make Mailer an interface

email/mailer.go

@@ -0,0 +1,106 @@
+// Package email provides email sending functionality.
+package email
+
+import (
+	"bytes"
+	"fmt"
+	"html/template"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/jaytaylor/html2text"
+	"github.com/vanng822/go-premailer/premailer"
+)
+
+var templates *template.Template
+
+type Mailer interface {
+	Send(Message) error
+}
+
+// Message struct holds all parts of a specific email Message.
+type Message struct {
+	From     Email
+	To       Email
+	Subject  string
+	Template string
+	Content  any
+	html     string
+	text     string
+}
+
+// parse parses the corrsponding template and content
+func (m *Message) parse() error {
+	buf := new(bytes.Buffer)
+	if err := templates.ExecuteTemplate(buf, m.Template, m.Content); err != nil {
+		return err
+	}
+	prem, err := premailer.NewPremailerFromString(buf.String(), premailer.NewOptions())
+	if err != nil {
+		return err
+	}
+
+	html, err := prem.Transform()
+	if err != nil {
+		return err
+	}
+	m.html = html
+
+	text, err := html2text.FromString(html, html2text.Options{PrettyTables: true})
+	if err != nil {
+		return err
+	}
+	m.text = text
+	return nil
+}
+
+// Email struct holds email address and recipient name.
+type Email struct {
+	Name    string
+	Address string
+}
+
+// NewEmail returns an email address.
+func NewEmail(name string, address string) Email {
+	return Email{
+		Name:    name,
+		Address: address,
+	}
+}
+
+func parseTemplates() error {
+	templates = template.New("").Funcs(fMap)
+	return filepath.Walk("./templates", func(path string, info os.FileInfo, err error) error {
+		if strings.Contains(path, ".html") {
+			_, err = templates.ParseFiles(path)
+			return err
+		}
+		return err
+	})
+}
+
+var fMap = template.FuncMap{
+	"formatAsDate":     formatAsDate,
+	"formatAsDuration": formatAsDuration,
+}
+
+func formatAsDate(t time.Time) string {
+	year, month, day := t.Date()
+	return fmt.Sprintf("%d.%d.%d", day, month, year)
+}
+
+func formatAsDuration(t time.Time) string {
+	dur := time.Until(t)
+	hours := int(dur.Hours())
+	mins := int(dur.Minutes())
+
+	v := ""
+	if hours != 0 {
+		v += strconv.Itoa(hours) + " hours and "
+	}
+	v += strconv.Itoa(mins) + " minutes"
+	return v
+}