[#1541] neofs-cli: allow to print shards list output in JSON

Eventually more parameters will be supported (#1390) and after blobstor
configuration refactoring the output will certainly change. Implement
the simplest approach now.

Marshaling the result directly results in too ugly names and they cannot
be easily customized. Marshaling the results via `jsonpb` is better but
is not that flexible in terms of what we want to output.

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

cmd/neofs-cli/modules/control/shards_list.go

@@ -1,6 +1,8 @@
 package control
 
 import (
+	"bytes"
+	"encoding/json"
 	"fmt"
 
 	"github.com/mr-tron/base58"
@@ -25,6 +27,7 @@ func initControlShardsListCmd() {
 	flags := listShardsCmd.Flags()
 
 	flags.String(controlRPC, controlRPCDefault, controlRPCUsage)
+	flags.Bool(commonflags.JSON, false, "Print shard info as a JSON array")
 }
 
 func listShards(cmd *cobra.Command, _ []string) {
@@ -47,24 +50,37 @@ func listShards(cmd *cobra.Command, _ []string) {
 
 	verifyResponse(cmd, resp.GetSignature(), resp.GetBody())
 
+	isJSON, _ := cmd.Flags().GetBool(commonflags.JSON)
+	if isJSON {
+		prettyPrintShardsJSON(cmd, resp.GetBody().GetShards())
+	} else {
 		prettyPrintShards(cmd, resp.GetBody().GetShards())
+	}
+}
+
+func prettyPrintShardsJSON(cmd *cobra.Command, ii []*control.ShardInfo) {
+	out := make([]map[string]interface{}, 0, len(ii))
+	for _, i := range ii {
+		out = append(out, map[string]interface{}{
+			"shard_id":    base58.Encode(i.Shard_ID),
+			"mode":        shardModeToString(i.GetMode()),
+			"metabase":    i.GetMetabasePath(),
+			"blobstor":    i.GetBlobstorPath(),
+			"writecache":  i.GetWritecachePath(),
+			"error_count": i.GetErrorCount(),
+		})
+	}
+
+	buf := bytes.NewBuffer(nil)
+	enc := json.NewEncoder(buf)
+	enc.SetIndent("", "  ")
+	common.ExitOnErr(cmd, "cannot shard info to JSON: %w", enc.Encode(out))
+
+	cmd.Print(buf.String()) // pretty printer emits newline, to no need for Println
 }
 
 func prettyPrintShards(cmd *cobra.Command, ii []*control.ShardInfo) {
 	for _, i := range ii {
-		var mode string
-
-		switch i.GetMode() {
-		case control.ShardMode_READ_WRITE:
-			mode = "read-write"
-		case control.ShardMode_READ_ONLY:
-			mode = "read-only"
-		case control.ShardMode_DEGRADED:
-			mode = "degraded"
-		default:
-			mode = "unknown"
-		}
-
 		pathPrinter := func(name, path string) string {
 			if path == "" {
 				return ""
@@ -79,7 +95,20 @@ func prettyPrintShards(cmd *cobra.Command, ii []*control.ShardInfo) {
 			pathPrinter("Write-cache", i.GetWritecachePath())+
 			fmt.Sprintf("Error count: %d\n", i.GetErrorCount()),
 			base58.Encode(i.Shard_ID),
-			mode,
+			shardModeToString(i.GetMode()),
 		)
 	}
 }
+
+func shardModeToString(m control.ShardMode) string {
+	switch m {
+	case control.ShardMode_READ_WRITE:
+		return "read-write"
+	case control.ShardMode_READ_ONLY:
+		return "read-only"
+	case control.ShardMode_DEGRADED:
+		return "degraded"
+	default:
+		return "unknown"
+	}
+}