Do a large chunk of the move to go

This commit moves a huge chunk of the code to go. The TODO.md document
indicates what is left to be done.

cmd/purge.go

@@ -0,0 +1,117 @@
+package cmd
+
+import (
+	"os"
+
+	wisski_distillery "github.com/FAU-CDI/wisski-distillery"
+	"github.com/FAU-CDI/wisski-distillery/env"
+	"github.com/FAU-CDI/wisski-distillery/internal/logging"
+	"github.com/tkw1536/goprogram/exit"
+)
+
+// Provision is the 'provision' command
+var Purge wisski_distillery.Command = purge{}
+
+type purge struct {
+	Yes         bool `short:"y" long:"yes" description:"Skip asking for confirmation"`
+	Positionals struct {
+		Slug string `positional-arg-name:"slug" required:"1-1" description:"name of WissKI Instance to purge"`
+	} `positional-args:"true"`
+}
+
+func (purge) Description() wisski_distillery.Description {
+	return wisski_distillery.Description{
+		Requirements: env.Requirements{
+			NeedsConfig: true,
+		},
+		Command:     "purge",
+		Description: "Purges a WissKI Instance",
+	}
+}
+
+var errPurgeNoDetails = exit.Error{
+	Message:  "Unable to find instance details for purge: %s",
+	ExitCode: exit.ExitGeneric,
+}
+
+var errPurgeNoConfirmation = exit.Error{
+	Message:  "Aborting after request was not confirmed. Either type `yes` or pass `--yes` on the command line",
+	ExitCode: exit.ExitGeneric,
+}
+
+func (p purge) Run(context wisski_distillery.Context) error {
+	dis := context.Environment
+	slug := p.Positionals.Slug
+
+	// check the confirmation from the user
+	if !p.Yes {
+		context.Printf("About to remove repository %s. This cannot be undone.\n", slug)
+		context.Printf("Type 'yes' to continue: ")
+		line, err := context.ReadLine()
+		if err != nil || line != "yes" {
+			return errPurgeNoConfirmation
+		}
+	}
+
+	// load the instance (first via bookkeeping, then via defaults)
+	logging.LogMessage(context.IOStream, "Checking bookkeeping table")
+	instance, err := dis.Instance(slug)
+	if err == env.ErrInstanceNotFound {
+		context.Println("Not found in bookkeeping table, assuming defaults")
+		instance, err = dis.NewInstance(slug)
+	}
+	if err != nil {
+		return errPurgeNoDetails.WithMessageF(err)
+	}
+
+	// remove docker stack
+	logging.LogMessage(context.IOStream, "Stopping and removing docker container")
+	if err := instance.Stack().Down(context.IOStream); err != nil {
+		context.EPrintln(err)
+	}
+
+	// remove the filesystem
+	logging.LogMessage(context.IOStream, "Removing from filesystem %s", instance.FilesystemBase)
+	if err := os.RemoveAll(instance.FilesystemBase); err != nil {
+		context.EPrintln(err)
+	}
+
+	// remove the triplestore
+	logging.LogOperation(func() error {
+		logging.LogMessage(context.IOStream, "Removing user %s", instance.GraphDBUser)
+		if err := dis.TriplestorePurgeUser(instance.GraphDBUser); err != nil {
+			context.EPrintln(err)
+		}
+
+		logging.LogMessage(context.IOStream, "Removing repository %s", instance.GraphDBRepository)
+		if err := dis.TriplestorePurgeRepo(instance.GraphDBRepository); err != nil {
+			context.EPrintln(err)
+		}
+
+		return nil
+	}, context.IOStream, "Removing from Triplestore")
+
+	// remove the sql
+	logging.LogOperation(func() error {
+		logging.LogMessage(context.IOStream, "Removing user %s", instance.SqlUser)
+		if err := dis.SQLPurgeUser(instance.SqlUser); err != nil {
+			context.EPrintln(err)
+		}
+
+		logging.LogMessage(context.IOStream, "Removing database %s", instance.SqlDatabase)
+		if err := dis.SQLPurgeDatabase(instance.SqlDatabase); err != nil {
+			context.EPrintln(err)
+		}
+
+		return nil
+	}, context.IOStream, "Removing from SQL")
+
+	// remove from bookkeeping
+	logging.LogMessage(context.IOStream, "Removing instance from bookkeeping")
+	if err := instance.Delete(); err != nil {
+		context.EPrintln(err)
+	}
+
+	logging.LogMessage(context.IOStream, "Instance %s has been purged", slug)
+	return nil
+}