function passContext(ctx) {
  if (ctx?.context != null && typeof ctx.context === "object" && !Array.isArray(ctx.context)) {
    return { ...ctx.context };
  }
  return {};
}

function mergeData(data) {
  if (data != null && typeof data === "object" && !Array.isArray(data)) {
    return { ...data };
  }
  return {};
}

function filenameFromUrl(url) {
  try {
    const name = new URL(url).pathname.split("/").filter(Boolean).pop();
    return name || "attachment";
  } catch {
    return "attachment";
  }
}

function resolveUrl(ctx) {
  const fromConfig = ctx.config?.url;
  if (typeof fromConfig === "string" && fromConfig.length > 0) {
    return fromConfig;
  }

  const urlVar = ctx.config?.urlVar;
  if (typeof urlVar === "string" && urlVar.length > 0) {
    const value = ctx.data?.[urlVar];
    if (typeof value === "string" && value.length > 0) {
      return value;
    }
  }

  for (const key of ["attach", "url"]) {
    const value = ctx.data?.[key];
    if (typeof value === "string" && value.length > 0) {
      return value;
    }
  }

  return null;
}

async function fetchBinary(ctx) {
  const url = resolveUrl(ctx);
  if (!url) {
    throw new Error(
      "fetch-binary: url is required (ctx.config.url, ctx.config.urlVar, ctx.data.attach, or ctx.data.url)",
    );
  }

  const outputVar = typeof ctx.config?.outputVar === "string" && ctx.config.outputVar.length > 0
    ? ctx.config.outputVar
    : "file";

  log.info({ url, outputVar }, "fetch-binary: fetching");
  const response = await $axios.get(url, { responseType: "arraybuffer" });
  const file = Buffer.from(response.data ?? []);
  const contentType = String(response.headers?.["content-type"] ?? "application/octet-stream");
  const filename = ctx.config?.filename || ctx.data?.filename || filenameFromUrl(url);

  const extra = {
    [outputVar]: file,
    filename,
    contentType,
  };

  log.info(
    { outputVar, filename, contentType, length: file.length },
    "fetch-binary: saved",
  );

  return {
    output: { ...mergeData(ctx.data), ...extra },
    context: { ...passContext(ctx), ...extra },
  };
}

fetchBinary.meta = {
  description: "Download a binary URL and add the Buffer to output (keeps previous data fields)",
  previewConfigKey: "url",
  config: {
    url: { type: "string", required: false, description: "Direct download URL" },
    urlVar: { type: "string", required: false, description: "Key in ctx.data that holds the URL" },
    outputVar: { type: "string", default: "file", description: "output key for the Buffer" },
    filename: { type: "string", required: false, description: "Override saved filename" },
  },
  input: {
    attach: { type: "string", required: false, description: "Fallback URL" },
    url: { type: "string", required: false, description: "Fallback URL" },
    filename: { type: "string", required: false },
  },
  output: {
    file: { type: "buffer", description: "Downloaded bytes (or ctx.config.outputVar)" },
    filename: { type: "string" },
    contentType: { type: "string" },
  },
  context: {
    file: { type: "buffer", description: "Downloaded bytes (or ctx.config.outputVar)" },
    filename: { type: "string" },
    contentType: { type: "string" },
  },
  example: {
    data: { attach: "https://example.com/image.png" },
    config: { outputVar: "file" },
  },
};

export default fetchBinary;