package vidser

import (
	"bytes"
	"crypto/sha256"
	"errors"
	"sort"
	"time"

	"91porn-server/app/service/vidhelpser"
	"91porn-server/models/commod"
	"91porn-server/models/v/moduleconfmod"
	"91porn-server/models/v/vidmod"

	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/bson/primitive"
	"go.mongodb.org/mongo-driver/mongo/options"
)

var ErrRandomRefreshUnsupported = errors.New("the selected sort does not support random refresh")

func RefreshModuleVideos(uid uint64, subModuleID primitive.ObjectID, req RefreshModuleVideosReq) (RefreshModuleVideosResp, error) {
	resp := RefreshModuleVideosResp{
		AllVideoInfo: []*vidmod.VideoInfoResp{},
		RefreshMode:  moduleconfmod.RefreshModeRandomTopN,
		RefreshToken: req.RefreshToken,
	}
	subModule, err := moduleconfmod.GetByID(subModuleID)
	if err != nil {
		return resp, err
	}
	if !subModule.IsActiveAt(time.Now()) {
		return resp, nil
	}
	subModule.HaiJiaoStyle.EnsureSortRules()
	candidateN := 0
	for _, rule := range subModule.HaiJiaoStyle.SortRules {
		if rule.Val == commod.SortType(req.ModuleSort) && rule.RefreshMode == moduleconfmod.RefreshModeRandomTopN {
			candidateN = rule.RandomCandidateN
			break
		}
	}
	if candidateN == 0 {
		return resp, ErrRandomRefreshUnsupported
	}

	pageSize := req.PageSize
	if pageSize <= 0 {
		pageSize = 20
	}
	if pageSize > candidateN {
		pageSize = candidateN
	}
	filter := bson.M{
		"mId":      subModuleID.Hex(),
		"status":   vidmod.CheckPass,
		"newsType": vidmod.SP,
		"chosen":   false,
	}
	opt := options.Find().
		SetSort(bson.D{
			{Key: "liaoBaTopSort", Value: -1},
			{Key: "likeCount", Value: -1},
			{Key: "reviewAt", Value: -1},
			{Key: "_id", Value: -1},
		}).
		SetLimit(int64(candidateN)).
		SetProjection(bson.M{"richText": 0})
	videos, err := vidmod.GetVideoListByCond(filter, opt)
	if err != nil {
		return resp, err
	}
	resp.CandidateCount = len(videos)
	deterministicOrderVideos(videos, subModuleID.Hex()+":"+req.RefreshToken)
	if len(videos) > pageSize {
		videos = videos[:pageSize]
	}
	resp.HasNext = hasNextRefreshCandidate(resp.CandidateCount, len(videos))
	resp.AllVideoInfo = vidhelpser.NewEncodeVideoInfoNotStatusForUser(uid, videos)
	if resp.AllVideoInfo == nil {
		resp.AllVideoInfo = []*vidmod.VideoInfoResp{}
	}
	return resp, nil
}

func hasNextRefreshCandidate(candidateCount, returnedCount int) bool {
	return candidateCount > returnedCount
}

func deterministicOrderVideos(videos []*vidmod.VideoModel, seed string) {
	sort.SliceStable(videos, func(i, j int) bool {
		left := sha256.Sum256([]byte(seed + ":" + videos[i].ID.Hex()))
		right := sha256.Sum256([]byte(seed + ":" + videos[j].ID.Hex()))
		cmp := bytes.Compare(left[:], right[:])
		if cmp == 0 {
			return videos[i].ID.Hex() < videos[j].ID.Hex()
		}
		return cmp < 0
	})
}