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

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

// Reducer 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.
//
// Reducers also implement the Emitter interface to allow plugins to observe
// reduction lifecycle events (Start, Step, Stop).
type Reducer interface {
	emitter.Emitter[Event]

	// Reduce performs all reduction steps on the expression.
	// Emits StartEvent before reduction, StepEvent after each step, and
	// StopEvent after completion.
	// Returns the final reduced expression.
	Reduce()

	// Expression returns the current expression state.
	Expression() expr.Expression
}