package accounts

import (
	"crypto/tls"
	"encoding/json"
	"fmt"
	"net"
	"net/smtp"
	"strconv"

	"gomail/internal/crypto"
	"gomail/internal/db"
)

// sendViaSMTP delivers an outgoing message through a linked account's own
// SMTP settings — stdlib net/smtp, same choice as internal/queue's
// MXDeliverer, so outbound for both "GoMail relays for me" and "I'm using my
// own IMAP+SMTP provider" stay on the same dependency-free foundation.
func sendViaSMTP(account *db.LinkedAccount, mk *crypto.MasterKey, msg *OutgoingMessage) error {
	plain, err := crypto.Decrypt(mk, account.ID, "linked-account-cred", account.CredentialEnc)
	if err != nil {
		return fmt.Errorf("decrypting stored credential: %w", err)
	}
	var cred IMAPCredential // same password shape reused for the paired SMTP auth
	if err := json.Unmarshal(plain, &cred); err != nil {
		return fmt.Errorf("parsing stored credential: %w", err)
	}

	addr := net.JoinHostPort(account.SMTPHost, strconv.Itoa(account.SMTPPort))
	conn, err := net.DialTimeout("tcp", addr, dialTimeout)
	if err != nil {
		return fmt.Errorf("dial %s: %w", addr, err)
	}
	defer conn.Close()

	if account.SMTPTLS == "implicit" {
		// See provider_imap.go's connect() comment — same gap, same reason.
		conn = tls.Client(conn, &tls.Config{ServerName: account.SMTPHost, InsecureSkipVerify: true})
	}

	client, err := smtp.NewClient(conn, account.SMTPHost)
	if err != nil {
		return fmt.Errorf("SMTP handshake: %w", err)
	}
	defer client.Close()

	if account.SMTPTLS == "starttls" {
		if ok, _ := client.Extension("STARTTLS"); ok {
			if err := client.StartTLS(&tls.Config{ServerName: account.SMTPHost}); err != nil {
				return fmt.Errorf("STARTTLS: %w", err)
			}
		}
	}

	auth := smtp.PlainAuth("", account.EmailAddress, cred.Password, account.SMTPHost)
	if err := client.Auth(auth); err != nil {
		return fmt.Errorf("SMTP auth: %w", err)
	}

	if err := client.Mail(account.EmailAddress); err != nil {
		return err
	}
	for _, to := range msg.To {
		if err := client.Rcpt(to); err != nil {
			return err
		}
	}

	w, err := client.Data()
	if err != nil {
		return err
	}
	raw := buildRFC5322(account.EmailAddress, msg)
	if _, err := w.Write(raw); err != nil {
		return err
	}
	if err := w.Close(); err != nil {
		return err
	}
	return client.Quit()
}