diff --git a/sort-cli/Makefile b/sort-cli/Makefile
new file mode 100644
index 0000000..19ff9ab
--- /dev/null
+++ b/sort-cli/Makefile
@@ -0,0 +1,50 @@
+.DEFAULT_GOAL := help
+
+# ==================================================================================== #
+# HELPERS
+# ==================================================================================== #
+
+## help: print this help message
+.PHONY: help
+help:
+	@echo 'Usage:'
+	@sed -n 's/^##//p' ${MAKEFILE_LIST} | column -t -s ':' |  sed -e 's/^/ /'
+
+## all: tidy + audit + test/cover
+all: tidy audit test/cover
+
+# ==================================================================================== #
+# QUALITY CONTROL
+# ==================================================================================== #
+
+## tidy: format code and tidy modfile
+.PHONY: tidy
+tidy:
+	go fmt ./...
+	go mod tidy -v
+
+## audit: run quality control checks
+.PHONY: audit
+audit:
+	go mod verify
+	go vet ./...
+	go run honnef.co/go/tools/cmd/staticcheck@latest -checks=all,-ST1000,-U1000 ./...
+	go run golang.org/x/vuln/cmd/govulncheck@latest ./...
+	go test -race -buildvcs -vet=off ./...
+	go run github.com/golangci/golangci-lint/cmd/golangci-lint@latest run -v ./...
+
+
+# ==================================================================================== #
+# DEVELOPMENT
+# ==================================================================================== #
+
+## test: run all tests
+.PHONY: test
+test:
+	go test -v -race -buildvcs ./...
+
+## test/cover: run all tests and display coverage
+.PHONY: test/cover
+test/cover:
+	go test -v -race -buildvcs -coverprofile=/tmp/coverage.out ./...
+	go tool cover -html=/tmp/coverage.out
diff --git a/sort-cli/config.go b/sort-cli/config.go
new file mode 100644
index 0000000..5edf70d
--- /dev/null
+++ b/sort-cli/config.go
@@ -0,0 +1,26 @@
+package main
+
+import "flag"
+
+type Config struct {
+	Key     int
+	Numeric bool
+	Reverse bool
+	Unique  bool
+	Sources []string
+}
+
+func (c *Config) ParseFlags() {
+	flag.IntVar(&c.Key, "k", 0, "sort via column")
+	flag.BoolVar(&c.Numeric, "n", false, "compare according to string numerical value")
+	flag.BoolVar(&c.Reverse, "r", false, "reverse the result of comparisons")
+	flag.BoolVar(&c.Unique, "u", false, "output only the first of an equal run")
+
+	flag.Parse()
+
+	c.Sources = flag.Args()
+
+	if len(c.Sources) == 0 {
+		c.Sources = []string{"-"}
+	}
+}
diff --git a/sort-cli/content.go b/sort-cli/content.go
new file mode 100644
index 0000000..5222972
--- /dev/null
+++ b/sort-cli/content.go
@@ -0,0 +1,80 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"golang.org/x/exp/slices"
+	"io"
+	"log"
+	"strings"
+)
+
+type content [][]byte
+
+func (c *content) Sort(reverse bool) {
+	slices.SortFunc(*c, func(a, b []byte) int {
+		if reverse {
+			a, b = b, a
+		}
+
+		return slices.Compare(a, b)
+	})
+}
+
+func (c *content) Uniques() {
+	m := make(map[string]struct{}, len(*c))
+
+	*c = slices.DeleteFunc[content, []byte](*c, func(line []byte) bool {
+		if _, ok := m[string(line)]; !ok {
+			m[string(line)] = struct{}{}
+
+			return false
+		}
+
+		return true
+	})
+}
+
+func (c *content) String() string {
+	lines := *c
+
+	var n int
+	for _, line := range lines {
+		n += len(line)
+	}
+	n += len(lines) * len("\n")
+
+	var sb strings.Builder
+	sb.Grow(n)
+
+	for i, line := range lines {
+		if i > 0 {
+			sb.WriteString("\n")
+		}
+
+		for _, rn := range line {
+			sb.WriteByte(rn)
+		}
+	}
+
+	return sb.String()
+}
+
+func (c *content) Load(r io.Reader) {
+	br := bufio.NewReader(r)
+
+	for {
+		line, _, err := br.ReadLine()
+		if err != nil {
+			if errors.Is(io.EOF, err) {
+				*c = append(*c, line)
+
+				break
+			}
+
+			log.Fatalf("can't read line: %s", err)
+		}
+
+		*c = append(*c, line)
+	}
+}
diff --git a/sort-cli/content_test.go b/sort-cli/content_test.go
new file mode 100644
index 0000000..3858296
--- /dev/null
+++ b/sort-cli/content_test.go
@@ -0,0 +1,51 @@
+package main
+
+import (
+	"github.com/stretchr/testify/assert"
+	"strings"
+	"testing"
+)
+
+const input = `
+Zimbabwe
+Africa
+America
+Zimbabwe
+Africa
+`
+
+func TestLoad(t *testing.T) {
+	c := &content{}
+	c.Load(strings.NewReader(input))
+
+	assert.Equal(t, input, c.String())
+}
+
+func TestUnique(t *testing.T) {
+	cases := []struct {
+		Name     string
+		Content  string
+		Expected string
+	}{
+		{"Unique",
+			input,
+			`
+Zimbabwe
+Africa
+America`,
+		},
+	}
+
+	for _, tc := range cases {
+		tc := tc
+
+		t.Run(tc.Name, func(t *testing.T) {
+			c := &content{}
+			c.Load(strings.NewReader(tc.Content))
+
+			c.Uniques()
+
+			assert.Equal(t, tc.Expected, c.String())
+		})
+	}
+}
diff --git a/sort-cli/loader.go b/sort-cli/loader.go
new file mode 100644
index 0000000..fb9857a
--- /dev/null
+++ b/sort-cli/loader.go
@@ -0,0 +1,34 @@
+package main
+
+import (
+	"io"
+	"log"
+	"os"
+)
+
+func open(sources []string) io.Reader {
+	rs := make([]io.Reader, 0, len(sources))
+
+	for _, source := range sources {
+		var r io.Reader
+
+		if source == "-" {
+			r = os.Stdin
+		} else {
+			if _, err := os.Stat(source); err != nil {
+				log.Fatalf("file not exists: %s", source)
+			}
+
+			f, err := os.Open(source)
+			if err != nil {
+				log.Fatalf("file open file: %s", err)
+			}
+
+			r = f
+		}
+
+		rs = append(rs, r)
+	}
+
+	return io.MultiReader(rs...)
+}
diff --git a/sort-cli/main.go b/sort-cli/main.go
index 0bf900d..62b9d53 100644
--- a/sort-cli/main.go
+++ b/sort-cli/main.go
@@ -1,211 +1,31 @@
 package main
 
 import (
-	"bytes"
-	"flag"
-	"fmt"
-	"golang.org/x/exp/maps"
-	"io"
-	"log"
 	"os"
-	"sort"
-	"strings"
 )
 
-type Cfg struct {
-	Key     int
-	Numeric bool
-	Reverse bool
-	Unique  bool
-}
-
 func main() {
-	fmt.Print(run())
+	result := run()
+
+	if _, err := os.Stdout.WriteString(result); err != nil {
+		panic(err)
+	}
 
 	os.Exit(0)
 }
 
 func run() string {
-	var c Cfg
+	cfg := &Config{}
+	cfg.ParseFlags()
 
-	flag.IntVar(&c.Key, "k", 0, "sort via column")
-	flag.BoolVar(&c.Numeric, "n", false, "compare according to string numerical value")
-	flag.BoolVar(&c.Reverse, "r", false, "reverse the result of comparisons")
-	flag.BoolVar(&c.Unique, "u", false, "output only the first of an equal run")
-
-	flag.Parse()
-
-	return doSort(&c, flag.Args())
-}
-
-func doSort(cfg *Cfg, sources []string) string {
-	r := splitLines(load(sources), []byte("\n"), cfg.Key)
+	lines := content{}
+	lines.Load(open(cfg.Sources))
 
 	if cfg.Unique {
-		r = uniques(r)
+		lines.Uniques()
 	}
 
-	rs := &Rows{s: r, cfg: cfg}
-	sort.Sort(rs)
+	lines.Sort(cfg.Reverse)
 
-	return rs.String()
-}
-
-type Row struct {
-	Line   []byte
-	Column []byte
-}
-
-type Rows struct {
-	s   []*Row
-	cfg *Cfg
-}
-
-func (p *Rows) Len() int { return len(p.s) }
-func (p *Rows) Less(i, j int) bool {
-	s := p.s
-
-	lr := s[i]
-	rr := s[j]
-
-	if p.cfg.Reverse {
-		lr, rr = rr, lr
-	}
-
-	var l, r []rune
-
-	if p.cfg.Key == 0 {
-		l, r = bytes.Runes(lr.Line), bytes.Runes(rr.Line)
-	} else {
-		l, r = bytes.Runes(lr.Column), bytes.Runes(rr.Column)
-	}
-
-	ln := len(l)
-	rn := len(r)
-
-	for i := 0; i < min(ln, rn); i++ {
-		if l[i] == r[i] {
-			continue
-		}
-
-		return l[i] < r[i]
-	}
-
-	return ln < rn
-}
-
-func (p *Rows) Swap(i, j int) {
-	s := p.s
-
-	s[i], s[j] = s[j], s[i]
-}
-
-func (p *Rows) String() string {
-	r := p.s
-
-	var n int
-	for _, s := range r {
-		n += len(s.Line)
-	}
-	n += len(r) * len("\n")
-
-	var sb strings.Builder
-	sb.Grow(n)
-
-	for _, c := range r {
-		for _, rn := range c.Line {
-			sb.WriteByte(rn)
-		}
-
-		sb.WriteString("\n")
-	}
-
-	return sb.String()
-}
-
-func load(sources []string) []byte {
-	if len(sources) == 0 {
-		return loadStdin()
-	}
-
-	inputs := make([][]byte, 0, len(sources))
-	for _, path := range sources {
-		if path == "-" {
-			inputs = append(inputs, loadStdin())
-
-			continue
-		}
-
-		inputs = append(inputs, loadFile(path))
-	}
-
-	var totalSize int
-	for _, s := range inputs {
-		totalSize += len(s)
-	}
-
-	var b bytes.Buffer
-	b.Grow(totalSize)
-
-	for _, c := range inputs {
-		b.Write(c)
-	}
-
-	return b.Bytes()
-}
-
-func loadStdin() []byte {
-	b, err := io.ReadAll(os.Stdin)
-	if err != nil {
-		log.Fatalf("can't read stdin: %e", err)
-	}
-
-	return b
-}
-
-func loadFile(path string) []byte {
-	if _, err := os.Stat(path); err != nil {
-		log.Fatalf("file not exists: %s", path)
-	}
-
-	content, err := os.ReadFile(path)
-	if err != nil {
-		log.Fatalf("file open file: %s", err)
-	}
-
-	return content
-}
-
-func splitLines(b, sp []byte, key int) []*Row {
-	r := make([]*Row, 0, bytes.Count(b, sp))
-	for _, b := range bytes.Split(b, sp) {
-		var column []byte
-
-		if key != 0 {
-			bs := bytes.Split(b, []byte(" "))
-
-			if len(bs) < key {
-				continue // TODO is it error or not?
-				// log.Fatalf("Column for key \"%d\" doesn't exists", cfg.Key)
-			}
-
-			column = bs[key-1]
-		}
-
-		r = append(r, &Row{Line: b, Column: column})
-	}
-
-	return r
-}
-
-func uniques(r []*Row) []*Row {
-	m := make(map[string]*Row, len(r))
-
-	for _, r := range r {
-		r := r
-
-		m[string(r.Line)] = r
-	}
-
-	return maps.Values(m)
+	return lines.String()
 }