package collections

import (
	"context"
	"github.com/MontFerret/ferret/pkg/runtime/core"
)

type TapIterator struct {
	values    Iterator
	predicate core.Expression
}

func NewTapIterator(values Iterator, predicate core.Expression) (Iterator, error) {
	if values == nil {
		return nil, core.Error(core.ErrMissedArgument, "values")
	}

	if predicate == nil {
		return nil, core.Error(core.ErrMissedArgument, "predicate")
	}

	return &TapIterator{values, predicate}, nil
}

func (iterator *TapIterator) Next(ctx context.Context, scope *core.Scope) (*core.Scope, error) {
	nextScope, err := iterator.values.Next(ctx, scope)

	if err != nil {
		return nil, err
	}

	if nextScope == nil {
		return nil, nil
	}

	_, err = iterator.predicate.Exec(ctx, nextScope)

	if err != nil {
		return nil, err
	}

	return nextScope, nil
}