const { SerialPort } = require('serialport');
const errors = require('./errors');

const address        = 0x04;
const frameLength      = 13;
const timeoutMS     = 700;
const retryDelayMS = 200;

//Arrotondamenti
const r1  = v => Math.round(v * 10)      / 10;      // 0.1  — tensione totale, corrente, SOC%
const r3  = v => Math.round(v * 1000)    / 1000;     // 0.001 — tensioni cella, capacità Ah
const r2  = v => Math.round(v * 100)     / 100;      // 0.01  — temperature in kelvin (SignalK)

class BMS {
  constructor({ device, retries = 5, log = () => {} } = {}) {
    this.device  = device;
    this.retries = retries;
    this.log     = log;
    this.port    = null;
    this.status  = null;            // ultimo getStatus (n. celle, sensori temp)
    this._queue  = Promise.resolve(); // serializza le richieste sulla seriale
  }

  open() {
    return new Promise((resolve, reject) => {
      this.port = new SerialPort({
        path: this.device,
        baudRate: 9600,
        dataBits: 8,
        parity: 'none',
        stopBits: 1,
        autoOpen: false
      });
      this.port.open(err => err ? reject(err) : this.port.flush(() => resolve()));
    });
  }

  async close() {
    if (this.port && this.port.isOpen) {
      await new Promise(r => this.port.close(() => r()));
    }
    this.port = null;
  }

  static _crc(buf) {
    let s = 0;
    for (let i = 0; i < buf.length; i++) s = (s + buf[i]) & 0xFF;
    return s;
  }

  _buildFrame(cmd, extraHex = '') {
    const hex = `a5${address.toString(16).padStart(2, '0')}${cmd}08${extraHex}`.padEnd(24, '0');
    const buf = Buffer.from(hex, 'hex');
    return Buffer.concat([buf, Buffer.from([BMS._crc(buf)])]);
  }

  //Invii multipli
  _sendBatch(cmd, opts = {}) {
    const run = async () => {
      let lastErr;
      for (let i = 0; i < this.retries; i++) {
        try {
          const r = await this._send(cmd, opts);
          if (opts.returnList ? r && r.length : r) return r;
        } catch (e) {
          lastErr = e;
          this.log(`cmd ${cmd} try ${i + 1} failed: ${e.message}`);
        }
        await new Promise(r => setTimeout(r, retryDelayMS));
      }
      throw lastErr || new Error(`cmd ${cmd} failed after ${this.retries} retries`);
    };
    const next = this._queue.then(run, run);
    this._queue = next.catch(() => {}); // non rompere la coda al primo errore
    return next;
  }

  _send(cmd, { extraHex = '', maxResponses = 1, returnList = false } = {}) {
    return new Promise((resolve, reject) => {
      if (!this.port || !this.port.isOpen) return reject(new Error('serial not open'));
      const tx = this._buildFrame(cmd, extraHex);
      const frames = [];
      let buf = Buffer.alloc(0);

      const cleanup = () => {
        clearTimeout(timer);
        this.port.off('data', onData);
      };

      const finish = () => {
        cleanup();
        if (returnList || frames.length > 1) return resolve(frames);
        return resolve(frames[0] || null);
      };

      const onData = chunk => {
        buf = buf.length ? Buffer.concat([buf, chunk]) : chunk;
        while (buf.length >= frameLength) {
          const frame = buf.subarray(0, frameLength);
          buf = buf.subarray(frameLength);
          if (BMS._crc(frame.subarray(0, 12)) !== frame[12]) {
            this.log(`crc mismatch: ${frame.toString('hex')}`);
            continue;
          }
          if (frame[2].toString(16).padStart(2, '0') !== cmd) {
            this.log(`unexpected cmd: ${frame.toString('hex')}`);
            continue;
          }
          frames.push(frame.subarray(4, 12));
          if (frames.length >= maxResponses) return finish();
        }
      };

      const timer = setTimeout(() => {
        if (frames.length === 0) { cleanup(); return reject(new Error('serial timeout')); }
        finish();
      }, timeoutMS);

      this.port.flush(() => {
        this.port.on('data', onData);
        this.port.write(tx, err => { if (err) { cleanup(); reject(err); } });
      });
    });
  }

  // 0x90 — voltage / current / SOC
  async getSoc() {
    const d = await this._sendBatch('90');
    if (!d) return null;
    return {
      total_voltage: r1(d.readInt16BE(0) / 10),
      current:       r1((d.readInt16BE(4) - 30000) / 10), // < 0 charging, > 0 discharging
      soc_percent:   r1(d.readInt16BE(6) / 10)
    };
  }

  // 0x91 — range tensioni cella
  async getCellVoltageRange() {
    const d = await this._sendBatch('91');
    if (!d) return null;
    return {
      highest_voltage: r3(d.readInt16BE(0) / 1000),
      highest_cell:    d.readInt8(2),
      lowest_voltage:  r3(d.readInt16BE(3) / 1000),
      lowest_cell:     d.readInt8(5)
    };
  }

  // 0x92 — range temperature
  async getTemperatureRange() {
    const d = await this._sendBatch('92');
    if (!d) return null;
    return {
      highest_temperature: d.readInt8(0) - 40,
      highest_sensor:      d.readInt8(1),
      lowest_temperature:  d.readInt8(2) - 40,
      lowest_sensor:       d.readInt8(3)
    };
  }

  // 0x93 — MOSFET + capacità residua
  async getMosfetStatus() {
    const d = await this._sendBatch('93');
    if (!d) return null;
    const m = d.readInt8(0);
    return {
      mode: m === 0 ? 'stationary' : m === 1 ? 'charging' : 'discharging',
      charging_mosfet:    !!d[1],
      discharging_mosfet: !!d[2],
      capacity_ah:        r3(d.readInt32BE(4) / 1000)
    };
  }

  // 0x94 — status (n. celle, sensori, cicli, DI/DO)
  async getStatus() {
    const d = await this._sendBatch('94');
    if (!d) return null;
    const stateByte  = d.readInt8(4);
    const stateNames = ['DI1','DI2','DI3','DI4','DO1','DO2','DO3','DO4'];
    const states = {};
    for (let i = 0; i < 8; i++) states[stateNames[i]] = !!((stateByte >> i) & 1);
    const data = {
      cells:               d.readInt8(0),
      temperature_sensors: d.readInt8(1),
      charger_running:     !!d[2],
      load_running:        !!d[3],
      states,
      cycles:              d.readInt16BE(5)
    };
    this.status = data;
    return data;
  }

  async _ensureStatus() {
    if (!this.status) await this.getStatus();
    if (!this.status) throw new Error('cannot read BMS status');
    return this.status;
  }

  _splitFrames(frames, total, perFrame, parser) {
    const out = {};
    let expected = 1;
    for (const f of frames) {
      const { idx, vals } = parser(f);
      if (idx !== expected) { this.log(`frame out of order: exp ${expected} got ${idx}`); continue; }
      for (let i = 0; i < perFrame; i++) {
        const k = (expected - 1) * perFrame + i + 1;
        if (k > total) return out;
        out[k] = vals[i];
      }
      expected++;
    }
    return out;
  }

  // 0x95 — tensioni cella (3/frame)
  async getCellVoltages() {
    const st = await this._ensureStatus();
    const max = Math.ceil(st.cells / 3);
    const frames = await this._sendBatch('95', { maxResponses: max, returnList: true });
    if (!frames) return null;
    const cells = this._splitFrames(frames, st.cells, 3, f => ({
      idx: f.readInt8(0),
      vals: [f.readInt16BE(1), f.readInt16BE(3), f.readInt16BE(5)]
    }));
    for (const k of Object.keys(cells)) cells[k] = cells[k] / 1000;
    return cells;
  }

  // 0x96 — temperature (7/frame, raw - 40 = °C)
  async getTemperatures() {
    const st = await this._ensureStatus();
    const max = Math.ceil(st.temperature_sensors / 7);
    const frames = await this._sendBatch('96', { maxResponses: max, returnList: true });
    if (!frames) return null;
    const t = this._splitFrames(frames, st.temperature_sensors, 7, f => ({
      idx: f.readInt8(0),
      vals: [f.readInt8(1), f.readInt8(2), f.readInt8(3), f.readInt8(4), f.readInt8(5), f.readInt8(6), f.readInt8(7)]
    }));
    for (const k of Object.keys(t)) t[k] = t[k] - 40;
    return t;
  }

  // 0x98 — errori (bitmap)
  async getErrors() {
    const d = await this._sendBatch('98');
    if (!d) return [];
    const errors = [];
    for (let i = 0; i < d.length; i++) {
      const b = d[i];
      if (!b) continue;
      for (let bit = 0; bit < 8; bit++) {
        if ((b >> bit) & 1) {
          errors.push((errors[i] && errors[i][bit]) || `unknown(${i}.${bit})`);
        }
      }
    }
    return errors;
  }
}

module.exports = BMS;