add: more exercises to funcs

25-functions/exercises/rewrite-log-parser-using-funcs/main.go

@@ -0,0 +1,94 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// result stores the parsed result for a domain
+type result struct {
+	domain string
+	visits int
+	// add more metrics if needed
+}
+
+// parser keep tracks of the parsing
+type parser struct {
+	sum     map[string]result // metrics per domain
+	domains []string          // unique domain names
+	total   int               // total visits for all domains
+	lines   int               // number of parsed lines (for the error messages)
+}
+
+func main() {
+	p := parser{sum: make(map[string]result)}
+
+	// Scan the standard-in line by line
+	in := bufio.NewScanner(os.Stdin)
+	for in.Scan() {
+		p.lines++
+
+		// Parse the fields
+		fields := strings.Fields(in.Text())
+		if len(fields) != 2 {
+			fmt.Printf("wrong input: %v (line #%d)\n", fields, p.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], p.lines)
+			return
+		}
+
+		// Collect the unique domains
+		if _, ok := p.sum[domain]; !ok {
+			p.domains = append(p.domains, domain)
+		}
+
+		// Keep track of total and per domain visits
+		p.total += visits
+
+		// You cannot assign to composite values
+		// p.sum[domain].visits += visits
+
+		// create and assign a new copy of `visit`
+		p.sum[domain] = result{
+			domain: domain,
+			visits: visits + p.sum[domain].visits,
+		}
+	}
+
+	// Print the visits per domain
+	sort.Strings(p.domains)
+
+	fmt.Printf("%-30s %10s\n", "DOMAIN", "VISITS")
+	fmt.Println(strings.Repeat("-", 45))
+
+	for _, domain := range p.domains {
+		parsed := p.sum[domain]
+		fmt.Printf("%-30s %10d\n", domain, parsed.visits)
+	}
+
+	// Print the total visits for all domains
+	fmt.Printf("\n%-30s %10d\n", "TOTAL", p.total)
+
+	// Let's handle the error
+	if err := in.Err(); err != nil {
+		fmt.Println("> Err:", err)
+	}
+}