package main

import (
	"bufio"
	"fmt"
	"io"
	"log"
	"os"
)

func main() {
   if len(os.Args) != 2 {
      log.Fatalln("one argument: file name")
   }

   f, err := os.Open(os.Args[1])
   if err != nil {
      log.Fatalf("failed to open file %s: %s", os.Args[1], err.Error())
   }
   defer f.Close()

   var i int

   o := os.Stdout
   defer o.Close()

   // File should always start with '1'
   i++
   if _, err = o.WriteString(fmt.Sprintf("%d\n", i)); err != nil {
      log.Fatalln("failed to write index:", err)
   }

   r := bufio.NewReader(f)

   var emptyLine bool
   for {
      emptyLine = false

      l, err := r.ReadString('\n')
      if err == io.EOF {
         break
      }
      if err != nil {
         log.Fatalln("failed to read line:", err)
      }

      if len(l) == 1 {
         emptyLine = true
      }

      if _, err = o.WriteString(l); err != nil {
         log.Fatalln("failed to write to output:", err)
      }

      if emptyLine {
         i++
         if _, err := o.WriteString(fmt.Sprintf("%d\n", i)); err != nil {
            log.Fatalln("failed to write index:", err)
         }
      }
   }


}