%s%02d%02d%02d%02d", aftersalesSerialPrefix, yy, mm, dd, seq)

		var existing models.AftersalesOrder
		result := database.DB.Unscoped().Where("serial_number = ?", candidate).First(&existing)
		if result.Error != nil {
			return candidate, nil
		}
		seq++
	}
	return "", errors.New("生成唯一序列号失败，请重试")
}

// Create 创建售后工单
func (s *AftersalesService) Create(dto models.CreateAftersalesOrderDTO, userId uint) (*models.AftersalesOrder, error) {
	serialNumber, err := s.generateUniqueSerial()
	if err != nil {
		return nil, err
	}

	technicianID := dto.TechnicianID
	if technicianID == nil {
		uid := userId
		technicianID = &uid
	}

	order := models.AftersalesOrder{
		SerialNumber:        serialNumber,
		CompanyName:         dto.CompanyName,
		CompanyAddress:      dto.CompanyAddress,
		ContactName:         dto.ContactName,
		ContactPhone:        dto.ContactPhone,
		ServiceType:         dto.ServiceType,
		IssueDescription:    dto.IssueDescription,
		TechnicianID:        technicianID,
		CreatedBy:           &userId,
		WorkOrderStatus:     WorkOrderStatusCreated,
		AuthorizationStatus: AuthorizationStatusPending,
	}

	if err := database.DB.Create(&order).Error; err != nil {
		return nil, fmt.Errorf("创建售后工单失败: %w", err)
	}

	_ = database.DB.Preload("Technician").Preload("Creator").Where("serial_number = ?", order.SerialNumber).First(&order)
	return &order, nil
}

// FindAll 获取售后工单列表
func (s *AftersalesService) FindAll(
	page int,
	limit int,
	search string,
	workOrderStatus string,
	serviceType string,
	technicianID *uint,
) ([]models.AftersalesOrder, int, int, error) {
	var orders []models.AftersalesOrder
	var total int64

	offset := (page - 1) * limit
	db := database.DB.Model(&models.AftersalesOrder{}).Preload("Technician").Preload("Creator")

	if search != "" {
		pattern := "%" + search + "%"
		db = db.Where("serial_number LIKE ? OR company_name LIKE ? OR contact_name LIKE ?", pattern, pattern, pattern)
	}
	if workOrderStatus != "" {
		db = db.Where("work_order_status = ?", workOrderStatus)
	}
	if serviceType != "" {
		db = db.Where("service_type = ?", serviceType)
	}
	if technicianID != nil {
		db = db.Where("technician_id = ?", *technicianID)
	}

	if err := db.Count(&total).Error; err != nil {
		return nil, 0, 0, fmt.Errorf("查询售后工单总数失败: %w", err)
	}

	if err := db.Order("created_at DESC").Offset(offset).Limit(limit).Find(&orders).Error; err != nil {
		return nil, 0, 0, fmt.Errorf("查询售后工单列表失败: %w", err)
	}

	totalPages := (int(total) + limit - 1) / limit
	return orders, int(total), totalPages, nil
}

// FindOne 获取单个售后工单
func (s *AftersalesService) FindOne(serialNumber string) (*models.AftersalesOrder, error) {
	var order models.AftersalesOrder
	result := database.DB.Preload("Technician").Preload("Creator").
		Where("serial_number = ?", normalizeAftersalesSerial(serialNumber)).First(&order)
	if result.Error != nil {
		return nil, fmt.Errorf("查询售后工单失败: %w", errors.New("序列号不存在"))
	}
	return &order, nil
}

// Update 更新售后工单基础信息
func (s *AftersalesService) Update(
	serialNumber string,
	dto models.UpdateAftersalesOrderDTO,
	currentUser models.User,
) (*models.AftersalesOrder, error) {
	var order models.AftersalesOrder
	result := database.DB.Where("serial_number = ?", normalizeAftersalesSerial(serialNumber)).First(&order)
	if result.Error != nil {
		return nil, fmt.Errorf("查询售后工单失败: %w", errors.New("序列号不存在"))
	}

	if order.WorkOrderStatus == WorkOrderStatusClosed {
		return nil, errors.New("工单已关闭，不可修改")
	}

	if currentUser.Role != "admin" {
		if order.TechnicianID == nil || *order.TechnicianID != currentUser.ID {
			return nil, errors.New("无权修改此工单")
		}
	}

	if dto.CompanyAddress != "" {
		order.CompanyAddress = dto.CompanyAddress
	}
	if dto.ContactName != "" {
		order.ContactName = dto.ContactName
	}
	if dto.ContactPhone != "" {
		order.ContactPhone = dto.ContactPhone
	}
	if dto.ServiceType != "" {
		order.ServiceType = dto.ServiceType
	}
	if dto.IssueDescription != "" {
		order.IssueDescription = dto.IssueDescription
	}
	if dto.ResolutionNote != "" {
		order.ResolutionNote = dto.ResolutionNote
	}
	if dto.TechnicianID != nil && currentUser.Role == "admin" {
		order.TechnicianID = dto.TechnicianID
	}

	if err := database.DB.Save(&order).Error; err != nil {
		return nil, fmt.Errorf("更新售后工单失败: %w", err)
	}

	_ = database.DB.Preload("Technician").Preload("Creator").Where("serial_number = ?", order.SerialNumber).First(&order)
	return &order, nil
}

// SubmitForConfirmation 技术员提交客户确认
func (s *AftersalesService) SubmitForConfirmation(
	serialNumber string,
	dto models.SubmitForConfirmationDTO,
	currentUser models.User,
) (*models.AftersalesOrder, error) {
	var order models.AftersalesOrder
	result := database.DB.Where("serial_number = ?", normalizeAftersalesSerial(serialNumber)).First(&order)
	if result.Error != nil {
		return nil, fmt.Errorf("查询售后工单失败: %w", errors.New("序列号不存在"))
	}

	if currentUser.Role != "admin" {
		if order.TechnicianID == nil || *order.TechnicianID != currentUser.ID {
			return nil, errors.New("无权操作此工单")
		}
	}

	if order.WorkOrderStatus != WorkOrderStatusCreated && order.WorkOrderStatus != WorkOrderStatusRejected {
		return nil, errors.New("当前工单状态不可提交确认")
	}

	order.ResolutionNote = dto.ResolutionNote
	order.WorkOrderStatus = WorkOrderStatusPendingConfirmation

	if err := database.DB.Save(&order).Error; err != nil {
		return nil, fmt.Errorf("提交客户确认失败: %w", err)
	}

	_ = database.DB.Preload("Technician").Preload("Creator").Where("serial_number = ?", order.SerialNumber).First(&order)
	return &order, nil
}

// PublicQuery 公开查询（脱敏视图）
func (s *AftersalesService) PublicQuery(serialNumber string) (*models.AftersalesPublicView, error) {
	var order models.AftersalesOrder
	result := database.DB.Preload("Technician").
		Where("serial_number = ?", normalizeAftersalesSerial(serialNumber)).First(&order)
	if result.Error != nil {
		return nil, fmt.Errorf("查询售后工单失败: %w", errors.New("序列号不存在"))
	}

	// 首次扫码记录时间
	if order.ScannedAt == nil {
		now := time.Now()
		order.ScannedAt = &now
		_ = database.DB.Model(&order).Update("scanned_at", now).Error
	}

	view := &models.AftersalesPublicView{
		SerialNumber:        order.SerialNumber,
		CompanyName:         order.CompanyName,
		CompanyAddress:      order.CompanyAddress,
		ContactName:         order.ContactName,
		ServiceType:         order.ServiceType,
		IssueDescription:    order.IssueDescription,
		ResolutionNote:      order.ResolutionNote,
		WorkOrderStatus:     order.WorkOrderStatus,
		AuthorizationStatus: order.AuthorizationStatus,
		CreatedAt:           order.CreatedAt,
		ConfirmedAt:         order.ConfirmedAt,
		Signature:           order.Signature,
	}
	if order.Technician != nil {
		view.TechnicianName = order.Technician.Name
	}
	return view, nil
}

// CustomerConfirm 客户授权/未授权确认
func (s *AftersalesService) CustomerConfirm(serialNumber string, dto models.CustomerConfirmDTO) (*models.AftersalesPublicView, error) {
	normalized := normalizeAftersalesSerial(serialNumber)

	if !checkConfirmRateLimit(normalized) {
		return nil, errors.New("操作过于频繁，请稍后再试")
	}

	var order models.AftersalesOrder
	result := database.DB.Where("serial_number = ?", normalized).First(&order)
	if result.Error != nil {
		return nil, fmt.Errorf("查询售后工单失败: %w", errors.New("序列号不存在"))
	}

	if order.WorkOrderStatus != WorkOrderStatusPendingConfirmation {
		return nil, errors.New("当前工单状态不可确认")
	}

	now := time.Now()
	switch dto.Action {
	case "authorize":
		if err := validateSignature(dto.Signature); err != nil {
			return nil, err
		}
		order.WorkOrderStatus = WorkOrderStatusClosed
		order.AuthorizationStatus = AuthorizationStatusAuthorized
		order.ConfirmedAt = &now
		order.Signature = strings.TrimSpace(dto.Signature)
	case "reject":
		reason := strings.TrimSpace(dto.RejectReason)
		if reason == "" {
			return nil, errors.New("请填写退回原因")
		}
		order.WorkOrderStatus = WorkOrderStatusRejected
		order.AuthorizationStatus = AuthorizationStatusUnauthorized
		order.RejectCount++
		order.ResolutionNote = order.ResolutionNote + "\n\n[客户退回] " + reason
	default:
		return nil, errors.New("无效的操作")
	}

	if err := database.DB.Save(&order).Error; err != nil {
		return nil, fmt.Errorf("提交确认失败: %w", err)
	}

	return s.PublicQuery(normalized)
}

// Reassign 重新分配技术员（仅管理员）
func (s *AftersalesService) Reassign(serialNumber string, technicianID uint) (*models.AftersalesOrder, error) {
	var order models.AftersalesOrder
	result := database.DB.Where("serial_number = ?", normalizeAftersalesSerial(serialNumber)).First(&order)
	if result.Error != nil {
		return nil, fmt.Errorf("查询售后工单失败: %w", errors.New("序列号不存在"))
	}

	if order.WorkOrderStatus == WorkOrderStatusClosed {
		return nil, errors.New("工单已关闭，不可重新分配")
	}

	var technician models.User
	if err := database.DB.First(&technician, technicianID).Error; err != nil {
		return nil, errors.New("指定的技术员不存在")
	}
	if technician.Role != "admin" && technician.Role != "technician" {
		return nil, errors.New("指定的用户不是技术员或管理员")
	}

	order.TechnicianID = &technicianID
	if err := database.DB.Save(&order).Error; err != nil {
		return nil, fmt.Errorf("重新分配技术员失败: %w", err)
	}

	_ = database.DB.Preload("Technician").Preload("Creator").Where("serial_number = ?", order.SerialNumber).First(&order)
	return &order, nil
}

// ForceClose 管理员强制关闭工单
func (s *AftersalesService) ForceClose(serialNumber string) (*models.AftersalesOrder, error) {
	var order models.AftersalesOrder
	result := database.DB.Where("serial_number = ?", normalizeAftersalesSerial(serialNumber)).First(&order)
	if result.Error != nil {
		return nil, fmt.Errorf("查询售后工单失败: %w", errors.New("序列号不存在"))
	}

	if order.WorkOrderStatus == WorkOrderStatusClosed {
		return nil, errors.New("工单已关闭")
	}

	now := time.Now()
	order.WorkOrderStatus = WorkOrderStatusClosed
	order.AuthorizationStatus = AuthorizationStatusAuthorized
	order.ConfirmedAt = &now

	if err := database.DB.Save(&order).Error; err != nil {
		return nil, fmt.Errorf("强制关闭工单失败: %w", err)
	}

	_ = database.DB.Preload("Technician").Preload("Creator").Where("serial_number = ?", order.SerialNumber).First(&order)
	return &order, nil
}

// Delete 物理删除售后工单（仅管理员）
func (s *AftersalesService) Delete(serialNumber string) error {
	var order models.AftersalesOrder
	result := database.DB.Where("serial_number = ?", normalizeAftersalesSerial(serialNumber)).First(&order)
	if result.Error != nil {
		return fmt.Errorf("查询售后工单失败: %w", errors.New("序列号不存在"))
	}

	if err := database.DB.Delete(&order).Error; err != nil {
		return fmt.Errorf("删除售后工单失败: %w", err)
	}
	return nil
}

// GenerateQRCode 生成售后工单二维码
func (s *AftersalesService) GenerateQRCode(
	serialNumber string,
	baseUrl string,
	requestHost string,
	protocol string,
) (string, string, error) {
	var order models.AftersalesOrder
	result := database.DB.Where("serial_number = ?", normalizeAftersalesSerial(serialNumber)).First(&order)
	if result.Error != nil {
		return "", "", fmt.Errorf("查询售后工单失败: %w", errors.New("序列号不存在"))
	}

	// 售后码二维码直接指向 /aftersales/{serialNumber}
	if baseUrl == "" {
		baseUrl = fmt.Sprintf("%s://%s/aftersales/%s", protocol, requestHost, order.SerialNumber)
	}

	filePath := fmt.Sprintf("temp_qr_%s.png", uuid.New().String())
	writer, err := standard.New(filePath, standard.WithQRWidth(6))
	if err != nil {
		return "", "", fmt.Errorf("二维码写入器创建失败: %w", err)
	}

	qrc, errCode := qr.New(baseUrl)
	if errCode != nil {
		os.Remove(filePath)
		return "", "", fmt.Errorf("二维码创建失败: %w", errCode)
	}

	if errSave := qrc.Save(writer); errSave != nil {
		os.Remove(filePath)
		return "", "", fmt.Errorf("二维码保存失败: %w", errSave)
	}

	fileContent, errRead := os.ReadFile(filePath)
	if errRead != nil {
		os.Remove(filePath)
		return "", "", fmt.Errorf("二维码文件读取失败: %w", errRead)
	}
	os.Remove(filePath)

	qrCodeBase64 := fmt.Sprintf("data:image/png;base64,%s", base64.StdEncoding.EncodeToString(fileContent))
	return qrCodeBase64, baseUrl, nil
}