// ex1.4 solves exercise 1.4
package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	counts := make(map[string]int)
	files := make(map[string]map[string]bool)
	inputs := os.Args[1:]
	if len(inputs) == 0 {
		countLines(os.Stdin, counts, files)
	} else {
		for _, arg := range inputs {
			f, err := os.Open(arg)
			if err != nil {
				fmt.Fprintf(os.Stderr, "ex1.4: %v\n", err)
				continue
			}
			if err := countLines(f, counts, files); err != nil {
				panic(err)
			}
			f.Close()
		}
	}
	for line, n := range counts {
		if n > 1 {
			fmt.Printf("%d\t%q\n", n, line)
			for file := range files[line] {
				fmt.Printf("\tin %q\n", file)
			}
		}
	}
}

func countLines(f *os.File, counts map[string]int, files map[string]map[string]bool) error {
	input := bufio.NewScanner(f)
	for input.Scan() {
		line := input.Text()
		counts[line]++

		if _, ok := files[line]; !ok {
			files[line] = make(map[string]bool)
		}
		files[line][f.Name()] = true
	}
	return input.Err()
}