// internal/notify/notify.go

// Package notify is Keel's desktop-notification effector: a best-effort
// "interrupt the user" primitive behind a Notifier port. On Linux with
// notify-send installed it pops a toast; everywhere else it is a silent nop.
// Mirrors internal/enforce: a pure OS primitive, all policy lives in callers.
package notify

import (
	"context"
	"fmt"
	"os/exec"
)

// Notifier shows a desktop notification. Best-effort: it returns an error for
// diagnostics, but callers never block on it and treat failure as "no toast."
type Notifier interface {
	Notify(ctx context.Context, title, body string) error
}

// NewNotifier returns the notify-send adapter when that binary is on PATH, else
// a nop. This makes a missing binary (or a non-Linux host) degrade to silence
// rather than an error.
func NewNotifier() Notifier {
	if path, err := exec.LookPath("notify-send"); err == nil {
		return sendNotifier{bin: path}
	}
	return nopNotifier{}
}

// sendNotifier shells out to notify-send. The app name groups Keel's toasts.
type sendNotifier struct{ bin string }

func (s sendNotifier) Notify(ctx context.Context, title, body string) error {
	cmd := exec.CommandContext(ctx, s.bin, "--app-name=Keel", title, body)
	if err := cmd.Run(); err != nil {
		return fmt.Errorf("notify: notify-send: %w", err)
	}
	return nil
}

// nopNotifier is the silent fallback.
type nopNotifier struct{}

func (nopNotifier) Notify(context.Context, string, string) error { return nil }