'use strict';

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

module.exports = Stampit()
    .init(function () {
        const FC = 15;
        let init = () => {
            this.log.debug('initiating write multiple coils request handler.');
            this.responseDelay = this.responseDelay || 0;
            this.setRequestHandler(FC, onRequest);
        };

        let _onRequest = (pdu, cb) => {
            this.log.debug('handling write multiple coils request.');

            if (pdu.length < 3) {
                cb(Put().word8(0x8F).word8(0x02).buffer());
            } else {
                // const fc        = pdu.readUInt8(0);
                const start     = pdu.readUInt16BE(1);
                const quantity  = pdu.readUInt16BE(3);
                const byteCount = pdu.readUInt8(5);

                this.emit('preWriteMultipleCoilsRequest', start, quantity, byteCount);

                let mem = this.getCoils();

                // error response
                if (!quantity || start + quantity > mem.length * 8) {
                    cb(Put().word8(0x8F).word8(0x02).buffer());
                } else {
                    let response = Put().word8(0x0F).word16be(start).word16be(quantity).buffer();
                    let oldValue;
                    let newValue, current = pdu.readUInt8(6);
                    let j = 0;

                    for (let i = start; i < start + quantity; i += 1) {
                        // reading old value from the coils register
                        oldValue = mem.readUInt8(Math.floor(i / 8));

                        // apply new value
                        if ((Math.pow(2, j % 8) & current)) {
                            newValue = oldValue | Math.pow(2, i % 8);
                        } else {
                            newValue = oldValue & ~Math.pow(2, i % 8);
                        }

                        // write to buffer
                        mem.writeUInt8(newValue, Math.floor(i / 8));

                        // read new value from request pdu
                        j += 1;

                        if (j % 8 === 0 && j < quantity) {
                            current = pdu.readUInt8(6 + Math.floor(j / 8));
                        }
                    }

                    this.emit('postWriteMultipleCoilsRequest', start, quantity, byteCount);

                    cb(response);
                }
            }
        };

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

        init();
    });