interfaces: refactor

interfaces/05-log-parser/testing/report/parser.go

@@ -0,0 +1,52 @@
+// 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 report
+
+import (
+	"fmt"
+)
+
+// Parser parses the log file and generates a summary report.
+type Parser struct {
+	summary *Summary // summarizes the parsing results
+	lines   int      // number of parsed lines (for the error messages)
+	lerr    error    // the last error occurred
+}
+
+// New returns a new parsing state.
+func New() *Parser {
+	return &Parser{summary: newSummary()}
+}
+
+// Parse parses a log line and adds it to the summary.
+func (p *Parser) Parse(line string) {
+	// if there was an error do not continue
+	if p.lerr != nil {
+		return
+	}
+
+	// chain the parser's error to the result's
+	res, err := parse(line)
+	if p.lines++; err != nil {
+		p.lerr = fmt.Errorf("line #%d: %s", p.lines, err)
+		return
+	}
+
+	p.summary.update(res)
+}
+
+// Summarize summarizes the parsing results.
+// Only use it after the parsing is done.
+func (p *Parser) Summarize() *Summary {
+	return p.summary
+}
+
+// Err returns the last error encountered
+func (p *Parser) Err() error {
+	return p.lerr
+}

interfaces/05-log-parser/testing/report/parser_test.go

@@ -0,0 +1,55 @@
+package report_test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/inancgumus/learngo/28-methods/logparser-testing/report"
+)
+
+func newParser(lines string) *report.Parser {
+	p := report.New()
+	p.Parse(lines)
+	return p
+}
+
+func TestParserLineErrs(t *testing.T) {
+	p := newParser("a.com 1 2")
+	p.Parse("b.com -1 -1")
+
+	want := "#2"
+	err := p.Err().Error()
+
+	if !strings.Contains(err, want) {
+		t.Errorf("want: %q; got: %q", want, err)
+	}
+}
+
+func TestParserStopsOnErr(t *testing.T) {
+	p := newParser("a.com 10 20")
+	p.Parse("b.com -1 -1")
+	p.Parse("neverparses.com 30 40")
+
+	s := p.Summarize()
+	if want, got := 10, s.Total().Visits; want != got {
+		t.Errorf("want: %d; got: %d", want, got)
+	}
+}
+
+func TestParserIncorrectFields(t *testing.T) {
+	tests := []struct {
+		in, name string
+	}{
+		{"a.com", "missing fields"},
+		{"a.com -1 2", "incorrect visits"},
+		{"a.com 1 -1", "incorrect time spent"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if p := newParser(tt.in); p.Err() == nil {
+				t.Errorf("in: %q; got: nil err", tt.in)
+			}
+		})
+	}
+}

interfaces/05-log-parser/testing/report/result.go

@@ -0,0 +1,60 @@
+// 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 report
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// always put all the related things together as in here
+
+// Result stores metrics for a domain
+// it uses the value mechanics,
+// because it doesn't have to update anything
+type Result struct {
+	Domain    string `json:"domain"`
+	Visits    int    `json:"visits"`
+	TimeSpent int    `json:"time_spent"`
+	// add more metrics if needed
+}
+
+// add adds the metrics of another Result to itself and returns a new Result
+func (r Result) add(other Result) Result {
+	return Result{
+		Domain:    r.Domain,
+		Visits:    r.Visits + other.Visits,
+		TimeSpent: r.TimeSpent + other.TimeSpent,
+	}
+}
+
+// parse parses a single log line
+func parse(line string) (r Result, err error) {
+	fields := strings.Fields(line)
+	if len(fields) != 3 {
+		return r, fmt.Errorf("missing fields: %v", fields)
+	}
+
+	f := new(field)
+	r.Domain = fields[0]
+	r.Visits = f.atoi("visits", fields[1])
+	r.TimeSpent = f.atoi("time spent", fields[2])
+	return r, f.err
+}
+
+// field helps for field parsing
+type field struct{ err error }
+
+func (f *field) atoi(name, val string) int {
+	n, err := strconv.Atoi(val)
+	if n < 0 || err != nil {
+		f.err = fmt.Errorf("incorrect %s: %q", name, val)
+	}
+	return n
+}

interfaces/05-log-parser/testing/report/summary.go

@@ -0,0 +1,86 @@
+// 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 report
+
+import (
+	"sort"
+)
+
+// Summary aggregates the parsing results
+type Summary struct {
+	sum     map[string]Result // metrics per domain
+	domains []string          // unique domain names
+	total   Result            // total visits for all domains
+}
+
+// newSummary constructs and initializes a new summary
+// You can't use its methods without pointer mechanics
+func newSummary() *Summary {
+	return &Summary{sum: make(map[string]Result)}
+}
+
+// Update updates the report for the given parsing result
+func (s *Summary) update(r Result) {
+	domain := r.Domain
+	if _, ok := s.sum[domain]; !ok {
+		s.domains = append(s.domains, domain)
+	}
+
+	// let the result handle the addition
+	// this allows us to manage the result in once place
+	// and this way it becomes easily extendable
+	s.total = s.total.add(r)
+	s.sum[domain] = r.add(s.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 (s *Summary) Iterator() (next func() bool, cur func() Result) {
+	sort.Strings(s.domains)
+
+	// remember the last iterated result
+	var last int
+
+	next = func() bool {
+		defer func() { last++ }()
+		return len(s.domains) > last
+	}
+
+	cur = func() Result {
+		// returns a copy so the caller cannot change it
+		name := s.domains[last-1]
+		return s.sum[name]
+	}
+
+	return
+}
+
+// Total returns the total metrics
+func (s *Summary) Total() Result {
+	return s.total
+}
+
+// For the interfaces section
+//
+// MarshalJSON marshals a report to JSON
+// Alternative: unexported embedding
+// func (s *Summary) MarshalJSON() ([]byte, error) {
+// 	type total struct {
+// 		*Result
+// 		IgnoreDomain *string `json:"domain,omitempty"`
+// 	}
+
+// 	return json.Marshal(struct {
+// 		Sum     map[string]Result `json:"summary"`
+// 		Domains []string          `json:"domains"`
+// 		Total   total             `json:"total"`
+// 	}{
+// 		Sum: s.sum, Domains: s.domains, Total: total{Result: &s.total},
+// 	})
+// }

interfaces/05-log-parser/testing/report/summary_test.go

@@ -0,0 +1,44 @@
+package report_test
+
+import (
+	"testing"
+
+	"github.com/inancgumus/learngo/28-methods/logparser-testing/report"
+)
+
+func TestSummaryTotal(t *testing.T) {
+	p := newParser("a.com 1 2")
+	p.Parse("b.com 3 4")
+
+	s := p.Summarize()
+
+	want := report.Result{Domain: "", Visits: 4, TimeSpent: 6}
+	if got := s.Total(); want != got {
+		t.Errorf("want: %+v; got: %+v", want, got)
+	}
+}
+
+func TestSummaryIterator(t *testing.T) {
+	p := newParser("a.com 1 2")
+	p.Parse("a.com 3 4")
+	p.Parse("b.com 5 6")
+
+	s := p.Summarize()
+	next, cur := s.Iterator()
+
+	wants := []report.Result{
+		{Domain: "a.com", Visits: 4, TimeSpent: 6},
+		{Domain: "b.com", Visits: 5, TimeSpent: 6},
+	}
+
+	for _, want := range wants {
+		t.Run(want.Domain, func(t *testing.T) {
+			if got := next(); !got {
+				t.Errorf("next(): want: %t; got: %t", true, got)
+			}
+			if got := cur(); want != got {
+				t.Errorf("cur(): want: %+v; got: %+v", want, got)
+			}
+		})
+	}
+}