const OPENROUTER_URL = "https://openrouter.ai/api/v1/chat/completions";

function toDataUrlMaybe(item) {
  if (!item) return null;
  if (typeof item === "string") {
    if (item.startsWith("http://") || item.startsWith("https://") || item.startsWith("data:image/")) return item;
    return `data:image/png;base64,${item}`;
  }
  if (item.url) return item.url;
  if (item.image_url?.url) return item.image_url.url;
  if (item.imageUrl?.url) return item.imageUrl.url;
  if (item.b64_json) return `data:image/png;base64,${item.b64_json}`;
  if (item.data) return `data:image/png;base64,${item.data}`;
  return null;
}

function extractImageFromResponse(json) {
  const msg = json?.choices?.[0]?.message;
  if (!msg) return null;

  // Primary docs format: message.images[].image_url.url
  if (Array.isArray(msg.images) && msg.images.length) {
    for (const image of msg.images) {
      const url = image?.image_url?.url || image?.imageUrl?.url || image?.url;
      if (url) return url;
      const maybe = toDataUrlMaybe(image);
      if (maybe) return maybe;
    }
  }

  // Fallback: content parts
  if (Array.isArray(msg.content)) {
    for (const part of msg.content) {
      if (part?.type === "image_url") {
        const u = part?.image_url?.url || part?.imageUrl?.url || part?.url;
        if (u) return u;
      }
      if (part?.type === "output_image" && part?.image_url?.url) return part.image_url.url;
    }
  }

  // Extra fallback pools
  const fallbackPools = [json?.images, json?.data, msg?.data, json?.choices?.[0]?.images];
  for (const pool of fallbackPools) {
    if (Array.isArray(pool) && pool.length) {
      const maybe = toDataUrlMaybe(pool[0]);
      if (maybe) return maybe;
    }
  }

  return null;
}

export async function generateImageFrame({
  apiKey,
  model,
  textPrompt,
  previousFrames = [],
  imageSize = "1K",
  aspectRatio = "1:1"
}) {
  // Docs recommend text first, then images in content array
  const content = [{ type: "text", text: textPrompt }];
  for (const frame of previousFrames.slice(-2)) {
    content.push({
      type: "image_url",
      image_url: { url: frame }
    });
  }

  const body = {
    model,
    modalities: ["image"], // As requested: image only
    messages: [{ role: "user", content }],
    image_config: {
      image_size: imageSize,
      aspect_ratio: aspectRatio
    },
    stream: false
  };

  const res = await fetch(OPENROUTER_URL, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${apiKey}`,
      "HTTP-Referer": window.location.origin,
      "X-Title": "vibegif.lol"
    },
    body: JSON.stringify(body)
  });

  const json = await res.json().catch(() => ({}));
  if (!res.ok) {
    const msg = json?.error?.message || `OpenRouter error (${res.status})`;
    throw new Error(msg);
  }

  const image = extractImageFromResponse(json);
  if (!image) throw new Error("No image found in model response.");
  return image;
}