/*
Copyright 2018 The Kubernetes Authors.

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 metadata

import (
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"net"
	"net/http"
	"net/url"
	"strings"
	"time"

	"encoding/json"
	"reflect"

	"os"
)

/* const vars */
const (
	ENDPOINT           = "http://100.100.100.200"
	DNS_NAMESERVERS    = "dns-conf/nameservers"
	EIPV4              = "eipv4"
	HOSTNAME           = "hostname"
	IMAGE_ID           = "image-id"
	INSTANCE_ID        = "instance-id"
	MAC                = "mac"
	NETWORK_TYPE       = "network-type"
	NTP_CONF_SERVERS   = "ntp-conf/ntp-servers"
	OWNER_ACCOUNT_ID   = "owner-account-id"
	PRIVATE_IPV4       = "private-ipv4"
	REGION             = "region-id"
	SERIAL_NUMBER      = "serial-number"
	SOURCE_ADDRESS     = "source-address"
	VPC_CIDR_BLOCK     = "vpc-cidr-block"
	VPC_ID             = "vpc-id"
	VSWITCH_CIDR_BLOCK = "vswitch-cidr-block"
	VSWITCH_ID         = "vswitch-id"
	ZONE               = "zone-id"
	RAM_SECURITY       = "Ram/security-credentials"
)

// IMetaDataRequest interface
type IMetaDataRequest interface {
	Version(version string) IMetaDataRequest
	ResourceType(rtype string) IMetaDataRequest
	Resource(resource string) IMetaDataRequest
	SubResource(sub string) IMetaDataRequest
	Url() (string, error)
	Do(api interface{}) error
}

// MetaData wrap http client
type MetaData struct {
	// mock for unit test.
	mock   requestMock
	client *http.Client
}

// NewMetaData returns MetaData
func NewMetaData(client *http.Client) *MetaData {
	if client == nil {
		client = &http.Client{}
	}
	return &MetaData{
		client: client,
	}
}

// NewMockMetaData returns mock MetaData
func NewMockMetaData(client *http.Client, sendRequest requestMock) *MetaData {
	if client == nil {
		client = &http.Client{}
	}
	return &MetaData{
		client: client,
		mock:   sendRequest,
	}
}

// New returns MetaDataRequest
func (m *MetaData) New() *MetaDataRequest {
	return &MetaDataRequest{
		client:      m.client,
		sendRequest: m.mock,
	}
}

// HostName returns host name
func (m *MetaData) HostName() (string, error) {
	var hostname ResultList
	err := m.New().Resource(HOSTNAME).Do(&hostname)
	if err != nil {
		return "", err
	}
	return hostname.result[0], nil
}

// ImageID returns image id
func (m *MetaData) ImageID() (string, error) {
	var image ResultList
	err := m.New().Resource(IMAGE_ID).Do(&image)
	if err != nil {
		return "", err
	}
	return image.result[0], err
}

// InstanceID returns instance Id
func (m *MetaData) InstanceID() (string, error) {
	var instanceid ResultList
	err := m.New().Resource(INSTANCE_ID).Do(&instanceid)
	if err != nil {
		return "", err
	}
	return instanceid.result[0], err
}

// Mac returns mac address
func (m *MetaData) Mac() (string, error) {
	var mac ResultList
	err := m.New().Resource(MAC).Do(&mac)
	if err != nil {
		return "", err
	}
	return mac.result[0], nil
}

// NetworkType returns network type
func (m *MetaData) NetworkType() (string, error) {
	var network ResultList
	err := m.New().Resource(NETWORK_TYPE).Do(&network)
	if err != nil {
		return "", err
	}
	return network.result[0], nil
}

// OwnerAccountID returns owner account id
func (m *MetaData) OwnerAccountID() (string, error) {
	var owner ResultList
	err := m.New().Resource(OWNER_ACCOUNT_ID).Do(&owner)
	if err != nil {
		return "", err
	}
	return owner.result[0], nil
}

// PrivateIPv4 returns private ipv4 ip address
func (m *MetaData) PrivateIPv4() (string, error) {
	var private ResultList
	err := m.New().Resource(PRIVATE_IPV4).Do(&private)
	if err != nil {
		return "", err
	}
	return private.result[0], nil
}

// Region returns region
func (m *MetaData) Region() (string, error) {
	var region ResultList
	err := m.New().Resource(REGION).Do(&region)
	if err != nil {
		return "", err
	}
	return region.result[0], nil
}

// SerialNumber returns serial number
func (m *MetaData) SerialNumber() (string, error) {
	var serial ResultList
	err := m.New().Resource(SERIAL_NUMBER).Do(&serial)
	if err != nil {
		return "", err
	}
	return serial.result[0], nil
}

// SourceAddress returns source address
func (m *MetaData) SourceAddress() (string, error) {
	var source ResultList
	err := m.New().Resource(SOURCE_ADDRESS).Do(&source)
	if err != nil {
		return "", err
	}
	return source.result[0], nil

}

// VpcCIDRBlock returns vpc cidr block
func (m *MetaData) VpcCIDRBlock() (string, error) {
	var vpcCIDR ResultList
	err := m.New().Resource(VPC_CIDR_BLOCK).Do(&vpcCIDR)
	if err != nil {
		return "", err
	}
	return vpcCIDR.result[0], err
}

// VpcID returns vpc id
func (m *MetaData) VpcID() (string, error) {
	var vpcId ResultList
	err := m.New().Resource(VPC_ID).Do(&vpcId)
	if err != nil {
		return "", err
	}
	return vpcId.result[0], err
}

// VswitchCIDRBlock returns vswitch cidr block
func (m *MetaData) VswitchCIDRBlock() (string, error) {
	var cidr ResultList
	err := m.New().Resource(VSWITCH_CIDR_BLOCK).Do(&cidr)
	if err != nil {
		return "", err
	}
	return cidr.result[0], err
}

// VswitchID returns vswitch id
func (m *MetaData) VswitchID() (string, error) {
	var vswithcid ResultList
	err := m.New().Resource(VSWITCH_ID).Do(&vswithcid)
	if err != nil {
		return "", err
	}
	return vswithcid.result[0], err
}

// EIPv4 returns eip
func (m *MetaData) EIPv4() (string, error) {
	var eip ResultList
	err := m.New().Resource(EIPV4).Do(&eip)
	if err != nil {
		return "", err
	}
	return eip.result[0], nil
}

// DNSNameServers returns dns servers
func (m *MetaData) DNSNameServers() ([]string, error) {
	var data ResultList
	err := m.New().Resource(DNS_NAMESERVERS).Do(&data)
	if err != nil {
		return []string{}, err
	}
	return data.result, nil
}

// NTPConfigServers returns ntp servers
func (m *MetaData) NTPConfigServers() ([]string, error) {
	var data ResultList
	err := m.New().Resource(NTP_CONF_SERVERS).Do(&data)
	if err != nil {
		return []string{}, err
	}
	return data.result, nil
}

// Zone returns zone id
func (m *MetaData) Zone() (string, error) {
	var zone ResultList
	err := m.New().Resource(ZONE).Do(&zone)
	if err != nil {
		return "", err
	}
	return zone.result[0], nil
}

// RoleName returns role name
func (m *MetaData) RoleName() (string, error) {
	var roleName ResultList
	err := m.New().Resource("ram/security-credentials/").Do(&roleName)
	if err != nil {
		return "", err
	}
	return roleName.result[0], nil
}

// RamRoleToken returns ram role token
func (m *MetaData) RamRoleToken(role string) (RoleAuth, error) {
	var roleauth RoleAuth
	err := m.New().Resource(RAM_SECURITY).SubResource(role).Do(&roleauth)
	if err != nil {
		return RoleAuth{}, err
	}
	return roleauth, nil
}

type requestMock func(resource string) (string, error)

// MetaDataRequest struct
type MetaDataRequest struct {
	version      string
	resourceType string
	resource     string
	subResource  string
	client       *http.Client

	sendRequest requestMock
}

// Version sets version
func (vpc *MetaDataRequest) Version(version string) IMetaDataRequest {
	vpc.version = version
	return vpc
}

// ResourceType sets resource type
func (vpc *MetaDataRequest) ResourceType(rtype string) IMetaDataRequest {
	vpc.resourceType = rtype
	return vpc
}

// Resource sets resource
func (vpc *MetaDataRequest) Resource(resource string) IMetaDataRequest {
	vpc.resource = resource
	return vpc
}

// SubResource set sub resource
func (vpc *MetaDataRequest) SubResource(sub string) IMetaDataRequest {
	vpc.subResource = sub
	return vpc
}

var retry = AttemptStrategy{
	Min:   5,
	Total: 5 * time.Second,
	Delay: 200 * time.Millisecond,
}

// Url returns url
func (vpc *MetaDataRequest) Url() (string, error) {
	if vpc.version == "" {
		vpc.version = "latest"
	}
	if vpc.resourceType == "" {
		vpc.resourceType = "meta-data"
	}
	if vpc.resource == "" {
		return "", errors.New("the resource you want to visit must not be nil!")
	}
	endpoint := os.Getenv("METADATA_ENDPOINT")
	if endpoint == "" {
		endpoint = ENDPOINT
	}
	r := fmt.Sprintf("%s/%s/%s/%s", endpoint, vpc.version, vpc.resourceType, vpc.resource)
	if vpc.subResource == "" {
		return r, nil
	}
	return fmt.Sprintf("%s/%s", r, vpc.subResource), nil
}

// Do try to do MetaDataRequest
func (vpc *MetaDataRequest) Do(api interface{}) (err error) {
	var res = ""
	for r := retry.Start(); r.Next(); {
		if vpc.sendRequest != nil {
			res, err = vpc.sendRequest(vpc.resource)
		} else {
			res, err = vpc.send()
		}
		if !shouldRetry(err) {
			break
		}
	}
	if err != nil {
		return err
	}
	return vpc.Decode(res, api)
}

// Decode returns decoded content
func (vpc *MetaDataRequest) Decode(data string, api interface{}) error {
	if data == "" {
		url, _ := vpc.Url()
		return fmt.Errorf("metadata: alivpc decode data must not be nil. url=[%s]\n", url)
	}
	switch api.(type) {
	case *ResultList:
		api.(*ResultList).result = strings.Split(data, "\n")
		return nil
	case *RoleAuth:
		return json.Unmarshal([]byte(data), api)
	default:
		return fmt.Errorf("metadata: unknow type to decode, type=%s\n", reflect.TypeOf(api))
	}
}

func (vpc *MetaDataRequest) send() (string, error) {
	url, err := vpc.Url()
	if err != nil {
		return "", err
	}
	requ, err := http.NewRequest(http.MethodGet, url, nil)

	if err != nil {
		return "", err
	}
	resp, err := vpc.client.Do(requ)
	if err != nil {
		return "", err
	}
	if resp.StatusCode != 200 {
		return "", fmt.Errorf("Aliyun Metadata API Error: Status Code: %d", resp.StatusCode)
	}
	defer resp.Body.Close()

	data, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return "", err
	}
	return string(data), nil
}

// TimeoutError interface
type TimeoutError interface {
	error
	Timeout() bool // Is the error a timeout?
}

func shouldRetry(err error) bool {
	if err == nil {
		return false
	}

	_, ok := err.(TimeoutError)
	if ok {
		return true
	}

	switch err {
	case io.ErrUnexpectedEOF, io.EOF:
		return true
	}
	switch e := err.(type) {
	case *net.DNSError:
		return true
	case *net.OpError:
		switch e.Op {
		case "read", "write":
			return true
		}
	case *url.Error:
		// url.Error can be returned either by net/url if a URL cannot be
		// parsed, or by net/http if the response is closed before the headers
		// are received or parsed correctly. In that later case, e.Op is set to
		// the HTTP method name with the first letter uppercased. We don't want
		// to retry on POST operations, since those are not idempotent, all the
		// other ones should be safe to retry.
		switch e.Op {
		case "Get", "Put", "Delete", "Head":
			return shouldRetry(e.Err)
		default:
			return false
		}
	}
	return false
}

// ResultList struct
type ResultList struct {
	result []string
}

// RoleAuth struct
type RoleAuth struct {
	AccessKeyId     string
	AccessKeySecret string
	Expiration      time.Time
	SecurityToken   string
	LastUpdated     time.Time
	Code            string
}