email

type Chain struct {

	// OnAttempt, if non-nil, is invoked synchronously after each inner Send
	// with the index of the transport and the error it returned (nil on
	// success). Hook is intended for metrics; keep it cheap and non-blocking.
	OnAttempt func(idx int, err error)
	// contains filtered or unexported fields
}

type Message struct {
	// To is the recipient address (RFC 5322). Exactly one recipient is
	// supported; for multi-recipient sends, call Send once per recipient so
	// each delivery can be tracked and retried independently.
	To string

	// From is the sender address (RFC 5322). May be left empty when using a
	// transport that injects a default From (e.g. SMTPConfig.From).
	From string

	// Subject is the email subject line.
	Subject string

	// HTML is the HTML body. Optional if Text is set.
	HTML string

	// Text is the plain-text body. Optional if HTML is set.
	Text string
}

type SMTPConfig struct {
	// Host is the SMTP server hostname (e.g. "smtp.gmail.com").
	Host string

	// Port is the SMTP server port. Common values:
	//   25  - plain (dev / on-prem only).
	//   587 - submission with STARTTLS upgrade.
	//   465 - implicit TLS (a.k.a. SMTPS).
	Port int

	// User and Pass are credentials for PLAIN auth. If User is empty, no auth
	// is attempted.
	User string
	Pass string

	// From is the default From address used when Message.From is empty.
	From string

	// TLS enables implicit TLS on dial (use with port 465).
	TLS bool

	// StartTLS issues a STARTTLS upgrade after EHLO (use with port 587).
	StartTLS bool

	// InsecureSkipVerify disables TLS certificate verification. ONLY use this
	// in tests against self-signed servers; never enable it in production.
	InsecureSkipVerify bool

	// DialTimeout caps how long Dial may block. Defaults to 10s.
	DialTimeout time.Duration
}

type Transport interface {
	// Send delivers m. It must validate m and return a wrapped ErrInvalidMessage
	// for malformed inputs, or a wrapped ErrTransport (or other error) for
	// backend failures.
	Send(ctx context.Context, m Message) error
}