Add --output-file and pretty-print option

Allow local file as input for release index and corresponding
release metadata

main.go

@@ -6,6 +6,7 @@ import (
 	"flag"
 	"fmt"
 	"net/http"
+	"net/url"
 	"os"
 	"time"
 )
@@ -168,6 +169,10 @@ func run() error {
 	flag.StringVar(&releasesURL, "releases", "", "Release index location for the required stream")
 	var overrideFilename string
 	flag.StringVar(&overrideFilename, "override", "", "Override file location for the required stream")
+	var outputFile string
+	flag.StringVar(&outputFile, "output-file", "", "Save output into a file")
+	var prettyPrint bool
+	flag.BoolVar(&prettyPrint, "pretty-print", false, "Pretty-print output")
 
 	flag.Parse()
 
@@ -176,20 +181,36 @@ func run() error {
 	}
 
 	releasePath, err := ReleaseURL(releasesURL)
-
 	if err != nil {
 		return fmt.Errorf("Error with Release Index: %v", err)
 	}
 
-	resp, err := http.Get(releasePath)
+	parsedURL, err := url.Parse(releasePath)
 	if err != nil {
-		return fmt.Errorf("Error while fetching: %v", err)
+		return fmt.Errorf("Error while parsing release path: %v", err)
 	}
 
-	defer resp.Body.Close()
+	var decoder *json.Decoder
+	if parsedURL.Scheme == "" {
+		// It is most likely a local file.
+		releasesMetadataFile, err := os.Open(releasePath)
+		if err != nil {
+			return fmt.Errorf("Error opening file: %v", err)
+		}
+
+		defer releasesMetadataFile.Close()
+		decoder = json.NewDecoder(releasesMetadataFile)
+	} else {
+		resp, err := http.Get(releasePath)
+		if err != nil {
+			return fmt.Errorf("Error while fetching: %v", err)
+		}
+
+		defer resp.Body.Close()
+		decoder = json.NewDecoder(resp.Body)
+	}
 
 	var release Release
-	decoder := json.NewDecoder(resp.Body)
 	if err = decoder.Decode(&release); err != nil {
 		return fmt.Errorf("Error while decoding json: %v", err)
 	}
@@ -206,13 +227,6 @@ func run() error {
 		Architectures: streamArch,
 	}
 
-	streamFile, err := os.Create("stream.json")
-	if err != nil {
-		return fmt.Errorf("Can't open file: %v", err)
-	}
-
-	defer streamFile.Close()
-
 	if overrideFilename != "" {
 		overrideFile, err := os.Open(overrideFilename)
 		if err != nil {
@@ -247,11 +261,34 @@ func run() error {
 			return fmt.Errorf("Error during Unmarshal: %v", err)
 		}
 	}
-	// Save final json into file
-	encoder := json.NewEncoder(streamFile)
-	if err = encoder.Encode(&streamMetadata); err != nil {
+
+	// If outputFile option not specified print on stdout
+	if outputFile != "" {
+		streamFile, err := os.Create(outputFile)
+		if err != nil {
+			return fmt.Errorf("Can't open file: %v", err)
+		}
+
+		defer streamFile.Close()
+		// Save final json output into file
+		encoder := json.NewEncoder(streamFile)
+		if prettyPrint {
+			encoder.SetIndent("", "    ")
+		}
+		if err = encoder.Encode(&streamMetadata); err != nil {
+			return fmt.Errorf("Error while encoding: %v", err)
+		}
+		return nil
+	}
+
+	encoder := json.NewEncoder(os.Stdout)
+	if prettyPrint {
+		encoder.SetIndent("", "    ")
+	}
+	if err := encoder.Encode(&streamMetadata); err != nil {
 		return fmt.Errorf("Error while encoding: %v", err)
 	}
+
 	return nil
 }
 

release_index.go

@@ -4,6 +4,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"net/url"
+	"os"
 )
 
 // ReleaseIndex for accessing Release Index metadata
@@ -19,13 +21,31 @@ type Index struct {
 // ReleaseURL gets path for latest release.json available
 func ReleaseURL(releaseIndexURL string) (string, error) {
 	var relIndex ReleaseIndex
-	resp, err := http.Get(releaseIndexURL)
+	parsedURL, err := url.Parse(releaseIndexURL)
 	if err != nil {
 		return "", err
 	}
-	defer resp.Body.Close()
 
-	decoder := json.NewDecoder(resp.Body)
+	var decoder *json.Decoder
+	if parsedURL.Scheme == "" {
+		// It is most likely a local file.
+		releases, err := os.Open(releaseIndexURL)
+		if err != nil {
+			return "", err
+		}
+
+		defer releases.Close()
+		decoder = json.NewDecoder(releases)
+	} else {
+		resp, err := http.Get(releaseIndexURL)
+		if err != nil {
+			return "", err
+		}
+
+		defer resp.Body.Close()
+		decoder = json.NewDecoder(resp.Body)
+	}
+
 	if err := decoder.Decode(&relIndex); err != nil {
 		return "", err
 	}