// Copyright 2015 Joyent, Inc.

module.exports = SSHBuffer;

var assert = require('assert-plus'); var Buffer = require('safer-buffer').Buffer;

function SSHBuffer(opts) {

assert.object(opts, 'options');
if (opts.buffer !== undefined)
        assert.buffer(opts.buffer, 'options.buffer');

this._size = opts.buffer ? opts.buffer.length : 1024;
this._buffer = opts.buffer || Buffer.alloc(this._size);
this._offset = 0;

}

SSHBuffer.prototype.toBuffer = function () {

return (this._buffer.slice(0, this._offset));

};

SSHBuffer.prototype.atEnd = function () {

return (this._offset >= this._buffer.length);

};

SSHBuffer.prototype.remainder = function () {

return (this._buffer.slice(this._offset));

};

SSHBuffer.prototype.skip = function (n) {

this._offset += n;

};

SSHBuffer.prototype.expand = function () {

this._size *= 2;
var buf = Buffer.alloc(this._size);
this._buffer.copy(buf, 0);
this._buffer = buf;

};

SSHBuffer.prototype.readPart = function () {

return ({data: this.readBuffer()});

};

SSHBuffer.prototype.readBuffer = function () {

var len = this._buffer.readUInt32BE(this._offset);
this._offset += 4;
assert.ok(this._offset + len <= this._buffer.length,
    'length out of bounds at +0x' + this._offset.toString(16) +
    ' (data truncated?)');
var buf = this._buffer.slice(this._offset, this._offset + len);
this._offset += len;
return (buf);

};

SSHBuffer.prototype.readString = function () {

return (this.readBuffer().toString());

};

SSHBuffer.prototype.readCString = function () {

var offset = this._offset;
while (offset < this._buffer.length &&
    this._buffer[offset] !== 0x00)
        offset++;
assert.ok(offset < this._buffer.length, 'c string does not terminate');
var str = this._buffer.slice(this._offset, offset).toString();
this._offset = offset + 1;
return (str);

};

SSHBuffer.prototype.readInt = function () {

var v = this._buffer.readUInt32BE(this._offset);
this._offset += 4;
return (v);

};

SSHBuffer.prototype.readInt64 = function () {

assert.ok(this._offset + 8 < this._buffer.length,
    'buffer not long enough to read Int64');
var v = this._buffer.slice(this._offset, this._offset + 8);
this._offset += 8;
return (v);

};

SSHBuffer.prototype.readChar = function () {

var v = this._buffer[this._offset++];
return (v);

};

SSHBuffer.prototype.writeBuffer = function (buf) {

while (this._offset + 4 + buf.length > this._size)
        this.expand();
this._buffer.writeUInt32BE(buf.length, this._offset);
this._offset += 4;
buf.copy(this._buffer, this._offset);
this._offset += buf.length;

};

SSHBuffer.prototype.writeString = function (str) {

this.writeBuffer(Buffer.from(str, 'utf8'));

};

SSHBuffer.prototype.writeCString = function (str) {

while (this._offset + 1 + str.length > this._size)
        this.expand();
this._buffer.write(str, this._offset);
this._offset += str.length;
this._buffer[this._offset++] = 0;

};

SSHBuffer.prototype.writeInt = function (v) {

while (this._offset + 4 > this._size)
        this.expand();
this._buffer.writeUInt32BE(v, this._offset);
this._offset += 4;

};

SSHBuffer.prototype.writeInt64 = function (v) {

assert.buffer(v, 'value');
if (v.length > 8) {
        var lead = v.slice(0, v.length - 8);
        for (var i = 0; i < lead.length; ++i) {
                assert.strictEqual(lead[i], 0,
                    'must fit in 64 bits of precision');
        }
        v = v.slice(v.length - 8, v.length);
}
while (this._offset + 8 > this._size)
        this.expand();
v.copy(this._buffer, this._offset);
this._offset += 8;

};

SSHBuffer.prototype.writeChar = function (v) {

while (this._offset + 1 > this._size)
        this.expand();
this._buffer[this._offset++] = v;

};

SSHBuffer.prototype.writePart = function (p) {

this.writeBuffer(p.data);

};

SSHBuffer.prototype.write = function (buf) {

while (this._offset + buf.length > this._size)
        this.expand();
buf.copy(this._buffer, this._offset);
this._offset += buf.length;

};