// Copyright 2015 Joyent, Inc.

module.exports = {
	bufferSplit: bufferSplit,
	addRSAMissing: addRSAMissing,
	calculateDSAPublic: calculateDSAPublic,
	mpNormalize: mpNormalize,
	ecNormalize: ecNormalize,
	countZeros: countZeros,
	assertCompatible: assertCompatible,
	isCompatible: isCompatible
};

var assert = require('assert-plus');
var PrivateKey = require('./private-key');

var MAX_CLASS_DEPTH = 3;

function isCompatible(obj, klass, needVer) {
	if (obj === null || typeof (obj) !== 'object')
		return (false);
	if (needVer === undefined)
		needVer = klass.prototype._sshpkApiVersion;
	if (obj instanceof klass &&
	    klass.prototype._sshpkApiVersion[0] == needVer[0])
		return (true);
	var proto = Object.getPrototypeOf(obj);
	var depth = 0;
	while (proto.constructor.name !== klass.name) {
		proto = Object.getPrototypeOf(proto);
		if (!proto || ++depth > MAX_CLASS_DEPTH)
			return (false);
	}
	if (proto.constructor.name !== klass.name)
		return (false);
	var ver = proto._sshpkApiVersion;
	if (ver === undefined)
		ver = klass._oldVersionDetect(obj);
	if (ver[0] != needVer[0] || ver[1] < needVer[1])
		return (false);
	return (true);
}

function assertCompatible(obj, klass, needVer, name) {
	if (name === undefined)
		name = 'object';
	assert.ok(obj, name + ' must not be null');
	assert.object(obj, name + ' must be an object');
	if (needVer === undefined)
		needVer = klass.prototype._sshpkApiVersion;
	if (obj instanceof klass &&
	    klass.prototype._sshpkApiVersion[0] == needVer[0])
		return;
	var proto = Object.getPrototypeOf(obj);
	var depth = 0;
	while (proto.constructor.name !== klass.name) {
		proto = Object.getPrototypeOf(proto);
		assert.ok(proto && ++depth <= MAX_CLASS_DEPTH,
		    name + ' must be a ' + klass.name + ' instance');
	}
	assert.strictEqual(proto.constructor.name, klass.name,
	    name + ' must be a ' + klass.name + ' instance');
	var ver = proto._sshpkApiVersion;
	if (ver === undefined)
		ver = klass._oldVersionDetect(obj);
	assert.ok(ver[0] == needVer[0] && ver[1] >= needVer[1],
	    name + ' must be compatible with ' + klass.name + ' klass ' +
	    'version ' + needVer[0] + '.' + needVer[1]);
}

/* Count leading zero bits on a buffer */
function countZeros(buf) {
	var o = 0, obit = 8;
	while (o < buf.length) {
		var mask = (1 << obit);
		if ((buf[o] & mask) === mask)
			break;
		obit--;
		if (obit < 0) {
			o++;
			obit = 8;
		}
	}
	return (o*8 + (8 - obit) - 1);
}

function bufferSplit(buf, chr) {
	assert.buffer(buf);
	assert.string(chr);

	var parts = [];
	var lastPart = 0;
	var matches = 0;
	for (var i = 0; i < buf.length; ++i) {
		if (buf[i] === chr.charCodeAt(matches))
			++matches;
		else if (buf[i] === chr.charCodeAt(0))
			matches = 1;
		else
			matches = 0;

		if (matches >= chr.length) {
			var newPart = i + 1;
			parts.push(buf.slice(lastPart, newPart - matches));
			lastPart = newPart;
			matches = 0;
		}
	}
	if (lastPart <= buf.length)
		parts.push(buf.slice(lastPart, buf.length));

	return (parts);
}

function ecNormalize(buf, addZero) {
	assert.buffer(buf);
	if (buf[0] === 0x00 && buf[1] === 0x04) {
		if (addZero)
			return (buf);
		return (buf.slice(1));
	} else if (buf[0] === 0x04) {
		if (!addZero)
			return (buf);
	} else {
		while (buf[0] === 0x00)
			buf = buf.slice(1);
		if (buf[0] === 0x02 || buf[0] === 0x03)
			throw (new Error('Compressed elliptic curve points ' +
			    'are not supported'));
		if (buf[0] !== 0x04)
			throw (new Error('Not a valid elliptic curve point'));
		if (!addZero)
			return (buf);
	}
	var b = new Buffer(buf.length + 1);
	b[0] = 0x0;
	buf.copy(b, 1);
	return (b);
}

function mpNormalize(buf) {
	assert.buffer(buf);
	while (buf.length > 1 && buf[0] === 0x00 && (buf[1] & 0x80) === 0x00)
		buf = buf.slice(1);
	if ((buf[0] & 0x80) === 0x80) {
		var b = new Buffer(buf.length + 1);
		b[0] = 0x00;
		buf.copy(b, 1);
		buf = b;
	}
	return (buf);
}

function bigintToMpBuf(bigint) {
	var buf = new Buffer(bigint.toByteArray());
	buf = mpNormalize(buf);
	return (buf);
}

function calculateDSAPublic(g, p, x) {
	assert.buffer(g);
	assert.buffer(p);
	assert.buffer(x);
	try {
		var bigInt = require('jsbn').BigInteger;
	} catch (e) {
		throw (new Error('To load a PKCS#8 format DSA private key, ' +
		    'the node jsbn library is required.'));
	}
	g = new bigInt(g);
	p = new bigInt(p);
	x = new bigInt(x);
	var y = g.modPow(x, p);
	var ybuf = bigintToMpBuf(y);
	return (ybuf);
}

function addRSAMissing(key) {
	assert.object(key);
	assertCompatible(key, PrivateKey, [1, 1]);
	try {
		var bigInt = require('jsbn').BigInteger;
	} catch (e) {
		throw (new Error('To write a PEM private key from ' +
		    'this source, the node jsbn lib is required.'));
	}

	var d = new bigInt(key.part.d.data);
	var buf;

	if (!key.part.dmodp) {
		var p = new bigInt(key.part.p.data);
		var dmodp = d.mod(p.subtract(1));

		buf = bigintToMpBuf(dmodp);
		key.part.dmodp = {name: 'dmodp', data: buf};
		key.parts.push(key.part.dmodp);
	}
	if (!key.part.dmodq) {
		var q = new bigInt(key.part.q.data);
		var dmodq = d.mod(q.subtract(1));

		buf = bigintToMpBuf(dmodq);
		key.part.dmodq = {name: 'dmodq', data: buf};
		key.parts.push(key.part.dmodq);
	}
}