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,${item}`;
  }
  if (item.url) return item.url;
  if (item.image_url?.url) return item.image_url.url;
  if (item.b64_json) return `data:image/png;base64,${item.b64_json}`;
  if (item.data) return `data:image/png;base64,${item.data}`;
  return null;
}

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

  const msg = c.message || {};
  const content = msg.content;

  if (Array.isArray(content)) {
    for (const part of content) {
      if (part?.type === "image_url") {
        const u = part?.image_url?.url || part?.url;
        if (u) return u;
      }
      if (part?.type === "output_image" && part?.image_url?.url) return part.image_url.url;
      if (part?.type === "text" && typeof part.text === "string") {
        const m = part.text.match(/https?:\/\/\S+\.(?:png|jpg|jpeg|webp|gif)/i);
        if (m) return m[0];
      }
    }
  }

  const fallbackPools = [
    json?.images,
    json?.data,
    msg?.images,
    c?.images
  ];

  for (const pool of fallbackPools) {
    if (Array.isArray(pool) && pool.length) {
      const x = toDataUrlMaybe(pool[0]);
      if (x) return x;
    }
  }

  if (typeof content === "string") {
    const m = content.match(/https?:\/\/\S+\.(?:png|jpg|jpeg|webp|gif)/i);
    if (m) return m[0];
  }

  return null;
}

export async function generateImageFrame({
  apiKey,
  model,
  textPrompt,
  previousFrames = [],
  imageSize = "1K",
  aspectRatio = "1:1"
}) {
  const messages = [];

  // rolling window of 2 frames only
  const recent = previousFrames.slice(-2);

  if (recent.length) {
    for (const frame of recent) {
      messages.push({
        role: "user",
        content: [
          { type: "image_url", image_url: { url: frame } }
        ]
      });
    }
  }

  messages.push({
    role: "user",
    content: [
      { type: "text", text: textPrompt }
    ]
  });

  const body = {
    model,
    modalities: ["image"],
    messages,
    image_config: {
      image_size: imageSize,
      aspect_ratio: aspectRatio
    }
  };

  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;
}