PrivateCaptcha/pkg/common/mailer.go

package common

import (
	"bytes"
	"context"
	"crypto/sha1"
	"encoding/hex"
	htmltpl "html/template"
	"log/slog"
	"sync"
	texttpl "text/template"
	"time"
)

type Mailer interface {
	SendTwoFactor(ctx context.Context, email string, code int, ua string, location string) error
	SendWelcome(ctx context.Context, email, name string) error
	SendOrgInvite(ctx context.Context, email, name string, orgName, orgOwnerEmail, orgOwnerName, orgURL string, requiresRegister bool) error
}

type NotificationCondition int

const (
	EmptyNotificationCondition NotificationCondition = iota
	NotificationWithSubscription
	NotificationWithoutSubscription
)

type ScheduledNotification struct {
	ReferenceID  string
	UserID       int32
	Subject      string
	Data         interface{}
	DateTime     time.Time
	TemplateHash string
	Persistent   bool
	Condition    NotificationCondition
}

func NewEmailTemplate(name, contentHTML, contentText string) *EmailTemplate {
	return &EmailTemplate{
		name:        name,
		contentHTML: contentHTML,
		contentText: contentText,
	}
}

type EmailTemplate struct {
	name        string
	hash        string
	mux         sync.Mutex
	contentHTML string
	contentText string

	// Parsed templates - lazy initialized
	parsedHTML *htmltpl.Template
	parsedText *texttpl.Template
	parseOnce  sync.Once
}

func (et *EmailTemplate) Name() string        { return et.name }
func (et *EmailTemplate) ContentHTML() string { return et.contentHTML }
func (et *EmailTemplate) ContentText() string { return et.contentText }

func (et *EmailTemplate) Hash() string {
	et.mux.Lock()
	defer et.mux.Unlock()

	if len(et.hash) == 0 {
		h := sha1.New()
		if len(et.contentHTML) > 0 {
			h.Write([]byte(et.contentHTML))
		} else if len(et.contentText) > 0 {
			h.Write([]byte(et.contentText))
		} else {
			h.Write([]byte(et.name))
		}
		et.hash = hex.EncodeToString(h.Sum(nil))
	}

	return et.hash
}

func (et *EmailTemplate) ensureParsed(ctx context.Context) {
	et.parseOnce.Do(func() {
		if len(et.contentHTML) > 0 {
			if tpl, err := htmltpl.New("HtmlBody").Parse(et.contentHTML); err != nil {
				slog.ErrorContext(ctx, "Failed to parse HTML template", ErrAttr(err))
			} else {
				et.parsedHTML = tpl
			}
		}
		if len(et.contentText) > 0 {
			if tpl, err := texttpl.New("TextBody").Parse(et.contentText); err != nil {
				slog.ErrorContext(ctx, "Failed to parse text template", ErrAttr(err))
			} else {
				et.parsedText = tpl
			}
		}
	})
}

func (et *EmailTemplate) RenderHTML(ctx context.Context, data interface{}) (string, error) {
	et.ensureParsed(ctx)

	var buf bytes.Buffer
	if et.parsedHTML != nil {
		if err := et.parsedHTML.Execute(&buf, data); err != nil {
			slog.ErrorContext(ctx, "Failed to execute HTML template", ErrAttr(err))
			return "", err
		}
	}

	return buf.String(), nil
}

func (et *EmailTemplate) RenderText(ctx context.Context, data interface{}) (string, error) {
	et.ensureParsed(ctx)

	var buf bytes.Buffer
	if et.parsedText != nil {
		if err := et.parsedText.Execute(&buf, data); err != nil {
			slog.ErrorContext(ctx, "Failed to execute Text template", ErrAttr(err))
			return "", err
		}
	}

	return buf.String(), nil
}