package postcard

import (
	"context"
	"fmt"
)

// Message is the Send contract for plugin callers.
type Message struct {
	Template string
	To       []string
	Cc       []string
	Bcc      []string
	ReplyTo  string
	Vars     map[string]any
	Subject  string
}

// Mailer sends a registered template through the configured driver.
type Mailer interface {
	Send(ctx context.Context, msg Message) error
}

// Options configure an app-scoped mailer.
type Options struct {
	From     string
	CSS      string
	BrandCSS string
}

type mailer struct {
	catalog *Catalog
	driver  Driver
	opts    Options
}

// NewMailer returns a mailer that renders from cat and delivers through driver.
func NewMailer(cat *Catalog, driver Driver, opts Options) Mailer {
	if cat == nil {
		cat = NewCatalog()
	}
	return &mailer{catalog: cat, driver: driver, opts: opts}
}

// Send renders msg.Template and delivers it. It performs no locale selection;
// the caller must pass the full dotted name, including any -en suffix.
func (m *mailer) Send(ctx context.Context, msg Message) error {
	if m == nil {
		return fmt.Errorf("postcard: mailer is nil")
	}
	if m.driver == nil {
		return fmt.Errorf("postcard: driver is nil")
	}
	if msg.Template == "" {
		return fmt.Errorf("postcard: template is empty")
	}
	if len(msg.To) == 0 && len(msg.Cc) == 0 && len(msg.Bcc) == 0 {
		return fmt.Errorf("postcard: no recipients")
	}
	rendered, err := m.catalog.render(msg, renderOptions{
		css:      m.opts.CSS,
		brandCSS: m.opts.BrandCSS,
	})
	if err != nil {
		return err
	}
	rendered.From = m.opts.From
	if err := m.driver.Send(ctx, rendered); err != nil {
		return fmt.Errorf("postcard: %w", err)
	}
	return nil
}