import { parse as parseQueryString } from 'node:querystring';

/**
 * 小飞侠路由回调实际推送多为 multipart/form-data（非 JSON / urlencoded）。
 * 解析失败时保留 _rawText，便于第三方日志排查。
 */
export function parseCourierCallbackBody(
  rawText: string,
  contentType: string,
): Record<string, unknown> {
  const ct = contentType.toLowerCase();
  const trimmed = rawText.trim();
  if (!trimmed) return {};

  if (ct.includes('multipart/form-data') || looksLikeMultipart(trimmed)) {
    const multipart = parseMultipartFormData(rawText, contentType);
    if (multipart && Object.keys(multipart).length > 0) return multipart;
  }

  if (ct.includes('application/json') || trimmed.startsWith('{') || trimmed.startsWith('[')) {
    try {
      const parsed = JSON.parse(trimmed) as unknown;
      return parsed && typeof parsed === 'object'
        ? (parsed as Record<string, unknown>)
        : { value: parsed };
    } catch {
      return { _rawText: rawText.slice(0, 4000) };
    }
  }

  if (ct.includes('application/x-www-form-urlencoded') || looksLikeUrlEncoded(trimmed)) {
    return flattenQueryValues(parseQueryString(trimmed));
  }

  return { _rawText: rawText.slice(0, 4000) };
}

function looksLikeMultipart(raw: string): boolean {
  return raw.startsWith('--') && /Content-Disposition:\s*form-data/i.test(raw);
}

function looksLikeUrlEncoded(raw: string): boolean {
  if (looksLikeMultipart(raw)) return false;
  return /^[^=&\s]+=/.test(raw) && !raw.includes('\n');
}

function flattenQueryValues(
  parsed: Record<string, string | string[] | undefined>,
): Record<string, unknown> {
  const out: Record<string, unknown> = {};
  for (const [key, value] of Object.entries(parsed)) {
    if (Array.isArray(value)) out[key] = value[value.length - 1];
    else if (value !== undefined) out[key] = value;
  }
  return out;
}

/** 仅解析文本字段（小飞侠回调无文件） */
export function parseMultipartFormData(
  rawText: string,
  contentType: string,
): Record<string, unknown> | null {
  const boundary = extractBoundary(contentType, rawText);
  if (!boundary) return null;

  const delimiter = `--${boundary}`;
  const parts = rawText.split(delimiter);
  const result: Record<string, unknown> = {};

  for (const part of parts) {
    const trimmedPart = part.replace(/^\r?\n/, '').replace(/\r?\n$/, '');
    if (!trimmedPart || trimmedPart === '--' || trimmedPart.startsWith('--')) continue;

    let headers = '';
    let body = '';
    const crlfIdx = trimmedPart.indexOf('\r\n\r\n');
    const lfIdx = trimmedPart.indexOf('\n\n');
    if (crlfIdx >= 0 && (lfIdx < 0 || crlfIdx <= lfIdx)) {
      headers = trimmedPart.slice(0, crlfIdx);
      body = trimmedPart.slice(crlfIdx + 4);
    } else if (lfIdx >= 0) {
      headers = trimmedPart.slice(0, lfIdx);
      body = trimmedPart.slice(lfIdx + 2);
    } else {
      continue;
    }

    body = body.replace(/\r?\n$/, '');

    const nameMatch = /Content-Disposition:[^\r\n]*;\s*name="([^"]+)"/i.exec(headers);
    if (!nameMatch?.[1]) continue;
    if (/filename=/i.test(headers)) continue;
    result[nameMatch[1]] = body;
  }

  return Object.keys(result).length > 0 ? result : null;
}

function extractBoundary(contentType: string, rawText: string): string | null {
  const fromHeader = /boundary=(?:"([^"]+)"|([^;\s]+))/i.exec(contentType);
  if (fromHeader?.[1] || fromHeader?.[2]) {
    return (fromHeader[1] || fromHeader[2] || '').trim() || null;
  }
  const firstLine = rawText.split(/\r?\n/, 1)[0]?.trim() ?? '';
  if (firstLine.startsWith('--') && firstLine.length > 2) {
    return firstLine.slice(2).replace(/--$/, '') || null;
  }
  return null;
}