functions.go

package expr

import (
	"reflect"
	"strings"
	"time"

	"github.com/EchoUtopia/zerror"
)

type function struct {
	name string
	iFn  interface{}
	// the following will be set by register
	// if argsNumber is -1, no limit set
	argsNumber int
	isVariadic bool
	fn         reflect.Value
	returnType reflect.Type
}

var errorType = reflect.TypeOf((*error)(nil)).Elem()

func checkFunction(name string, i interface{}) (reflect.Type, reflect.Value, error) {
	v := reflect.ValueOf(i)
	t := v.Type()
	if t.Kind() != reflect.Func {
		return nil, reflect.Value{}, zerror.BadRequest.Errorf(`[%s] is not func`, name)
	}
	// TODO: support variadic
	if t.IsVariadic() {
		return nil, reflect.Value{}, zerror.BadRequest.WithMsg(`variadic function not supported`)
	}
	for i := 0; i < t.NumIn(); i++ {
		nik := t.In(i).Kind()
		if nik != reflect.Int64 && nik != reflect.Float64 && nik != reflect.Bool && nik != reflect.String {
			return nil, reflect.Value{}, zerror.BadRequest.WithMsg(`function variables only support float64, int64, string and bool`)
		}
	}
	if t.NumOut() > 2 {
		return nil, reflect.Value{}, zerror.BadRequest.WithMsg(`function returns more than 2 vars`)
	} else if t.NumOut() == 2 {
		if t.Out(1) != errorType {
			return nil, reflect.Value{}, zerror.BadRequest.WithMsg(`function second return var must be error`)
		}
	} else if t.NumOut() == 1 {
		if t.Out(0) == errorType {
			return nil, reflect.Value{}, zerror.BadRequest.WithMsg(`func first return var can not be error`)
		}
	}
	returnType := t.Out(0)
	returnKind := returnType.Kind()
	returnBool := returnKind == reflect.Bool
	if !returnBool && returnKind != reflect.Int64 && returnKind != reflect.Float64 && returnKind != reflect.String {
		return nil, reflect.Value{}, zerror.BadRequest.WithMsg(`function first return val type must be one of string, int64, float64 and bool`)
	}
	return returnType, v, nil
}

var builtinFuncs = map[string]interface{}{
	`contains`:   contains,
	`endsWith`:   endsWith,
	`startsWith`: startsWith,
	`length`:     length,
	`toLower`:    toLower,
	`toUpper`:    toUpper,
	`trim`:       trim,
	`concat`:     concat,
	`now`:        now,
}

func now() string {
	return time.Now().Format(time.RFC3339)
}

func contains(s, substr string) bool {
	return strings.Contains(s, substr)
}

func endsWith(s, suffix string) bool {
	return strings.HasSuffix(s, suffix)
}

func startsWith(s, prefix string) bool {
	return strings.HasPrefix(s, prefix)
}

func length(s string) int64 {
	return int64(len(s))
}

func toLower(s string) string {
	return strings.ToLower(s)
}

func toUpper(s string) string {
	return strings.ToUpper(s)
}

func trim(s string) string {
	return strings.TrimSpace(s)
}

func concat(sa, sb string) string {
	return sa + sb
}