allow custom mail templates (#533)

config.yml.sample

@@ -13,6 +13,13 @@ web:
   external_url: http://localhost:8888
   request_logging: true
 
+mail:
+  # Path where custom email templates (.gotpl and .gohtml) are stored.
+  # If the directory is empty on startup, the default embedded templates
+  # will be written there so you can modify them.
+  # Leave empty to use embedded templates only.
+  templates_path: ""
+
 webhook:
   url: ""
   authentication: ""

docs/documentation/configuration/overview.md

@@ -74,6 +74,7 @@ mail:
   from: Wireguard Portal <noreply@wireguard.local>
   link_only: false
   allow_peer_email: false
+  templates_path: ""
 
 auth:
   oidc: []
@@ -485,6 +486,11 @@ To send emails to all peers that have a valid email-address as user-identifier,
   If false, and the peer has no valid user record linked, emails will not be sent.
   If a peer has linked a valid user, the email address is always taken from the user record.
 
+### `templates_path`
+- **Default:** *(empty)*
+- **Environment Variable:** `WG_PORTAL_MAIL_TEMPLATES_PATH`
+- **Description:** Path to the email template files that override embedded templates. Check [usage documentation](../usage/mail-templates.md) for an example.`
+
 ---
 
 ## Auth

docs/documentation/usage/mail-templates.md

@@ -0,0 +1,49 @@
+WireGuard Portal sends emails when you share a configuration with a user. 
+By default, the application uses embedded templates. You can fully customize these emails by pointing the Portal 
+to a folder containing your own templates. If the folder is empty on startup, the default embedded templates 
+are written there to get you started.
+
+## Configuration
+
+To enable custom templates, set the `mail.templates_path` option in the application configuration file 
+or the `WG_PORTAL_MAIL_TEMPLATES_PATH` environment variable to a valid folder path.
+
+For example:
+
+```yaml
+mail:
+  # ... other mail options ...
+  # Path where custom email templates (.gotpl and .gohtml) are stored.
+  # If the directory is empty on startup, the default embedded templates
+  # will be written there so you can modify them.
+  # Leave empty to use embedded templates only.
+  templates_path: "/opt/wg-portal/mail-templates"
+```
+
+## Template files and names
+
+The system expects the following template names. Place files with these names in your `templates_path` to override the defaults.
+You do not need to override all templates, only the ones you want to customize should be present.
+
+- Text templates (`.gotpl`):
+  - `mail_with_link.gotpl`
+  - `mail_with_attachment.gotpl`
+- HTML templates (`.gohtml`):
+  - `mail_with_link.gohtml`
+  - `mail_with_attachment.gohtml`
+
+Both [text](https://pkg.go.dev/text/template) and [HTML templates](https://pkg.go.dev/html/template) are standard Go 
+templates and receive the following data fields, depending on the email type:
+
+- Common fields:
+  - `PortalUrl` (string) - external URL of the Portal
+  - `PortalName` (string) - site title/company name
+  - `User` (*domain.User) - the recipient user (may be partially populated when sending to a peer email)
+- Link email (`mail_with_link.*`):
+  - `Link` (string) - the download link
+- Attachment email (`mail_with_attachment.*`):
+  - `ConfigFileName` (string) - filename of the attached WireGuard config
+  - `QrcodePngName` (string) - CID content-id of the embedded QR code image
+
+Tip: You can inspect the embedded templates in the repository under [`internal/app/mail/tpl_files/`](https://github.com/h44z/wg-portal/tree/master/internal/app/mail/tpl_files) for reference. 
+When the directory at `templates_path` is empty, these files are copied to your folder so you can edit them in place.

internal/app/mail/manager.go

@@ -72,7 +72,7 @@ func NewMailManager(
 	users UserDatabaseRepo,
 	wg WireguardDatabaseRepo,
 ) (*Manager, error) {
-	tplHandler, err := newTemplateHandler(cfg.Web.ExternalUrl, cfg.Web.SiteTitle)
+	tplHandler, err := newTemplateHandler(cfg.Web.ExternalUrl, cfg.Web.SiteTitle, cfg.Mail.TemplatesPath)
 	if err != nil {
 		return nil, fmt.Errorf("failed to initialize template handler: %w", err)
 	}

internal/app/mail/template.go

@@ -6,6 +6,10 @@ import (
 	"fmt"
 	htmlTemplate "html/template"
 	"io"
+	"io/fs"
+	"log/slog"
+	"os"
+	"path/filepath"
 	"text/template"
 
 	"github.com/h44z/wg-portal/internal/domain"
@@ -22,15 +26,50 @@ type TemplateHandler struct {
 	textTemplates *template.Template
 }
 
-func newTemplateHandler(portalUrl, portalName string) (*TemplateHandler, error) {
+func newTemplateHandler(portalUrl, portalName string, basePath string) (*TemplateHandler, error) {
+	// Always parse embedded defaults first
 	htmlTemplateCache, err := htmlTemplate.New("Html").ParseFS(TemplateFiles, "tpl_files/*.gohtml")
 	if err != nil {
-		return nil, fmt.Errorf("failed to parse html template files: %w", err)
+		return nil, fmt.Errorf("failed to parse embedded html template files: %w", err)
 	}
 
 	txtTemplateCache, err := template.New("Txt").ParseFS(TemplateFiles, "tpl_files/*.gotpl")
 	if err != nil {
-		return nil, fmt.Errorf("failed to parse text template files: %w", err)
+		return nil, fmt.Errorf("failed to parse embedded text template files: %w", err)
+	}
+
+	// If a basePath is provided, ensure existence, populate if empty, then parse to override
+	if basePath != "" {
+		if err := os.MkdirAll(basePath, 0755); err != nil {
+			return nil, fmt.Errorf("failed to create templates base directory %s: %w", basePath, err)
+		}
+
+		hasTemplates, err := dirHasTemplates(basePath)
+		if err != nil {
+			return nil, fmt.Errorf("failed to inspect templates directory: %w", err)
+		}
+
+		// If no templates present, copy embedded defaults to directory
+		if !hasTemplates {
+			if err := copyEmbeddedTemplates(basePath); err != nil {
+				return nil, fmt.Errorf("failed to populate templates directory: %w", err)
+			}
+		}
+
+		// Parse files from basePath to override embedded ones.
+		// Only parse when matches exist to allow partial overrides without errors.
+		if matches, _ := filepath.Glob(filepath.Join(basePath, "*.gohtml")); len(matches) > 0 {
+			slog.Debug("parsing html email templates from base path", "base-path", basePath, "files", matches)
+			if htmlTemplateCache, err = htmlTemplateCache.ParseFiles(matches...); err != nil {
+				return nil, fmt.Errorf("failed to parse html templates from base path: %w", err)
+			}
+		}
+		if matches, _ := filepath.Glob(filepath.Join(basePath, "*.gotpl")); len(matches) > 0 {
+			slog.Debug("parsing text email templates from base path", "base-path", basePath, "files", matches)
+			if txtTemplateCache, err = txtTemplateCache.ParseFiles(matches...); err != nil {
+				return nil, fmt.Errorf("failed to parse text templates from base path: %w", err)
+			}
+		}
 	}
 
 	handler := &TemplateHandler{
@@ -43,24 +82,71 @@ func newTemplateHandler(portalUrl, portalName string) (*TemplateHandler, error)
 	return handler, nil
 }
 
+// dirHasTemplates checks whether directory contains any .gohtml or .gotpl files.
+func dirHasTemplates(basePath string) (bool, error) {
+	entries, err := os.ReadDir(basePath)
+	if err != nil {
+		return false, err
+	}
+	for _, e := range entries {
+		if e.IsDir() {
+			continue
+		}
+		ext := filepath.Ext(e.Name())
+		if ext == ".gohtml" || ext == ".gotpl" {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+// copyEmbeddedTemplates writes embedded templates into basePath.
+func copyEmbeddedTemplates(basePath string) error {
+	list, err := fs.ReadDir(TemplateFiles, "tpl_files")
+	if err != nil {
+		return err
+	}
+	for _, entry := range list {
+		if entry.IsDir() {
+			continue
+		}
+		name := entry.Name()
+		// Only copy known template extensions
+		if ext := filepath.Ext(name); ext != ".gohtml" && ext != ".gotpl" {
+			continue
+		}
+		data, err := TemplateFiles.ReadFile(filepath.Join("tpl_files", name))
+		if err != nil {
+			return err
+		}
+		out := filepath.Join(basePath, name)
+		if err := os.WriteFile(out, data, 0644); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 // GetConfigMail returns the text and html template for the mail with a link.
 func (c TemplateHandler) GetConfigMail(user *domain.User, link string) (io.Reader, io.Reader, error) {
 	var tplBuff bytes.Buffer
 	var htmlTplBuff bytes.Buffer
 
 	err := c.textTemplates.ExecuteTemplate(&tplBuff, "mail_with_link.gotpl", map[string]any{
-		"User":      user,
-		"Link":      link,
-		"PortalUrl": c.portalUrl,
+		"User":       user,
+		"Link":       link,
+		"PortalUrl":  c.portalUrl,
+		"PortalName": c.portalName,
 	})
 	if err != nil {
 		return nil, nil, fmt.Errorf("failed to execute template mail_with_link.gotpl: %w", err)
 	}
 
 	err = c.htmlTemplates.ExecuteTemplate(&htmlTplBuff, "mail_with_link.gohtml", map[string]any{
-		"User":      user,
-		"Link":      link,
-		"PortalUrl": c.portalUrl,
+		"User":       user,
+		"Link":       link,
+		"PortalUrl":  c.portalUrl,
+		"PortalName": c.portalName,
 	})
 	if err != nil {
 		return nil, nil, fmt.Errorf("failed to execute template mail_with_link.gohtml: %w", err)

internal/config/config.go

@@ -195,6 +195,7 @@ func defaultConfig() *Config {
 		From:           getEnvStr("WG_PORTAL_MAIL_FROM", "Wireguard Portal <noreply@wireguard.local>"),
 		LinkOnly:       getEnvBool("WG_PORTAL_MAIL_LINK_ONLY", false),
 		AllowPeerEmail: getEnvBool("WG_PORTAL_MAIL_ALLOW_PEER_EMAIL", false),
+		TemplatesPath:  getEnvStr("WG_PORTAL_MAIL_TEMPLATES_PATH", ""),
 	}
 
 	cfg.Webhook.Url = getEnvStr("WG_PORTAL_WEBHOOK_URL", "") // no webhook by default

internal/config/mail.go

@@ -43,4 +43,8 @@ type MailConfig struct {
 	LinkOnly bool `yaml:"link_only"`
 	// AllowPeerEmail specifies whether emails should be sent to peers which have no valid user account linked, but an email address is set as "user".
 	AllowPeerEmail bool `yaml:"allow_peer_email"`
+	// TemplatesPath is an optional base path on the filesystem that contains email templates (.gotpl and .gohtml).
+	// If the directory exists but is empty, the embedded default templates will be written there on startup.
+	// If templates are present in the directory, they override the embedded defaults.
+	TemplatesPath string `yaml:"templates_path"`
 }

mkdocs.yml

@@ -81,6 +81,7 @@ nav:
           - Reverse Proxy (HTTPS): documentation/getting-started/reverse-proxy.md
       - Configuration:
           - Overview: documentation/configuration/overview.md
+          - Mail templates: documentation/configuration/mail-templates.md
           - Examples: documentation/configuration/examples.md
       - Usage:
           - General: documentation/usage/general.md
@@ -88,6 +89,7 @@ nav:
           - LDAP: documentation/usage/ldap.md
           - Security: documentation/usage/security.md
           - Webhooks: documentation/usage/webhooks.md
+          - Mail Templates: documentation/usage/mail-templates.md
           - REST API: documentation/rest-api/api-doc.md
       - Upgrade: documentation/upgrade/v1.md
       - Monitoring: documentation/monitoring/prometheus.md