feat(smtp): initial implementation — SMTP client with no-op fallback and template rendering (v1.0.0)
Introduces code.nochebuena.dev/einherjar/smtp — the email delivery starter for the
Einherjar framework. New module with no micro-lib counterpart. Pure stdlib — no
external dependencies beyond contracts and core.
Interfaces (CT-6: one TypeSpec per file):
- Sender — Send(ctx context.Context, msg Message) error
- Component — lifecycle.Component + observability.Checkable + Sender
- Message — To, CC, BCC, ReplyTo, Subject, Body, ContentType, Attachments
- Attachment — Name, ContentType string; Data io.Reader (consumed once on Send)
- Template — wraps html/template for email rendering
Implementation:
- New(logger, cfg) Component — returns noopClient when cfg.Host is empty;
SMTP absence must never block a transaction (e.g. account creation)
- noopClient: all lifecycle and Send methods return nil; Send logs Warn;
Priority LevelDegraded; Name "smtp"
- smtpClient: OnInit/OnStart/OnStop are no-ops (stateless stdlib client);
HealthCheck: TCP dial to Host:Port; Priority LevelDegraded
- Send: buildRawMessage → netsmtp.SendMail; BCC passed in SMTP envelope
(RCPT TO) but never written to message headers (RFC 5321/5322 compliance)
- buildRawMessage: plain message without attachments; multipart/mixed with
quoted-printable body + base64 attachments when Attachments non-empty;
multipart.NewWriter created first to obtain boundary before headers are written
- ParseFS(fsys, patterns...) (*Template, error) — wraps html/template.ParseFS
- Template.Render(name, data) (string, error) — executes named template
- net/smtp aliased as netsmtp to avoid package-name collision in package smtp
Config (EINHERJAR_SMTP_* env vars):
Host, Port(587), User, Password, From
- Component interface embeds observability.Identifiable; identifiable.go implements
ModulePath and ModuleVersion on both smtpClient and noopClient via
runtime/debug.ReadBuildInfo() — prints in launcher banner
2026-05-29 16:05:03 +00:00
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package smtp
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import "context"
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// Sender is the interface consumed by application services. Implementations
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// include the real SMTP client and a no-op client used when Host is empty.
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// Satisfied by [Component] — pass the result of [New] wherever a Sender is expected.
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type Sender interface {
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// Send delivers msg via SMTP. Returns nil on success or a typed [xerrors] error
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// on failure. In no-op mode, Send always returns nil.
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Send(ctx context.Context, msg Message) error
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}
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