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 using named variables.
type LambdaEngine struct {
	Config     *config.Config
	Expression *lambda.Expression
	emitter.Emitter
}

// NewLambdaEngine creates a new lambda engine.
func NewLambdaEngine(config *config.Config, expression interface{}) *LambdaEngine {
	expr := expression.(*lambda.Expression)
	return &LambdaEngine{Config: config, Expression: expr}
}

// Run begins the reduction process.
func (e *LambdaEngine) Run() {
	e.Emit("start")

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

	e.Emit("end")
}

// GetResult returns the stringified result.
func (e *LambdaEngine) GetResult() string {
	return lambda.Stringify(*e.Expression)
}