app: separate interface from implementation

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/app/app.go

@@ -1,7 +1,6 @@
 package app
 
 import (
-	"context"
 	"sync"
 
 	"git.gensokyo.uk/security/fortify/fst"
@@ -9,23 +8,11 @@ import (
 	"git.gensokyo.uk/security/fortify/internal/sys"
 )
 
-type App interface {
-	// ID returns a copy of App's unique ID.
-	ID() fst.ID
-	// Run sets up the system and runs the App.
-	Run(ctx context.Context, rs *RunState) error
-
-	Seal(config *fst.Config) error
-	String() string
-}
-
-type RunState struct {
-	// Start is true if fsu is successfully started.
-	Start bool
-	// ExitCode is the value returned by shim.
-	ExitCode int
-	// WaitErr is error returned by the underlying wait syscall.
-	WaitErr error
+func New(os sys.State) (fst.App, error) {
+	a := new(app)
+	a.id = new(fst.ID)
+	a.os = os
+	return a, fst.NewAppID(a.id)
 }
 
 type app struct {
@@ -63,10 +50,3 @@ func (a *app) String() string {
 
 	return "(unsealed fortified app)"
 }
-
-func New(os sys.State) (App, error) {
-	a := new(app)
-	a.id = new(fst.ID)
-	a.os = os
-	return a, fst.NewAppID(a.id)
-}