package main

import (
    "bufio"
_    "bytes"
    "fmt"
    "os"
    "time"
)

func canonicalize(s string) string {
    c := s + s[:len(s)-1]
    best := s
    for i := 1; i < len(s); i++ {
        if c[i:i+len(s)] < best {
            best = c[i : i+len(s)]
        }
    }
    return best
}

func main() {
    seen := make(map[string][]string)

    // START TIMER
    start := time.Now()

    f, err := os.Open("/etc/passwd")
    if err != nil {
      // or check error by using error checking func in os package
      fmt.Println("err file i/o")
      return
    }
    defer f.Close()


    reader := bufio.NewReader(f)

    for {
    s, _, err := reader.ReadLine()
        if err != nil {
          break
        }
        word := string(s) // it's AoB
        n := canonicalize(word)
        seen[n] = append(seen[n], word)
    }


    for _, words := range seen {
        if len(words) == 4 {
            fmt.Printf("%v\n", words)
            break
        }
    }

    // END TIMER AND PRINT RESULT
    end := time.Now()
    fmt.Printf("Result: %s (%d) nano(%d)\n", end.Sub(start), end.Unix()-start.Unix(), end.UnixNano()-start.UnixNano())
}