package main

import (
    "flag"
    "fmt"
    "io/ioutil"
    "log"
    "os"

    "github.com/emersion/go-imap"
    "github.com/emersion/go-imap/client"
)

var (
    server, email, password string
    workernum               int
    imapClient              *client.Client
    mailDirs                []string
    mailSumNums             uint32
)

func main() {
    //获取命令行参数
    flag.StringVar(&server, "server", "", "imap服务地址(包含端口)")
    flag.StringVar(&email, "email", "", "邮箱名")
    flag.StringVar(&password, "password", "", "密码")
    flag.IntVar(&workernum, "workernum", 10, "并发数:")
    flag.Parse()
    if flag.NFlag() < 3 {
        flag.PrintDefaults()
        os.Exit(1)
    }
    if server == "" || email == "" || password == "" || workernum == 0 {
        log.Fatal("服务器地址,用户名,密码,参数错误")
    }
    //连接imap服务
    imapClient, err := client.Dial(server)
    if err != nil {
        log.Fatal(err)
    }
    //登陆
    if err := imapClient.Login(email, password); err != nil {
        log.Fatal(err)
    }
    //创建邮件夹目录
    os.Mkdir(email, os.ModePerm)
    mailboxes := make(chan *imap.MailboxInfo, 20)
    go func() {
        imapClient.List("", "*", mailboxes)
    }()
    //列取邮件夹
    for m := range mailboxes {
        mailDirs = append(mailDirs, m.Name)
    }

    for _, mailDir := range mailDirs {
        //选中每个邮件夹
        mbox, err := imapClient.Select(mailDir, false)
        if err != nil {
            log.Fatal(err)
        }
        mailDirNums := mbox.Messages
        log.Printf("%s : %d", mailDir, mailDirNums)
        fileDir := fmt.Sprintf("%s/%s_%d", email, mailDir, mailDirNums)
        //创建邮件夹目录
        os.Mkdir(fileDir, os.ModePerm)
        mailSumNums += mailDirNums
    }
    log.Printf("总邮件数 : %d", mailSumNums)
    for _, mailDir := range mailDirs {
        //选中每个邮件夹
        mbox, err := imapClient.Select(mailDir, false)
        if err != nil {
            log.Fatal(err)
        }
        //循环该邮件夹中的邮件
        seqset := new(imap.SeqSet)
        seqset.AddRange(1, mbox.Messages)
        section := &imap.BodySectionName{}
        items := []imap.FetchItem{section.FetchItem()}

        messages := make(chan *imap.Message, mbox.Messages)
        go func() {
            imapClient.Fetch(seqset, items, messages)
        }()

        for msg := range messages {
            mailFile := fmt.Sprintf("%s/%s_%d/%d.eml", email, mailDir, mbox.Messages, msg.SeqNum)
            r := msg.GetBody(section)
            if r == nil {
                log.Printf("%s-%dServer didn't returned message body", mailDir, msg.SeqNum)
            }
            if r != nil {
                body, err := ioutil.ReadAll(r)
                if err != nil {
                    log.Printf("%s:%d ioutil.ReadAll error", mailDir, msg.SeqNum)
                }

                file6, err := os.OpenFile(mailFile, os.O_RDWR|os.O_CREATE, 0766)
                if err != nil {
                    log.Printf("%s:%d os.OpenFile error %s", mailDir, msg.SeqNum, mailFile)
                }
                file6.Write(body)
                file6.Close()
                log.Printf("%s :第 %d ", mailDir, msg.SeqNum)
            }
        }
    }
}