package customerauth

import (
	"context"
	"fmt"
	"log"
	"net/mail"
	"strings"
	"time"

	"github.com/mailersend/mailersend-go"
)

// MailerSendNotifier delivers transactional auth messages (email verification
// and password reset) through the MailerSend API. It implements the Notifier
// interface and is a drop-in replacement for LogNotifier in production.
type MailerSendNotifier struct {
	client *mailersend.Mailersend
	from   mail.Address
}

// NewMailerSendNotifier creates a new MailerSend-backed notifier. The apiKey
// is the MailerSend API token (MAILERSEND_API_KEY env var). The from address
// must include at least an email; the name portion is optional.
func NewMailerSendNotifier(apiKey string, from mail.Address) (*MailerSendNotifier, error) {
	if strings.TrimSpace(apiKey) == "" {
		return nil, fmt.Errorf("mailersend notifier: missing API key")
	}
	if strings.TrimSpace(from.Address) == "" {
		return nil, fmt.Errorf("mailersend notifier: missing from address")
	}
	return &MailerSendNotifier{
		client: mailersend.NewMailersend(apiKey),
		from:   from,
	}, nil
}

// SendEmailVerification sends the verification link to the customer's email
// address. Errors are logged but not returned (best-effort delivery matches the
// signature of the Notifier interface).
func (n *MailerSendNotifier) SendEmailVerification(email, link string) {
	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
	defer cancel()
	if err := n.send(ctx, email,
		"Verify your email address",
		fmt.Sprintf("Click the link to verify your email address:\n\n%s", link),
		fmt.Sprintf(`<p>Click <a href="%s">here</a> to verify your email address.</p>`, link),
	); err != nil {
		log.Printf("customerauth: send verification to %s: %v", email, err)
	}
}

// SendPasswordReset sends the password-reset link to the customer's email.
// Errors are logged but not returned.
func (n *MailerSendNotifier) SendPasswordReset(email, link string) {
	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
	defer cancel()
	if err := n.send(ctx, email,
		"Reset your password",
		fmt.Sprintf("Click the link to reset your password:\n\n%s\n\nIf you didn't request this, ignore this email.", link),
		fmt.Sprintf(`<p>Click <a href="%s">here</a> to reset your password.</p><p>If you didn't request this, ignore this email.</p>`, link),
	); err != nil {
		log.Printf("customerauth: send password reset to %s: %v", email, err)
	}
}

func (n *MailerSendNotifier) send(ctx context.Context, to, subject, textBody, htmlBody string) error {
	message := n.client.Email.NewMessage()
	message.SetFrom(mailersend.From{
		Name:  n.from.Name,
		Email: n.from.Address,
	})
	message.SetRecipients([]mailersend.Recipient{
		{Email: to},
	})
	message.SetSubject(subject)
	message.SetText(textBody)
	if htmlBody != "" {
		message.SetHTML(htmlBody)
	}
	_, err := n.client.Email.Send(ctx, message)
	if err != nil {
		return fmt.Errorf("mailersend: %w", err)
	}
	return nil
}