'use strict';

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

module.exports = Stampit()
    .init(function () {
        const FC = 16;
        let init = () => {
            this.log.debug('initiating write multiple registers request handler.');
            this.responseDelay = this.responseDelay || 0;
            this.setRequestHandler(FC, onRequest);
        };
    
        let _onRequest = (pdu, cb) => {
            if (pdu.length < 3) {
                cb(Put().word8(0x90).word8(0x02).buffer());
            } else {
                // const fc          = pdu.readUInt8(0);
                const start       = pdu.readUInt16BE(1);
                const byteStart   = start * 2;
                const quantity    = pdu.readUInt16BE(3);
                const byteCount   = pdu.readUInt8(5);

                if (quantity > 0x007b) {
                    cb(Put().word8(0x90).word8(0x03).buffer());
                } else {
                    this.emit('preWriteMultipleRegistersRequest', byteStart, quantity, byteCount);

                    let mem = this.getHolding();

                    if (!quantity || byteStart + (quantity * 2) > mem.length) {
                        cb(Put().word8(0x90).word8(0x02).buffer());
                    } else {
                        let response = Put().word8(0x10).word16be(start).word16be(quantity).buffer();
                        let j = 0;

                        for (let i = byteStart; i < byteStart + byteCount; i += 1) {
                            mem.writeUInt8(pdu.readUInt8(6 + j), i);
                            j++;
                        }

                        this.emit('postWriteMultipleRegistersRequest', byteStart, quantity, byteCount);

                        cb(response);
                    }
                }
            }
        };

        let onRequest = (pdu, cb) => {
            if (this.responseDelay) {
                setTimeout(_onRequest, this.responseDelay, pdu, cb);
            } else {
                setImmediate(_onRequest, pdu, cb);
            }
        };

        init();
    });