//  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 truncate_token_filter

import (
	"bytes"
	"unicode/utf8"

	"github.com/blevesearch/bleve/analysis"
	"github.com/blevesearch/bleve/registry"
)

const Name = "truncate_token"

type TruncateTokenFilter struct {
	length int
}

func NewTruncateTokenFilter(length int) *TruncateTokenFilter {
	return &TruncateTokenFilter{
		length: length,
	}
}

func (s *TruncateTokenFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
	rv := make(analysis.TokenStream, 0)

	for _, token := range input {
		wordLen := utf8.RuneCount(token.Term)
		if wordLen > s.length {
			runes := bytes.Runes(token.Term)[0:s.length]
			newterm := make([]byte, 0, s.length*4)
			for _, r := range runes {
				runeBytes := make([]byte, utf8.RuneLen(r))
				utf8.EncodeRune(runeBytes, r)
				newterm = append(newterm, runeBytes...)
			}
			token.Term = newterm
		}
		rv = append(rv, token)
	}

	return rv
}

func TruncateTokenFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
	length := 25

	lenVal, ok := config["length"].(float64)
	if ok {
		length = int(lenVal)
	}

	return NewTruncateTokenFilter(length), nil
}

func init() {
	registry.RegisterTokenFilter(Name, TruncateTokenFilterConstructor)
}