package postcard

import (
	"context"
	"fmt"
	"strings"

	"git.golem15.com/golem15/summercms/backpack"
	"git.golem15.com/golem15/summercms/pact"
)

// 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
}

// Activate publishes an app-scoped Mailer before plugin Boot. Catalog files
// are validated later at each plugin's Boot transition.
func Activate[P interface{ ID() string }](app *backpack.App, _ []P) error {
	if app == nil {
		return fmt.Errorf("postcard: app is nil")
	}
	opts := Options{}
	if app.Config != nil {
		opts.From = strings.TrimSpace(app.Config.String("mail.from"))
		opts.CSS = app.Config.String("mail.css")
		opts.BrandCSS = app.Config.String("mail.brandCss")
	}
	m := &mailer{
		catalog: NewCatalog(),
		driver:  NewMemoryDriver(),
		opts:    opts,
	}
	if err := app.Publish[Mailer](m); err != nil {
		return fmt.Errorf("postcard: %w", err)
	}
	return nil
}

// BootPlugin registers a plugin's declared mail templates and layouts.
// Missing files and unknown layout aliases fail with the dotted name.
func BootPlugin[P interface{ ID() string }](app *backpack.App, p P) error {
	hm, ok := any(p).(pact.HasMailTemplates)
	if !ok {
		return nil
	}
	got, ok := app.Lookup[Mailer]()
	if !ok {
		return fmt.Errorf("postcard: mailer not published")
	}
	m, ok := got.(*mailer)
	if !ok || m == nil || m.catalog == nil {
		return fmt.Errorf("postcard: mailer not published")
	}
	return m.catalog.Register(p.ID(), hm.MailTemplatesFS(), hm.MailTemplates(), hm.MailLayouts())
}