package logic

import (
	"main/dao/mysql"
	"main/models"
	"main/pkg/snowflake"
	"main/utils"
	"math/rand"
)

func GetAllStudentInfoLogic() (back *[]models.User, err error) {
	return mysql.GetAllStudentInfo()
}

func GetOneRandomStudentInfoLogic() (info models.User, err error) {
	back, err := mysql.GetOneRandomStudentInfo()
	if err != nil {
		return
	}
	info = *back
	return
}

func GetOneStudentInfoAccordScoreLogic() (info models.User, err error) {
	back, err := GetAllStudentInfoLogic()
	if err != nil {
		return
	}
	seed := snowflake.GenID()
	info = WeightedRandomSelect(*back, seed)
	return
}

func GetNStudentInfoAccordScoreLogic(p *models.ParamNum) (info []models.User, err error) {
	back, err := GetAllStudentInfoLogic()
	if err != nil {
		return
	}
	if p.Num > len(*back) {
		err = utils.ErrorBeyondNum
		return
	}
	seed := snowflake.GenID()
	for i := 0; i < p.Num; i++ {
		getInfo := WeightedRandomSelect(*back, seed)
		info = append(info, getInfo)
		removeUser(*back, getInfo)
	}
	return
}

func GetTargetStudentInfoLogic(p *models.ParamUser) (info models.User, err error) {
	back, err := mysql.GetTargetStudentInfo(p.User_id)
	if err != nil {
		return
	}
	info = *back
	return
}

func ChangeStuScoreLogic(p *models.ParamUser) (user *models.UserScore, err error) {
	user = new(models.UserScore)
	user.User_id = p.User_id
	user.User_score = p.User_score

	err = mysql.ChangeStuScore(user)
	return
}

func WeightedRandomSelect(users []models.User, seed int64) models.User {
	totalWeight := 0.0
	weights := make([]float64, len(users))
	for i, user := range users {
		if user.User_score == 0 {
			weights[i] = 3
		} else if user.User_score > 0 {
			weights[i] = 1.0 / float64(user.User_score)
		} else {
			weights[i] = 0 - float64(user.User_score) + 3
		}
		totalWeight += weights[i]
	}
	rand.Seed(seed)
	randomWeight := rand.Float64() * totalWeight
	for i, user := range users {
		if randomWeight < weights[i] {
			return user
		}
		randomWeight -= weights[i]
	}
	return users[0]
}

func removeUser(users []models.User, user models.User) []models.User {
	for i, u := range users {
		if u.User_id == user.User_id {
			return append(users[:i], users[i+1:]...)
		}
	}
	return users
}