add: iterator to log parser methods

x-tba/2-methods/xxx-log-parser-methods/report.go

@@ -7,6 +7,8 @@
 
 package main
 
+import "sort"
+
 // report aggregates the final report
 type report struct {
 	sum     map[string]result // metrics per domain
@@ -37,3 +39,26 @@ func (r *report) update(parsed parserResult) {
 	r.total = r.total.add(parsed.result)
 	r.sum[domain] = parsed.add(r.sum[domain])
 }
+
+// iterator returns `next()` to detect when the iteration ends,
+// and a `cur()` to return the current result.
+// iterator iterates sorted by domains.
+func (r *report) iterator() (next func() bool, cur func() result) {
+	sort.Strings(r.domains)
+
+	// remember the last iterated result
+	var last int
+
+	next = func() bool {
+		defer func() { last++ }()
+		return len(r.domains) > last
+	}
+
+	cur = func() result {
+		// returns a copy so the caller cannot change it
+		name := r.domains[last-1]
+		return r.sum[name]
+	}
+
+	return
+}

x-tba/2-methods/xxx-log-parser-methods/summarize.go

@@ -9,20 +9,18 @@ package main
 
 import (
 	"fmt"
-	"sort"
 	"strings"
 )
 
 // summarize prints the report and errors if any
 func summarize(r *report, errs ...error) {
-	sort.Strings(r.domains)
-
 	fmt.Printf("%-30s %10s\n", "DOMAIN", "VISITS")
 	fmt.Println(strings.Repeat("-", 45))
 
-	for _, domain := range r.domains {
-		parsed := r.sum[domain]
-		fmt.Printf("%-30s %10d\n", domain, parsed.visits)
+	next, cur := r.iterator()
+	for next() {
+		rec := cur()
+		fmt.Printf("%-30s %10d\n", rec.domain, rec.visits)
 	}
 	fmt.Printf("\n%-30s %10d\n", "TOTAL", r.total.visits)