// flymaster-client.js
// WebSerial implementation of the Flymaster GPS protocol

// Make FlymasterClient available globally
window.FlymasterClient = class FlymasterClient {
  /**
   * Convert a Uint8Array to a hex string
   * @param {Uint8Array} bytes - The bytes to convert
   * @returns {string} - The hex string representation
   */
  bytesToHexString(bytes) {
    if (!bytes || bytes.length === 0) return '';

    return Array.from(bytes)
      .map(byte => byte.toString(16).padStart(2, '0'))
      .join(' ');
  }

  constructor() {
    // Constants
    this.BAUDRATE = 57600;
    this.XON = 0x11;
    this.XOFF = 0x13;
    this.MAX_LINE = 90;
    this.DOWN_TIMEOUT = 1000; // 1 second in milliseconds (matching C++ implementation)

    // Packet IDs
    this.PACKET_FLIGHT_INFO = 0xa0a0;
    this.PACKET_KEY_POSITION = 0xa1a1;
    this.PACKET_DELTA_POSITION = 0xa2a2;
    this.PACKET_END_MARKER = 0xa3a3;

    // Acknowledgment bytes
    this.ACK_POSITIVE = 0xb1;
    this.ACK_NEGATIVE = 0xb3;

    // Serial port and streams
    this.port = null;
    this.reader = null;
    this.writer = null;

    // Device information
    this.gpsname = "";
    this.gpsunitid = 0;
    this.saved_tracks = [];
    this.selected_tracks = [];
    this.flightInfo = null;
  }

  /**
   * Request port access and open connection
   */
  async connect() {
    try {
      // Request a port and open it
      this.port = await navigator.serial.requestPort();
      await this.port.open({ 
        baudRate: this.BAUDRATE,
        dataBits: 8,
        stopBits: 1,
        parity: "none",
        flowControl: "none"
      });

      // Get reader and writer
      this.reader = this.port.readable.getReader();
      this.writer = this.port.writable.getWriter();

      console.log("Connected to device");
      return true;
    } catch (error) {
      console.error("Connection failed:", error);
      return false;
    }
  }

  /**
   * Close the connection
   */
  async disconnect() {
    if (this.reader) {
      await this.reader.releaseLock();
      this.reader = null;
    }

    if (this.writer) {
      await this.writer.releaseLock();
      this.writer = null;
    }

    if (this.port && this.port.readable) {
      await this.port.close();
      this.port = null;
    }

    console.log("Disconnected from device");
  }

  /**
   * Initialize the GPS device
   * This matches the C++ implementation in FlymasterGps::init_gps()
   */
  async initGps() {
    try {
      // Get device information
      const result = await this.sendCommand("PFMSNP");
      this.gpsname = result[0];

      // Compute unit id as a XOR of the result (matching C++ implementation)
      this.gpsunitid = 0;
      for (let i = 0; i < result.length; i++) {
        for (let j = 0; j < result[i].length; j++) {
          this.gpsunitid ^= result[i].charCodeAt(j) << ((j % 4) * 8);
        }
      }

      // Download track list
      await this.sendSmplCommand("PFMDNL", ["LST"]);

      this.saved_tracks = [];
      let totaltracks = 0;

      do {
        const trackres = await this.receiveData("PFMLST");
        totaltracks = parseInt(trackres[0]);
        const date = trackres[2];
        const start = trackres[3];
        const duration = trackres[4];

        // Parse date and time
        const [day, month, year] = date.split('.').map(n => parseInt(n));
        const [hour, minute, second] = start.split(':').map(n => parseInt(n));

        // Create date object (note: month is 0-indexed in JS Date)
        const startDate = new Date(2000 + year, month - 1, day, hour, minute, second);

        // Parse duration
        const [dHour, dMinute, dSecond] = duration.split(':').map(n => parseInt(n));

        // Calculate end date
        const endDate = new Date(startDate.getTime() + 
          (dHour * 3600 + dMinute * 60 + dSecond) * 1000);

        this.saved_tracks.push({
          startDate: startDate,
          endDate: endDate
        });

      } while (this.saved_tracks.length < totaltracks);

      console.log(`Initialized GPS: ${this.gpsname}, found ${this.saved_tracks.length} tracks`);
      return this.saved_tracks;
    } catch (error) {
      console.error("Error in initGps:", error);
      throw error;
    }
  }

  /**
   * Read a packet from the device
   * This matches the C++ implementation in FlymasterGps::read_packet()
   */
  async readPacket() {
    try {
      // Read initial packet data (at least header)
      const { value: initialBytes, done: initialDone } = await this.reader.read();
      if (initialDone || !initialBytes || initialBytes.length < 3) { // At minimum: 2 bytes ID + 1 byte length
        throw new Error("Failed to read packet header");
      }

      console.debug("Received initial bytes:", this.bytesToHexString(initialBytes));

      // Extract packet ID (first 2 bytes)
      const packetId = initialBytes[0] + (initialBytes[1] << 8);

      if (packetId === this.PACKET_END_MARKER) {
        return { end: true };
      }

      // Extract length (3rd byte)
      const length = initialBytes[2];

      // Calculate total expected packet size: 3 bytes header + data length + 1 byte checksum
      const totalExpectedSize = 3 + length + 1;

      // Create a buffer for the complete packet
      let packetBytes = new Uint8Array(totalExpectedSize);

      // Copy initial bytes to the packet buffer
      let bytesReceived = Math.min(initialBytes.length, totalExpectedSize);
      packetBytes.set(initialBytes.slice(0, bytesReceived), 0);

      // Continue reading until we have the complete packet
      while (bytesReceived < totalExpectedSize) {
        const { value: moreBytes, done: moreDone } = await this.reader.read();
        if (moreDone) {
          throw new Error("Connection closed while reading packet data");
        }

        if (!moreBytes || moreBytes.length === 0) {
          continue;
        }

        console.debug("Received more bytes:", this.bytesToHexString(moreBytes));

        // Calculate how many more bytes we need and how many we can copy
        const bytesNeeded = totalExpectedSize - bytesReceived;
        const bytesToCopy = Math.min(moreBytes.length, bytesNeeded);

        // Copy the bytes to the packet buffer
        packetBytes.set(moreBytes.slice(0, bytesToCopy), bytesReceived);
        bytesReceived += bytesToCopy;
      }

      console.debug("Complete packet assembled:", this.bytesToHexString(packetBytes));

      // Extract data (next 'length' bytes after header)
      const data = new Uint8Array(length);
      for (let i = 0; i < length; i++) {
        data[i] = packetBytes[3 + i];
      }

      // Extract checksum (last byte after data)
      const cksum = packetBytes[3 + length];

      // Compute checksum
      let c_cksum = length;
      for (let i = 0; i < data.length; i++) {
        c_cksum ^= data[i];
      }

      if (c_cksum !== cksum) {
        // Send negative acknowledgment
        await this.writer.write(new Uint8Array([this.ACK_NEGATIVE]));
        throw new Error("Data checksum error");
      }
      else {
        await this.writer.write(new Uint8Array([this.ACK_POSITIVE]));
      }

      return { packetId, data };
    } catch (error) {
      console.error("Error in readPacket:", error);
      throw error;
    }
  }

  /**
   * Download a single track
   * This matches the C++ implementation in FlymasterGps::download_strack()
   */
  async downloadStrack(trackIndex, progressCallback = null) {
    try {
      const track = this.saved_tracks[trackIndex];
      if (!track) {
        throw new Error(`Track ${trackIndex} not found`);
      }

      // Reset flight info before downloading
      this.flightInfo = null;

      const result = [];

      // Format date for command
      const startDate = track.startDate;
      const year = startDate.getFullYear() % 100;
      const month = (startDate.getMonth() + 1).toString().padStart(2, '0');
      const day = startDate.getDate().toString().padStart(2, '0');
      const hour = startDate.getHours().toString().padStart(2, '0');
      const minute = startDate.getMinutes().toString().padStart(2, '0');
      const second = startDate.getSeconds().toString().padStart(2, '0');

      const timestamp = `${year}${month}${day}${hour}${minute}${second}`;

      // Send download command
      await this.sendSmplCommand("PFMDNL", [timestamp]);

      let newTrack = true;
      let basePos = null;
      let pktCount = 0;
      let pcounter = 0;
      const expCount = Math.floor((track.endDate - track.startDate) / 1000);

      while (true) {
        const packet = await this.readPacket();

        // Check if end of transmission
        if (packet.end) {
          break;
        }

        if (packet.packetId === this.PACKET_FLIGHT_INFO) {
          // Flight information packet
          this.flightInfo = this.parseFlightInfo(packet.data);
          console.debug("Received flight info:", this.flightInfo);
        }
        else if (packet.packetId === this.PACKET_KEY_POSITION) {
          // Key position packet
          basePos = this.parseKeyPosition(packet.data);
          result.push(this.makePoint(basePos, newTrack));
          newTrack = false;
        } 
        else if (packet.packetId === this.PACKET_DELTA_POSITION) {
          // Delta position packet
          const deltas = this.parseDeltaPositions(packet.data);

          for (const delta of deltas) {
            // Apply delta to base position
            basePos.fix = delta.fix;
            basePos.latitude += delta.latoff;
            basePos.longitude += delta.lonoff;
            basePos.gpsaltitude += delta.gpsaltoff;
            basePos.baro += delta.baroff;
            basePos.time += delta.timeoff;

            pktCount += delta.timeoff;

            if (progressCallback && !(pcounter++ % 60)) {
              const continueDownload = progressCallback(pktCount, expCount);
              if (!continueDownload) {
                // Send negative acknowledgment
                await this.writer.write(new Uint8Array([this.ACK_NEGATIVE]));
                throw new Error("Download cancelled");
              }
            }

            result.push(this.makePoint(basePos, false));
          }
        }
      }

      return result;
    } catch (error) {
      console.error("Error in downloadStrack:", error);
      throw error;
    }
  }

  /**
   * Download all selected tracks
   * This matches the C++ implementation in FlymasterGps::download_tracklog()
   */
  async downloadTracklog(progressCallback = null) {
    try {
      const result = [];

      // Sort tracks from higher index to lower (older date first)
      // So that the resulting array is time sorted
      this.selected_tracks.sort((a, b) => b - a);

      for (let i = 0; i < this.selected_tracks.length; i++) {
        const points = await this.downloadStrack(this.selected_tracks[i], progressCallback);
        result.push(...points);
      }

      return result;
    } catch (error) {
      console.error("Error in downloadTracklog:", error);
      throw error;
    }
  }

  /**
   * Parse a flight info packet
   */
  parseFlightInfo(data) {
    if (!data || data.length < 58) {
      throw new Error("Invalid flight info data");
    }

    const view = new DataView(data.buffer);

    // Extract string fields
    const decoder = new TextDecoder('ascii');
    const compnum = decoder.decode(data.slice(8, 16)).replace(/\0/g, '');
    const pilotname = decoder.decode(data.slice(16, 31)).replace(/\0/g, '');
    const gliderbrand = decoder.decode(data.slice(31, 46)).replace(/\0/g, '');
    const glidermodel = decoder.decode(data.slice(46, 61)).replace(/\0/g, '');

    return {
      sw_version: view.getUint16(0, true),   // little-endian
      hw_version: view.getUint16(2, true),   // little-endian
      serial: view.getUint32(4, true),       // little-endian
      compnum: compnum,
      pilotname: pilotname,
      gliderbrand: gliderbrand,
      glidermodel: glidermodel
    };
  }

  /**
   * Parse a key position packet
   */
  parseKeyPosition(data) {
    if (!data || data.length < 17) {
      throw new Error("Invalid key position data");
    }

    const view = new DataView(data.buffer);

    return {
      fix: view.getInt8(0),
      latitude: view.getInt32(1, true),      // little-endian
      longitude: view.getInt32(5, true),     // little-endian
      gpsaltitude: view.getInt16(9, true),   // little-endian
      baro: view.getInt16(11, true),         // little-endian
      time: view.getUint32(13, true)         // little-endian
    };
  }

  /**
   * Parse delta positions from a packet
   */
  parseDeltaPositions(data) {
    if (!data) {
      throw new Error("Invalid delta position data");
    }

    const deltas = [];
    const DELTA_SIZE = 6; // Size of each delta structure
    const view = new DataView(data.buffer, data.byteOffset, data.byteLength);

    for (let i = 0; i + DELTA_SIZE <= data.length; i += DELTA_SIZE) {
      const delta = {
        fix: view.getInt8(i),
        latoff: view.getInt8(i + 1),
        lonoff: view.getInt8(i + 2),
        gpsaltoff: view.getInt8(i + 3),
        baroff: view.getInt8(i + 4),
        timeoff: view.getUint8(i + 5)
      };

      deltas.push(delta);
    }

    return deltas;
  }

  /**
   * Convert a position to a trackpoint
   * This matches the C++ implementation in make_point()
   */
  makePoint(pos, newTrack) {
    return {
      lat: pos.latitude / 60000.0,
      lon: -pos.longitude / 60000.0,
      gpsalt: pos.gpsaltitude,
      baroalt: (1 - Math.pow(Math.abs((pos.baro / 10.0) / 1013.25), 0.190284)) * 44307.69,
      time: pos.time + 946684800, // Convert from Y2K epoch to Unix epoch
      new_trk: newTrack
    };
  }

  /**
   * Generate NMEA command with checksum
   * This matches the C++ implementation in NMEAGps::gen_command()
   */
  genCommand(command, parameters = []) {
    let data = '$' + command + ',';
    let cksum = 0;

    // Calculate checksum for command
    for (let i = 0; i < command.length; i++) {
      cksum ^= command.charCodeAt(i);
    }
    cksum ^= ','.charCodeAt(0);

    // Add parameters and update checksum
    for (let i = 0; i < parameters.length; i++) {
      data += parameters[i];

      // Update checksum with parameter
      for (let j = 0; j < parameters[i].length; j++) {
        cksum ^= parameters[i].charCodeAt(j);
      }

      data += ',';
      cksum ^= ','.charCodeAt(0);
    }

    // Add checksum as hexadecimal
    data += '*' + cksum.toString(16).padStart(2, '0').toUpperCase() + '\r\n';
    return data;
  }

  /**
   * Send a command and get response
   * This matches the C++ implementation in NMEAGps::send_command()
   */
  async sendCommand(command, parameters = []) {
    await this.sendSmplCommand(command, parameters);
    return await this.receiveData(command);
  }

  /**
   * Send a command without waiting for response
   * This matches the C++ implementation in NMEAGps::send_smpl_command()
   */
  async sendSmplCommand(command, parameters = []) {
    const cmdStr = this.genCommand(command, parameters);
    const encoder = new TextEncoder();
    const data = encoder.encode(cmdStr);
    await this.writer.write(data);
    console.debug("Sent command", cmdStr);
  }

  /**
   * Read data from the device until a valid response is received
   * This matches the C++ implementation in NMEAGps::receive_data()
   */
  async receiveData(command) {
    const decoder = new TextDecoder();
    let received = 0;
    let recv_cmd = "";
    let param = "";
    let result = [];
    let incmd = false;
    let cksum = 0;

    const startTime = Date.now();

    while (Date.now() - startTime < this.DOWN_TIMEOUT) {
      const { value, done } = await this.reader.read();
      if (done) {
        break;
      }

      for (let i = 0; i < value.length; i++) {
        const ch = value[i];
        received++;

        // Ignore XON, XOFF
        if (ch === this.XON || ch === this.XOFF) {
          continue;
        }

        if (ch === 0x24) { // '$'
          incmd = true;
          cksum = 0;
          param = "";
          recv_cmd = "";
          result = [];
          continue;
        }

        if (!incmd) {
          continue;
        }

        if (ch !== 0x2A) { // Not '*'
          cksum ^= ch;
        }

        if (ch === 0x2C || ch === 0x2A) { // ',' or '*'
          if (param.length) {
            if (!recv_cmd.length) {
              recv_cmd = param;
            } else {
              result.push(param);
            }
          }
          param = "";

          if (ch === 0x2A) { // '*'
            // Read checksum (2 hex characters)
            const cksum_s = String.fromCharCode(value[++i]) + String.fromCharCode(value[++i]);
            const cksum_r = parseInt(cksum_s, 16);

            // Skip CR, LF
            i += 2;

            if (cksum_r === cksum && recv_cmd === command) {
              return result;
            }
          }
          continue;
        }

        param += String.fromCharCode(ch);
      }
    }

    throw new Error(`Timeout waiting for response to ${command}`);
  }

  /**
   * Get list of available tracks
   */
  getTrackList() {
    return this.saved_tracks.map((track, index) => {
      return {
        index: index,
        startDate: track.startDate,
        endDate: track.endDate,
        duration: Math.floor((track.endDate - track.startDate) / 1000)
      };
    });
  }

  /**
   * Select tracks for download
   */
  selectTracks(indices) {
    this.selected_tracks = indices;
  }

  /**
   * Download all selected tracks
   */
  async downloadSelectedTracks(progressCallback = null) {
    return await this.downloadTracklog(progressCallback);
  }

  /**
   * Get the flight info data
   * @returns {Object|null} The flight info data or null if not available
   */
  getFlightInfo() {
    return this.flightInfo;
  }
}

// Export the class
if (typeof module !== 'undefined' && module.exports) {
  module.exports = { FlymasterClient };
} else {
  window.FlymasterClient = FlymasterClient;
}