'use strict';

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

module.exports = Stampit()
    .init(function () {
        const FC = 6;

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

        let onResponse = (unitId, pdu, cb) => {
            const fc              = pdu.readUInt8(0);
            const registerAddress = pdu.readUInt16BE(1);
            const registerValue   = pdu.readUInt16BE(3);

            let resp = {
                unitId:             unitId,
                fc:                 fc,
                registerAddress:    registerAddress,
                registerValue:      registerValue,
                registerAddressRaw: pdu.slice(1,2),
                registerValueRaw:   pdu.slice(3,2)
            };

            if (fc !== FC) {
                cb(`WriteSingleRegister: Invalid FC ${fc}`);
            } else {
                cb(null, resp);
            }
        };

        this.writeSingleRegister = (unitId, address, value) => {
            return new Promise((resolve, reject) => {
                const payload = (value instanceof Buffer) ? value : Put().word16be(value).buffer();
                const pdu     = Put().word8be(FC).word16be(address).put(payload);

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

        init();
    
    });