//  Copyright (c) 2014 Couchbase, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 		http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package query

import (
	"encoding/json"
	"fmt"

	"github.com/blevesearch/bleve/index"
	"github.com/blevesearch/bleve/mapping"
	"github.com/blevesearch/bleve/search"
	"github.com/blevesearch/bleve/search/searcher"
)

type PhraseQuery struct {
	Terms       []string `json:"terms"`
	Field       string   `json:"field,omitempty"`
	BoostVal    *Boost   `json:"boost,omitempty"`
	termQueries []Query
}

// NewPhraseQuery creates a new Query for finding
// exact term phrases in the index.
// The provided terms must exist in the correct
// order, at the correct index offsets, in the
// specified field. Queried field must have been indexed with
// IncludeTermVectors set to true.
func NewPhraseQuery(terms []string, field string) *PhraseQuery {
	termQueries := make([]Query, 0)
	for _, term := range terms {
		if term != "" {
			tq := NewTermQuery(term)
			tq.SetField(field)
			termQueries = append(termQueries, tq)
		}
	}
	return &PhraseQuery{
		Terms:       terms,
		Field:       field,
		termQueries: termQueries,
	}
}

func (q *PhraseQuery) SetBoost(b float64) {
	boost := Boost(b)
	q.BoostVal = &boost
}

func (q *PhraseQuery) Boost() float64{
	return q.BoostVal.Value()
}

func (q *PhraseQuery) Searcher(i index.IndexReader, m mapping.IndexMapping, explain bool) (search.Searcher, error) {

	conjunctionQuery := NewConjunctionQuery(q.termQueries)
	conjunctionSearcher, err := conjunctionQuery.Searcher(i, m, explain)
	if err != nil {
		return nil, err
	}
	return searcher.NewPhraseSearcher(i, conjunctionSearcher.(*searcher.ConjunctionSearcher), q.Terms)
}

func (q *PhraseQuery) Validate() error {
	if len(q.termQueries) < 1 {
		return fmt.Errorf("phrase query must contain at least one term")
	}
	return nil
}

func (q *PhraseQuery) UnmarshalJSON(data []byte) error {
	type _phraseQuery PhraseQuery
	tmp := _phraseQuery{}
	err := json.Unmarshal(data, &tmp)
	if err != nil {
		return err
	}
	q.Terms = tmp.Terms
	q.Field = tmp.Field
	q.BoostVal = tmp.BoostVal
	q.termQueries = make([]Query, len(q.Terms))
	for i, term := range q.Terms {
		q.termQueries[i] = &TermQuery{Term: term, FieldVal: q.Field, BoostVal: q.BoostVal}
	}
	return nil
}