github.com/angenalZZZ/gofunc@v0.0.0-20210507121333-48ff1be3917b/f/reflect.go

package f

import (
	"fmt"
	"math"
	"reflect"
)

/*************************************************************
 * Reflection:
 * From package(go 1.13) "reflect" -> reflect/value.go
 *************************************************************/

// IsZero reports whether v is the zero value for its type.
// It panics if the argument is invalid.
// NOTICE: this's an built-in method in reflect/value.go since go 1.13
func IsZero(v reflect.Value) bool {
	switch v.Kind() {
	case reflect.Bool:
		return !v.Bool()
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return v.Int() == 0
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
		return v.Uint() == 0
	case reflect.Float32, reflect.Float64:
		return math.Float64bits(v.Float()) == 0
	case reflect.Complex64, reflect.Complex128:
		c := v.Complex()
		return math.Float64bits(real(c)) == 0 && math.Float64bits(imag(c)) == 0
	case reflect.Array:
		for i := 0; i < v.Len(); i++ {
			// if !v.Index(i).IsZero() {
			if !IsZero(v.Index(i)) {
				return false
			}
		}
		return true
	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice, reflect.UnsafePointer:
		return v.IsNil()
	case reflect.String:
		return v.Len() == 0
	case reflect.Struct:
		for i := 0; i < v.NumField(); i++ {
			// if !v.Index(i).IsZero() {
			if !IsZero(v.Field(i)) {
				return false
			}
		}
		return true
	default:
		// This should never happens, but will act as a safeguard for
		// later, as a default value doesn't makes sense here.
		panic(&reflect.ValueError{Method: "cannot check reflect.Value.IsZero", Kind: v.Kind()})
	}
}

// IsEmpty Is the variable empty.
func IsEmpty(val interface{}) bool {
	if val == nil {
		return true
	}

	v := reflect.ValueOf(val)
	switch v.Kind() {
	case reflect.String, reflect.Array, reflect.Chan:
		return v.Len() == 0
	case reflect.Map, reflect.Slice:
		return v.Len() == 0 || v.IsNil()
	case reflect.Bool:
		return !v.Bool()
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return v.Int() == 0
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
		return v.Uint() == 0
	case reflect.Float32, reflect.Float64:
		return v.Float() == 0
	case reflect.Interface, reflect.Ptr:
		if v.IsNil() {
			return true
		}
		return IsEmpty(v.Elem().Interface())
	}

	return reflect.DeepEqual(val, reflect.Zero(v.Type()).Interface())
}

// IsNil checks if a specified object is nil or not, without Failing.
func IsNil(object interface{}) bool {
	if object == nil {
		return true
	}

	value := reflect.ValueOf(object)
	kind := value.Kind()
	isNilKind := containsKind(
		[]reflect.Kind{
			reflect.Chan, reflect.Func,
			reflect.Interface, reflect.Map,
			reflect.Ptr, reflect.Slice},
		kind)

	if isNilKind && value.IsNil() {
		return true
	}

	return false
}

// Eq evaluates the comparison a == b
// Support:
// 	bool, int(X), uint(X), string, float(X)
func Eq(arg1 reflect.Value, arg2 reflect.Value) (bool, error) {
	v1 := indirectInterface(arg1)
	k1, err := basicKind(v1)
	if err != nil {
		return false, err
	}

	v2 := indirectInterface(arg2)
	k2, err := basicKind(v2)
	if err != nil {
		return false, err
	}

	truth := false
	if k1 != k2 {
		// Special case: Can compare integer values regardless of type's sign.
		switch {
		case k1 == intKind && k2 == uintKind:
			truth = v1.Int() >= 0 && uint64(v1.Int()) == v2.Uint()
		case k1 == uintKind && k2 == intKind:
			truth = v2.Int() >= 0 && v1.Uint() == uint64(v2.Int())
		}
		return truth, nil
	}

	switch k1 {
	case boolKind:
		truth = v1.Bool() == v2.Bool()
	case complexKind:
		truth = v1.Complex() == v2.Complex()
	case floatKind:
		truth = v1.Float() == v2.Float()
	case intKind:
		truth = v1.Int() == v2.Int()
	case stringKind:
		truth = v1.String() == v2.String()
	case uintKind:
		truth = v1.Uint() == v2.Uint()
	}

	return truth, nil
}

// ValueLen returns v's length.
func ValueLen(v reflect.Value) int {
	k := v.Kind()

	// (u)int use width.
	switch k {
	case reflect.Map, reflect.Array, reflect.Chan, reflect.Slice, reflect.String:
		return v.Len()
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
		return len(fmt.Sprint(v.Uint()))
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return len(fmt.Sprint(v.Int()))
	case reflect.Float32, reflect.Float64:
		return len(fmt.Sprint(v.Interface()))
	}

	// cannot get length
	return -1
}

// TypeElem returns the underlying type if the given type is a pointer.
func TypeElem(t reflect.Type) reflect.Type {
	for t != nil && t.Kind() == reflect.Ptr {
		t = t.Elem()
	}
	return t
}

/*************************************************************
 * Reflection Kind Extensions
 *************************************************************/

type kind int

const (
	invalidKind kind = iota
	boolKind
	complexKind
	intKind
	floatKind
	stringKind
	uintKind
)

func basicKind(v reflect.Value) (kind, error) {
	switch v.Kind() {
	case reflect.Bool:
		return boolKind, nil
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return intKind, nil
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
		return uintKind, nil
	case reflect.Float32, reflect.Float64:
		return floatKind, nil
	case reflect.Complex64, reflect.Complex128:
		return complexKind, nil
	case reflect.String:
		return stringKind, nil
	}

	// like: slice, array, map ...
	return invalidKind, ErrBadComparisonType
}

// indirectInterface returns the concrete value in an interface value,
// or else the zero reflect.Value.
// That is, if v represents the interface value x, the result is the same as reflect.ValueOf(x):
// the fact that x was an interface value is forgotten.
func indirectInterface(v reflect.Value) reflect.Value {
	if v.Kind() != reflect.Interface {
		return v
	}

	if v.IsNil() {
		return emptyValue
	}

	return v.Elem()
}

// containsKind checks if a specified kind in the slice of kinds.
func containsKind(kinds []reflect.Kind, kind reflect.Kind) bool {
	for i := 0; i < len(kinds); i++ {
		if kind == kinds[i] {
			return true
		}
	}

	return false
}