learngo/23-input-scanning/03-project-log-parser/main.go

// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
// For more tutorials  : https://learngoprogramming.com
// In-person training  : https://www.linkedin.com/in/inancgumus/
// Follow me on twitter: https://twitter.com/inancgumus

package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
	"strconv"
	"strings"
)

func main() {
	var (
		sum     map[string]int // total visits per domain
		domains []string       // unique domain names
		total   int            // total visits to all domains
		lines   int            // number of parsed lines (for the error messages)
	)

	sum = make(map[string]int)

	// Scan the standard-in line by line
	in := bufio.NewScanner(os.Stdin)
	for in.Scan() {
		lines++

		// Parse the fields
		fields := strings.Fields(in.Text())
		if len(fields) != 2 {
			fmt.Printf("wrong input: %v (line #%d)\n", fields, lines)
			return
		}

		domain := fields[0]

		// Sum the total visits per domain
		visits, err := strconv.Atoi(fields[1])
		if visits < 0 || err != nil {
			fmt.Printf("wrong input: %q (line #%d)\n", fields[1], lines)
			return
		}

		// Collect the unique domains
		if _, ok := sum[domain]; !ok {
			domains = append(domains, domain)
		}

		// Keep track of total and per domain visits
		total += visits
		sum[domain] += visits
	}

	// Print the visits per domain
	sort.Strings(domains)

	fmt.Printf("%-30s %10s\n", "DOMAIN", "VISITS")
	fmt.Println(strings.Repeat("-", 45))

	for _, domain := range domains {
		visits := sum[domain]
		fmt.Printf("%-30s %10d\n", domain, visits)
	}

	// Print the total visits for all domains
	fmt.Printf("\n%-30s %10d\n", "TOTAL", total)

	// Let's handle the error
	if err := in.Err(); err != nil {
		fmt.Println("> Err:", err)
	}
}