app: minor reorg

* add version number
* add more logging
* add command/subcommand

pkg/app/config.go

@@ -0,0 +1,67 @@
+package app
+
+import (
+	"errors"
+
+	"github.com/peterbourgon/ff/v4"
+)
+
+var (
+	ErrExtraArgs = errors.New("extra args present")
+)
+
+// app's config options from user
+type config struct {
+	logLevel *string
+	create   struct {
+		keyPemFilePath  *string
+		certPemFilePath *string
+		outFilePath     *string
+	}
+}
+
+// getConfig returns the app's configuration from either command line args,
+// or environment variables
+func (app *app) getConfig() {
+	// make config
+	cfg := &config{}
+
+	// commands:
+	// create
+	// TODO:
+	// upload
+	// unpack (both key & key+cert)
+
+	// apc-p15-tool -- root command
+	rootFlags := ff.NewFlagSet("apc-p15-tool")
+
+	cfg.logLevel = rootFlags.StringEnum('l', "loglevel", "log level: debug, info, warn, error, dpanic, panic, or fatal",
+		"info", "debug", "warn", "error", "dpanic", "panic", "fatal")
+
+	rootCmd := &ff.Command{
+		Name:  "apc-p15-tool",
+		Usage: "apc-p15-tool [FLAGS] SUBCOMMAND ...",
+		Flags: rootFlags,
+	}
+
+	// create -- subcommand
+	createFlags := ff.NewFlagSet("create").SetParent(rootFlags)
+
+	cfg.create.keyPemFilePath = createFlags.StringLong("keyfile", "", "path and filename of the rsa-2048 key in pem format")
+	cfg.create.certPemFilePath = createFlags.StringLong("certfile", "", "path and filename of the rsa-2048 key in pem format")
+	cfg.create.outFilePath = createFlags.StringLong("outfile", createDefaultOutFilePath, "path and filename to write the p15 file to")
+
+	createCmd := &ff.Command{
+		Name:      "create",
+		Usage:     "apc-p15-tool create --keyfile key.pem --certfile cert.pem [--outfile apctool.p15]",
+		ShortHelp: "create an apc p15 file from the specified key and cert pem files",
+		Flags:     createFlags,
+		Exec:      app.cmdCreate,
+	}
+
+	rootCmd.Subcommands = append(rootCmd.Subcommands, createCmd)
+
+	// set app cmd & cfg
+	app.cmd = rootCmd
+	app.config = cfg
+}