/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package utils

import (
	"crypto/md5"
	"crypto/rand"
	"encoding/base64"
	"encoding/hex"
	"hash"
	rand2 "math/rand"
	"net/url"
	"reflect"
	"strconv"
	"time"
)

type UUID [16]byte

const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"

func GetUUID() (uuidHex string) {
	uuid := NewUUID()
	uuidHex = hex.EncodeToString(uuid[:])
	return
}

func RandStringBytes(n int) string {
	b := make([]byte, n)
	for i := range b {
		b[i] = letterBytes[rand2.Intn(len(letterBytes))]
	}
	return string(b)
}

func GetMD5Base64(bytes []byte) (base64Value string) {
	md5Ctx := md5.New()
	md5Ctx.Write(bytes)
	md5Value := md5Ctx.Sum(nil)
	base64Value = base64.StdEncoding.EncodeToString(md5Value)
	return
}

func GetTimeInFormatISO8601() (timeStr string) {
	gmt := time.FixedZone("GMT", 0)

	return time.Now().In(gmt).Format("2006-01-02T15:04:05Z")
}

func GetTimeInFormatRFC2616() (timeStr string) {
	gmt := time.FixedZone("GMT", 0)

	return time.Now().In(gmt).Format("Mon, 02 Jan 2006 15:04:05 GMT")
}

func GetUrlFormedMap(source map[string]string) (urlEncoded string) {
	urlEncoder := url.Values{}
	for key, value := range source {
		urlEncoder.Add(key, value)
	}
	urlEncoded = urlEncoder.Encode()
	return
}

func InitStructWithDefaultTag(bean interface{}) {
	configType := reflect.TypeOf(bean)
	for i := 0; i < configType.Elem().NumField(); i++ {
		field := configType.Elem().Field(i)
		defaultValue := field.Tag.Get("default")
		if defaultValue == "" {
			continue
		}
		setter := reflect.ValueOf(bean).Elem().Field(i)
		switch field.Type.String() {
		case "int":
			intValue, _ := strconv.ParseInt(defaultValue, 10, 64)
			setter.SetInt(intValue)
		case "time.Duration":
			intValue, _ := strconv.ParseInt(defaultValue, 10, 64)
			setter.SetInt(intValue)
		case "string":
			setter.SetString(defaultValue)
		case "bool":
			boolValue, _ := strconv.ParseBool(defaultValue)
			setter.SetBool(boolValue)
		}
	}
}

func NewUUID() UUID {
	ns := UUID{}
	safeRandom(ns[:])
	u := newFromHash(md5.New(), ns, RandStringBytes(16))
	u[6] = (u[6] & 0x0f) | (byte(2) << 4)
	u[8] = (u[8]&(0xff>>2) | (0x02 << 6))

	return u
}

func newFromHash(h hash.Hash, ns UUID, name string) UUID {
	u := UUID{}
	h.Write(ns[:])
	h.Write([]byte(name))
	copy(u[:], h.Sum(nil))

	return u
}

func safeRandom(dest []byte) {
	if _, err := rand.Read(dest); err != nil {
		panic(err)
	}
}

func (u UUID) String() string {
	buf := make([]byte, 36)

	hex.Encode(buf[0:8], u[0:4])
	buf[8] = '-'
	hex.Encode(buf[9:13], u[4:6])
	buf[13] = '-'
	hex.Encode(buf[14:18], u[6:8])
	buf[18] = '-'
	hex.Encode(buf[19:23], u[8:10])
	buf[23] = '-'
	hex.Encode(buf[24:], u[10:])

	return string(buf)
}