// Copyright 2012-present Oliver Eilhard. All rights reserved.
// Use of this source code is governed by a MIT-license.
// See http://olivere.mit-license.org/license.txt for details.

package elastic

// CollapseBuilder enables field collapsing on a search request.
// See https://www.elastic.co/guide/en/elasticsearch/reference/5.3/search-request-collapse.html
// for details.
type CollapseBuilder struct {
	field                      string
	innerHit                   *InnerHit
	maxConcurrentGroupRequests *int
}

// NewCollapseBuilder creates a new CollapseBuilder.
func NewCollapseBuilder(field string) *CollapseBuilder {
	return &CollapseBuilder{field: field}
}

// Field to collapse.
func (b *CollapseBuilder) Field(field string) *CollapseBuilder {
	b.field = field
	return b
}

// InnerHit option to expand the collapsed results.
func (b *CollapseBuilder) InnerHit(innerHit *InnerHit) *CollapseBuilder {
	b.innerHit = innerHit
	return b
}

// MaxConcurrentGroupRequests is the maximum number of group requests that are
// allowed to be ran concurrently in the inner_hits phase.
func (b *CollapseBuilder) MaxConcurrentGroupRequests(max int) *CollapseBuilder {
	b.maxConcurrentGroupRequests = &max
	return b
}

// Source generates the JSON serializable fragment for the CollapseBuilder.
func (b *CollapseBuilder) Source() (interface{}, error) {
	// {
	//   "field": "user",
	//   "inner_hits": {
	//     "name": "last_tweets",
	//     "size": 5,
	//     "sort": [{ "date": "asc" }]
	//   },
	//   "max_concurrent_group_searches": 4
	// }
	src := map[string]interface{}{
		"field": b.field,
	}

	if b.innerHit != nil {
		hits, err := b.innerHit.Source()
		if err != nil {
			return nil, err
		}
		src["inner_hits"] = hits
	}

	if b.maxConcurrentGroupRequests != nil {
		src["max_concurrent_group_searches"] = *b.maxConcurrentGroupRequests
	}

	return src, nil
}