package main

import (
    "fmt"
    "flag"
    "io/ioutil"
    "log"
    "math"
    "net/http"
    "net/smtp"
    "os"
    "strconv"
    "strings"
    "time"

    "golang.org/x/net/html"
)

var ver = "0.1"

func main() {

    version := flag.Bool( "v", false, "print version" )
    file := flag.String( "f", "usd.dat", "print version" )
    flag.Parse()

    if ( *version ) {
        fmt.Fprintf( os.Stderr, "getexr - Get Exchange Rate  [ version = %s ]\n",ver )
        os.Exit( 0 )
    }

    // Get USD Rate
    url := "http://finance.yahoo.co.jp/"
    resp, err := http.Get( url )
    if err != nil {
        log.Fatal( err )
    }

    z := html.NewTokenizer( resp.Body )
    usd, err := ParseHtml( z )
    if err != nil {
        log.Fatal( err )
    }
    defer resp.Body.Close()

    // Compare Past Rate
    content, err := ioutil.ReadFile( *file )
    if err != nil {
        log.Fatal( err )
    }

    buf1 := strings.Split( string( content ), "\n" )
    buf2 := strings.Split( buf1[ len( buf1 ) - 2 ], "," )
    usd0, _ := strconv.ParseFloat( buf2[1], 32 )

    alart := false
    if ( math.Abs( usd0 - usd ) > 1.0 ) {
        alart = true
    }

    if ( alart ) {
        t := time.Now()
        now := t.Format( "2006-01-02 15:04:05" )

        // Save Rate
        buf := fmt.Sprintf( "%s,%.2f\n", now, usd )
        content = append( content,  buf... )

        err = ioutil.WriteFile( *file, content, 0777 )
        if err != nil {
            log.Fatal( err )
        }

        // Post E-mail
        err = SendMail( now, usd, "muty@willcom.com" )
        if err != nil {
            log.Fatal( err )
        }
        err = SendMail( now, usd, "pyon4pyon@yahoo.co.jp" )
        if err != nil {
            log.Fatal( err )
        }
    }
}

func ParseHtml( z *html.Tokenizer ) ( float64, error ) {
    for {
        tt := z.Next()
        switch tt {
        case html.ErrorToken:
            return 0.0, nil

        case html.StartTagToken:
            tag, _ := z.TagName()
            key, val, _ := z.TagAttr()
            if string( tag ) == "strong" && string( key ) == "class" && string( val ) == "bkLine" {
                z.Next()
                //fmt.Printf( "%s %s %s\n", key, val, z.Token() )
                return strconv.ParseFloat( z.Token().String(), 32 )
            }
        }
    }
}

func SendMail( now string, usd float64, addr string ) error {
    hostname := "sdm.sakura.ne.jp"
    auth := smtp.PlainAuth( "", "bad_user@sdm.sakura.ne.jp", "hogehoge3", hostname )
    to := []string{ addr }
    msg := []byte( "To: " + addr + "\r\n" +
                "Subject: Exchange-Mail\r\n" +
                "\r\n" +
                now + fmt.Sprintf( "\r\nrate changed\r\n[ USD/JPY : %.2f ].", usd ) + "\r\n" ) // mail body
    err := smtp.SendMail( hostname + ":587", auth, "bad_user@sdm.sakura.ne.jp", to, msg )
    if err != nil {
        return err
    }
    return nil
}