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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 312.
// Package storage is part of a hypothetical cloud storage server.
//!+main
package storage
import (
"fmt"
"log"
"net/smtp"
)
// NOTE: this differs slightly from the printed version.
var usage = make(map[string]int64)
func bytesInUse(username string) int64 { return usage[username] }
// E-mail sender configuration.
// NOTE: never put passwords in source code!
const sender = "notifications@example.com"
const password = "correcthorsebatterystaple"
const hostname = "smtp.example.com"
const template = `Warning: you are using %d bytes of storage,
%d%% of your quota.`
//!+factored
var notifyUser = func(username, msg string) {
auth := smtp.PlainAuth("", sender, password, hostname)
err := smtp.SendMail(hostname+":587", auth, sender,
[]string{username}, []byte(msg))
if err != nil {
log.Printf("smtp.SendEmail(%s) failed: %s", username, err)
}
}
func CheckQuota(username string) {
used := bytesInUse(username)
const quota = 1000000000 // 1GB
percent := 100 * used / quota
if percent < 90 {
return // OK
}
msg := fmt.Sprintf(template, used, percent)
notifyUser(username, msg)
}
//!-factored
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