// Package "engine" provides an extensible interface for users to interfact with
// λ-calculus.
package engine

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

// A process for reducing one λ-expression.
type Engine struct {
	Config     *config.Config
	Expression *lambda.Expression
	emitter.BaseEmitter[Event]
}

// Create a new engine, given an unreduced λ-expression.
func New(config *config.Config, expression *lambda.Expression) *Engine {
	return &Engine{
		Config:      config,
		Expression:  expression,
		BaseEmitter: *emitter.New[Event](),
	}
}

// Begin the reduction process.
func (e Engine) Run() {
	e.Emit(StartEvent)

	lambda.ReduceAll(e.Expression, func() {
		e.Emit(StepEvent)
	})

	e.Emit(StopEvent)
}