// Package normalorder contains an engine that reduces a 'lambda.Expression'
// in the normal order.
package normalorder

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

type process struct {
	expr lambda.Expression
}

func (e process) Get() (lambda.Expression, error) {
	return e.expr, nil
}

func (e *process) Set(l lambda.Expression) error {
	e.expr = l
	return nil
}

func (e *process) Step(i int) bool {
	for range i {
		next, reduced := ReduceOnce(e.expr)
		if !reduced {
			return false
		}

		e.expr = next
	}

	return true
}

// NewProcess creates a new redution process.
func NewProcess(expression lambda.Expression) (engine.Process[lambda.Expression], error) {
	return &process{expr: expression}, nil
}

var _ engine.Process[lambda.Expression] = (*process)(nil)
var _ engine.Engine[lambda.Expression] = NewProcess