resolves #6 add a decode command (#21)

cmd/decode.go

@@ -0,0 +1,85 @@
+package cmd
+
+import (
+ "bufio"
+ "bytes"
+ "compress/zlib"
+ "encoding/base64"
+ "fmt"
+ "io"
+ "net/url"
+ "os"
+ "path"
+ "strings"
+
+ "github.com/pkg/errors"
+ "github.com/spf13/cobra"
+)
+
+func Decode(_ *cobra.Command, args []string) {
+ input := args[0]
+ if input == "-" {
+ reader := bufio.NewReader(os.Stdin)
+ DecodeFromReader(reader)
+ } else {
+ DecodeFromInput(input)
+ }
+}
+
+func DecodeFromReader(reader io.Reader) {
+ text, err := GetTextFromReader(reader)
+ if err != nil {
+ exit(err)
+ }
+ result, err := DecodeInput(text)
+ if err != nil {
+ exit(err)
+ }
+ fmt.Println(result)
+}
+
+func DecodeFromInput(input string) {
+ result, err := DecodeInput(input)
+ if err != nil {
+ exit(err)
+ }
+ fmt.Println(result)
+}
+
+// takes a string encoded using deflate + base64 format and returns a decoded string
+func DecodeInput(input string) (string, error) {
+ // special case to extract the encoded diagram from a URL (GET request)
+ // expected format is: https://kroki.io/diagram/format/encoded
+ if strings.HasPrefix(input, "https://") || strings.HasPrefix(input, "http:https://") {
+ inputUrl, _ := getUrl(input)
+ if inputUrl != nil {
+ // get the last part of the URL
+ input = path.Base(inputUrl.Path)
+ }
+ }
+ result, err := base64.URLEncoding.DecodeString(input)
+ if err != nil {
+ return "", errors.Wrap(err, "fail to decode the input")
+ }
+ reader, err := zlib.NewReader(bytes.NewReader(result))
+ if err != nil {
+ return "", errors.Wrap(err, "fail to create the reader")
+ }
+ out := new(strings.Builder)
+ _, _ = io.Copy(out, reader)
+ return out.String(), nil
+}
+
+func getUrl(input string) (*url.URL, error) {
+ _, err := url.ParseRequestURI(input)
+ if err != nil {
+ return nil, err
+ }
+
+ u, err := url.Parse(input)
+ if err != nil || u.Scheme == "" || u.Host == "" {
+ return u, errors.New("invalid URL")
+ }
+
+ return u, nil
+}

cmd/decode_test.go

@@ -0,0 +1,36 @@
+package cmd
+
+import (
+ "bytes"
+ "testing"
+)
+
+func TestDecodeFromReader(t *testing.T) {
+ cases := []struct {
+ input string
+ expected string
+ }{
+ {
+ input: "eNpKyUwvSizIUHBXqPZIzcnJ17ULzy_KSakFBAAA__9sQAjG",
+ expected: "digraph G {Hello->World}\n",
+ },
+ {
+ input: "https://kroki.io/graphviz/svg/eNpKyUwvSizIUHBXqPZIzcnJ17ULzy_KSakFBAAA__9sQAjG",
+ expected: "digraph G {Hello->World}\n",
+ },
+ {
+ input: "http:https://localhost:8000/graphviz/svg/eNpKyUwvSizIUHBXqPZIzcnJ17ULzy_KSakFBAAA__9sQAjG",
+ expected: "digraph G {Hello->World}\n",
+ },
+ }
+ for _, c := range cases {
+ buf := bytes.NewBuffer([]byte(""))
+ buf.Write([]byte(c.input))
+ result := CaptureOutput(func() {
+ DecodeFromReader(buf)
+ })
+ if result != c.expected {
+ t.Errorf("DecodeFromReader error\nexpected: %s\nactual: %s", c.expected, result)
+ }
+ }
+}

cmd/root.go

@@ -30,6 +30,13 @@ var encodeCmd = &cobra.Command{
  Run: Encode,
 }
 
+var decodeCmd = &cobra.Command{
+ Use: "decode input",
+ Short: "Decode an encoded (deflate + base64) diagram",
+ Args: cobra.ExactArgs(1),
+ Run: Decode,
+}
+
 var versionCmd = &cobra.Command{
  Use: "version",
  Short: "Print the version of kroki",
@@ -56,6 +63,7 @@ func init() {
  RootCmd.AddCommand(versionCmd)
  RootCmd.AddCommand(convertCmd)
  RootCmd.AddCommand(encodeCmd)
+ RootCmd.AddCommand(decodeCmd)
 
  SetupConfig()
 

go.sum

@@ -40,6 +40,8 @@ github.com/ugorji/go/codec v0.0.0-20181204163529-d75b2dcb6bc8/go.mod h1:VFNgLljT
 github.com/xordataexchange/crypt v0.0.3-0.20170626215501-b2862e3d0a77/go.mod h1:aYKd//L2LvnjZzWKhF00oedf4jCCReLcmhLdhm1A27Q=
 github.com/yuzutech/kroki-go v0.5.0 h1:XWmxmG22/7PXsqt1TihYjYqmAcs3AO3JtvuwGF20Ehs=
 github.com/yuzutech/kroki-go v0.5.0/go.mod h1:Cys0gjXdlViePdrZ4AKMUyX4yVIAoIhMBhvpYPJahrk=
+github.com/yuzutech/kroki-go v0.5.0 h1:XWmxmG22/7PXsqt1TihYjYqmAcs3AO3JtvuwGF20Ehs=
+github.com/yuzutech/kroki-go v0.5.0/go.mod h1:Cys0gjXdlViePdrZ4AKMUyX4yVIAoIhMBhvpYPJahrk=
 golang.org/x/crypto v0.0.0-20181203042331-505ab145d0a9/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/sys v0.0.0-20181205085412-a5c9d58dba9a h1:1n5lsVfiQW3yfsRGu98756EH1YthsFqr/5mxHduZW2A=
 golang.org/x/sys v0.0.0-20181205085412-a5c9d58dba9a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=