Command: Cat command to concatenate and print detectors

Created command to accept list of detectors to concatenate and
print detectors. This is similar to cat command in unix.

cli/cmd/cat.go

@@ -0,0 +1,101 @@
+/*
+ * Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * or in the "license" file accompanying this file. This file 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 (
+	"encoding/json"
+	entity "esad/internal/entity/ad"
+	"esad/internal/handler/ad"
+	"fmt"
+	"github.com/spf13/cobra"
+)
+
+const (
+	commandCat = "cat"
+)
+
+//catCmd prints detectors configuration based on id and name pattern.
+var catCmd = &cobra.Command{
+	Use:   commandCat + " [flags] [list of detectors]",
+	Short: "Concatenate and print detectors based on id or name pattern",
+	Long:  `concatenate and print detectors based on pattern, use "" to make sure the name is not matched with pwd lists'`,
+	Run: func(cmd *cobra.Command, args []string) {
+		//If no args, display usage
+		if len(args) < 1 {
+			if err := cmd.Usage(); err != nil {
+				fmt.Println(err)
+			}
+			return
+		}
+		idStatus, _ := cmd.Flags().GetBool("id")
+		commandHandler, err := getCommandHandler()
+		if err != nil {
+			fmt.Println(err)
+		}
+		// default is name
+		action := ad.GetAnomalyDetectorsByNamePattern
+		if idStatus {
+			action = getDetectorsByID
+		}
+		if results := getDetectors(commandHandler, args, action); results != nil {
+			printDetectors(results)
+		}
+	},
+}
+
+func getDetectors(
+	commandHandler *ad.Handler, args []string, get func(*ad.Handler, string) (
+		[]*entity.DetectorOutput, error)) []*entity.DetectorOutput {
+	var results []*entity.DetectorOutput
+	for _, detector := range args {
+		output, err := get(commandHandler, detector)
+		if err != nil {
+			fmt.Println(err)
+			return nil
+		}
+		results = append(results, output...)
+	}
+	return results
+}
+
+//getDetectorsByID gets detector output based on ID as argument
+func getDetectorsByID(commandHandler *ad.Handler, ID string) ([]*entity.DetectorOutput, error) {
+
+	output, err := ad.GetAnomalyDetectorByID(commandHandler, ID)
+	if err != nil {
+		return nil, err
+	}
+	return []*entity.DetectorOutput{output}, nil
+}
+
+//printDetectors displays the list of output. Since this is json format, use indent function to
+// pretty print before printing on console
+func printDetectors(results []*entity.DetectorOutput) {
+	if results == nil {
+		return
+	}
+	for _, d := range results {
+		formattedOutput, err := json.MarshalIndent(d, "", "  ")
+		if err != nil {
+			fmt.Println(err)
+			return
+		}
+		fmt.Println(string(formattedOutput))
+	}
+}
+
+func init() {
+	esadCmd.AddCommand(catCmd)
+	catCmd.Flags().BoolP("name", "", true, "Input is name or pattern")
+	catCmd.Flags().BoolP("id", "", false, "Input is id")
+}