feat: first steps towards watchable ps output

See coop-cloud/organising#178.

cli/app/ps.go

@@ -3,6 +3,7 @@ package app
 import (
 	"fmt"
 	"strings"
+	"time"
 
 	abraFormatter "coopcloud.tech/abra/cli/formatter"
 	"coopcloud.tech/abra/cli/internal"
@@ -15,48 +16,33 @@ import (
 	"github.com/urfave/cli/v2"
 )
 
+var watch bool
+var watchFlag = &cli.BoolFlag{
+	Name:        "watch",
+	Aliases:     []string{"w"},
+	Value:       false,
+	Usage:       "Watch status by polling repeatedly",
+	Destination: &watch,
+}
+
 var appPsCommand = &cli.Command{
 	Name:    "ps",
 	Usage:   "Check app status",
 	Aliases: []string{"p"},
+	Flags: []cli.Flag{
+		watchFlag,
+	},
 	Action: func(c *cli.Context) error {
-		app := internal.ValidateApp(c)
-
-		cl, err := client.New(app.Server)
-		if err != nil {
-			logrus.Fatal(err)
+		if !watch {
+			showPSOutput(c)
+			return nil
 		}
 
-		filters := filters.NewArgs()
-		filters.Add("name", app.StackName())
-
-		containers, err := cl.ContainerList(c.Context, types.ContainerListOptions{Filters: filters})
-		if err != nil {
-			logrus.Fatal(err)
+		// TODO: how do we make this update in-place in an x-platform way?
+		for {
+			showPSOutput(c)
+			time.Sleep(2 * time.Second)
 		}
-
-		tableCol := []string{"image", "created", "status", "ports", "names"}
-		table := abraFormatter.CreateTable(tableCol)
-
-		for _, container := range containers {
-			var containerNames []string
-			for _, containerName := range container.Names {
-				trimmed := strings.TrimPrefix(containerName, "/")
-				containerNames = append(containerNames, trimmed)
-			}
-
-			tableRow := []string{
-				abraFormatter.RemoveSha(container.Image),
-				abraFormatter.HumanDuration(container.Created),
-				container.Status,
-				formatter.DisplayablePorts(container.Ports),
-				strings.Join(containerNames, "\n"),
-			}
-			table.Append(tableRow)
-		}
-
-		table.Render()
-		return nil
 	},
 	BashComplete: func(c *cli.Context) {
 		appNames, err := config.GetAppNames()
@@ -71,3 +57,43 @@ var appPsCommand = &cli.Command{
 		}
 	},
 }
+
+// showPSOutput renders ps output.
+func showPSOutput(c *cli.Context) {
+	app := internal.ValidateApp(c)
+
+	cl, err := client.New(app.Server)
+	if err != nil {
+		logrus.Fatal(err)
+	}
+
+	filters := filters.NewArgs()
+	filters.Add("name", app.StackName())
+
+	containers, err := cl.ContainerList(c.Context, types.ContainerListOptions{Filters: filters})
+	if err != nil {
+		logrus.Fatal(err)
+	}
+
+	tableCol := []string{"image", "created", "status", "ports", "names"}
+	table := abraFormatter.CreateTable(tableCol)
+
+	for _, container := range containers {
+		var containerNames []string
+		for _, containerName := range container.Names {
+			trimmed := strings.TrimPrefix(containerName, "/")
+			containerNames = append(containerNames, trimmed)
+		}
+
+		tableRow := []string{
+			abraFormatter.RemoveSha(container.Image),
+			abraFormatter.HumanDuration(container.Created),
+			container.Status,
+			formatter.DisplayablePorts(container.Ports),
+			strings.Join(containerNames, "\n"),
+		}
+		table.Append(tableRow)
+	}
+
+	table.Render()
+}