"use strict";
/**
 * @module opcua.miscellaneous
 */
var util = require("util");
var assert = require("node-opcua-assert");

var EventEmitter = require("events").EventEmitter;


var PacketAssembler = require("node-opcua-packet-assembler").PacketAssembler;
var BinaryStream = require("node-opcua-binary-stream").BinaryStream;

var readMessageHeader = require("node-opcua-chunkmanager").readMessageHeader;

var buffer_utils = require("node-opcua-buffer-utils");
var createFastUninitializedBuffer = buffer_utils.createFastUninitializedBuffer;

var get_clock_tick = require("node-opcua-utils").get_clock_tick;


function readRawMessageHeader(data) {
    var messageHeader = readMessageHeader(new BinaryStream(data));
    return {
        length: messageHeader.length,
        messageHeader: messageHeader
    };
}
exports.readRawMessageHeader = readRawMessageHeader;

/**
 * @class MessageBuilderBase
 * @extends EventEmitter
 * @uses PacketAssembler
 * @constructor
 * @param options {Object}
 * @param [options.signatureLength=0] {Number}
 *
 */
var MessageBuilderBase = function (options) {

    options = options || {};

    this.signatureLength = options.signatureLength || 0;

    this.options = options;

    this.packetAssembler = new PacketAssembler({readMessageFunc: readRawMessageHeader});

    var self = this;
    this.packetAssembler.on("message", function (messageChunk) {
        self._feed_messageChunk(messageChunk);
    });
    this.packetAssembler.on("newMessage", function (info, data) {

        // record tick 0: when the first data is received
        self._tick0 = get_clock_tick();
        /**
         *
         * notify the observers that a new message is being built
         * @event start_chunk
         * @param info
         * @param data
         */
        self.emit("start_chunk", info, data);
    });

    this.security_defeated = false;
    this.total_body_size = 0;
    this.total_message_size = 0;
    this._init_new();
};

util.inherits(MessageBuilderBase, EventEmitter);

MessageBuilderBase.prototype._init_new = function () {
    this.security_defeated = false;
    this.status_error = false;
    this.total_body_size = 0;
    this.total_message_size = 0;
    this.blocks = [];
    this.message_chunks = [];
};

MessageBuilderBase.prototype._read_headers = function (binaryStream) {

    this.messageHeader = readMessageHeader(binaryStream);
    assert(binaryStream.length === 8);
    this.secureChannelId = binaryStream.readUInt32();
    assert(binaryStream.length === 12);

    // verifying secureChannelId
    if (this.expected_secureChannelId && this.secureChannelId !== this.expected_secureChannelId) {
        return this._report_error("Invalid secure channel Id");
    }
    return true;
};

/**
 * append a message chunk
 * @method _append
 * @param message_chunk
 * @private
 */
MessageBuilderBase.prototype._append = function (message_chunk) {

    if (this.status_error) {
        // the message builder is in error mode and further message chunks should be discarded.
        return false;
    }

    this.message_chunks.push(message_chunk);
    this.total_message_size += message_chunk.length;

    var binaryStream = new BinaryStream(message_chunk);

    if (!this._read_headers(binaryStream)) {
        return false;
    }
    assert(binaryStream.length >= 12);

    // verify message chunk length
    if (this.messageHeader.length !== message_chunk.length) {
        return this._report_error("Invalid messageChunk size: " +
            "the provided chunk is " + message_chunk.length + " bytes long " +
            "but header specifies " + this.messageHeader.length);
    }

    // the start of the message body block
    var offsetBodyStart = binaryStream.length;

    // the end of the message body block
    var offsetBodyEnd = binaryStream._buffer.length;

    this.total_body_size += (offsetBodyEnd - offsetBodyStart);
    this.offsetBodyStart = offsetBodyStart;

    // add message body to a queue
    // note : Buffer.slice create a shared memory !
    //        use Buffer.clone
    var shared_buf = message_chunk.slice(offsetBodyStart, offsetBodyEnd);
    var cloned_buf = createFastUninitializedBuffer(shared_buf.length);
    shared_buf.copy(cloned_buf, 0, 0);
    this.blocks.push(cloned_buf);

};

/**
 * Feed message builder with some data
 * @method feed
 * @param data
 */
MessageBuilderBase.prototype.feed = function (data) {

    if (!this.security_defeated && !this.status_error) {
        this.packetAssembler.feed(data);
    }
};


MessageBuilderBase.prototype._feed_messageChunk = function (messageChunk) {

    assert(messageChunk);
    var messageHeader = readMessageHeader(new BinaryStream(messageChunk));

    /**
     * notify the observers that new message chunk has been received
     * @event chunk
     * @param messageChunk {Buffer} the raw message chunk
     */
    this.emit("chunk", messageChunk);

    if (messageHeader.isFinal === "F") {

        // last message
        this._append(messageChunk);
        if (this.status_error) { return false; }

        var full_message_body = Buffer.concat(this.blocks);

        //record tick 1: when a complete message has been received ( all chunks assembled)
        this._tick1 = get_clock_tick();

        /**
         * notify the observers that a full message has been received
         * @event full_message_body
         * @param full_message_body {Buffer} the full message body made of all concatenated chunks.
         */
        this.emit("full_message_body", full_message_body);

        if (this._decode_message_body) {
            this._decode_message_body(full_message_body);
        }

        // be ready for next block
        this._init_new();
        return true;

    } else if (messageHeader.isFinal === "A") {
        return this._report_error("received and Abort Message");

    } else if (messageHeader.isFinal === "C") {
        return this._append(messageChunk);
    }

};

MessageBuilderBase.prototype._report_error = function (errorMessage) {

    this.status_error = true;
    //console.log("MESSAGE BUILDER ERROR".yellow, errorMessage.red);
    /**
     * notify the observers that an error has occurred
     * @event error
     * @param error {Error} the error to raise
     */
    this.emit("error", new Error(errorMessage), this.sequenceHeader ? this.sequenceHeader.requestId : null);
    return false;
};

exports.MessageBuilderBase = MessageBuilderBase;