add external pager support via ES_JSON_PAGER (#65)

pkg/cfg/config.go

@@ -106,6 +106,8 @@ type Config struct {
 
 	FromNode, ToNode             string // cluster reroute move: -f + -t
 	AllowPrimary, AcceptDataLoss bool   // cluster reroute cancel: -p,-a
+
+	Pager string // api repl: -p || PAGER
 }
 
 func NewConfig() *Config {

pkg/cfg/term.go

@@ -36,3 +36,14 @@ func GetTermWidth() int {
 
 	return 80
 }
+
+func GetTermHeight() int {
+	if term.IsTerminal(int(os.Stdout.Fd())) {
+		_, height, err := term.GetSize(int(os.Stdout.Fd()))
+		if err == nil {
+			return height
+		}
+	}
+
+	return 25
+}

pkg/es/api.go

@@ -141,14 +141,50 @@ func ApiRepl(conf *cfg.Config) error {
 			fmt.Printf("failed to call API: %s\n", esErrorString(err))
 		}
 
-		if err := prettyfiJson(conf, raw); err != nil {
-			fmt.Println(err)
-		}
+		pageJsonOutput(conf, raw)
 	}
 
 	return nil
 }
 
+func pageJsonOutput(conf *cfg.Config, raw []byte) {
+	tmpconf := &cfg.Config{HaveJQ: conf.HaveJQ}
+
+	if conf.Pager != "" {
+		tmpconf.HaveJQ = false
+	}
+
+	output, err := prettyfiJson(tmpconf, raw)
+	if err != nil {
+		fmt.Println(err)
+	}
+
+	lines := len(strings.Split(output, "\n"))
+	height := cfg.GetTermHeight()
+
+	if lines > height {
+		if conf.Pager != "" {
+			cmd := strings.Split(conf.Pager, " ")
+			pager := exec.Command(cmd[0], cmd[1:]...)
+
+			var buf bytes.Buffer
+			buf.WriteString(output)
+
+			pager.Stdout = os.Stdout
+			pager.Stdin = &buf
+			pager.Stderr = os.Stderr
+
+			err := pager.Run()
+
+			if err != nil {
+				fmt.Printf("failed to execute pager '%s': %s", conf.Pager, err)
+			}
+		} else {
+			printer.Pager("json output", output)
+		}
+	}
+}
+
 func encodeAuth(username, password string) string {
 	return base64.StdEncoding.EncodeToString([]byte(username + ":" + password))
 }
@@ -197,7 +233,7 @@ func CallAPI(conf *cfg.Config, verb, path, data string) ([]byte, error) {
 	return body, nil
 }
 
-func prettyfiJson(conf *cfg.Config, raw []byte) error {
+func prettyfiJson(conf *cfg.Config, raw []byte) (string, error) {
 	if conf.HaveJQ {
 		cmd := exec.CommandContext(context.Background(), "jq", "-C")
 		cmd.Stdin = bytes.NewReader(raw)
@@ -207,23 +243,18 @@ func prettyfiJson(conf *cfg.Config, raw []byte) error {
 
 		err := cmd.Run()
 		if err != nil {
-			return err
+			return "", err
 		}
 
-		fmt.Println(out.String())
-
-		return nil
+		return out.String(), nil
 	}
-
 	var pretty bytes.Buffer
 	err := json.Indent(&pretty, raw, "", "\t")
 	if err != nil {
-		return fmt.Errorf("json parse error: %s", err)
+		return "", fmt.Errorf("json parse error: %s", err)
 	}
 
-	fmt.Println(pretty.String())
-
-	return nil
+	return pretty.String(), nil
 }
 
 // interactively  read  arbitrary  JSON  data  from  STDIN,  which  is

pkg/es/index_template_settings.go

@@ -39,9 +39,11 @@ func getIndexTemplateSettings(conf *cfg.Config, tplname string, table *printer.T
 	}
 
 	if conf.Debug {
-		if err := prettyfiJson(conf, raw); err != nil {
+		output, err := prettyfiJson(conf, raw)
+		if err != nil {
 			return err
 		}
+		fmt.Println(output)
 	}
 
 	if len(data.IndexTemplates) == 0 {