Adding http-digital-clock.

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Arseny Balobanov 2020-02-15 22:41:14 +03:00
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## 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)
}
```

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// +build !solution
package main
func main() {
}

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package main
import (
"context"
"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
}
ctx, cancel := context.WithTimeout(context.Background(), time.Second*30)
defer cancel()
testtool.WaitForPort(ctx, port)
if ctx.Err() != nil {
err = ctx.Err()
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
}

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// +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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