fix: adapt fal image sizing parameters

lib/ai/providers/fal-image.ts

@@ -59,6 +59,34 @@ const GPT_IMAGE_2_EDIT_IMAGE_SIZE_PRESETS = new Set([
   "landscape_16_9",
 ]);
 const GPT_IMAGE_2_EDIT_QUALITIES = new Set(["low", "medium", "high"]);
+const FAL_ASPECT_RATIO_VALUES = new Set([
+  "21:9",
+  "16:9",
+  "3:2",
+  "4:3",
+  "5:4",
+  "1:1",
+  "4:5",
+  "3:4",
+  "2:3",
+  "9:16",
+  "9:21",
+]);
+const FAL_IMAGE_SIZE_PRESETS = new Set([
+  "square_hd",
+  "square",
+  "portrait_4_3",
+  "portrait_16_9",
+  "landscape_4_3",
+  "landscape_16_9",
+]);
+const FAL_IMAGE_SIZE_BY_ASPECT_RATIO: Record<string, string> = {
+  "1:1": "square_hd",
+  "4:3": "landscape_4_3",
+  "3:4": "portrait_4_3",
+  "16:9": "landscape_16_9",
+  "9:16": "portrait_16_9",
+};
 
 type FalImageSize = string | { width: number; height: number };
 
@@ -172,6 +200,7 @@ function normalizeAspectRatio(aspectRatio?: string) {
       "3:4",
       "2:3",
       "9:16",
+      "9:21",
       "4:1",
       "1:4",
       "8:1",
@@ -191,6 +220,82 @@ function normalizeResolution(imageSize?: string) {
   return DEFAULT_RESOLUTION;
 }
 
+function normalizeExplicitAspectRatio(aspectRatio?: string) {
+  const normalized = normalizeAspectRatio(aspectRatio);
+  if (normalized === "auto") return undefined;
+  return FAL_ASPECT_RATIO_VALUES.has(normalized) ? normalized : undefined;
+}
+
+function normalizeAnyExplicitAspectRatio(aspectRatio?: string) {
+  const normalized = normalizeAspectRatio(aspectRatio);
+  return normalized === "auto" ? undefined : normalized;
+}
+
+function parseAspectRatioValue(aspectRatio?: string) {
+  const normalized = normalizeAnyExplicitAspectRatio(aspectRatio);
+  if (!normalized) return undefined;
+  const [width, height] = normalized.split(":").map((part) => Number(part));
+  if (!Number.isFinite(width) || !Number.isFinite(height) || width <= 0 || height <= 0) {
+    return undefined;
+  }
+  return width / height;
+}
+
+function roundToMultiple(value: number, multiple: number) {
+  return Math.max(multiple, Math.round(value / multiple) * multiple);
+}
+
+function resolveFalCustomImageSize(aspectRatio?: string, resolution?: string): FalImageSize {
+  const ratio = parseAspectRatioValue(aspectRatio) || 1;
+  const bucket = normalizeResolution(resolution);
+  const areaByBucket: Record<string, number> = {
+    "0.5K": 768 * 768,
+    "1K": 1024 * 1024,
+    "2K": 1536 * 1536,
+    "4K": 2048 * 2048,
+  };
+  const targetArea = areaByBucket[bucket] || areaByBucket["1K"];
+  const width = roundToMultiple(Math.sqrt(targetArea * ratio), 16);
+  const height = roundToMultiple(width / ratio, 16);
+  return { width, height };
+}
+
+function normalizeFalImageSize(imageSize?: string, aspectRatio?: string): FalImageSize {
+  const rawSize = String(imageSize || "").trim();
+  const normalizedSize = rawSize.toLowerCase().replace(/\s+/g, "");
+  if (FAL_IMAGE_SIZE_PRESETS.has(normalizedSize)) {
+    return normalizedSize;
+  }
+
+  const customSizeMatch = normalizedSize.match(/^(\d{2,5})[x×](\d{2,5})$/i);
+  if (customSizeMatch) {
+    const width = Number(customSizeMatch[1]);
+    const height = Number(customSizeMatch[2]);
+    if (
+      Number.isFinite(width) &&
+      Number.isFinite(height) &&
+      width >= 256 &&
+      height >= 256 &&
+      width <= 4096 &&
+      height <= 4096
+    ) {
+      return {
+        width: roundToMultiple(width, 16),
+        height: roundToMultiple(height, 16),
+      };
+    }
+  }
+
+  const normalizedAspectRatio = normalizeAnyExplicitAspectRatio(aspectRatio);
+  if (normalizedAspectRatio && FAL_IMAGE_SIZE_BY_ASPECT_RATIO[normalizedAspectRatio]) {
+    return FAL_IMAGE_SIZE_BY_ASPECT_RATIO[normalizedAspectRatio];
+  }
+
+  return normalizedAspectRatio
+    ? resolveFalCustomImageSize(normalizedAspectRatio, rawSize)
+    : "square_hd";
+}
+
 function normalizeOutputFormat(outputFormat?: string) {
   if (!outputFormat) return DEFAULT_OUTPUT_FORMAT;
   const normalized = outputFormat.trim().toLowerCase();
@@ -228,6 +333,31 @@ function normalizeFalEndpointId(modelId: string, hasInputImages: boolean) {
   return endpoint;
 }
 
+function isFalNanoBananaModelId(modelId: string) {
+  const normalized = modelId.trim().toLowerCase().replace(/\/edit$/, "");
+  return FAL_NANO_BANANA_MODEL_IDS.has(normalized);
+}
+
+function isFalFluxKontextDevModelId(modelId: string) {
+  return modelId.trim().toLowerCase().replace(/\/$/, "") === "fal-ai/flux-kontext/dev";
+}
+
+function isFalKontextModelId(modelId: string) {
+  return modelId.trim().toLowerCase().includes("kontext");
+}
+
+function shouldUseFalImageSize(modelId: string, hasInputImages: boolean) {
+  if (hasInputImages) return false;
+  const normalized = modelId.trim().toLowerCase();
+  if (isFalNanoBananaModelId(normalized) || isFalKontextModelId(normalized)) return false;
+  return (
+    normalized.startsWith("fal-ai/flux/") ||
+    normalized.startsWith("fal-ai/flux-lora") ||
+    normalized.includes("/flux/dev") ||
+    normalized.includes("/flux/schnell")
+  );
+}
+
 function normalizeGptImage2EditQuality(value?: string) {
   if (!value) return "high";
   const normalized = value.trim().toLowerCase();
@@ -266,7 +396,12 @@ function normalizeGptImage2EditImageSize(
 
   const sizeBucket = rawSize.toUpperCase();
   const ratio = normalizeAspectRatio(aspectRatio).toLowerCase();
-  return GPT_IMAGE_2_EDIT_SIZE_BY_BUCKET[sizeBucket]?.[ratio] || "auto";
+  return (
+    GPT_IMAGE_2_EDIT_SIZE_BY_BUCKET[sizeBucket]?.[ratio] ||
+    (normalizeAnyExplicitAspectRatio(aspectRatio)
+      ? resolveFalCustomImageSize(aspectRatio, sizeBucket)
+      : "auto")
+  );
 }
 
 function getFalImageSizeLabel(size: FalImageSize) {
@@ -519,24 +654,47 @@ function buildFalRequestPayload(params: {
       input.openai_api_key = openaiApiKey;
     }
   } else {
+    const explicitAspectRatio = normalizeExplicitAspectRatio(aspectRatio);
     input = {
       prompt,
       num_images: imageCount,
-      aspect_ratio: aspectRatio,
-      resolution,
       output_format: outputFormat,
       safety_tolerance: safetyTolerance,
-      limit_generations: true,
     };
 
-    if (imageUrls.length > 0) {
+    if (isFalNanoBananaModelId(falEndpointId)) {
-      input.image_urls = imageUrls;
+      input.aspect_ratio = aspectRatio;
+      input.resolution = resolution;
+      input.limit_generations = true;
+    } else if (isFalFluxKontextDevModelId(falEndpointId) && imageUrls.length > 0) {
+      input.image_url = imageUrls[0];
+      input.enable_safety_checker = true;
+      input.resolution_mode = explicitAspectRatio || "match_input";
+    } else if (isFalKontextModelId(falEndpointId)) {
+      if (explicitAspectRatio) {
+        input.aspect_ratio = explicitAspectRatio;
+      }
+      if (imageUrls.length > 0) {
+        input.image_url = imageUrls[0];
+        if (imageUrls.length > 1 || falEndpointId.toLowerCase().includes("/multi")) {
+          input.image_urls = imageUrls;
+        }
+      }
+    } else if (shouldUseFalImageSize(falEndpointId, imageUrls.length > 0)) {
+      input.image_size = normalizeFalImageSize(params.imageParams?.imageSize, aspectRatio);
+      input.enable_safety_checker = true;
+    } else if (explicitAspectRatio) {
+      input.aspect_ratio = explicitAspectRatio;
     }
 
     if (seed !== undefined) {
       input.seed = seed;
     }
 
+    if (imageUrls.length > 0 && !input.image_url && !input.image_urls) {
+      input.image_urls = imageUrls;
+    }
+
     if (typeof params.imageParams?.enableWebSearch === "boolean") {
       input.enable_web_search = params.imageParams.enableWebSearch;
     }
@@ -606,6 +764,7 @@ export async function submitFalImageTask(params: {
     imageCount: request.imageCount,
     hasInputImages: request.imageUrls.length > 0,
     resolution: request.outputSizeLabel,
+    inputKeys: Object.keys(request.input),
   });
 
   const enqueueResult = await fal.queue.submit(request.falEndpointId, {
@@ -680,6 +839,7 @@ export function createFalImage({ apiKey, baseURL }: FalImageConfig) {
           aspectRatio: request.aspectRatio,
           resolution: request.outputSizeLabel,
           hasInputImages: request.imageUrls.length > 0,
+          inputKeys: Object.keys(request.input),
         });
 
         const fal = await createFalClientFromApiKey(apiKey);