add video-ids output format for list cmd

cmd/youtubedr/info.go

@@ -76,8 +76,10 @@ var infoCmd = &cobra.Command{
 			})
 		}
 
-		exitOnError(writeOutput(os.Stdout, &videoInfo, func(w io.Writer) {
-			writeInfoOutput(w, &videoInfo)
+		exitOnError(writeOutput(os.Stdout, &videoInfo, map[string]outputWriter{
+			outputFormatPlain: func(w io.Writer) {
+				writeInfoOutput(w, &videoInfo)
+			},
 		}))
 	},
 }

cmd/youtubedr/list.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"strings"
 
 	"github.com/olekukonko/tablewriter"
 	"github.com/spf13/cobra"
@@ -41,13 +42,26 @@ var (
 				})
 			}
 
-			exitOnError(writeOutput(os.Stdout, &playlistInfo, func(w io.Writer) {
-				writePlaylistOutput(w, &playlistInfo)
+			exitOnError(writeOutput(os.Stdout, &playlistInfo, map[string]outputWriter{
+				outputFormatPlain: func(w io.Writer) {
+					writePlaylistOutput(w, &playlistInfo)
+				},
+				outputVideoIds: func(w io.Writer) {
+					writePlaylistVideoIdsOutput(w, &playlistInfo)
+				},
 			}))
 		},
 	}
 )
 
+func writePlaylistVideoIdsOutput(w io.Writer, info *PlaylistInfo) {
+	var ids []string
+	for _, v := range info.Videos {
+		ids = append(ids, v.ID)
+	}
+	fmt.Println(strings.Join(ids, " "))
+}
+
 func writePlaylistOutput(w io.Writer, info *PlaylistInfo) {
 	fmt.Println("Title:      ", info.Title)
 	fmt.Println("Author:     ", info.Author)

cmd/youtubedr/output_format.go

@@ -14,12 +14,13 @@ import (
 var outputFormat string
 
 const (
+	outputVideoIds    = "video-ids"
 	outputFormatPlain = "plain"
 	outputFormatJSON  = "json"
 	outputFormatXML   = "xml"
 )
 
-var outputFormats = []string{outputFormatPlain, outputFormatJSON, outputFormatXML}
+var outputFormats = []string{outputFormatPlain, outputFormatJSON, outputFormatXML, outputVideoIds}
 
 func addFormatFlag(flagSet *pflag.FlagSet) {
 	flagSet.StringVarP(&outputFormat, "format", "f", outputFormatPlain, "The output format ("+strings.Join(outputFormats, "/")+")")
@@ -37,10 +38,16 @@ func checkOutputFormat() error {
 
 type outputWriter func(w io.Writer)
 
-func writeOutput(w io.Writer, v interface{}, plainWriter outputWriter) error {
+func writeOutput(w io.Writer, v interface{}, writers map[string]outputWriter) error {
 	switch outputFormat {
+	case outputVideoIds:
+		fallthrough
 	case outputFormatPlain:
-		plainWriter(w)
+		writer, ok := writers[outputFormat]
+		if !ok {
+			return errInvalidFormat(outputFormat)
+		}
+		writer(w)
 		return nil
 	case outputFormatJSON:
 		encoder := json.NewEncoder(w)