// Package runtime provides the abstract Reducer interface for all expression
// reduction strategies.
package runtime

import (
	"git.maximhutz.com/max/lambda/pkg/emitter"
	"git.maximhutz.com/max/lambda/pkg/repr"
)

// Runtime defines the interface for expression reduction strategies.
// Different evaluation modes (normal order, applicative order, SKI combinators,
// etc.) implement this interface with their own reduction logic.
//
// Runtimes also implement the Emitter interface to allow plugins to observe
// reduction lifecycle events (Start, Step, Stop).
type Runtime interface {
	emitter.Emitter[Event]

	// Run a single step. Returns whether the runtime is complete or not.
	Step() bool

	// Run until completion.
	Run()

	// Copy the state of the runtime.
	Expression() repr.Repr
}