// Package bench is a package which contains
// programs of Go Benchmark Competition.
package bench

import (
	"bufio"
	"bytes"
	"errors"
	"fmt"
	"io"
	"os"
	"strings"
)

// Find reads the text file on the `path`,
// finds the `s` words on the file and
// returns the row numbers and indices
// in the form of `r:c,r:c,...r:c`,
// at which the `s` word exists.

// Methods:
// BenchmarkFind 30000 41445 ns/op (Mon Mar 23 14:10:47 CET 2015)
// BenchmarkFind 50000 28312 ns/op (Mon Mar 23 19:26:33 CET 2015)
func Find(path, word string) (string, error) {
	if len(word) == 0 {
		return "", errors.New("word cannot be empty")
	}

	file, _ := os.Open(path)
	defer file.Close()

	reader := bufio.NewReader(file)

	var found []string
	var row int

	for {
		offset := 0
		line, err := reader.ReadSlice(0x0a)
		if err == io.EOF {
			break
		}

		row++

		for {
			index := bytes.Index(line, []byte(word))
			offset = offset + index
			if index != -1 && offset < len(line) {
				found = append(found, fmt.Sprintf("%d:%d", row, offset))
				offset++
				line = line[offset:]
			} else {
				break
			}
		}
	}

	return strings.Join(found, ","), nil
}