export function parseCsv(content) {
  const rows = parseRows(content);
  if (rows.length === 0) return [];

  const headers = rows[0].map((header) => header.trim());
  return rows.slice(1)
    .filter((row) => row.some((cell) => cell.trim() !== ""))
    .map((row) => {
      const record = {};
      headers.forEach((header, index) => {
        record[header] = row[index] ?? "";
      });
      return record;
    });
}

export function stringifyCsv(records) {
  if (records.length === 0) return "";

  const headers = [
    "platform",
    "metric_label",
    "name",
    "url",
    "hotness_raw",
    "hotness_number",
    "unit",
    "confidence",
    "evidence",
    "status",
    "fetched_at",
    "error",
  ];

  const lines = [headers.join(",")];
  for (const record of records) {
    lines.push(headers.map((header) => csvEscape(record[header] ?? "")).join(","));
  }
  return `${lines.join("\n")}\n`;
}

function parseRows(content) {
  const rows = [];
  let row = [];
  let cell = "";
  let inQuotes = false;

  for (let i = 0; i < content.length; i += 1) {
    const char = content[i];
    const next = content[i + 1];

    if (char === "\"" && inQuotes && next === "\"") {
      cell += "\"";
      i += 1;
      continue;
    }

    if (char === "\"") {
      inQuotes = !inQuotes;
      continue;
    }

    if (char === "," && !inQuotes) {
      row.push(cell);
      cell = "";
      continue;
    }

    if ((char === "\n" || char === "\r") && !inQuotes) {
      if (char === "\r" && next === "\n") i += 1;
      row.push(cell);
      rows.push(row);
      row = [];
      cell = "";
      continue;
    }

    cell += char;
  }

  if (cell.length > 0 || row.length > 0) {
    row.push(cell);
    rows.push(row);
  }

  return rows;
}

function csvEscape(value) {
  const text = String(value);
  if (/[",\r\n]/.test(text)) {
    return `"${text.replace(/"/g, "\"\"")}"`;
  }
  return text;
}