interfaces: refactor

interfaces/05-log-parser/refactor-notes/refactor-03/changes.md

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+### PROBLEM
++ ...
+
+## SOLUTION
++ `parser struct` -> `pipeline struct`
++ `parse()` -> `pipe(pipeline)`
+

interfaces/05-log-parser/refactor-notes/refactor-03/main.go

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+// 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 (
+	"fmt"
+)
+
+func main() {
+	pipes := pipeline{
+		// read:     textParser(),
+		// write:    textSummary(),
+		// filterBy: notUsing(domainExtFilter("io", "com")),
+		// groupBy:  domainGrouper,
+	}
+
+	res, err := pipe(pipes)
+	if err != nil {
+		fmt.Println("> Err:", err)
+		return
+	}
+
+	summarize(res)
+}

interfaces/05-log-parser/refactor-notes/refactor-03/parser.go

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+// 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"
+)
+
+// pipeline determines the behavior of log processing
+type pipeline struct {
+}
+
+// pipe the log lines through funcs and produce a result
+func pipe(opts pipeline) ([]result, error) {
+	var (
+		l   = 1
+		in  = bufio.NewScanner(os.Stdin)
+		sum = make(map[string]result)
+	)
+
+	// parse the log lines
+	for in.Scan() {
+		r, err := parseResult(in.Text())
+		if err != nil {
+			return nil, fmt.Errorf("line %d: %v", l, err)
+		}
+
+		l++
+
+		// group the log lines by domain
+		sum[r.domain] = addResult(r, sum[r.domain])
+	}
+
+	// collect the grouped results
+	res := make([]result, 0, len(sum))
+	for _, r := range sum {
+		res = append(res, r)
+	}
+
+	return res, in.Err()
+}

interfaces/05-log-parser/refactor-notes/refactor-03/result.go

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+// 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 (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+const fieldsLength = 4
+
+// result stores the parsed result for a domain
+type result struct {
+	domain, page    string
+	visits, uniques int
+	// add more metrics if needed
+}
+
+// parseResult from a log line
+func parseResult(line string) (r result, err error) {
+	fields := strings.Fields(line)
+	if len(fields) != fieldsLength {
+		return r, fmt.Errorf("wrong input: %v", fields)
+	}
+
+	r.domain = fields[0]
+	r.page = fields[1]
+
+	r.visits, err = strconv.Atoi(fields[2])
+	if err != nil || r.visits < 0 {
+		return r, fmt.Errorf("wrong input: %q", fields[2])
+	}
+
+	r.uniques, err = strconv.Atoi(fields[3])
+	if err != nil || r.uniques < 0 {
+		return r, fmt.Errorf("wrong input: %q", fields[3])
+	}
+
+	return r, nil
+}
+
+// addResult to another one
+func addResult(r, other result) result {
+	r.visits += other.visits
+	r.uniques += other.uniques
+	return r
+}

interfaces/05-log-parser/refactor-notes/refactor-03/summarize.go

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+// 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 (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+// summarize summarizes and prints the parsing result
+// + violation: accesses the parsing internals: p.domains + p.sum + p.total
+// + give it the []result only.
+// + let it calculate the total.
+const (
+
+	//          DOMAINS PAGES VISITS UNIQUES
+	//             ^      ^     ^    ^
+	//             |      |     |    |
+	header     = "%-25s %-10s %10s %10s\n"
+	line       = "%-25s %-10s %10d %10d\n"
+	footer     = "\n%-36s %10d %10d\n" // -> "" VISITS UNIQUES
+	dash       = "-"
+	dashLength = 58
+)
+
+// summarize summarizes and prints the parsing result
+func summarize(res []result) {
+	sort.Slice(res, func(i, j int) bool {
+		return res[i].domain <= res[j].domain
+	})
+
+	fmt.Printf(header, "DOMAIN", "PAGES", "VISITS", "UNIQUES")
+	fmt.Println(strings.Repeat("-", dashLength))
+
+	var total result
+
+	for _, r := range res {
+		total = addResult(total, r)
+		fmt.Printf(line, r.domain, r.page, r.visits, r.uniques)
+	}
+	fmt.Printf(footer, "TOTAL", total.visits, total.uniques)
+}