package service

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"github.com/topfans/backend/services/statisticService/model"
	"github.com/topfans/backend/services/statisticService/sink"
	pb "github.com/topfans/backend/pkg/proto/statistic"
)

// 业务侧错误
var (
	ErrInvalidEventID      = errors.New("invalid event_id")
	ErrInvalidEventType   = errors.New("invalid event_type")
	ErrPropertiesTooLarge = errors.New("properties too large")
)

// MaxPropertiesSize properties JSON 最大 1KB（防止 abuse）
const MaxPropertiesSize = 1024

// DefaultEventTypeWhitelist 默认事件类型白名单
var DefaultEventTypeWhitelist = []string{
	"asset.like",
	"asset.mint",
	"exhibition.start",
	"exhibition.end",
	"exhibition.revenue",
	"asset.level_up",
	"crystal.change",
}

// EventService 事件业务逻辑层
type EventService struct {
	sink      sink.EventSink
	whiteList map[string]bool
}

// NewEventService 构造 EventService
func NewEventService(s sink.EventSink, whiteList []string) *EventService {
	wl := make(map[string]bool, len(whiteList))
	for _, t := range whiteList {
		wl[t] = true
	}
	return &EventService{sink: s, whiteList: wl}
}

// validate 校验事件
func (s *EventService) validate(e *model.Event) error {
	if e == nil {
		return ErrInvalidEventID
	}
	if e.EventID == "" {
		return ErrInvalidEventID
	}
	if !s.whiteList[e.EventType] {
		return fmt.Errorf("%w: %s", ErrInvalidEventType, e.EventType)
	}
	b, _ := json.Marshal(e.Properties)
	if len(b) > MaxPropertiesSize {
		return fmt.Errorf("%w: %d > %d", ErrPropertiesTooLarge, len(b), MaxPropertiesSize)
	}
	return nil
}

// TrackEvent 提交单个事件（非阻塞推入 sink）
func (s *EventService) TrackEvent(ctx context.Context, e *model.Event) (*pb.TrackEventResponse, error) {
	if e.ReceivedAt.IsZero() {
		e.ReceivedAt = time.Now()
	}
	if err := s.validate(e); err != nil {
		return nil, err
	}
	if err := s.sink.Submit(ctx, e); err != nil {
		return &pb.TrackEventResponse{Accepted: 0, Rejected: 1}, nil
	}
	return &pb.TrackEventResponse{Accepted: 1, Rejected: 0}, nil
}

// BatchTrackEvent 批量提交
func (s *EventService) BatchTrackEvent(ctx context.Context, es []*model.Event) (*pb.TrackEventResponse, error) {
	accepted, rejected := int32(0), int32(0)
	for _, e := range es {
		if e.ReceivedAt.IsZero() {
			e.ReceivedAt = time.Now()
		}
		if err := s.validate(e); err != nil {
			rejected++
			continue
		}
		if err := s.sink.Submit(ctx, e); err != nil {
			rejected++
		} else {
			accepted++
		}
	}
	return &pb.TrackEventResponse{Accepted: accepted, Rejected: rejected}, nil
}