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

class FlymasterClient {
  constructor() {
    // Constants
    this.BAUDRATE = 57600;
    this.XON = 0x11;
    this.XOFF = 0x13;
    this.MAX_LINE = 90;
    this.DOWN_TIMEOUT = 1000; // 1 second in milliseconds
    
    // 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 = [];
  }

  /**
   * 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" // We'll handle XON/XOFF in software
      });
      
      // 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
   */
  async initGps() {
    // Get device information
    const result = await this.sendCommand("PFMSNP");
    this.gpsname = result[0];
    
    // Compute unit id as a XOR of the result
    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;
  }

  /**
   * Generate NMEA command with checksum
   */
  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
   */
  async sendCommand(command, parameters = []) {
    await this.sendSmplCommand(command, parameters);
    return await this.receiveData(command);
  }

  /**
   * Send a command without waiting for response
   */
  async sendSmplCommand(command, parameters = []) {
    const cmdStr = this.genCommand(command, parameters);
    const encoder = new TextEncoder();
    const data = encoder.encode(cmdStr);
    await this.writer.write(data);
  }

  /**
   * Read data from the device until a valid response is received
   */
  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) // '*'
          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");
  }

  /**
   * Read a binary packet from the device
   */
  async readPacket() {
    // Read packet ID (2 bytes)
    const { value: idBytes } = await this.reader.read();
    const packetId = idBytes[0] + (idBytes[1] << 8);
    
    if (packetId === this.PACKET_END_MARKER) {
      return { end: true };
    }
    
    // Read length (1 byte)
    const { value: lengthByte } = await this.reader.read();
    const length = lengthByte[0];
    
    // Read data
    let data = new Uint8Array(length);
    let bytesRead = 0;
    
    while (bytesRead < length) {
      const { value } = await this.reader.read();
      const remaining = length - bytesRead;
      const bytesToCopy = Math.min(remaining, value.length);
      
      data.set(value.slice(0, bytesToCopy), bytesRead);
      bytesRead += bytesToCopy;
    }
    
    // Read checksum
    const { value: cksumByte } = await this.reader.read();
    const cksum = cksumByte[0];
    
    // 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");
    }
    
    return { packetId, data };
  }

  /**
   * Download a specific track
   */
  async downloadTrack(trackIndex, progressCallback = null) {
    const track = this.saved_tracks[trackIndex];
    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) {
      try {
        const packet = await this.readPacket();
        
        // Check if end of transmission
        if (packet.end) break;
        
        if (packet.packetId === this.PACKET_FLIGHT_INFO) {
          // Flight information packet
          // We could parse this, but for now we'll just acknowledge it
        } 
        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));
          }
        }
        
        // Send positive acknowledgment
        await this.writer.write(new Uint8Array([this.ACK_POSITIVE]));
      } catch (error) {
        console.error("Error reading packet:", error);
        break;
      }
    }
    
    return result;
  }

  /**
   * Parse a key position packet
   */
  parseKeyPosition(data) {
    const view = new DataView(data.buffer);
    
    return {
      latitude: view.getInt32(0, true),      // little-endian
      longitude: view.getInt32(4, true),     // little-endian
      gpsaltitude: view.getInt16(8, true),   // little-endian
      baro: view.getInt16(10, true),         // little-endian
      time: view.getUint32(12, true),        // little-endian
      fix: data[16]
    };
  }

  /**
   * Parse delta positions from a packet
   */
  parseDeltaPositions(data) {
    const deltas = [];
    const DELTA_SIZE = 9; // Size of each delta structure
    
    for (let i = 0; i + DELTA_SIZE <= data.length; i += DELTA_SIZE) {
      deltas.push({
        fix: data[i],
        latoff: new Int16Array(data.buffer.slice(i + 1, i + 3))[0],
        lonoff: new Int16Array(data.buffer.slice(i + 3, i + 5))[0],
        gpsaltoff: data[i + 5],
        baroff: data[i + 6],
        timeoff: new Uint16Array(data.buffer.slice(i + 7, i + 9))[0]
      });
    }
    
    return deltas;
  }

  /**
   * Convert a position to a trackpoint
   */
  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
    };
  }

  /**
   * 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.sort((a, b) => b - a); // Sort in descending order
  }

  /**
   * Download all selected tracks
   */
  async downloadSelectedTracks(progressCallback = null) {
    let allPoints = [];
    
    for (const trackIndex of this.selected_tracks) {
      const points = await this.downloadTrack(trackIndex, progressCallback);
      allPoints = allPoints.concat(points);
    }
    
    return allPoints;
  }
}

// Example usage:
async function connectToFlymaster() {
  const client = new FlymasterClient();
  
  try {
    // Connect to device
    const connected = await client.connect();
    if (!connected) {
      console.error("Failed to connect to device");
      return;
    }
    
    // Initialize GPS
    await client.initGps();
    
    // Get track list
    const tracks = client.getTrackList();
    console.log("Available tracks:", tracks);
    
    // Select tracks to download (e.g., the most recent one)
    client.selectTracks([0]);
    
    // Download selected tracks with progress callback
    const points = await client.downloadSelectedTracks((current, total) => {
      const percent = Math.floor((current / total) * 100);
      console.log(`Download progress: ${percent}%`);
      return true; // Return false to cancel download
    });
    
    console.log(`Downloaded ${points.length} points`);
    
    // Disconnect
    await client.disconnect();
    
    return points;
  } catch (error) {
    console.error("Error:", error);
    await client.disconnect();
  }
}

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