'use strict';

const Stampit = require('stampit');
const Put     = require('put');


module.exports = Stampit()
    .init(function () {
        const FC = 16;

        let init = () => this.addResponseHandler(FC, onResponse);

        let onResponse = (unitId, pdu, cb) => {
            const fc = pdu.readUInt8(0);

            if (fc !== FC) {
                cb(`WriteMultipleRegisters: Invalid FC ${fc}`);
            } else {
                const startAddress = pdu.readUInt16BE(1);
                const quantity     = pdu.readUInt16BE(3);

                let resp = {
                    unitId:         unitId,
                    fc:             fc,
                    startAddress:   startAddress,
                    quantity:       quantity
                };
                cb(null, resp);
            }
        };

        this.writeMultipleRegisters = (unitId, startAddress, data) => {
            return new Promise((resolve, reject) => {
                let pdu = Put().word8(FC).word16be(startAddress);
                if (data instanceof Buffer) {
                    if (data.length / 2 > 0x007b) {
                        reject('Length is too big');
                        return;
                    }

                    pdu.word16be(data.length / 2).word8(data.length).put(data);
                } else if (data instanceof Array) {
                    if (data.length > 0x007b) {
                        reject('Length is too big');
                        return;
                    }

                    let byteCount = Math.ceil(data.length * 2);
                    pdu.word16be(data.length).word8(byteCount);

                    for (let i = 0; i < data.length; i += 1) {
                        pdu.word16be(data[i]);
                    }
                } else {
                    reject('Invalid data');
                    return;
                }

                this.queueRequest(unitId, FC, pdu.buffer(), (err, resp) => {
                    if (err) {
                        reject(err);
                    } else {
                        resolve(resp);
                    }
                });
            });
        };

        init();
    
    });