package app

import (
	"fmt"
	"log/slog"
)

// Subsystem represents a sub-system of the application, with its setup and
// teardown functions and dependencies.
type Subsystem struct {
	logger   *slog.Logger
	name     string
	setup    setupFn
	teardown teardownFn
	depends  []*Subsystem
}

// SubsystemOpts contains user-exposed options when defining a subsystem.
type SubsystemOpts struct {
	// Setup is the setup function for the subsystem.
	Setup setupFn
	// Teardown is the teardown function for the subsystem.
	Teardown teardownFn
	// Depends is a list of subsystems that this subsystem depends on.
	Depends []*Subsystem
}

// NewSubsystem creates a new Subsystem instance with the given name and options.
func NewSubsystem(name string, opts SubsystemOpts) *Subsystem {
	return &Subsystem{
		name:     name,
		setup:    opts.Setup,
		teardown: opts.Teardown,
		depends:  opts.Depends,
	}
}

// Logger returns the logger for the subsystem.
func (s *Subsystem) Logger() *slog.Logger {
	if s.logger == nil {
		panic(fmt.Sprintf("subsytem %s used before logger was initialized", s.name))
	}
	return s.logger
}