// Copyright 2019 gf Author(https://github.com/gogf/gf). All Rights Reserved.
//
// This Source Code Form is subject to the terms of the MIT License.
// If a copy of the MIT was not distributed with this file,
// You can obtain one at https://github.com/gogf/gf.

// Package empty provides functions for checking empty variables.
package empty

import (
	"reflect"
)

// apiString is used for type assert api for String().
type apiString interface {
	String() string
}

// apiInterfaces is used for type assert api for Interfaces.
type apiInterfaces interface {
	Interfaces() []interface{}
}

// apiMapStrAny is the interface support for converting struct parameter to map.
type apiMapStrAny interface {
	MapStrAny() map[string]interface{}
}

// IsEmpty checks whether given <value> empty.
// It returns true if <value> is in: 0, nil, false, "", len(slice/map/chan) == 0,
// or else it returns false.
func IsEmpty(value interface{}) bool {
	if value == nil {
		return true
	}
	switch value := value.(type) {
	case int:
		return value == 0
	case int8:
		return value == 0
	case int16:
		return value == 0
	case int32:
		return value == 0
	case int64:
		return value == 0
	case uint:
		return value == 0
	case uint8:
		return value == 0
	case uint16:
		return value == 0
	case uint32:
		return value == 0
	case uint64:
		return value == 0
	case float32:
		return value == 0
	case float64:
		return value == 0
	case bool:
		return value == false
	case string:
		return value == ""
	case []byte:
		return len(value) == 0
	case []rune:
		return len(value) == 0
	default:
		// Common interfaces checks.
		if f, ok := value.(apiString); ok {
			return f.String() == ""
		}
		if f, ok := value.(apiInterfaces); ok {
			return len(f.Interfaces()) == 0
		}
		if f, ok := value.(apiMapStrAny); ok {
			return len(f.MapStrAny()) == 0
		}
		// Finally using reflect.
		var rv reflect.Value
		if v, ok := value.(reflect.Value); ok {
			rv = v
		} else {
			rv = reflect.ValueOf(value)
		}
		switch rv.Kind() {
		case reflect.Chan,
			reflect.Map,
			reflect.Slice,
			reflect.Array:
			return rv.Len() == 0

		case reflect.Func,
			reflect.Ptr,
			reflect.Interface,
			reflect.UnsafePointer:
			if rv.IsNil() {
				return true
			}
		}
	}
	return false
}

// IsNil checks whether given <value> is nil.
// Note that it might use reflect feature which affects performance a little bit.
func IsNil(value interface{}) bool {
	if value == nil {
		return true
	}
	var rv reflect.Value
	if v, ok := value.(reflect.Value); ok {
		rv = v
	} else {
		rv = reflect.ValueOf(value)
	}
	switch rv.Kind() {
	case reflect.Chan,
		reflect.Map,
		reflect.Slice,
		reflect.Func,
		reflect.Ptr,
		reflect.Interface,
		reflect.UnsafePointer:
		return rv.IsNil()
	}
	return false
}