// 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

import (
	"encoding/json"
	"errors"
)

// SuggestField can be used by the caller to specify a suggest field
// at index time. For a detailed example, see e.g.
// https://www.elastic.co/blog/you-complete-me.
type SuggestField struct {
	inputs         []string
	weight         int
	contextQueries []SuggesterContextQuery
}

func NewSuggestField(input ...string) *SuggestField {
	return &SuggestField{
		inputs: input,
		weight: -1,
	}
}

func (f *SuggestField) Input(input ...string) *SuggestField {
	if f.inputs == nil {
		f.inputs = make([]string, 0)
	}
	f.inputs = append(f.inputs, input...)
	return f
}

func (f *SuggestField) Weight(weight int) *SuggestField {
	f.weight = weight
	return f
}

func (f *SuggestField) ContextQuery(queries ...SuggesterContextQuery) *SuggestField {
	f.contextQueries = append(f.contextQueries, queries...)
	return f
}

// MarshalJSON encodes SuggestField into JSON.
func (f *SuggestField) MarshalJSON() ([]byte, error) {
	source := make(map[string]interface{})

	if f.inputs != nil {
		switch len(f.inputs) {
		case 1:
			source["input"] = f.inputs[0]
		default:
			source["input"] = f.inputs
		}
	}

	if f.weight >= 0 {
		source["weight"] = f.weight
	}

	switch len(f.contextQueries) {
	case 0:
	case 1:
		src, err := f.contextQueries[0].Source()
		if err != nil {
			return nil, err
		}
		source["contexts"] = src
	default:
		ctxq := make(map[string]interface{})
		for _, query := range f.contextQueries {
			src, err := query.Source()
			if err != nil {
				return nil, err
			}
			m, ok := src.(map[string]interface{})
			if !ok {
				return nil, errors.New("SuggesterContextQuery must be of type map[string]interface{}")
			}
			for k, v := range m {
				ctxq[k] = v
			}
		}
		source["contexts"] = ctxq
	}

	return json.Marshal(source)
}