add: file parser mega project

25-project-file-parser-structs/log.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org 4
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-project-file-parser-structs/main.go

@@ -0,0 +1,80 @@
+// 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"
+	"strconv"
+	"strings"
+)
+
+// domain represents a domain log record
+type domain struct {
+	name   string
+	visits int
+}
+
+// parser parses a log file and provides an iterator to iterate upon the domains
+//
+// the parser struct is carefully crafted to be usable using its zero values except the map field
+type parser struct {
+	sum     map[string]int // visits per unique domain
+	domains []domain       // unique domain names
+	total   int            // total visits to all domains
+	lines   int            // number of parsed lines (for the error messages)
+}
+
+func main() {
+	in := bufio.NewScanner(os.Stdin)
+
+	p := parser{
+		sum: make(map[string]int),
+	}
+
+	// Scan the standard-in line by line
+	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
+		}
+		name, visits := fields[0], fields[1]
+
+		// Sum the total visits per domain
+		n, _ := strconv.Atoi(visits)
+		if n < 0 {
+			fmt.Printf("wrong input: %q (line #%d)\n", visits, p.lines)
+			return
+		}
+
+		d := domain{name: name, visits: n}
+
+		// Collect the unique domains
+		if _, ok := p.sum[name]; !ok {
+			p.domains = append(p.domains, d)
+		}
+
+		p.sum[d.name] += n
+		p.total += d.visits
+	}
+
+	// Print the visits per domain
+	for _, d := range p.domains {
+		vis := p.sum[d.name]
+
+		fmt.Printf("%-25s -> %d\n", d.name, vis)
+	}
+
+	// Print the total visits for all domains
+	fmt.Printf("\n%-25s -> %d\n", "TOTAL", p.total)
+}