package main

import (
	"context"
	"fmt"
	"io/ioutil"
	"os"

	"golang.org/x/oauth2/google"
	admin "google.golang.org/api/admin/directory/v1"
	"google.golang.org/api/option"
)

type Group struct {
	groupEmail       string
	groupName        string
	numberOfMembers  int64
}

type GroupMember struct {
	groupEmail  string
	memberEmail string
}

var googleWorkspaceScopesForGroupAndMember = []string{
	admin.AdminDirectoryGroupMemberReadonlyScope,
	admin.AdminDirectoryGroupReadonlyScope,
}

// グループのメールアドレス（本来はもっと多い）
// グループのメールアドレスもDirectory APIで取得できるが今回は省略
var groups = []Group{
	{
		groupEmail:       "hoge-developer@test.com",
		groupName:        "hoge developer team",
		numberOfMembers: 5,
	},
	{
		groupEmail:       "fuga-owner@test.com",
		groupName:        "fuga owner team",
		numberOfMembers: 10,
	},
}

func GetGroupMember() ([]GroupMember, error) {
	var groupMemberList []GroupMember
	// 取得を行うためのAdmin Serviceを取得
	srv, err := getService()
	if err != nil {
		return nil, fmt.Errorf("get admin service: %w", err)
	}
	for _, g := range groups {
		if g.numberOfMembers != 0 {
			// この中でDirectory APIを叩いている
			members, err := createGroupMemberList(srv, g.groupEmail)
			if err != nil {
				return nil, fmt.Errorf("create group member list: %w", err)
			}
			groupMemberList = append(groupMemberList, members...)
		}
	}

	return groupMemberList, nil
}

func createGroupMemberList(srv *admin.Service, email string) ([]GroupMember, error) {
	// APIを叩く
	rm, err := srv.Members.List(email).Do()
	if err != nil {
		return nil, fmt.Errorf("get member list: %w", err)
	}
	var memberList []GroupMember
	// リスト作成処理
	for _, m := range rm.Members {
		memberList = append(memberList, GroupMember{groupEmail: email, memberEmail: m.Email})
	}

	return memberList, nil
}

func getService() (*admin.Service, error) {
	serviceAccountJSON, err := ioutil.ReadFile("key/service-account-key.json")
	if err != nil {
		return nil, fmt.Errorf("read service account key: %w", err)
	}
	config, err := google.JWTConfigFromJSON(serviceAccountJSON, googleWorkspaceScopesForGroupAndMember...)
	if err != nil {
		return nil, fmt.Errorf("authorize service account key: %w", err)
	}
	config.Subject = "<管理者のメールアドレス>"
	config.Scopes = googleWorkspaceScopesForGroupAndMember
	ctx := context.Background()
	srv, err := admin.NewService(ctx, option.WithHTTPClient(config.Client(ctx)))
	if err != nil {
		return nil, fmt.Errorf("get new service: %w", err)
	}
	return srv, nil
}

func main() {
	groupMembers, err := GetGroupMember()
	if err != nil {
		fmt.Println(err)
        os.Exit(1)
	}

	for _, member := range groupMembers {
		// 何か処理する
		fmt.Println(member)
	}
}

func GetGroupMember() ([]GroupMember, error) {
	var groupMemberList []GroupMember
	// 取得を行うためのAdmin Serviceを取得
	srv, err := getService()
	if err != nil {
		return nil, fmt.Errorf("get admin service: %w", err)
	}
	for _, g := range groups {
		if g.numberOfMembers != 0 {
			// Serviceとグループのメールアドレスを渡すことで、メンバー情報を取得
			// この中でAPIを叩いている
			members, err := createGroupMemberList(srv, g.groupEmail)
			if err != nil {
				return nil, fmt.Errorf("create group member list: %w", err)
			}
			groupMemberList = append(groupMemberList, members...)
            // Sleepを設定
			time.Sleep(time.Millisecond * 250)
		}
	}

	return groupMemberList, nil
}

func createGroupMemberList(srv *admin.Service, email string) ([]GroupMember, error) {
	maxRetries := 10
	var memberList []GroupMember

	for i := 0; i <= maxRetries; i++ {
		// APIを叩く
		rm, err := srv.Members.List(email).Do()
		if err != nil {
			var gerr *googleapi.Error
			if ok := errors.As(err, &gerr); ok {
                // エラーコードが500系列であれば、リトライ
				if gerr.Code >= 500 {
                    // 繰り返しの数を用いて待ち時間を生成
					waitTime := int(math.Pow(2, float64(i+1)) * float64(100))
					fmt.Println(waitTime)
                    // 待つ
					time.Sleep(time.Millisecond * time.Duration(waitTime))
				} else {
					return nil, fmt.Errorf("get member list: %w", err)
				}
			}
		} else {
			// リスト作成処理
			for _, m := range rm.Members {
				memberList = append(memberList, GroupMember{groupEmail: email, memberEmail: m.Email})
			}
			return memberList, nil
		}
	}
	return nil, fmt.Errorf("reaching max retries in createGroupMemberList")
}