import { URL } from "node:url";

export function buildUrl(base: string, params: Record<string, string>): URL {
  const url = new URL(base);
  url.search = new URLSearchParams(params).toString();
  return url;
}

export async function fetchJson<T = any>(url: URL, context: string): Promise<T> {
  const response = await fetch(url);
  if (!response.ok) {
    throw new Error(`${context}: HTTP ${response.status}`);
  }
  return response.json();
}

export async function getDefaultConfigAndSplit(datasetId: string): Promise<{ config: string; split: string }> {
  const infoUrl = buildUrl("https://datasets-server.huggingface.co/info", { dataset: datasetId });
  const info = await fetchJson<any>(infoUrl, "Failed to get dataset info");
  const datasetInfo = info?.dataset_info;
  if (!datasetInfo) throw new Error("dataset_info missing in /info response");

  // Get the first available config
  const configNames = Object.keys(datasetInfo);
  if (configNames.length === 0) throw new Error("No configurations found for dataset");
  
  const config = configNames[0];
  const configInfo = datasetInfo[config];
  const splits = configInfo.splits || {};
  const splitNames = Object.keys(splits);
  if (splitNames.length === 0) throw new Error("No splits found for dataset");
  
  const split = splitNames[0];
  return { config, split };
}

export async function searchDatasets(query: string): Promise<Array<{ id: string; title: string; url: string }>> {
  const url = buildUrl("https://huggingface.co/api/datasets", { search: query, limit: "20" });
  const datasets = await fetchJson<any[]>(url, "Dataset search failed");
  return datasets.map((dataset: any) => ({
    id: dataset.id,
    title: dataset.id,
    url: `https://huggingface.co/datasets/${dataset.id}`,
  }));
}

export async function fetchDatasetAggregate(datasetId: string): Promise<{
  id: string;
  title: string;
  text: string;
  url: string;
}> {
  const { config, split } = await getDefaultConfigAndSplit(datasetId);

  const rowsUrl = buildUrl("https://datasets-server.huggingface.co/rows", {
    dataset: datasetId,
    config,
    split,
    offset: "0",
    length: "50",
  });

  let text: string;
  try {
    const rowsResponse = await fetch(rowsUrl);
    if (rowsResponse.ok) {
      const rowsResult = await rowsResponse.json();
      text = `Sample data (${config}/${split}):\n${JSON.stringify(rowsResult.rows || [], null, 2)}`;
    } else {
      text = "Sample data: Not available";
    }
  } catch {
    text = "Sample data: Not available";
  }

  return {
    id: datasetId,
    title: datasetId,
    text,
    url: `https://huggingface.co/datasets/${datasetId}`,
  };
}

export function textContent(payload: unknown) {
  return { content: [{ type: "text" as const, text: JSON.stringify(payload) }] };
}