feat: implement generation preconditions check and integrate with generation commands

operations/generation/preconditions.ts

@@ -0,0 +1,78 @@
+import type { ImageDocument } from "@core/document";
+import { getLayerMask } from "@core/layer-mask-utils";
+import { createDocumentReadIndex, resolveIndexedLayerBounds } from "@editor/document-indexes";
+import type { SelectionState } from "@editor/state";
+import type { GenerateSettings } from "@editor/tools";
+
+export type GenerationPrecondition =
+  | { ready: true }
+  | { ready: false; message: string };
+
+export function checkGenerationPreconditions(
+  document: ImageDocument,
+  selection: SelectionState,
+  settings: GenerateSettings,
+): GenerationPrecondition {
+  if (!settings.prompt.trim()) return missing("Enter a prompt to generate an image.");
+
+  const artboard = selection.artboardId
+    ? document.artboards.find((candidate) => candidate.id === selection.artboardId)
+    : document.artboards[0];
+  if (!artboard) return missing("Create an artboard before generating an image.");
+  if (settings.mode === "text-to-image") return { ready: true };
+
+  if (selection.layerIds.length !== 1 || !selection.layerIds[0]) {
+    return missing(modeSelectionMessage(settings.mode));
+  }
+
+  const index = createDocumentReadIndex(document);
+  const layerInfo = index.layerInfoById.get(selection.layerIds[0]);
+  if (!layerInfo || layerInfo.artboardId !== artboard.id || layerInfo.layer.type === "group") {
+    return missing(modeSelectionMessage(settings.mode));
+  }
+
+  const asset = index.assetById.get(layerInfo.layer.assetId);
+  if (!asset) return missing("The selected layer is missing its source image.");
+  if (asset.intrinsicSize.w <= 0 || asset.intrinsicSize.h <= 0) return missing("The selected image has an invalid size.");
+
+  if (settings.mode === "outpaint") {
+    const padding = settings.outpaint;
+    if (padding.left + padding.top + padding.right + padding.bottom <= 0) {
+      return missing("Add outpaint padding on at least one side.");
+    }
+  }
+
+  if (settings.mode !== "inpaint") return { ready: true };
+
+  const layerMask = getLayerMask(layerInfo.layer);
+  if (!layerMask?.enabled) return missing("Add and enable a layer mask on the selected image before inpainting.");
+  const maskLayer = index.layerById.get(layerMask.maskLayerId);
+  if (!maskLayer || maskLayer.type === "group") return missing("The selected layer mask is missing.");
+  const maskAsset = index.assetById.get(maskLayer.assetId);
+  if (!maskAsset) return missing("The selected layer mask is missing its image data.");
+  if (Math.round(asset.intrinsicSize.w) !== Math.round(maskAsset.intrinsicSize.w) || Math.round(asset.intrinsicSize.h) !== Math.round(maskAsset.intrinsicSize.h)) {
+    return missing("The selected layer and mask image sizes must match.");
+  }
+
+  const layerBounds = resolveIndexedLayerBounds(index, layerInfo.layer);
+  const maskBounds = resolveIndexedLayerBounds(index, maskLayer);
+  if (!layerBounds || !maskBounds || !rectsAligned(layerBounds, maskBounds) || Math.abs(layerInfo.layer.transform.rotation - maskLayer.transform.rotation) > 0.001) {
+    return missing("Align the selected layer and its mask before inpainting.");
+  }
+
+  return { ready: true };
+}
+
+function modeSelectionMessage(mode: GenerateSettings["mode"]): string {
+  if (mode === "image-to-image") return "Select exactly one image or raster layer for image-to-image generation.";
+  if (mode === "inpaint") return "Select exactly one masked image or raster layer to inpaint.";
+  return "Select exactly one image or raster layer to outpaint.";
+}
+
+function missing(message: string): GenerationPrecondition {
+  return { ready: false, message };
+}
+
+function rectsAligned(a: { x: number; y: number; w: number; h: number }, b: { x: number; y: number; w: number; h: number }): boolean {
+  return Math.abs(a.x - b.x) <= 0.5 && Math.abs(a.y - b.y) <= 0.5 && Math.abs(a.w - b.w) <= 0.5 && Math.abs(a.h - b.h) <= 0.5;
+}