add du command support (#2802)

This command works like `du` command in unices i.e. summarize disk
usage of given TARGET recursively.

cmd/du-main.go

@@ -0,0 +1,174 @@
+/*
+ * MinIO Client (C) 2019 MinIO, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+import (
+	"fmt"
+	"net/url"
+	"strings"
+
+	humanize "github.com/dustin/go-humanize"
+	"github.com/fatih/color"
+	"github.com/minio/cli"
+	json "github.com/minio/mc/pkg/colorjson"
+	"github.com/minio/mc/pkg/console"
+	"github.com/minio/mc/pkg/probe"
+)
+
+// du specific flags.
+var (
+	duFlags = []cli.Flag{
+		cli.IntFlag{
+			Name:  "depth, d",
+			Usage: "print the total for a folder prefix only if it is N or fewer levels below the command line argument",
+		},
+	}
+)
+
+// Summarize disk usage.
+var duCmd = cli.Command{
+	Name:   "du",
+	Usage:  "Summarize disk usage folder prefixes recursively.",
+	Action: mainDu,
+	Before: setGlobalsFromContext,
+	Flags:  append(append(duFlags, ioFlags...), globalFlags...),
+	CustomHelpTemplate: `NAME:
+  {{.HelpName}} - {{.Usage}}
+
+USAGE:
+  {{.HelpName}} [FLAGS] TARGET
+
+FLAGS:
+  {{range .VisibleFlags}}{{.}}
+  {{end}}
+ENVIRONMENT VARIABLES:
+   MC_ENCRYPT_KEY: list of comma delimited prefix=secret values
+
+EXAMPLES:
+   1. Summarize disk usage of 'jazz-songs' bucket recursively.
+      $ {{.HelpName}} s3/jazz-songs
+
+   2. Summarize disk usage of 'louis' prefix in 'jazz-songs' bucket upto two levels.
+      $ {{.HelpName}} --depth=2 s3/jazz-songs/louis/
+`,
+}
+
+// Structured message depending on the type of console.
+type duMessage struct {
+	Prefix string `json:"prefix"`
+	Size   string `json:"size"`
+	Status string `json:"status"`
+}
+
+// Colorized message for console printing.
+func (r duMessage) String() string {
+	return console.Colorize("Du", fmt.Sprintf("%s\t%s", r.Size, r.Prefix))
+}
+
+// JSON'ified message for scripting.
+func (r duMessage) JSON() string {
+	msgBytes, e := json.MarshalIndent(r, "", " ")
+	fatalIf(probe.NewError(e), "Unable to marshal into JSON.")
+	return string(msgBytes)
+}
+
+func du(urlStr string, depth int, encKeyDB map[string][]prefixSSEPair) (int64, error) {
+	targetAlias, targetURL, _ := mustExpandAlias(urlStr)
+	if !strings.HasSuffix(targetURL, "/") {
+		targetURL += "/"
+	}
+
+	clnt, pErr := newClientFromAlias(targetAlias, targetURL)
+	if pErr != nil {
+		errorIf(pErr.Trace(urlStr), "Failed to summarize disk usage `"+urlStr+"`.")
+		return 0, exitStatus(globalErrorExitStatus) // End of journey.
+	}
+
+	isRecursive := false
+	isIncomplete := false
+	contentCh := clnt.List(isRecursive, isIncomplete, DirFirst)
+	size := int64(0)
+	for content := range contentCh {
+		if content.Err != nil {
+			errorIf(content.Err.Trace(urlStr), "Failed to find disk usage of `"+urlStr+"` recursively.")
+			return 0, exitStatus(globalErrorExitStatus)
+		}
+
+		if content.URL.String() == targetURL {
+			continue
+		}
+
+		if content.Type.IsDir() {
+			depth := depth
+			if depth > 0 {
+				depth--
+			}
+
+			subDirAlias := content.URL.Path
+			if targetAlias != "" {
+				subDirAlias = targetAlias + "/" + content.URL.Path
+			}
+			used, err := du(subDirAlias, depth, encKeyDB)
+			if err != nil {
+				return 0, err
+			}
+			size += used
+		} else {
+			size += content.Size
+		}
+	}
+
+	if depth != 0 {
+		u, err := url.Parse(targetURL)
+		if err != nil {
+			panic(err)
+		}
+
+		printMsg(duMessage{
+			Prefix: strings.Trim(u.Path, "/"),
+			Size:   humanize.Bytes(uint64(size)),
+			Status: "success",
+		})
+	}
+
+	return size, nil
+}
+
+// main for du command.
+func mainDu(ctx *cli.Context) error {
+	// Parse encryption keys per command.
+	encKeyDB, err := getEncKeys(ctx)
+	fatalIf(err, "Unable to parse encryption keys.")
+
+	// du specific flags.
+	depth := ctx.Int("depth")
+	if depth == 0 {
+		depth = -1
+	}
+
+	// Set color.
+	console.SetColor("Remove", color.New(color.FgGreen, color.Bold))
+
+	var duErr error
+	for _, urlStr := range ctx.Args() {
+		if _, err := du(urlStr, depth, encKeyDB); duErr == nil {
+			duErr = err
+		}
+	}
+
+	return duErr
+}

cmd/main.go

@@ -328,6 +328,7 @@ var appCmds = []cli.Command{
 	updateCmd,
 	versionCmd,
 	treeCmd,
+	duCmd,
 }
 
 func registerApp(name string) *cli.App {