package postcard

import (
	"context"
	"fmt"
	"log/slog"
	"strings"
	"time"

	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/compass"
	"git.golem15.com/golem15/summercms/modules/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
	_, smtp := m.driver.(*SMTPDriver)
	if err := validateRendered(rendered, smtp); err != nil {
		return err
	}
	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")
	}
	driver, opts, err := driverFromApp(app)
	if err != nil {
		return err
	}
	m := &mailer{
		catalog: NewCatalog(),
		driver:  driver,
		opts:    opts,
	}
	if err := app.Publish[Mailer](m); err != nil {
		return fmt.Errorf("postcard: %w", err)
	}
	return nil
}

func driverFromApp(app *backpack.App) (Driver, Options, error) {
	opts := Options{}
	name := "memory"
	smtp := SMTPConfig{Port: 587, Timeout: 10 * time.Second}
	if app != nil && app.Config != nil {
		c := app.Config
		if v := strings.TrimSpace(c.String("mail.driver")); v != "" {
			name = strings.ToLower(v)
		}
		opts.From = strings.TrimSpace(c.String("mail.from"))
		opts.CSS = c.String("mail.css")
		opts.BrandCSS = c.String("mail.brandCss")
		smtp = smtpFromConfig(c)
	}
	switch name {
	case "memory":
		return NewMemoryDriver(), opts, nil
	case "log":
		return NewLogDriver(loggerFromApp(app)), opts, nil
	case "smtp":
		d, err := NewSMTPDriver(smtp)
		if err != nil {
			return nil, opts, err
		}
		return d, opts, nil
	default:
		return nil, opts, fmt.Errorf("postcard: unknown mail.driver %q (use memory, log, or smtp)", name)
	}
}

func smtpFromConfig(c *compass.Config) SMTPConfig {
	cfg := SMTPConfig{
		Host:     strings.TrimSpace(c.String("mail.smtp.host")),
		Port:     c.Int("mail.smtp.port"),
		Username: c.String("mail.smtp.username"),
		Password: c.String("mail.smtp.password"),
		TLS:      strings.TrimSpace(c.String("mail.smtp.tls")),
		Timeout:  10 * time.Second,
	}
	if raw := strings.TrimSpace(c.String("mail.smtp.timeout")); raw != "" {
		if d, err := time.ParseDuration(raw); err == nil {
			cfg.Timeout = d
		} else if n := c.Int("mail.smtp.timeout"); n > 0 {
			cfg.Timeout = time.Duration(n) * time.Second
		}
	}
	return cfg
}

func loggerFromApp(app *backpack.App) *slog.Logger {
	if app != nil {
		if log, ok := app.Lookup[*slog.Logger](); ok && log != nil {
			return log
		}
	}
	return slog.Default()
}

// 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())
}