diff --git a/interfaces/log-parser/logs/log.json b/interfaces/log-parser/logs/log.json
deleted file mode 100644
index f930f01..0000000
--- a/interfaces/log-parser/logs/log.json
+++ /dev/null
@@ -1,18 +0,0 @@
-[
-    {"domain": "learngoprogramming.com", "page": "/", "visits": 10, "uniques": 5},
-    {"domain": "learngoprogramming.com", "page": "/courses", "visits": 15, "uniques": 10},
-    {"domain": "learngoprogramming.com", "page": "/courses", "visits": 10, "uniques": 5},
-    {"domain": "learngoprogramming.com", "page": "/articles", "visits": 20, "uniques": 15},
-    {"domain": "learngoprogramming.com", "page": "/articles", "visits": 5, "uniques": 2},
-    {"domain": "golang.org", "page": "/", "visits": 40, "uniques": 20},
-    {"domain": "golang.org", "page": "/", "visits": 20, "uniques": 10},
-    {"domain": "golang.org", "page": "/blog", "visits": 45, "uniques": 25},
-    {"domain": "golang.org", "page": "/blog", "visits": 15, "uniques": 5},
-    {"domain": "blog.golang.org", "page": "/courses", "visits": 60, "uniques": 30},
-    {"domain": "blog.golang.org", "page": "/courses", "visits": 30, "uniques": 20},
-    {"domain": "blog.golang.org", "page": "/updates", "visits": 20, "uniques": 10},
-    {"domain": "blog.golang.org", "page": "/reference", "visits": 65, "uniques": 35},
-    {"domain": "blog.golang.org", "page": "/reference", "visits": 15, "uniques": 5},
-    {"domain": "inanc.io", "page": "/about", "visits": 30, "uniques": 15},
-    {"domain": "inanc.io", "page": "/about","visits": 70, "uniques": 35}
-]
\ No newline at end of file
diff --git a/interfaces/log-parser/logs/log.jsonl b/interfaces/log-parser/logs/log.jsonl
new file mode 100644
index 0000000..5d36a54
--- /dev/null
+++ b/interfaces/log-parser/logs/log.jsonl
@@ -0,0 +1,16 @@
+{"domain": "learngoprogramming.com", "page": "/", "visits": 10, "uniques": 5}
+{"domain": "learngoprogramming.com", "page": "/courses", "visits": 15, "uniques": 10}
+{"domain": "learngoprogramming.com", "page": "/courses", "visits": 10, "uniques": 5}
+{"domain": "learngoprogramming.com", "page": "/articles", "visits": 20, "uniques": 15}
+{"domain": "learngoprogramming.com", "page": "/articles", "visits": 5, "uniques": 2}
+{"domain": "golang.org", "page": "/", "visits": 40, "uniques": 20}
+{"domain": "golang.org", "page": "/", "visits": 20, "uniques": 10}
+{"domain": "golang.org", "page": "/blog", "visits": 45, "uniques": 25}
+{"domain": "golang.org", "page": "/blog", "visits": 15, "uniques": 5}
+{"domain": "blog.golang.org", "page": "/courses", "visits": 60, "uniques": 30}
+{"domain": "blog.golang.org", "page": "/courses", "visits": 30, "uniques": 20}
+{"domain": "blog.golang.org", "page": "/updates", "visits": 20, "uniques": 10}
+{"domain": "blog.golang.org", "page": "/reference", "visits": 65, "uniques": 35}
+{"domain": "blog.golang.org", "page": "/reference", "visits": 15, "uniques": 5}
+{"domain": "inanc.io", "page": "/about", "visits": 30, "uniques": 15}
+{"domain": "inanc.io", "page": "/about","visits": 70, "uniques": 35}
\ No newline at end of file
diff --git a/interfaces/log-parser/oop/analysis.go b/interfaces/log-parser/oop/analysis.go
deleted file mode 100644
index ac0ba1d..0000000
--- a/interfaces/log-parser/oop/analysis.go
+++ /dev/null
@@ -1,62 +0,0 @@
-// 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 "sort"
-
-type analysis struct {
-	sum      map[string]result // metrics per group key
-	keys     []string          // unique group keys
-	groupKey groupFunc
-	filter   filterFunc
-}
-
-func newAnalysis() *analysis {
-	return &analysis{
-		sum:      make(map[string]result),
-		groupKey: domainGrouper,
-		filter:   noopFilter,
-	}
-}
-
-// transform the result
-func (a *analysis) transform(r result) {
-	if !a.filter(r) {
-		return
-	}
-
-	key := a.groupKey(r)
-	if _, ok := a.sum[key]; !ok {
-		a.keys = append(a.keys, key)
-	}
-
-	a.sum[key] = r.add(a.sum[key])
-}
-
-// each yields an analysis result
-func (a *analysis) each(yield resultFn) error {
-	sort.Strings(a.keys)
-
-	for _, key := range a.keys {
-		yield(a.sum[key])
-	}
-
-	return nil
-}
-
-func (a *analysis) groupBy(g groupFunc) {
-	if g != nil {
-		a.groupKey = g
-	}
-}
-
-func (a *analysis) filterBy(f filterFunc) {
-	if f != nil {
-		a.filter = f
-	}
-}
diff --git a/interfaces/log-parser/oop/chartreport.go b/interfaces/log-parser/oop/chartreport.go
index efaaf14..ca388be 100644
--- a/interfaces/log-parser/oop/chartreport.go
+++ b/interfaces/log-parser/oop/chartreport.go
@@ -8,7 +8,7 @@ package main
 // 	width, height int
 // }
 
-// func (s *chartReport) report(results iterator) error {
+// func (s *chartReport) digest(results iterator) error {
 // 	w := os.Stdout
 
 // 	donut := chart.DonutChart{
diff --git a/interfaces/log-parser/oop/filter.go b/interfaces/log-parser/oop/filter.go
new file mode 100644
index 0000000..3a6caca
--- /dev/null
+++ b/interfaces/log-parser/oop/filter.go
@@ -0,0 +1,43 @@
+// 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
+
+type filter struct {
+	src     iterator
+	filters []filterFunc
+}
+
+func filterBy(fn ...filterFunc) *filter {
+	return &filter{filters: fn}
+}
+
+// transform the result
+func (f *filter) digest(results iterator) error {
+	f.src = results
+	return nil
+}
+
+// each yields an analysis result
+func (f *filter) each(yield resultFn) error {
+	return f.src.each(func(r result) {
+		if !f.check(r) {
+			return
+		}
+		yield(r)
+	})
+}
+
+// check all the filters against the result
+func (f *filter) check(r result) bool {
+	for _, fi := range f.filters {
+		if !fi(r) {
+			return false
+		}
+	}
+	return true
+}
diff --git a/interfaces/log-parser/oop/group.go b/interfaces/log-parser/oop/group.go
new file mode 100644
index 0000000..3a3c86f
--- /dev/null
+++ b/interfaces/log-parser/oop/group.go
@@ -0,0 +1,49 @@
+// 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 (
+	"sort"
+)
+
+type group struct {
+	sum  map[string]result // metrics per group key
+	keys []string          // unique group keys
+	key  groupFunc
+}
+
+func groupBy(key groupFunc) *group {
+	return &group{
+		sum: make(map[string]result),
+		key: key,
+	}
+}
+
+// digest the results
+func (g *group) digest(results iterator) error {
+	return results.each(func(r result) {
+		k := g.key(r)
+
+		if _, ok := g.sum[k]; !ok {
+			g.keys = append(g.keys, k)
+		}
+
+		g.sum[k] = r.add(g.sum[k])
+	})
+}
+
+// each yields the grouped results
+func (g *group) each(yield resultFn) error {
+	sort.Strings(g.keys)
+
+	for _, k := range g.keys {
+		yield(g.sum[k])
+	}
+
+	return nil
+}
diff --git a/interfaces/log-parser/oop/jsonlog.go b/interfaces/log-parser/oop/jsonlog.go
index 1789e44..5e4f440 100644
--- a/interfaces/log-parser/oop/jsonlog.go
+++ b/interfaces/log-parser/oop/jsonlog.go
@@ -8,10 +8,9 @@
 package main
 
 import (
+	"bufio"
 	"encoding/json"
-	"fmt"
 	"io"
-	"io/ioutil"
 )
 
 type jsonLog struct {
@@ -25,37 +24,20 @@ func newJSONLog(r io.Reader) *jsonLog {
 func (j *jsonLog) each(yield resultFn) error {
 	defer readClose(j.reader)
 
-	bytes, err := ioutil.ReadAll(j.reader)
-	if err != nil {
-		return err
-	}
+	dec := json.NewDecoder(bufio.NewReader(j.reader))
 
-	return extractJSON(bytes, yield)
-}
+	for {
+		var r result
 
-func extractJSON(bytes []byte, yield resultFn) error {
-	var rs []struct {
-		Domain  string
-		Page    string
-		Visits  int
-		Uniques int
-	}
-
-	if err := json.Unmarshal(bytes, &rs); err != nil {
-		if serr, ok := err.(*json.SyntaxError); ok {
-			return fmt.Errorf("%v %q", serr, bytes[:serr.Offset])
+		err := dec.Decode(&r)
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return err
 		}
-		return err
-	}
 
-	for _, r := range rs {
-		yield(result{
-			domain:  r.Domain,
-			page:    r.Page,
-			visits:  r.Visits,
-			uniques: r.Uniques,
-		})
+		yield(r)
 	}
-
 	return nil
 }
diff --git a/interfaces/log-parser/oop/logcount.go b/interfaces/log-parser/oop/logcount.go
new file mode 100644
index 0000000..60a8b46
--- /dev/null
+++ b/interfaces/log-parser/oop/logcount.go
@@ -0,0 +1,33 @@
+// 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"
+
+// logCount counts the yielded records
+type logCount struct {
+	iterator
+	n int
+}
+
+func (lc *logCount) each(yield resultFn) error {
+	err := lc.iterator.each(func(r result) {
+		lc.n++
+		yield(r)
+	})
+
+	if err != nil {
+		// lc.n+1: iterator.each won't call yield on err
+		return fmt.Errorf("record %d: %v", lc.n+1, err)
+	}
+	return nil
+}
+
+func (lc *logCount) count() int {
+	return lc.n
+}
diff --git a/interfaces/log-parser/oop/main.go b/interfaces/log-parser/oop/main.go
index ffe93fc..80f8dee 100644
--- a/interfaces/log-parser/oop/main.go
+++ b/interfaces/log-parser/oop/main.go
@@ -9,18 +9,11 @@ package main
 
 import (
 	"log"
-	// "fmt"
 	"os"
 )
 
 func main() {
-	an := newAnalysis()
-	// an.filterBy(notUsing(domainExtFilter("io", "com")))
-	// an.filterBy(domainFilter("org"))
-	// an.groupBy(domainGrouper)
-
-	src := newTextLog(os.Stdin)
-	dst := newTextReport()
+	// newGrouper(domainGrouper)
 
 	// s := &chartReport{
 	//  title:  "visits per domain",
@@ -28,7 +21,17 @@ func main() {
 	//  height: 800,
 	// }
 
-	pipe := newPipeline(src, dst, an)
+	// pipe, err := fromFile("../logs/log.jsonl")
+	// if err != nil {
+	// 	log.Fatalln(err)
+	// }
+
+	pipe := newPipeline(
+		newTextLog(os.Stdin),
+		newTextReport(),
+		filterBy(domainExtFilter("com", "io")),
+		groupBy(domainGrouper),
+	)
 
 	if err := pipe.run(); err != nil {
 		log.Fatalln(err)
diff --git a/interfaces/log-parser/oop/pipeline.go b/interfaces/log-parser/oop/pipeline.go
index 481df94..ddc1b37 100644
--- a/interfaces/log-parser/oop/pipeline.go
+++ b/interfaces/log-parser/oop/pipeline.go
@@ -8,61 +8,71 @@
 package main
 
 import (
+	"fmt"
 	"os"
 	"strings"
 )
 
 type resultFn func(result)
 
-type iterator interface {
-	each(resultFn) error
-}
+type iterator interface{ each(resultFn) error }
+type digester interface{ digest(iterator) error }
 
-type transformer interface {
-	transform(result)
+type transform interface {
+	digester
 	iterator
 }
 
-type reporter interface {
-	report(iterator) error
-}
-
 type pipeline struct {
-	src  iterator
-	dst  reporter
-	tran transformer
+	src   iterator
+	trans []transform
+	dst   digester
 }
 
-func newPipeline(source iterator, r reporter, t transformer) *pipeline {
+func (p *pipeline) run() error {
+	defer func() {
+		n := p.src.(*logCount).count()
+		fmt.Printf("%d records processed.\n", n)
+	}()
+
+	last := p.src
+
+	for _, t := range p.trans {
+		if err := t.digest(last); err != nil {
+			return err
+		}
+		last = t
+	}
+
+	return p.dst.digest(last)
+}
+
+func newPipeline(src iterator, dst digester, t ...transform) *pipeline {
 	return &pipeline{
-		src:  source,
-		dst:  r,
-		tran: t,
+		src:   &logCount{iterator: src},
+		dst:   dst,
+		trans: t,
 	}
 }
 
 // fromFile generates a default report
-func fromFile(path string) (err error) {
+func fromFile(path string) (*pipeline, error) {
 	f, err := os.Open(path)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	var src iterator
 	switch {
 	case strings.HasSuffix(path, ".txt"):
 		src = newTextLog(f)
-	case strings.HasSuffix(path, ".json"):
+	case strings.HasSuffix(path, ".jsonl"):
 		src = newJSONLog(f)
 	}
 
-	p := newPipeline(src, newTextReport(), newAnalysis())
-	return p.run()
-}
-
-func (p *pipeline) run() error {
-	if err := p.src.each(p.tran.transform); err != nil {
-		return err
-	}
-	return p.dst.report(p.tran)
+	return newPipeline(
+		src,
+		newTextReport(),
+		groupBy(domainGrouper),
+	), nil
 }
diff --git a/interfaces/log-parser/oop/result.go b/interfaces/log-parser/oop/result.go
index 65c22bf..df256e6 100644
--- a/interfaces/log-parser/oop/result.go
+++ b/interfaces/log-parser/oop/result.go
@@ -1,5 +1,12 @@
 package main
 
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
 const fieldsLength = 4
 
 type result struct {
@@ -14,3 +21,42 @@ func (r result) add(other result) result {
 	r.uniques += other.uniques
 	return r
 }
+
+// UnmarshalText to a *result
+func (r *result) UnmarshalText(p []byte) (err error) {
+	fields := strings.Fields(string(p))
+	if len(fields) != fieldsLength {
+		return fmt.Errorf("wrong number of fields %q", fields)
+	}
+
+	r.domain, r.page = fields[0], fields[1]
+
+	r.visits, err = strconv.Atoi(fields[2])
+	if err != nil || r.visits < 0 {
+		return fmt.Errorf("wrong input %q", fields[2])
+	}
+
+	r.uniques, err = strconv.Atoi(fields[3])
+	if err != nil || r.uniques < 0 {
+		return fmt.Errorf("wrong input %q", fields[3])
+	}
+	return nil
+}
+
+// UnmarshalJSON to a *result
+func (r *result) UnmarshalJSON(data []byte) error {
+	var re struct {
+		Domain  string
+		Page    string
+		Visits  int
+		Uniques int
+	}
+
+	if err := json.Unmarshal(data, &re); err != nil {
+		return err
+	}
+
+	*r = result{re.Domain, re.Page, re.Visits, re.Uniques}
+
+	return nil
+}
diff --git a/interfaces/log-parser/oop/textlog.go b/interfaces/log-parser/oop/textlog.go
index 7137194..6e1749c 100644
--- a/interfaces/log-parser/oop/textlog.go
+++ b/interfaces/log-parser/oop/textlog.go
@@ -9,10 +9,7 @@ package main
 
 import (
 	"bufio"
-	"fmt"
 	"io"
-	"strconv"
-	"strings"
 )
 
 type textLog struct {
@@ -26,41 +23,17 @@ func newTextLog(r io.Reader) *textLog {
 func (p *textLog) each(yield resultFn) error {
 	defer readClose(p.reader)
 
-	var (
-		l  = 1
-		in = bufio.NewScanner(p.reader)
-	)
+	in := bufio.NewScanner(p.reader)
 
 	for in.Scan() {
-		r, err := extractFields(in.Text())
-		if err != nil {
-			return fmt.Errorf("line %d: %v", l, err)
+		r := new(result)
+
+		if err := r.UnmarshalText(in.Bytes()); err != nil {
+			return err
 		}
 
-		yield(r)
-		l++
+		yield(*r)
 	}
 
 	return in.Err()
 }
-
-func extractFields(s string) (r result, err error) {
-	fields := strings.Fields(s)
-	if len(fields) != fieldsLength {
-		return r, fmt.Errorf("wrong number of fields %q", fields)
-	}
-
-	r.domain, r.page = fields[0], 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
-}
diff --git a/interfaces/log-parser/oop/textreport.go b/interfaces/log-parser/oop/textreport.go
index 9cc98b9..7404b0a 100644
--- a/interfaces/log-parser/oop/textreport.go
+++ b/interfaces/log-parser/oop/textreport.go
@@ -27,7 +27,7 @@ func newTextReport() *textReport {
 	return new(textReport)
 }
 
-func (s *textReport) report(results iterator) error {
+func (s *textReport) digest(results iterator) error {
 	w := tabwriter.NewWriter(os.Stdout, minWidth, tabWidth, padding, ' ', flags)
 
 	write := fmt.Fprintf