//  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 analysis

import (
	"bytes"
	"unicode/utf8"
)

func DeleteRune(in []rune, pos int) []rune {
	if pos >= len(in) {
		return in
	}
	copy(in[pos:], in[pos+1:])
	return in[:len(in)-1]
}

func InsertRune(in []rune, pos int, r rune) []rune {
	// create a new slice 1 rune larger
	rv := make([]rune, len(in)+1)
	// copy the characters before the insert pos
	copy(rv[0:pos], in[0:pos])
	// set the inserted rune
	rv[pos] = r
	// copy the characters after the insert pos
	copy(rv[pos+1:], in[pos:])
	return rv
}

func BuildTermFromRunes(runes []rune) []byte {
	rv := make([]byte, 0, len(runes)*4)
	for _, r := range runes {
		runeBytes := make([]byte, utf8.RuneLen(r))
		utf8.EncodeRune(runeBytes, r)
		rv = append(rv, runeBytes...)
	}
	return rv
}

func TruncateRunes(input []byte, num int) []byte {
	runes := bytes.Runes(input)
	runes = runes[:len(runes)-num]
	out := BuildTermFromRunes(runes)
	return out
}