go-web-starter-kit/common/email/api.go

package common_email

import (
  "github.com/wneessen/go-mail"
  "encoding/json"
  "context"
  "log"
  "github.com/redis/go-redis/v9"
  "github.com/yuin/goldmark"
  "MY/webapp/config"
  "path/filepath"
  "text/template"
  "os"
  "strings"
)

func NewSender(ctx context.Context) (Sender){
  client := redis.NewClient(&redis.Options{
    Addr: config.Settings.Redis.HostPort,
    Password: config.Settings.Redis.Password,
    DB: config.Settings.Redis.DB,
  })

  return Sender{client, ctx}
}

func NewRouter(ctx context.Context) (Router, error) {
  var router Router
  var err error

  router.ctx = ctx

  router.redis_client = redis.NewClient(&redis.Options{
    Addr: config.Settings.Redis.HostPort,
    Password: config.Settings.Redis.Password,
    DB: config.Settings.Redis.DB,
  })

  router.smtp_client, err = mail.NewClient(config.Settings.Email.Host,
    mail.WithPort(config.Settings.Email.Port),
    mail.WithTLSPolicy(mail.NoTLS))

  return router, err
}

func (router *Router) Close() {
  router.redis_client.Close()
  router.smtp_client.Close()
}

func (sender *Sender) Close() {
  sender.redis_client.Close()
}

func (router *Router) Render(tmpl_path string, data any) (string, string, error) {
  tmpl_path = filepath.Join(config.Settings.Email.Templates, tmpl_path)

  // load the markdown file
  md_file, err := os.ReadFile(tmpl_path)
  if err != nil { return "", "", err }

  // template it
  tmpl, err := template.New(tmpl_path).Parse(string(md_file))
  if err != nil { return "", "", err }

  out := new(strings.Builder)
  err = tmpl.Execute(out, data)
  if err != nil { return "", "",  err }
  text_out := out.String()

  // convert to html
  out.Reset()
  err = goldmark.Convert([]byte(text_out), out)
  if err != nil { return "", "", err }

  html_out := out.String()

  // return the template .md as plain text and .html as html
  return string(text_out), string(html_out), nil
}

func (router *Router) DeliverEmail(msg EmailMessage) error {
  email_msg := mail.NewMsg()
  err := email_msg.From(msg.From)
  if err != nil { return err }

  err = email_msg.To(msg.To)
  if err != nil { return err }

  email_msg.Subject(msg.Subject)

  if config.Settings.Email.XMailer != "" {
    email_msg.SetGenHeader(mail.HeaderXMailer, config.Settings.Email.XMailer)
  }

  if config.Settings.Email.UserAgent != "" {
    email_msg.SetGenHeader(mail.HeaderUserAgent, config.Settings.Email.UserAgent)
  }

  text, html, err := router.Render(msg.Template, nil)
  if err != nil { return err }

  email_msg.SetBodyString(mail.TypeTextHTML, html)
  email_msg.AddAlternativeString(mail.TypeTextPlain, text)

  err = router.smtp_client.DialAndSendWithContext(router.ctx, email_msg)
  if err != nil { return err }

  return nil
}

func (router *Router) ReceiveEmail() (EmailMessage, error) {
  var msg EmailMessage

  result, err := router.redis_client.BRPop(
    router.ctx, 0,
    config.Settings.Email.RedisQueue).Result()
  if err != nil { return msg, err }

  // NOTE: 0=queue name, 1=message
  err = json.Unmarshal([]byte(result[1]), &msg)
  if err != nil { return msg, err }

  return msg, nil
}

func (router *Router) HandleEmailRequest() error {
  msg, err := router.ReceiveEmail()
  if err != nil { return err }

  err = router.DeliverEmail(msg)
  if err != nil { return err }

  return nil
}

func (sender *Sender) QueueEmail(msg EmailMessage) error {
  msg_json, err := json.Marshal(msg)
  if err != nil { return err }

  _, err = sender.redis_client.LPush(
    sender.ctx,
    config.Settings.Email.RedisQueue,
    string(msg_json)).Result()
  if err != nil { return err }

  return nil
}

func OneShotSend(msg EmailMessage) {
  ctx := context.Background()

  sender := NewSender(ctx)
  defer sender.Close()

  err := sender.QueueEmail(msg)

  if err != nil { 
    log.Print(err)
  }
}