diff --git a/.deadlines.yml b/.deadlines.yml
index 294f508..e7c2dc8 100644
--- a/.deadlines.yml
+++ b/.deadlines.yml
@@ -12,3 +12,13 @@
       score: 100
     - task: fetchall
       score: 100
+
+- group:    Basics
+  start:    20-02-2020 18:00
+  deadline: 02-03-2020 23:59
+  tasks:
+    - task: digitalclock
+      score: 300
+
+    - task: urlshortener
+      score: 200
diff --git a/digitalclock/README.md b/digitalclock/README.md
new file mode 100644
index 0000000..4528ad2
--- /dev/null
+++ b/digitalclock/README.md
@@ -0,0 +1,114 @@
+## digitalclock
+
+В этой задаче нужно написать http server,
+который по запросу `/?time=hh:mm:ss` вернет PNG с данным временем.
+
+Сервер должен слушать порт, переданный через аргумент `--port`.
+
+### Примеры
+
+Запуск:
+```
+$ digitalclock -port 6029
+```
+
+После запуска можно открыть в браузере `http://localhost:6029/?time=15:04:05` и получить png наподобие этой:
+
+![Image description](assets/150405.png)
+
+Если параметр `time` не задан (или равен ""), сервен должен вернуть текущее время.
+В этом случае при обновлении страницы картинка должна меняться.
+
+В запросе также нужно поддержать параметр 1 <=`k` <= 30,
+который отвечает за увеличение картинки в `k` раз:
+
+http://localhost:6029/?time=15:04:05?k=15
+
+![Image description](assets/150405_15.png)
+
+На невалидных `time` и `k` сервер должен возврщать произвольное сообщение об ошибке и http status 400 (Bad Request):
+
+```
+$ curl -i "http://localhost:6029/?k=100" 
+HTTP/1.1 400 Bad Request
+Content-Type: text/plain; charset=utf-8
+X-Content-Type-Options: nosniff
+Date: Fri, 14 Feb 2020 02:02:41 GMT
+Content-Length: 10
+
+invalid k
+```
+
+В случае успеха приложение должно возвращать http status 200 (OK),
+а также проставлять http header `Content-Type: image/png`:
+
+```
+$ curl -i "http://localhost:6029/"                   
+HTTP/1.1 200 OK
+Content-Type: image/png
+Date: Fri, 14 Feb 2020 02:08:19 GMT
+Content-Length: 193
+...
+```
+
+### Формат
+
+`hh:mm:ss`
+
+В [./symbols.go](./symbols.go) определены строковые константы, кодирующие цифры и двоеточие.
+Один символ константы (отличный от '\n') - 1 пиксель.
+'.' должны кодироваться в белый цвет, '1' - в бирюзовый (переменная **Cyan** в [./symbols.go](./symbols.go)).
+Все константы имеют одинаковую высоту `h`, все цифры имеют одинаковую ширину `w`.
+
+`k` отличный от 1 (default) превращает каждый пиксель `p` картинки в блок `k x k` пикселей `p`.
+Высота результирующей картинки - `h * k`, ширина - `(6 * w + 2 * w_colon) * k`,
+где `w_colon` ширина константы, соответствующей ':'.
+
+### Проверка решения
+
+Для запуска тестов нужно выполнить следующую команду:
+
+```
+go test -v ./digitalclock/...
+```
+
+### Запуск программы
+
+```
+go run -v ./digitalclock/...
+```
+
+### Компиляция
+
+```
+go install ./digitalclock/...
+```
+
+После выполнения в `$GOPATH/bin` появится исполняемый файл с именем `digitalclock`.
+
+### Walkthrough
+
+1. парсинг аргументов командной строки https://gobyexample.com/command-line-flags
+2. http server: https://p.go.manytask.org/00-intro/lecture.slide#23
+3. url params: https://golang.org/pkg/net/url/#URL.Query
+3. форматирование времени: https://gobyexample.com/time-formatting-parsing
+4. работа с картинками: https://golang.org/pkg/image/
+
+Пример, создания простой png размера 5x5:
+```go
+package main
+
+import (
+        "image"
+        "image/color"
+        "image/png"
+        "os"
+)
+
+func main() {
+        img := image.NewRGBA(image.Rect(0, 0, 5, 5))
+        img.Set(2, 2, color.RGBA{255, 0, 0, 255})
+        f, _ := os.Create("/tmp/img.png")
+        png.Encode(f, img)
+}
+```
diff --git a/digitalclock/assets/150405.png b/digitalclock/assets/150405.png
new file mode 100644
index 0000000..e9c67b2
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diff --git a/digitalclock/assets/150405_15.png b/digitalclock/assets/150405_15.png
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diff --git a/digitalclock/main.go b/digitalclock/main.go
new file mode 100644
index 0000000..cab7d3a
--- /dev/null
+++ b/digitalclock/main.go
@@ -0,0 +1,7 @@
+// +build !solution
+
+package main
+
+func main() {
+
+}
diff --git a/digitalclock/main_test.go b/digitalclock/main_test.go
new file mode 100644
index 0000000..b5b70cc
--- /dev/null
+++ b/digitalclock/main_test.go
@@ -0,0 +1,243 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"image"
+	"image/png"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"os"
+	"os/exec"
+	"path"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"gitlab.com/slon/shad-go/tools/testtool"
+)
+
+const importPath = "gitlab.com/slon/shad-go/digitalclock"
+
+var binCache testtool.BinCache
+
+func TestMain(m *testing.M) {
+	os.Exit(func() int {
+		var teardown testtool.CloseFunc
+		binCache, teardown = testtool.NewBinCache()
+		defer teardown()
+
+		return m.Run()
+	}())
+}
+
+func startServer(t *testing.T) (port string, stop func()) {
+	binary, err := binCache.GetBinary(importPath)
+	require.NoError(t, err)
+
+	port, err = testtool.GetFreePort()
+	require.NoError(t, err, "unable to get free port")
+
+	cmd := exec.Command(binary, "-port", port)
+	cmd.Stdout = nil
+	cmd.Stderr = os.Stderr
+
+	require.NoError(t, cmd.Start())
+
+	done := make(chan error)
+	go func() {
+		done <- cmd.Wait()
+	}()
+
+	stop = func() {
+		_ = cmd.Process.Kill()
+		<-done
+	}
+
+	if err = testtool.WaitForPort(t, time.Second*30, port); err != nil {
+		stop()
+	}
+
+	require.NoError(t, err)
+	return
+}
+
+func readImage(fname string) (image.Image, error) {
+	f, err := os.Open(fname)
+	if err != nil {
+		return nil, fmt.Errorf("unable to open %s: %w", fname, err)
+	}
+	defer func() { _ = f.Close() }()
+
+	img, _, err := image.Decode(f)
+	if err != nil {
+		return nil, fmt.Errorf("unable to decode %s: %w", fname, err)
+	}
+
+	return img, nil
+}
+
+func abs(a, b uint32) int64 {
+	if a > b {
+		return int64(a - b)
+	}
+	return int64(b - a)
+}
+
+func calcImgDiff(i1, i2 image.Image) float64 {
+	w, h := i1.Bounds().Dx(), i1.Bounds().Dy()
+
+	var sum int64
+	for x := 0; x < w; x++ {
+		for y := 0; y < h; y++ {
+			r1, g1, b1, _ := i1.At(x, y).RGBA()
+			r2, g2, b2, _ := i2.At(x, y).RGBA()
+			sum += abs(r1, r2)
+			sum += abs(g1, g2)
+			sum += abs(b1, b2)
+		}
+	}
+
+	return float64(sum) / (float64(w*h) * 0xffff * 3) * 100.0
+}
+
+func queryImage(t *testing.T, c *http.Client, url string) image.Image {
+	t.Logf("querying: %s", url)
+
+	resp, err := c.Get(url)
+	require.NoError(t, err)
+	defer func() { _ = resp.Body.Close() }()
+
+	require.Equal(t, http.StatusOK, resp.StatusCode)
+	require.Equal(t, "image/png", resp.Header.Get("Content-Type"))
+
+	img, err := png.Decode(resp.Body)
+	require.Nil(t, err)
+
+	return img
+}
+
+func TestDigitalClock_valid(t *testing.T) {
+	port, stop := startServer(t)
+	defer stop()
+
+	files, err := ioutil.ReadDir("./testdata")
+	require.Nil(t, err)
+
+	c := &http.Client{Timeout: time.Second * 10}
+
+	for _, f := range files {
+		t.Run(f.Name(), func(t *testing.T) {
+			parts := strings.SplitN(strings.TrimSuffix(f.Name(), ".png"), "_", 2)
+
+			v := url.Values{}
+			v.Add("time", parts[0])
+			v.Add("k", parts[1])
+
+			u := fmt.Sprintf("http://localhost:%s/?%s", port, v.Encode())
+			img := queryImage(t, c, u)
+
+			expected, err := readImage(path.Join("testdata", f.Name()))
+			require.NoError(t, err)
+
+			w, h := img.Bounds().Dx(), img.Bounds().Dy()
+			ew, eh := expected.Bounds().Dx(), expected.Bounds().Dy()
+			if w != ew || h != eh {
+				t.Errorf("expected size %d x %d got %d x %d", ew, eh, w, h)
+			}
+
+			diff := calcImgDiff(img, expected)
+			t.Logf("image diff: %.2f %%", diff)
+			require.True(t, diff < 1.0,
+				fmt.Sprintf("%s images are too different (%.2f %%)", f.Name(), diff))
+		})
+	}
+}
+
+func TestDigitalClock_invalid(t *testing.T) {
+	port, stop := startServer(t)
+	defer stop()
+
+	c := &http.Client{Timeout: time.Second * 10}
+
+	type TestCase struct {
+		Time string `json:"time"`
+		K    string `json:"k"`
+	}
+
+	testName := func(tc *TestCase) string {
+		data, err := json.Marshal(tc)
+		require.Nil(t, err)
+		return string(data)
+	}
+
+	for _, tc := range []*TestCase{
+		{K: "0"},
+		{K: "31"},
+		{K: "2.5"},
+		{K: "f"},
+		{Time: "15:04"},
+		{Time: "15:04:0"},
+		{Time: "3:04:05"},
+		{Time: "15:4:05"},
+		{Time: "24:00:00"},
+		{Time: "00:00:60"},
+		{Time: "f"},
+	} {
+		t.Run(testName(tc), func(t *testing.T) {
+			v := url.Values{}
+			if tc.Time != "" {
+				v.Add("time", tc.Time)
+			}
+			if tc.K != "" {
+				v.Add("k", tc.K)
+			}
+
+			u := fmt.Sprintf("http://localhost:%s/?%s", port, v.Encode())
+			t.Logf("querying: %s", u)
+
+			resp, err := c.Get(u)
+			require.NoError(t, err)
+			defer func() { _ = resp.Body.Close() }()
+
+			require.Equal(t, http.StatusBadRequest, resp.StatusCode)
+		})
+	}
+}
+
+func TestDigitalClock_now(t *testing.T) {
+	port, stop := startServer(t)
+	defer stop()
+
+	c := &http.Client{Timeout: time.Second * 10}
+
+	for _, k := range []int{1, 10, 29} {
+		k := k
+		t.Run(fmt.Sprintf("k=%d", k), func(t *testing.T) {
+			v := url.Values{"k": []string{strconv.Itoa(k)}}
+			u := fmt.Sprintf("http://localhost:%s/?%s", port, v.Encode())
+			img := queryImage(t, c, u)
+
+			w, h := img.Bounds().Dx(), img.Bounds().Dy()
+			ew, eh := getExpectedWidth(k), getExpectedHeight(k)
+			if w != ew || h != eh {
+				t.Errorf("expected size %d x %d got %d x %d", ew, eh, w, h)
+			}
+		})
+	}
+}
+
+func getSymbolWidth(s string) int {
+	return len(strings.SplitN(s, "\n", 2)[0])
+}
+
+func getExpectedWidth(k int) int {
+	return (getSymbolWidth(Zero)*6 + getSymbolWidth(Colon)*2) * k
+}
+
+func getExpectedHeight(k int) int {
+	return len(strings.Split(Zero, "\n")) * k
+}
diff --git a/digitalclock/symbols.go b/digitalclock/symbols.go
new file mode 100644
index 0000000..8578102
--- /dev/null
+++ b/digitalclock/symbols.go
@@ -0,0 +1,152 @@
+// +build !change
+
+package main
+
+import "image/color"
+
+var Cyan = color.RGBA{R: 100, G: 200, B: 200, A: 0xff}
+
+const (
+	Zero = `........
+.111111.
+.111111.
+.11..11.
+.11..11.
+.11..11.
+.11..11.
+.11..11.
+.11..11.
+.111111.
+.111111.
+........`
+
+	One = `........
+.....11.
+.....11.
+.....11.
+.....11.
+.....11.
+.....11.
+.....11.
+.....11.
+.....11.
+.....11.
+........`
+
+	Two = `........
+.111111.
+.111111.
+.....11.
+.....11.
+.111111.
+.111111.
+.11.....
+.11.....
+.111111.
+.111111.
+........`
+
+	Three = `........
+.111111.
+.111111.
+.....11.
+.....11.
+.111111.
+.111111.
+.....11.
+.....11.
+.111111.
+.111111.
+........`
+
+	Four = `........
+.11..11.
+.11..11.
+.11..11.
+.11..11.
+.111111.
+.111111.
+.....11.
+.....11.
+.....11.
+.....11.
+........`
+
+	Five = `........
+.111111.
+.111111.
+.11.....
+.11.....
+.111111.
+.111111.
+.....11.
+.....11.
+.111111.
+.111111.
+........`
+
+	Six = `........
+.111111.
+.111111.
+.11.....
+.11.....
+.111111.
+.111111.
+.11..11.
+.11..11.
+.111111.
+.111111.
+........`
+
+	Seven = `........
+.111111.
+.111111.
+.....11.
+.....11.
+.....11.
+.....11.
+.....11.
+.....11.
+.....11.
+.....11.
+........`
+
+	Eight = `........
+.111111.
+.111111.
+.11..11.
+.11..11.
+.111111.
+.111111.
+.11..11.
+.11..11.
+.111111.
+.111111.
+........`
+
+	Nine = `........
+.111111.
+.111111.
+.11..11.
+.11..11.
+.111111.
+.111111.
+.....11.
+.....11.
+.....11.
+.....11.
+........`
+
+	Colon = `....
+....
+....
+....
+.11.
+.11.
+....
+.11.
+.11.
+....
+....
+....`
+)
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new file mode 100644
index 0000000..b9965aa
Binary files /dev/null and b/digitalclock/testdata/22:55:07_23.png differ
diff --git a/digitalclock/testdata/23:43:50_25.png b/digitalclock/testdata/23:43:50_25.png
new file mode 100644
index 0000000..7db2d18
Binary files /dev/null and b/digitalclock/testdata/23:43:50_25.png differ
diff --git a/go.mod b/go.mod
index a13edd4..13e7d01 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,7 @@ module gitlab.com/slon/shad-go
 go 1.13
 
 require (
+	github.com/go-resty/resty/v2 v2.1.0
 	github.com/spf13/cobra v0.0.5
 	github.com/stretchr/testify v1.4.0
 	go.uber.org/goleak v1.0.0
diff --git a/go.sum b/go.sum
index 177e085..51612cd 100644
--- a/go.sum
+++ b/go.sum
@@ -8,11 +8,15 @@ github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSs
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
+github.com/go-resty/resty/v2 v2.1.0 h1:Z6IefCpUMfnvItVJaJXWv/pMiiD11So35QgwEELsldE=
+github.com/go-resty/resty/v2 v2.1.0/go.mod h1:dZGr0i9PLlaaTD4H/hoZIDjQ+r6xq8mgbRzHZf7f2J8=
 github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
 github.com/inconshreveable/mousetrap v1.0.0 h1:Z8tu5sraLXCXIcARxBp/8cbvlwVa7Z1NHg9XEKhtSvM=
 github.com/inconshreveable/mousetrap v1.0.0/go.mod h1:PxqpIevigyE2G7u3NXJIT2ANytuPF1OarO4DADm73n8=
+github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/magiconair/properties v1.8.0/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
 github.com/mitchellh/go-homedir v1.1.0/go.mod h1:SfyaCUpYCn1Vlf4IUYiD9fPX4A5wJrkLzIz1N1q0pr0=
@@ -48,6 +52,8 @@ golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859 h1:R/3boaszxrf1GEUWTVDzSKVwLmSJpwZ1yqXm8j0v2QI=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20190628185345-da137c7871d7 h1:rTIdg5QFRR7XCaK4LCjBiPbx8j4DQRpdYMnGn/bJUEU=
+golang.org/x/net v0.0.0-20190628185345-da137c7871d7/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58 h1:8gQV6CLnAEikrhgkHFbMAEhagSSnXWGV915qUMm9mrU=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20181205085412-a5c9d58dba9a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -63,6 +69,7 @@ golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898 h1:/atklqdjdhuosWIl6AIbO
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
diff --git a/urlshortener/README.md b/urlshortener/README.md
new file mode 100644
index 0000000..bb9425a
--- /dev/null
+++ b/urlshortener/README.md
@@ -0,0 +1,99 @@
+## urlshortener
+
+В этой задаче нужно написать http сервер со следующим API:
+
+* POST /shorten {"url": "\<URL\>"} -> {"key": "\<KEY\>"}
+* GET /go/\<KEY\> -> 302
+
+GET и POST - это методы HTTP. GET запрос используется для того, чтобы получать данные, а POST - чтобы добавлять и модифицировать.
+
+В тело `/shorten` запроса будет передаваться json вида
+```
+{"url":"https://github.com/golang/go/wiki/CodeReviewComments"}
+```
+
+Сервер должен ответить json'ом следующего вида:
+```
+{
+  "url": "https://github.com/golang/go/wiki/CodeReviewComments",
+  "key": "ed1De1"
+}
+```
+
+`ed1De1` здесь - это сгенерированное сервисом число.
+
+После такого `/shorten` можно делать `/go/ed1De1`.
+Ответ должен иметь иметь HTTP код 302.
+302 указывает на то, что запрошенный ресурс был временно перемещен на другой адрес (передаваемый в HTTP header'е `Location`).
+
+Если открыть http://localhost:6029/go/ed1De1 в браузере, тот перенаправит на https://github.com/golang/go/wiki/CodeReviewComments.
+
+Сервер должен слушать порт, переданный через аргумент `--port`.
+
+### Примеры
+
+Запуск:
+```
+$ urlshortener -port 6029
+```
+
+Успешное добавление URL'а (200, Content-Type: application/json):
+```
+$ curl -i -X POST  "localhost:6029/shorten" -d '{"url":"https://github.com/golang/go/wiki/CodeReviewComments"}'
+HTTP/1.1 200 OK
+Content-Type: application/json
+Date: Sat, 15 Feb 2020 23:35:26 GMT
+Content-Length: 82
+
+{"url":"https://github.com/golang/go/wiki/CodeReviewComments","key":"65ed150831"}
+```
+
+Невалидный json (400):
+```
+$ curl -i -X POST  "localhost:6029/shorten" -d '{"url":"https://github.com'                                   
+HTTP/1.1 400 Bad Request
+Content-Type: text/plain; charset=utf-8
+X-Content-Type-Options: nosniff
+Date: Sat, 15 Feb 2020 23:30:27 GMT
+Content-Length: 16
+
+invalid request
+```
+
+Успешный запрос (302, Location header):
+```
+$ curl -i -X GET  "localhost:6029/go/c1464c853a"                                                               
+HTTP/1.1 302 Found
+Content-Type: text/html; charset=utf-8
+Location: https://github.com/golang/go/wiki/CodeReviewComments
+Date: Sat, 15 Feb 2020 23:25:26 GMT
+Content-Length: 75
+
+<a href="https://github.com/golang/go/wiki/CodeReviewComments">Found</a>.
+```
+
+Несуществующий key (404):
+```
+$ curl -i -X GET  "localhost:6029/go/uaaab"
+HTTP/1.1 404 Not Found
+Content-Type: text/plain; charset=utf-8
+X-Content-Type-Options: nosniff
+Date: Sat, 15 Feb 2020 23:26:48 GMT
+Content-Length: 14
+
+key not found
+```
+
+### Состояние
+
+Своё состояние сервис должен целиком хранить в памяти.
+Стандартный http server на каждый запрос запускает handler в отдельной горутине (https://golang.org/pkg/net/http/#Serve),
+поэтому доступ к состоянию нужно защитить. Например, это можно сделать с помощью [мьютекса](https://golang.org/pkg/sync/#Mutex).
+
+## Ссылки
+
+1. Пример web сервера и работы с общим состоянием: https://p.go.manytask.org/00-intro/lecture.slide#24
+2. протокол HTTP: https://ru.wikipedia.org/wiki/HTTP
+3. http multiplexer: https://golang.org/pkg/net/http/#ServeMux
+4. десериализация json'а: https://golang.org/pkg/encoding/json/#example_Unmarshal
+5. генерация случайных данных: https://golang.org/pkg/math/rand/
diff --git a/urlshortener/main.go b/urlshortener/main.go
new file mode 100644
index 0000000..cab7d3a
--- /dev/null
+++ b/urlshortener/main.go
@@ -0,0 +1,7 @@
+// +build !solution
+
+package main
+
+func main() {
+
+}
diff --git a/urlshortener/main_test.go b/urlshortener/main_test.go
new file mode 100644
index 0000000..b67497b
--- /dev/null
+++ b/urlshortener/main_test.go
@@ -0,0 +1,200 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"os/exec"
+	"reflect"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/go-resty/resty/v2"
+	"github.com/stretchr/testify/require"
+	"gitlab.com/slon/shad-go/tools/testtool"
+)
+
+const importPath = "gitlab.com/slon/shad-go/urlshortener"
+
+var binCache testtool.BinCache
+
+func TestMain(m *testing.M) {
+	os.Exit(func() int {
+		var teardown testtool.CloseFunc
+		binCache, teardown = testtool.NewBinCache()
+		defer teardown()
+
+		return m.Run()
+	}())
+}
+
+func startServer(t *testing.T) (port string, stop func()) {
+	binary, err := binCache.GetBinary(importPath)
+	require.NoError(t, err)
+
+	port, err = testtool.GetFreePort()
+	require.NoError(t, err, "unable to get free port")
+
+	cmd := exec.Command(binary, "-port", port)
+	cmd.Stdout = nil
+	cmd.Stderr = os.Stderr
+
+	require.NoError(t, cmd.Start())
+
+	done := make(chan error)
+	go func() {
+		done <- cmd.Wait()
+	}()
+
+	stop = func() {
+		_ = cmd.Process.Kill()
+		<-done
+	}
+
+	if err = testtool.WaitForPort(t, time.Second*5, port); err != nil {
+		stop()
+	}
+
+	require.NoError(t, err)
+	return
+}
+
+func add(t *testing.T, c *resty.Client, shortenerURL, request string) string {
+	type Response struct {
+		URL string `json:"url"`
+		Key string `json:"key"`
+	}
+
+	resp, err := c.R().
+		SetBody(map[string]interface{}{"url": request}).
+		SetResult(&Response{}).
+		Post(shortenerURL)
+
+	require.NoError(t, err)
+	require.Equal(t, http.StatusOK, resp.StatusCode())
+	response := resp.Result().(*Response)
+	require.Equal(t, request, response.URL)
+	require.Contains(t, resp.Header().Get("Content-Type"), "application/json")
+
+	return response.Key
+}
+
+func TestURLShortener_redirect(t *testing.T) {
+	port, stop := startServer(t)
+	defer stop()
+
+	var mu sync.Mutex
+	redirects := make(map[string]struct{})
+
+	redirectTarget := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		mu.Lock()
+		redirects[r.RequestURI] = struct{}{}
+		mu.Unlock()
+		_, _ = fmt.Fprintln(w, "hello")
+	}))
+
+	client := resty.New()
+	addURL := fmt.Sprintf("http://localhost:%s/shorten", port)
+
+	requests := make(map[string]struct{})
+	for i := 0; i < 10; i++ {
+		path := "/" + testtool.RandomName()
+		req := redirectTarget.URL + path
+		requests[path] = struct{}{}
+		key := add(t, client, addURL, req)
+
+		getURL := fmt.Sprintf("http://localhost:%s/go/%s", port, key)
+		resp, err := client.R().Get(getURL)
+		require.NoError(t, err)
+		require.Equal(t, http.StatusOK, resp.StatusCode())
+	}
+
+	mu.Lock()
+	defer mu.Unlock()
+
+	require.True(t, reflect.DeepEqual(requests, redirects),
+		fmt.Sprintf("expected: %+v, got: %+v", requests, redirects))
+}
+
+func TestURLShortener_badRequest(t *testing.T) {
+	port, stop := startServer(t)
+	defer stop()
+
+	u := fmt.Sprintf("http://localhost:%s/shorten", port)
+	resp, err := resty.New().R().
+		SetHeader("Content-Type", "application/json").
+		SetBody([]byte(`{"url":"abc}`)).
+		Post(u)
+
+	require.NoError(t, err)
+	require.Equal(t, http.StatusBadRequest, resp.StatusCode())
+}
+
+func TestURLShortener_badKey(t *testing.T) {
+	port, stop := startServer(t)
+	defer stop()
+
+	u := fmt.Sprintf("http://localhost:%s/go/%s", port, testtool.RandomName())
+	resp, err := resty.New().
+		SetRedirectPolicy(resty.RedirectPolicyFunc(func(*http.Request, []*http.Request) error {
+			return http.ErrUseLastResponse
+		})).R().
+		Get(u)
+
+	require.NoError(t, err)
+	require.Equal(t, http.StatusNotFound, resp.StatusCode())
+}
+
+func TestURLShortener_consistency(t *testing.T) {
+	port, stop := startServer(t)
+	defer stop()
+
+	client := resty.New()
+
+	get := func(originalURL, key string) {
+		getURL := fmt.Sprintf("http://localhost:%s/go/%s", port, key)
+
+		resp, err := client.
+			SetRedirectPolicy(resty.RedirectPolicyFunc(func(*http.Request, []*http.Request) error {
+				return http.ErrUseLastResponse
+			})).R().
+			Get(getURL)
+
+		require.NoError(t, err)
+		require.Equal(t, http.StatusFound, resp.StatusCode())
+		require.Contains(t, resp.Header().Get("Location"), originalURL)
+	}
+
+	var urls []string
+	for i := 0; i < 10; i++ {
+		urls = append(urls, testtool.RandomName())
+	}
+
+	keyToURL := make(map[string]string)
+	urlToKey := make(map[string]string)
+
+	addURL := fmt.Sprintf("http://localhost:%s/shorten", port)
+	for _, u := range urls {
+		key := add(t, client, addURL, u)
+
+		url, ok := keyToURL[key]
+		require.False(t, ok, fmt.Sprintf("duplicate key %s for urls [%s, %s]", key, u, url))
+
+		urlToKey[u] = key
+		keyToURL[key] = u
+	}
+
+	for _, u := range urls {
+		get(u, urlToKey[u])
+	}
+
+	for _, u := range urls {
+		key := add(t, client, addURL, u)
+
+		url, ok := keyToURL[key]
+		require.True(t, ok, fmt.Sprintf("different keys for the same url %s", u))
+		require.Equal(t, url, u)
+	}
+}