/vendor/github.com/jinzhu/gorm/utils.go

package gorm

import (
	"bytes"
	"database/sql/driver"
	"fmt"
	"reflect"
	"regexp"
	"runtime"
	"strings"
	"sync"
	"time"
)

// NowFunc returns current time, this function is exported in order to be able
// to give the flexibility to the developer to customize it according to their
// needs, e.g:
//    gorm.NowFunc = func() time.Time {
//      return time.Now().UTC()
//    }
var NowFunc = func() time.Time {
	return time.Now()
}

// Copied from golint
var commonInitialisms = []string{"API", "ASCII", "CPU", "CSS", "DNS", "EOF", "GUID", "HTML", "HTTP", "HTTPS", "ID", "IP", "JSON", "LHS", "QPS", "RAM", "RHS", "RPC", "SLA", "SMTP", "SSH", "TLS", "TTL", "UI", "UID", "UUID", "URI", "URL", "UTF8", "VM", "XML", "XSRF", "XSS"}
var commonInitialismsReplacer *strings.Replacer

func init() {
	var commonInitialismsForReplacer []string
	for _, initialism := range commonInitialisms {
		commonInitialismsForReplacer = append(commonInitialismsForReplacer, initialism, strings.Title(strings.ToLower(initialism)))
	}
	commonInitialismsReplacer = strings.NewReplacer(commonInitialismsForReplacer...)
}

type safeMap struct {
	m map[string]string
	l *sync.RWMutex
}

func (s *safeMap) Set(key string, value string) {
	s.l.Lock()
	defer s.l.Unlock()
	s.m[key] = value
}

func (s *safeMap) Get(key string) string {
	s.l.RLock()
	defer s.l.RUnlock()
	return s.m[key]
}

func newSafeMap() *safeMap {
	return &safeMap{l: new(sync.RWMutex), m: make(map[string]string)}
}

var smap = newSafeMap()

type strCase bool

const (
	lower strCase = false
	upper strCase = true
)

// ToDBName convert string to db name
func ToDBName(name string) string {
	if v := smap.Get(name); v != "" {
		return v
	}

	if name == "" {
		return ""
	}

	var (
		value                        = commonInitialismsReplacer.Replace(name)
		buf                          = bytes.NewBufferString("")
		lastCase, currCase, nextCase strCase
	)

	for i, v := range value[:len(value)-1] {
		nextCase = strCase(value[i+1] >= 'A' && value[i+1] <= 'Z')
		if i > 0 {
			if currCase == upper {
				if lastCase == upper && nextCase == upper {
					buf.WriteRune(v)
				} else {
					if value[i-1] != '_' && value[i+1] != '_' {
						buf.WriteRune('_')
					}
					buf.WriteRune(v)
				}
			} else {
				buf.WriteRune(v)
			}
		} else {
			currCase = upper
			buf.WriteRune(v)
		}
		lastCase = currCase
		currCase = nextCase
	}

	buf.WriteByte(value[len(value)-1])

	s := strings.ToLower(buf.String())
	smap.Set(name, s)
	return s
}

// SQL expression
type expr struct {
	expr string
	args []interface{}
}

// Expr generate raw SQL expression, for example:
//     DB.Model(&product).Update("price", gorm.Expr("price * ? + ?", 2, 100))
func Expr(expression string, args ...interface{}) *expr {
	return &expr{expr: expression, args: args}
}

func indirect(reflectValue reflect.Value) reflect.Value {
	for reflectValue.Kind() == reflect.Ptr {
		reflectValue = reflectValue.Elem()
	}
	return reflectValue
}

func toQueryMarks(primaryValues [][]interface{}) string {
	var results []string

	for _, primaryValue := range primaryValues {
		var marks []string
		for _,_ = range primaryValue {
			marks = append(marks, "?")
		}

		if len(marks) > 1 {
			results = append(results, fmt.Sprintf("(%v)", strings.Join(marks, ",")))
		} else {
			results = append(results, strings.Join(marks, ""))
		}
	}
	return strings.Join(results, ",")
}

func toQueryCondition(scope *Scope, columns []string) string {
	var newColumns []string
	for _, column := range columns {
		newColumns = append(newColumns, scope.Quote(column))
	}

	if len(columns) > 1 {
		return fmt.Sprintf("(%v)", strings.Join(newColumns, ","))
	}
	return strings.Join(newColumns, ",")
}

func toQueryValues(values [][]interface{}) (results []interface{}) {
	for _, value := range values {
		for _, v := range value {
			results = append(results, v)
		}
	}
	return
}

func fileWithLineNum() string {
	for i := 2; i < 15; i++ {
		_, file, line, ok := runtime.Caller(i)
		if ok && (!regexp.MustCompile(`jinzhu/gorm/.*.go`).MatchString(file) || regexp.MustCompile(`jinzhu/gorm/.*test.go`).MatchString(file)) {
			return fmt.Sprintf("%v:%v", file, line)
		}
	}
	return ""
}

func isBlank(value reflect.Value) bool {
	return reflect.DeepEqual(value.Interface(), reflect.Zero(value.Type()).Interface())
}

func toSearchableMap(attrs ...interface{}) (result interface{}) {
	if len(attrs) > 1 {
		if str, ok := attrs[0].(string); ok {
			result = map[string]interface{}{str: attrs[1]}
		}
	} else if len(attrs) == 1 {
		if attr, ok := attrs[0].(map[string]interface{}); ok {
			result = attr
		}

		if attr, ok := attrs[0].(interface{}); ok {
			result = attr
		}
	}
	return
}

func equalAsString(a interface{}, b interface{}) bool {
	return toString(a) == toString(b)
}

func toString(str interface{}) string {
	if values, ok := str.([]interface{}); ok {
		var results []string
		for _, value := range values {
			results = append(results, toString(value))
		}
		return strings.Join(results, "_")
	} else if bytes, ok := str.([]byte); ok {
		return string(bytes)
	} else if reflectValue := reflect.Indirect(reflect.ValueOf(str)); reflectValue.IsValid() {
		return fmt.Sprintf("%v", reflectValue.Interface())
	}
	return ""
}

func makeSlice(elemType reflect.Type) interface{} {
	if elemType.Kind() == reflect.Slice {
		elemType = elemType.Elem()
	}
	sliceType := reflect.SliceOf(elemType)
	slice := reflect.New(sliceType)
	slice.Elem().Set(reflect.MakeSlice(sliceType, 0, 0))
	return slice.Interface()
}

func strInSlice(a string, list []string) bool {
	for _, b := range list {
		if b == a {
			return true
		}
	}
	return false
}

// getValueFromFields return given fields's value
func getValueFromFields(value reflect.Value, fieldNames []string) (results []interface{}) {
	// If value is a nil pointer, Indirect returns a zero Value!
	// Therefor we need to check for a zero value,
	// as FieldByName could panic
	if indirectValue := reflect.Indirect(value); indirectValue.IsValid() {
		for _, fieldName := range fieldNames {
			if fieldValue := indirectValue.FieldByName(fieldName); fieldValue.IsValid() {
				result := fieldValue.Interface()
				if r, ok := result.(driver.Valuer); ok {
					result, _ = r.Value()
				}
				results = append(results, result)
			}
		}
	}
	return
}

func addExtraSpaceIfExist(str string) string {
	if str != "" {
		return " " + str
	}
	return ""
}