jirfag/go-queryset

package gorm3

import (
    "time"

    "github.com/jinzhu/gorm"
)

func getGormDB() *gorm.DB {
    db, _ := gorm.Open("mysql",
        "user:password@/dbname?charset=utf8&parseTime=True&loc=Local")
    return db
}

// User struct represents user model.
type User struct {
    gorm.Model
    Rating      int
    RatingMarks int
}

func getTodayBegin() time.Time {
    year, month, day := time.Now().Date()
    return time.Date(year, month, day, 0, 0, 0, 0, time.Now().Location())
}

func queryUsersWithMaxRating(db *gorm.DB) *gorm.DB {
    return db.Order("rating DESC")
}

func queryUsersRegisteredToday(db *gorm.DB) *gorm.DB {
    return db.Where("created_at >= ?", getTodayBegin())
}

// GetUsersWithMaxRating returns limit users with maximal rating
func GetUsersWithMaxRating(limit int) ([]User, error) {
    var users []User
    err := queryUsersWithMaxRating(getGormDB()).
        Limit(limit).
        Find(&users).Error
    if err != nil {
        return nil, err
    }
    return users, nil
}

// GetUsersRegisteredToday returns all users registered today
func GetUsersRegisteredToday(limit int) ([]User, error) {
    var users []User
    err := queryUsersRegisteredToday(getGormDB()).
        Limit(limit).
        Find(&users).Error
    if err != nil {
        return nil, err
    }
    return users, nil
}

// GetUsersRegisteredTodayWithMaxRating returns all users
// registered today with max rating
func GetUsersRegisteredTodayWithMaxRating(limit int) ([]User, error) {
    var users []User
    err := getGormDB().
        Scopes(queryUsersWithMaxRating, queryUsersRegisteredToday).
        Limit(limit).
        Find(&users).Error
    if err != nil {
        return nil, err
    }
    return users, nil
}