Enhance canvas connection validation and image resolution handling

- Introduced new functions for validating canvas connections, ensuring proper source and target node types.
- Updated edge and node mutation logic to enforce connection policies and improve error handling.
- Enhanced image resolution handling by integrating a new image source resolution function for better URL retrieval.
- Refactored existing validation logic to streamline connection checks and improve maintainability.

lib/canvas-connection-policy.ts

@@ -0,0 +1,87 @@
+import { isAdjustmentNodeType } from "@/lib/canvas-node-types";
+
+export const CANVAS_NODE_DND_MIME = "application/lemonspace-node-type";
+
+const ADJUSTMENT_ALLOWED_SOURCE_TYPES = new Set<string>([
+  "image",
+  "asset",
+  "ai-image",
+  "curves",
+  "color-adjust",
+  "light-adjust",
+  "detail-adjust",
+]);
+
+const RENDER_ALLOWED_SOURCE_TYPES = new Set<string>([
+  "image",
+  "asset",
+  "ai-image",
+  "curves",
+  "color-adjust",
+  "light-adjust",
+  "detail-adjust",
+]);
+
+const ADJUSTMENT_DISALLOWED_TARGET_TYPES = new Set<string>(["prompt", "ai-image"]);
+
+export type CanvasConnectionValidationReason =
+  | "incomplete"
+  | "self-loop"
+  | "unknown-node"
+  | "adjustment-source-invalid"
+  | "adjustment-incoming-limit"
+  | "adjustment-target-forbidden"
+  | "render-source-invalid";
+
+export function validateCanvasConnectionPolicy(args: {
+  sourceType: string;
+  targetType: string;
+  targetIncomingCount: number;
+}): CanvasConnectionValidationReason | null {
+  const { sourceType, targetType, targetIncomingCount } = args;
+
+  if (isAdjustmentNodeType(targetType)) {
+    if (!ADJUSTMENT_ALLOWED_SOURCE_TYPES.has(sourceType)) {
+      return "adjustment-source-invalid";
+    }
+    if (targetIncomingCount >= 1) {
+      return "adjustment-incoming-limit";
+    }
+  }
+
+  if (targetType === "render" && !RENDER_ALLOWED_SOURCE_TYPES.has(sourceType)) {
+    return "render-source-invalid";
+  }
+
+  if (
+    isAdjustmentNodeType(sourceType) &&
+    ADJUSTMENT_DISALLOWED_TARGET_TYPES.has(targetType)
+  ) {
+    return "adjustment-target-forbidden";
+  }
+
+  return null;
+}
+
+export function getCanvasConnectionValidationMessage(
+  reason: CanvasConnectionValidationReason,
+): string {
+  switch (reason) {
+    case "incomplete":
+      return "Unvollstaendige Verbindung.";
+    case "self-loop":
+      return "Node kann nicht mit sich selbst verbunden werden.";
+    case "unknown-node":
+      return "Verbindung enthaelt unbekannte Nodes.";
+    case "adjustment-source-invalid":
+      return "Adjustment-Nodes akzeptieren nur Bild-, Asset-, KI-Bild- oder Adjustment-Input.";
+    case "adjustment-incoming-limit":
+      return "Adjustment-Nodes erlauben genau eine eingehende Verbindung.";
+    case "adjustment-target-forbidden":
+      return "Adjustment-Ausgaben koennen nicht an Prompt- oder KI-Bild-Nodes angeschlossen werden.";
+    case "render-source-invalid":
+      return "Render akzeptiert nur Bild-, Asset-, KI-Bild- oder Adjustment-Input.";
+    default:
+      return "Verbindung ist fuer diese Node-Typen nicht erlaubt.";
+  }
+}