// MediaMTX Config Builder
// Purpose: Converts the rover server's media settings into the complete MediaMTX runtime configuration.
// Scope: Keeps deployment-specific hosts in the configuration database while protocol policy remains application-owned.
const path = require('path');

function normalizeAdditionalHosts(rawHosts) {
  if (rawHosts == null) return [];
  if (!Array.isArray(rawHosts)) {
    throw new Error('media.additionalHosts must be a list');
  }

  /*
    MediaMTX accepts both IP addresses and DNS names here. Preserve that flexibility because
    an installation can need a public candidate and a LAN candidate at the same time. Empty
    entries and duplicates are removed so a harmless config typo does not create redundant
    ICE candidates, while the values themselves remain entirely instance-owned.
  */
  return [...new Set(rawHosts.map((value) => String(value || '').trim()).filter(Boolean))];
}

function buildMediaMtxConfig({ config, serverPort, snapshotWriterPath }) {
  const media = config?.media || {};
  const webrtcPort = media.webrtcPort ?? 8189;
  const configuredHosts = normalizeAdditionalHosts(media.additionalHosts);
  let publicHostname = '';
  try {
    publicHostname = new URL(config?.publicUrl).hostname;
  } catch {
    // The assembled configuration schema normally prevents this. Keeping the
    // builder tolerant makes its pure tests and startup error path explicit.
  }
  // The canonical public hostname is always advertised once. Operators only
  // maintain genuinely additional LAN names, aliases, or fixed IP addresses.
  const additionalHosts = [...new Set([publicHostname, ...configuredHosts].filter(Boolean))];
  const authPort = Number(serverPort) || 8080;

  return {
    logLevel: 'info',
    api: true,
    apiAddress: '127.0.0.1:9997',
    metrics: true,
    metricsAddress: '127.0.0.1:9998',
    pprof: false,
    pprofAddress: '127.0.0.1:9999',

    /*
      Rover publishers and readers always request TCP explicitly. Declaring only TCP here
      also prevents MediaMTX from opening the separate RTP/RTCP UDP listeners, which are not
      useful for this local-network deployment and performed poorly in the measured tests.
    */
    rtsp: true,
    rtspAddress: ':8554',
    rtspTransports: ['tcp'],
    rtmp: false,
    hls: false,

    webrtc: true,
    // WHEP and WHIP signaling is public only through the Node /video proxy.
    // The configured ICE transport port remains directly reachable by browsers.
    webrtcAddress: '127.0.0.1:8889',
    webrtcLocalUDPAddress: `:${webrtcPort}`,
    webrtcLocalTCPAddress: `:${webrtcPort}`,
    webrtcAdditionalHosts: additionalHosts,
    webrtcICEServers2: [
      { url: 'stun:stun.l.google.com:19302' },
      { url: 'stun:stun1.l.google.com:19302' },
      { url: 'stun:stun2.l.google.com:19302' },
      { url: 'stun:stun3.l.google.com:19302' },
      { url: 'stun:stun4.l.google.com:19302' },
      { url: 'stun:stun.cloudflare.com:3478' },
    ],

    // Every publisher and server-local reader uses RTSP over TCP. Disable SRT
    // completely so MediaMTX cannot reintroduce the GoSRT/libSRT ACKACK mismatch.
    srt: false,

    authMethod: 'http',
    authHTTPAddress: `http://127.0.0.1:${authPort}/mediamtx/auth`,
    authHTTPExclude: [
      { action: 'api' },
      { action: 'metrics' },
      { action: 'pprof' },
    ],
    paths: {
      '~^room-audio/': { source: 'publisher' },
      all: {
        source: 'publisher',
        sourceOnDemand: false,
        runOnReady: path.resolve(snapshotWriterPath),
        runOnReadyRestart: true,
      },
    },
  };
}

module.exports = {
  buildMediaMtxConfig,
  normalizeAdditionalHosts,
};