/**
 * Convert proxy URIs (ss://, vmess://, trojan://) to Clash YAML flow-style proxy lines.
 * Returns a string like `  - {name: "NodeName", type: ss, server: ..., port: ..., ...}`
 * or null if the URI is unsupported/invalid.
 */
export function uriToClashLine(uri: string): string | null {
  try {
    if (uri.startsWith('ss://')) return ssToClash(uri);
    if (uri.startsWith('vmess://')) return vmessToClash(uri);
    if (uri.startsWith('trojan://')) return trojanToClash(uri);
    return null;
  } catch {
    return null;
  }
}

/** Escape a string value for use inside double-quoted YAML flow style */
function esc(s: string): string {
  return s.replace(/\\/g, '\\\\').replace(/"/g, '\\"');
}

function ssToClash(uri: string): string | null {
  const url = new URL(uri);
  const name = decodeURIComponent(url.hash.slice(1));
  const server = url.hostname;
  const port = url.port;

  // userinfo is base64(method:password)
  const decoded = Buffer.from(url.username, 'base64').toString();
  const firstColon = decoded.indexOf(':');
  if (firstColon === -1) return null;
  const cipher = decoded.slice(0, firstColon);
  const password = decoded.slice(firstColon + 1);

  return `  - {name: "${esc(name)}", type: ss, server: ${server}, port: ${port}, cipher: ${cipher}, password: "${esc(password)}"}`;
}

function vmessToClash(uri: string): string | null {
  const b64 = uri.replace('vmess://', '');
  const json = JSON.parse(Buffer.from(b64, 'base64').toString());

  const name = json.ps || 'VMess';
  const server = json.add;
  const port = json.port;
  const uuid = json.id;

  if (!server || !port || !uuid) return null;

  let line = `  - {name: "${esc(name)}", type: vmess, server: ${server}, port: ${port}, uuid: ${uuid}, alterId: 0, cipher: auto`;

  if (json.tls === 'tls') {
    line += ', tls: true';
    if (json.sni) line += `, sni: ${json.sni}`;
  }

  if (json.net === 'ws') {
    line += ', network: ws';
    const wsOpts: string[] = [];
    if (json.path) wsOpts.push(`path: "${esc(json.path)}"`);
    if (json.host) wsOpts.push(`headers: {Host: ${json.host}}`);
    if (wsOpts.length > 0) {
      line += `, ws-opts: {${wsOpts.join(', ')}}`;
    }
  }

  line += '}';
  return line;
}

function trojanToClash(uri: string): string | null {
  const url = new URL(uri);
  const name = decodeURIComponent(url.hash.slice(1));
  const server = url.hostname;
  const port = url.port;
  const password = url.username;
  const sni = url.searchParams.get('sni') || server;

  return `  - {name: "${esc(name)}", type: trojan, server: ${server}, port: ${port}, password: "${esc(password)}", sni: ${sni}}`;
}