From f277b9f0622938bde15fe884da2e0917d729258d Mon Sep 17 00:00:00 2001
From: Tom Wiesing <tkw01536@gmail.com>
Date: Thu, 24 Nov 2022 10:43:20 +0100
Subject: [PATCH] storage: Add a more generic API

---
 internal/dis/component/meta/storage.go      | 40 +++++++++++++++++++++
 internal/wisski/ingredient/mstore/mstore.go | 22 +++++-------
 2 files changed, 49 insertions(+), 13 deletions(-)

diff --git a/internal/dis/component/meta/storage.go b/internal/dis/component/meta/storage.go
index 1267940..095603b 100644
--- a/internal/dis/component/meta/storage.go
+++ b/internal/dis/component/meta/storage.go
@@ -6,6 +6,7 @@ import (
 
 	"github.com/FAU-CDI/wisski-distillery/internal/dis/component/sql"
 	"github.com/FAU-CDI/wisski-distillery/internal/models"
+	"github.com/tkw1536/goprogram/lib/collection"
 	"gorm.io/gorm"
 )
 
@@ -176,3 +177,42 @@ func (s Storage) Purge() error {
 	}
 	return nil
 }
+
+// TypedKey represents a convenience wrapper for a given with a given value.
+type TypedKey[Value any] Key
+
+func (f TypedKey[Value]) Get(s *Storage) (value Value, err error) {
+	err = s.Get(Key(f), &value)
+	return
+}
+
+func (f TypedKey[Value]) GetOrSet(s *Storage, dflt Value) (value Value, err error) {
+	value, err = f.Get(s)
+	if err == ErrMetadatumNotSet {
+		value = dflt
+		err = f.Set(s, value)
+	}
+	return
+}
+
+func (f TypedKey[Value]) GetAll(m *Storage) (values []Value, err error) {
+	err = m.GetAll(Key(f), func(index, total int) any {
+		if values == nil {
+			values = make([]Value, total)
+		}
+		return &values[index]
+	})
+	return values, err
+}
+
+func (f TypedKey[Value]) Set(m *Storage, value Value) error {
+	return m.Set(Key(f), value)
+}
+
+func (f TypedKey[Value]) SetAll(m *Storage, values ...Value) error {
+	return m.SetAll(Key(f), collection.AsAny(values)...)
+}
+
+func (f TypedKey[Value]) Delete(m *Storage) error {
+	return m.Delete(Key(f))
+}
diff --git a/internal/wisski/ingredient/mstore/mstore.go b/internal/wisski/ingredient/mstore/mstore.go
index 31e9440..7f75cb8 100644
--- a/internal/wisski/ingredient/mstore/mstore.go
+++ b/internal/wisski/ingredient/mstore/mstore.go
@@ -3,7 +3,6 @@ package mstore
 import (
 	"github.com/FAU-CDI/wisski-distillery/internal/dis/component/meta"
 	"github.com/FAU-CDI/wisski-distillery/internal/wisski/ingredient"
-	"github.com/tkw1536/goprogram/lib/collection"
 )
 
 // MStore implements metadata storage for this WissKI
@@ -13,29 +12,26 @@ type MStore struct {
 }
 
 // For is a Store for the provided value
-type For[Value any] meta.Key
+type For[Value any] meta.TypedKey[Value]
 
 func (f For[Value]) Get(m *MStore) (value Value, err error) {
-	err = m.Storage.Get(meta.Key(f), &value)
-	return
+	return meta.TypedKey[Value](f).Get(m.Storage)
 }
 
 func (f For[Value]) GetAll(m *MStore) (values []Value, err error) {
-	err = m.Storage.GetAll(meta.Key(f), func(index, total int) any {
-		if values == nil {
-			values = make([]Value, total)
-		}
-		return &values[index]
-	})
-	return values, err
+	return meta.TypedKey[Value](f).GetAll(m.Storage)
+}
+
+func (f For[Value]) GetOrSet(m *MStore, dflt Value) (value Value, err error) {
+	return meta.TypedKey[Value](f).GetOrSet(m.Storage, dflt)
 }
 
 func (f For[Value]) Set(m *MStore, value Value) error {
-	return m.Storage.Set(meta.Key(f), value)
+	return meta.TypedKey[Value](f).Set(m.Storage, value)
 }
 
 func (f For[Value]) SetAll(m *MStore, values ...Value) error {
-	return m.Storage.SetAll(meta.Key(f), collection.AsAny(values)...)
+	return meta.TypedKey[Value](f).SetAll(m.Storage, values...)
 }
 
 func (f For[Value]) Delete(m *MStore) error {