// imported from https://github.com/socketio/engine.io-parser/tree/2.2.x

/**
 * Module dependencies.
 */

var utf8 = require('./utf8')

/**
 * Current protocol version.
 */
export const protocol = 3

const hasBinary = (packets) => {
    for (const packet of packets) {
        if (packet.data instanceof ArrayBuffer || ArrayBuffer.isView(packet.data)) {
            return true
        }
    }
    return false
}

/**
 * Packet types.
 */

export const packets = {
    open: 0    // non-ws
    , close: 1    // non-ws
    , ping: 2
    , pong: 3
    , message: 4
    , upgrade: 5
    , noop: 6
}

var packetslist = Object.keys(packets)

/**
 * Premade error packet.
 */

var err = { type: 'error', data: 'parser error' }

const EMPTY_BUFFER = Buffer.concat([])

/**
 * Encodes a packet.
 *
 *     <packet type id> [ <data> ]
 *
 * Example:
 *
 *     5hello world
 *     3
 *     4
 *
 * Binary is encoded in an identical principle
 *
 * @api private
 */

export function encodePacket(packet, supportsBinary, utf8encode, callback) {
    if (typeof supportsBinary === 'function') {
        callback = supportsBinary
        supportsBinary = null
    }

    if (typeof utf8encode === 'function') {
        callback = utf8encode
        utf8encode = null
    }

    if (Buffer.isBuffer(packet.data)) {
        return encodeBuffer(packet, supportsBinary, callback)
    } else if (packet.data && (packet.data.buffer || packet.data) instanceof ArrayBuffer) {
        return encodeBuffer({ type: packet.type, data: arrayBufferToBuffer(packet.data) }, supportsBinary, callback)
    }

    // Sending data as a utf-8 string
    var encoded = packets[packet.type]

    // data fragment is optional
    if (undefined !== packet.data) {
        encoded += utf8encode ? utf8.encode(String(packet.data), { strict: false }) : String(packet.data)
    }

    return callback('' + encoded)
};

/**
 * Encode Buffer data
 */

function encodeBuffer(packet, supportsBinary, callback) {
    if (!supportsBinary) {
        return encodeBase64Packet(packet, callback)
    }

    var data = packet.data
    var typeBuffer = Buffer.allocUnsafe(1)
    typeBuffer[0] = packets[packet.type]
    return callback(Buffer.concat([typeBuffer, data]))
}

/**
 * Encodes a packet with binary data in a base64 string
 *
 * @param {Object} packet, has `type` and `data`
 * @return {String} base64 encoded message
 */

export function encodeBase64Packet(packet, callback) {
    var data = Buffer.isBuffer(packet.data) ? packet.data : arrayBufferToBuffer(packet.data)
    var message = 'b' + packets[packet.type]
    message += data.toString('base64')
    return callback(message)
};

/**
 * Decodes a packet. Data also available as an ArrayBuffer if requested.
 *
 * @return {Object} with `type` and `data` (if any)
 * @api private
 */

export function decodePacket(data, binaryType, utf8decode) {
    if (data === undefined) {
        return err
    }

    var type

    // String data
    if (typeof data === 'string') {

        type = data.charAt(0)

        if (type === 'b') {
            return decodeBase64Packet(data.slice(1), binaryType)
        }

        if (utf8decode) {
            data = tryDecode(data)
            if (data === false) {
                return err
            }
        }

        if (Number(type) != type || !packetslist[type]) {
            return err
        }

        if (data.length > 1) {
            return { type: packetslist[type], data: data.slice(1) }
        } else {
            return { type: packetslist[type] }
        }
    }

    // Binary data
    if (binaryType === 'arraybuffer') {
        // wrap Buffer/ArrayBuffer data into an Uint8Array
        var intArray = new Uint8Array(data)
        type = intArray[0]
        return { type: packetslist[type], data: intArray.buffer.slice(1) }
    }

    if (data instanceof ArrayBuffer) {
        data = arrayBufferToBuffer(data)
    }
    type = data[0]
    return { type: packetslist[type], data: data.slice(1) }
};

function tryDecode(data) {
    try {
        data = utf8.decode(data, { strict: false })
    } catch (e) {
        return false
    }
    return data
}

/**
 * Decodes a packet encoded in a base64 string.
 *
 * @param {String} base64 encoded message
 * @return {Object} with `type` and `data` (if any)
 */

export function decodeBase64Packet(msg, binaryType) {
    var type = packetslist[msg.charAt(0)]
    var data = Buffer.from(msg.slice(1), 'base64')
    if (binaryType === 'arraybuffer') {
        var abv = new Uint8Array(data.length)
        for (var i = 0; i < abv.length; i++) {
            abv[i] = data[i]
        }
        // @ts-ignore
        data = abv.buffer
    }
    return { type: type, data: data }
};

/**
 * Encodes multiple messages (payload).
 *
 *     <length>:data
 *
 * Example:
 *
 *     11:hello world2:hi
 *
 * If any contents are binary, they will be encoded as base64 strings. Base64
 * encoded strings are marked with a b before the length specifier
 *
 * @param {Array} packets
 * @api private
 */

export function encodePayload(packets, supportsBinary, callback) {
    if (typeof supportsBinary === 'function') {
        callback = supportsBinary
        supportsBinary = null
    }

    if (supportsBinary && hasBinary(packets)) {
        return encodePayloadAsBinary(packets, callback)
    }

    if (!packets.length) {
        return callback('0:')
    }

    function encodeOne(packet, doneCallback) {
        encodePacket(packet, supportsBinary, false, function (message) {
            doneCallback(null, setLengthHeader(message))
        })
    }

    map(packets, encodeOne, function (err, results) {
        return callback(results.join(''))
    })
};

function setLengthHeader(message) {
    return message.length + ':' + message
}

/**
 * Async array map using after
 */

function map(ary, each, done) {
    const results = new Array(ary.length)
    let count = 0

    for (let i = 0; i < ary.length; i++) {
        each(ary[i], (error, msg) => {
            results[i] = msg
            if (++count === ary.length) {
                done(null, results)
            }
        })
    }
}

/*
 * Decodes data when a payload is maybe expected. Possible binary contents are
 * decoded from their base64 representation
 *
 * @param {String} data, callback method
 * @api public
 */

export function decodePayload(data, binaryType, callback) {
    if (typeof data !== 'string') {
        return decodePayloadAsBinary(data, binaryType, callback)
    }

    if (typeof binaryType === 'function') {
        callback = binaryType
        binaryType = null
    }

    if (data === '') {
        // parser error - ignoring payload
        return callback(err, 0, 1)
    }

    var length = '', n, msg, packet

    for (var i = 0, l = data.length; i < l; i++) {
        var chr = data.charAt(i)

        if (chr !== ':') {
            length += chr
            continue
        }

        // @ts-ignore
        if (length === '' || (length != (n = Number(length)))) {
            // parser error - ignoring payload
            return callback(err, 0, 1)
        }

        msg = data.slice(i + 1, i + 1 + n)

        if (length != msg.length) {
            // parser error - ignoring payload
            return callback(err, 0, 1)
        }

        if (msg.length) {
            packet = decodePacket(msg, binaryType, false)

            if (err.type === packet.type && err.data === packet.data) {
                // parser error in individual packet - ignoring payload
                return callback(err, 0, 1)
            }

            var more = callback(packet, i + n, l)
            if (false === more) return
        }

        // advance cursor
        i += n
        length = ''
    }

    if (length !== '') {
        // parser error - ignoring payload
        return callback(err, 0, 1)
    }

};

/**
 *
 * Converts a buffer to a utf8.js encoded string
 *
 * @api private
 */

function bufferToString(buffer) {
    var str = ''
    for (var i = 0, l = buffer.length; i < l; i++) {
        str += String.fromCharCode(buffer[i])
    }
    return str
}

/**
 *
 * Converts a utf8.js encoded string to a buffer
 *
 * @api private
 */

function stringToBuffer(string) {
    var buf = Buffer.allocUnsafe(string.length)
    for (var i = 0, l = string.length; i < l; i++) {
        buf.writeUInt8(string.charCodeAt(i), i)
    }
    return buf
}

/**
 *
 * Converts an ArrayBuffer to a Buffer
 *
 * @api private
 */

function arrayBufferToBuffer(data) {
    // data is either an ArrayBuffer or ArrayBufferView.
    var length = data.byteLength || data.length
    var offset = data.byteOffset || 0

    return Buffer.from(data.buffer || data, offset, length)
}

/**
 * Encodes multiple messages (payload) as binary.
 *
 * <1 = binary, 0 = string><number from 0-9><number from 0-9>[...]<number
 * 255><data>
 *
 * Example:
 * 1 3 255 1 2 3, if the binary contents are interpreted as 8 bit integers
 *
 * @param {Array} packets
 * @return {Buffer} encoded payload
 * @api private
 */

export function encodePayloadAsBinary(packets, callback) {
    if (!packets.length) {
        return callback(EMPTY_BUFFER)
    }

    map(packets, encodeOneBinaryPacket, function (err, results) {
        return callback(Buffer.concat(results))
    })
};

function encodeOneBinaryPacket(p, doneCallback) {

    function onBinaryPacketEncode(packet) {

        var encodingLength = '' + packet.length
        var sizeBuffer

        if (typeof packet === 'string') {
            sizeBuffer = Buffer.allocUnsafe(encodingLength.length + 2)
            sizeBuffer[0] = 0 // is a string (not true binary = 0)
            for (var i = 0; i < encodingLength.length; i++) {
                sizeBuffer[i + 1] = parseInt(encodingLength[i], 10)
            }
            sizeBuffer[sizeBuffer.length - 1] = 255
            return doneCallback(null, Buffer.concat([sizeBuffer, stringToBuffer(packet)]))
        }

        sizeBuffer = Buffer.allocUnsafe(encodingLength.length + 2)
        sizeBuffer[0] = 1 // is binary (true binary = 1)
        for (var i = 0; i < encodingLength.length; i++) {
            sizeBuffer[i + 1] = parseInt(encodingLength[i], 10)
        }
        sizeBuffer[sizeBuffer.length - 1] = 255

        doneCallback(null, Buffer.concat([sizeBuffer, packet]))
    }

    encodePacket(p, true, true, onBinaryPacketEncode)

}


/*
 * Decodes data when a payload is maybe expected. Strings are decoded by
 * interpreting each byte as a key code for entries marked to start with 0. See
 * description of encodePayloadAsBinary
 * @param {Buffer} data, callback method
 * @api public
 */

export function decodePayloadAsBinary(data, binaryType, callback) {
    if (typeof binaryType === 'function') {
        callback = binaryType
        binaryType = null
    }

    var bufferTail = data
    var buffers = []
    var i

    while (bufferTail.length > 0) {
        var strLen = ''
        var isString = bufferTail[0] === 0
        for (i = 1; ; i++) {
            if (bufferTail[i] === 255) break
            // 310 = char length of Number.MAX_VALUE
            if (strLen.length > 310) {
                return callback(err, 0, 1)
            }
            strLen += '' + bufferTail[i]
        }
        bufferTail = bufferTail.slice(strLen.length + 1)

        var msgLength = parseInt(strLen, 10)

        var msg = bufferTail.slice(1, msgLength + 1)
        if (isString) msg = bufferToString(msg)
        buffers.push(msg)
        bufferTail = bufferTail.slice(msgLength + 1)
    }

    var total = buffers.length
    for (i = 0; i < total; i++) {
        var buffer = buffers[i]
        callback(decodePacket(buffer, binaryType, true), i, total)
    }
}