package service

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"time"

	"affiliate_dash/internal/model"
	"affiliate_dash/internal/pkg/timeutil"

	"github.com/google/uuid"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

// 充值约束：最小 10 元；1 元 = 100 积分，即 1 分人民币 = 1 积分。
const (
	RechargeMinAmountCNYCents = 1000 // 10 元（单位：分）
	RechargePointsPerCNYCent  = 1    // 每 1 分人民币兑换积分
)

type RechargeService struct {
	db        *gorm.DB
	fulfill   *FulfillmentService
	uploadDir string
}

func NewRechargeService(db *gorm.DB, fulfill *FulfillmentService, uploadDir string) *RechargeService {
	return &RechargeService{db: db, fulfill: fulfill, uploadDir: uploadDir}
}

type CreateRechargeInput struct {
	MerchantID  uint
	ActorUserID uint
	AmountCNY   int64 // 人民币，单位：分
	Vouchers    []string
	Note        string
}

func (s *RechargeService) CreateRecharge(in CreateRechargeInput) (*model.RechargeApplication, error) {
	if in.MerchantID == 0 {
		return nil, errors.New("无效的商户")
	}
	if in.AmountCNY < RechargeMinAmountCNYCents {
		return nil, errors.New("最小充值金额为 10 元")
	}
	if len(in.Vouchers) == 0 {
		return nil, errors.New("请上传打款凭证截图")
	}
	cleaned := make([]string, 0, len(in.Vouchers))
	for _, v := range in.Vouchers {
		v = strings.TrimSpace(v)
		if v != "" {
			cleaned = append(cleaned, v)
		}
	}
	if len(cleaned) == 0 {
		return nil, errors.New("请上传打款凭证截图")
	}
	if len(cleaned) > 5 {
		return nil, errors.New("凭证截图最多 5 张")
	}
	if len(in.Note) > 512 {
		return nil, errors.New("备注最长 512 个字符")
	}

	app := &model.RechargeApplication{
		MerchantID:    in.MerchantID,
		ApplicationNo: newRechargeApplicationNo(),
		AmountCNY:     in.AmountCNY,
		PointsAmount:  in.AmountCNY * RechargePointsPerCNYCent,
		Status:        model.RechargeStatusPending,
		Vouchers:      cleaned,
		Note:          strings.TrimSpace(in.Note),
	}
	if err := s.db.Create(app).Error; err != nil {
		return nil, err
	}
	_ = writeAudit(s.db, &app.MerchantID, &in.ActorUserID, nil, "recharge.create", "recharge_application", fmt.Sprint(app.ID), map[string]interface{}{"application_no": app.ApplicationNo, "amount_cny": app.AmountCNY})
	return app, nil
}

func (s *RechargeService) ListRechargeApplications(merchantID uint, page, size int, status string) ([]model.RechargeApplication, int64, error) {
	page, size = normalizePage(page, size)
	tx := s.db.Model(&model.RechargeApplication{}).Where("merchant_id = ?", merchantID)
	if status != "" {
		tx = tx.Where("status = ?", status)
	}
	var total int64
	if err := tx.Count(&total).Error; err != nil {
		return nil, 0, err
	}
	var list []model.RechargeApplication
	err := tx.Preload("Merchant").Order("id DESC").Offset((page - 1) * size).Limit(size).Find(&list).Error
	return list, total, err
}

func (s *RechargeService) ListAllRechargeApplications(page, size int, status string) ([]model.RechargeApplication, int64, error) {
	page, size = normalizePage(page, size)
	tx := s.db.Model(&model.RechargeApplication{})
	if status != "" {
		tx = tx.Where("status = ?", status)
	}
	var total int64
	if err := tx.Count(&total).Error; err != nil {
		return nil, 0, err
	}
	var list []model.RechargeApplication
	err := tx.Preload("Merchant").Order("id DESC").Offset((page - 1) * size).Limit(size).Find(&list).Error
	return list, total, err
}

type ReviewRechargeInput struct {
	ApplicationID uint
	Approved      bool
	ReviewNote    string
	ActorUserID   uint
}

// ReviewRecharge 审核充值申请；通过时在申请与入账共用一个事务内调用 AdjustWallet
// （幂等键 = 申请单号），保证审核状态与钱包入账一致。
func (s *RechargeService) ReviewRecharge(in ReviewRechargeInput) (*model.RechargeApplication, error) {
	var out model.RechargeApplication
	err := s.db.Transaction(func(tx *gorm.DB) error {
		var app model.RechargeApplication
		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).First(&app, in.ApplicationID).Error; err != nil {
			return errors.New("充值申请不存在")
		}
		if app.Status != model.RechargeStatusPending {
			return errors.New("该申请已审核，不能重复操作")
		}

		status := model.RechargeStatusRejected
		if in.Approved {
			status = model.RechargeStatusApproved
		}
		now := time.Now()
		updates := map[string]interface{}{
			"status":      status,
			"review_note": strings.TrimSpace(in.ReviewNote),
			"reviewed_at": now,
			"reviewed_by": in.ActorUserID,
		}
		if err := tx.Model(&app).Updates(updates).Error; err != nil {
			return err
		}

		if in.Approved {
			wallet, err := s.fulfill.AdjustWallet(WalletAdjustInput{
				MerchantID:     app.MerchantID,
				ActorUserID:    in.ActorUserID,
				Amount:         app.PointsAmount,
				IdempotencyKey: app.ApplicationNo,
				Note:           fmt.Sprintf("充值入账 %s（%s）", app.ApplicationNo, app.Note),
			})
			if err != nil {
				return fmt.Errorf("积分入账失败：%w", err)
			}
			_ = wallet
		}

		out = app
		out.Status = status
		out.ReviewNote = strings.TrimSpace(in.ReviewNote)
		out.ReviewedAt = &now
		return writeAudit(tx, &app.MerchantID, &in.ActorUserID, nil, "recharge.review", "recharge_application", fmt.Sprint(app.ID), map[string]interface{}{"application_no": app.ApplicationNo, "approved": in.Approved, "points_amount": app.PointsAmount})
	})
	if err != nil {
		return nil, err
	}
	return &out, nil
}

type SaveAlertInput struct {
	Enabled         bool
	ThresholdPoints int64
	WebhookURL      string
}

func (s *RechargeService) GetAlertConfig(merchantID uint) (*model.MerchantAlertConfig, error) {
	var cfg model.MerchantAlertConfig
	err := s.db.Where("merchant_id = ?", merchantID).First(&cfg).Error
	if errors.Is(err, gorm.ErrRecordNotFound) {
		return &model.MerchantAlertConfig{MerchantID: merchantID}, nil
	}
	if err != nil {
		return nil, err
	}
	return &cfg, nil
}

func (s *RechargeService) SaveAlertConfig(merchantID uint, in SaveAlertInput) (*model.MerchantAlertConfig, error) {
	if in.ThresholdPoints < 0 {
		return nil, errors.New("预警阈值不能为负")
	}
	if in.WebhookURL == "" || len(in.WebhookURL) > 1024 {
		return nil, errors.New("请填写 Webhook URL")
	}
	if in.Enabled {
		if !strings.HasPrefix(in.WebhookURL, "http://") && !strings.HasPrefix(in.WebhookURL, "https://") {
			return nil, errors.New("Webhook URL 必须以 http(s):// 开头")
		}
	}
	var cfg model.MerchantAlertConfig
	err := s.db.Where("merchant_id = ?", merchantID).First(&cfg).Error
	switch {
	case errors.Is(err, gorm.ErrRecordNotFound):
		cfg = model.MerchantAlertConfig{MerchantID: merchantID, Enabled: in.Enabled, ThresholdPoints: in.ThresholdPoints, WebhookURL: strings.TrimSpace(in.WebhookURL)}
		if err := s.db.Create(&cfg).Error; err != nil {
			return nil, err
		}
	case err != nil:
		return nil, err
	default:
		cfg.Enabled = in.Enabled
		cfg.ThresholdPoints = in.ThresholdPoints
		cfg.WebhookURL = strings.TrimSpace(in.WebhookURL)
		if err := s.db.Save(&cfg).Error; err != nil {
			return nil, err
		}
	}
	return &cfg, nil
}

// CheckLowBalanceAndNotify 余额低于阈值时向配置的 Webhook 推送告警。
func (s *RechargeService) CheckLowBalanceAndNotify(merchantID uint) {
	cfg, err := s.GetAlertConfig(merchantID)
	if err != nil || !cfg.Enabled || cfg.ThresholdPoints <= 0 {
		return
	}
	wallet, err := s.fulfill.GetWallet(merchantID)
	if err != nil {
		return
	}
	if wallet.AvailableBalance >= cfg.ThresholdPoints {
		return
	}
	var merchant model.Merchant
	if err := s.db.Select("code", "name").First(&merchant, merchantID).Error; err != nil {
		merchant.Name = fmt.Sprintf("商户#%d", merchantID)
	}
	payload := map[string]interface{}{
		"msgtype": "text",
		"text": map[string]string{
			"content": fmt.Sprintf("余额告警：商户 %s（#%d）当前积分余额 %d，已低于阈值 %d，请及时处理充值。", merchant.Name, merchantID, wallet.AvailableBalance, cfg.ThresholdPoints),
		},
	}
	raw, _ := json.Marshal(payload)
	client := &http.Client{Timeout: 10 * time.Second}
	resp, err := client.Post(cfg.WebhookURL, "application/json", bytes.NewReader(raw))
	if err != nil {
		log.Printf("低余额告警推送失败 merchant=%d: %v", merchantID, err)
		return
	}
	defer resp.Body.Close()
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		log.Printf("低余额告警推送非 2xx merchant=%d status=%d", merchantID, resp.StatusCode)
	}
}

// SaveUploadFile 保存上传的图片到 uploadDir，返回可通过 /uploads 访问的 URL。
// 通过文件魔数校验真实图片格式（jpg/png/gif/webp），存储扩展名以实际格式为准。
func (s *RechargeService) SaveUploadFile(r io.Reader, _ string, maxBytes int64) (string, error) {
	data, err := io.ReadAll(io.LimitReader(r, maxBytes+1))
	if err != nil {
		return "", errors.New("读取上传文件失败")
	}
	if len(data) == 0 {
		return "", errors.New("上传文件为空")
	}
	if int64(len(data)) > maxBytes {
		return "", fmt.Errorf("图片大小不能超过 %dMB", maxBytes/1024/1024)
	}
	ext := detectImageExt(data)
	if ext == "" {
		return "", errors.New("仅支持 jpg/png/gif/webp 图片")
	}
	name := uuid.NewString() + "." + ext
	if err := os.MkdirAll(s.uploadDir, 0o755); err != nil {
		return "", errors.New("创建上传目录失败")
	}
	if err := os.WriteFile(filepath.Join(s.uploadDir, name), data, 0o644); err != nil {
		return "", errors.New("保存上传文件失败")
	}
	return "/uploads/" + name, nil
}

// detectImageExt 根据文件头魔数识别图片格式；非法文件返回空串。
func detectImageExt(data []byte) string {
	switch {
	case len(data) >= 3 && data[0] == 0xFF && data[1] == 0xD8 && data[2] == 0xFF:
		return "jpg"
	case len(data) >= 8 && data[0] == 0x89 && data[1] == 'P' && data[2] == 'N' && data[3] == 'G':
		return "png"
	case len(data) >= 6 && data[0] == 'G' && data[1] == 'I' && data[2] == 'F' && data[3] == '8':
		return "gif"
	case len(data) >= 12 && data[0] == 'R' && data[1] == 'I' && data[2] == 'F' && data[3] == 'F' &&
		data[8] == 'W' && data[9] == 'E' && data[10] == 'B' && data[11] == 'P':
		return "webp"
	default:
		return ""
	}
}

func newRechargeApplicationNo() string {
	return "RC" + timeutil.Now().Format(timeutil.OrderNoLayout) + strings.ReplaceAll(uuid.NewString()[:8], "-", "")
}