internal/app: define flasher app type

The App type is used to initialize an instance of flasher
with its configuration, logger and other attributes.

internal/app/app.go

@@ -0,0 +1,81 @@
+package app
+
+import (
+	"context"
+	"os"
+	"os/signal"
+	"sync"
+	"syscall"
+
+	runtime "github.com/banzaicloud/logrus-runtime-formatter"
+	"github.com/metal-toolbox/flasher/internal/model"
+	"github.com/sirupsen/logrus"
+)
+
+// Config holds configuration data when running mctl
+// App holds attributes for the mtl application
+type App struct {
+	// Sync waitgroup to wait for running go routines on termination.
+	SyncWG *sync.WaitGroup
+	// Flasher configuration.
+	Config *model.Config
+	// TermCh is the channel to terminate the app based on a signal
+	TermCh chan os.Signal
+	// Logger is the app logger
+	Logger *logrus.Logger
+}
+
+// New returns returns a new instance of the flasher app
+func New(ctx context.Context, appKind model.AppKind, inventorySourceKind, cfgFile string, loglevel int) (*App, error) {
+	// load configuration
+	cfg := &model.Config{
+		AppKind:         appKind,
+		InventorySource: inventorySourceKind,
+	}
+
+	if err := cfg.Load(cfgFile); err != nil {
+		return nil, err
+	}
+
+	app := &App{
+		Config: cfg,
+		SyncWG: &sync.WaitGroup{},
+		Logger: logrus.New(),
+		TermCh: make(chan os.Signal),
+	}
+
+	runtimeFormatter := &runtime.Formatter{
+		ChildFormatter: &logrus.JSONFormatter{},
+		File:           true,
+		Line:           true,
+		BaseNameOnly:   true,
+	}
+
+	// set log level, format
+	switch loglevel {
+	case model.LogLevelDebug:
+		app.Logger.Level = logrus.DebugLevel
+
+		// set runtime formatter options
+		runtimeFormatter.BaseNameOnly = true
+		runtimeFormatter.File = true
+		runtimeFormatter.Line = true
+
+	case model.LogLevelTrace:
+		app.Logger.Level = logrus.TraceLevel
+
+		// set runtime formatter options
+		runtimeFormatter.File = true
+		runtimeFormatter.Line = true
+		runtimeFormatter.Package = true
+	default:
+		app.Logger.Level = logrus.InfoLevel
+	}
+
+	app.Logger.SetFormatter(runtimeFormatter)
+
+	// register for SIGINT, SIGTERM
+	signal.Notify(app.TermCh, syscall.SIGINT, syscall.SIGTERM)
+
+	return app, nil
+}