function _valToString(val)
{
	if (val === undefined || val === null)
		return '[' + typeof(val) + ']';
	return val.toString() + '[' + typeof(val) + ']';
}

var _hex2dec_table = {
	0:0, 1:1, 2:2, 3:3, 4:4, 5:5, 6:6, 7:7, 8:8, 9:9,
	a:10, b:11, c:12, d:13, e:14, f:15,
	A:10, B:11, C:12, D:13, E:14, F:15
};
function _hex2dec(hex)
{
	return _hex2dec_table[hex.charAt(0)]*16 + _hex2dec_table[hex.charAt(1)];
}

var _failed = false;
var _asserted = false;
function _warn(text)
{
	document.getElementById('d').appendChild(document.createElement('li')).appendChild(document.createTextNode(text));
}
function _fail(text)
{
	_warn(text);
	_failed = true;
}

function _assert(cond, text)
{
	_asserted = true;
	if (! cond)
		_fail('Failed assertion: ' + text);
}

function _assertSame(a, b, text_a, text_b)
{
	_asserted = true;
	if (a !== b)
		_fail('Failed assertion ' + text_a + ' === ' + text_b +
				' (got ' + _valToString(a) + ', expected ' + _valToString(b) + ')');
}

function _assertDifferent(a, b, text_a, text_b)
{
	_asserted = true;
	if (a === b)
		_fail('Failed assertion ' + text_a + ' !== ' + text_b +
				' (got ' + _valToString(a) + ', expected not ' + _valToString(b) + ')');
}

function _assertEqual(a, b, text_a, text_b)
{
	_asserted = true;
	if (a != b)
		_fail('Failed assertion ' + text_a + ' == ' + text_b +
				' (got ' + _valToString(a) + ', expected ' + _valToString(b) + ')');
}

function _assertMatch(a, b, text_a, text_b)
{
	_asserted = true;
	if (! a.match(b))
		_fail('Failed assertion ' + text_a + ' matches ' + text_b +
				' (got ' + _valToString(a) + ')');
}


var _manual_check = false;

function _requireManualCheck()
{
	_manual_check = true;
}

function _crash()
{
	_fail('Aborted due to predicted crash');
}

var _getImageDataCalibrated = false;
var _getImageDataIsPremul, _getImageDataIsBGRA;

function _getPixel(canvas, x,y)
{
	var ctx = canvas.getContext('2d');
	if (ctx && typeof(ctx.getImageData) != 'undefined')
	{
		try {
			var imgdata = ctx.getImageData(x, y, 1, 1);
		} catch (e) {
			// probably a security exception caused by having drawn
			// data: URLs onto the canvas
			imgdata = null;
		}
		if (imgdata)
		{
			// Work around getImageData bugs, since we want the other tests to
			// carry on working as well as possible
			if (! _getImageDataCalibrated)
			{
				var c2 = document.createElement('canvas');
				c2.width = c2.height = 1;
				var ctx2 = c2.getContext('2d');
				ctx2.fillStyle = 'rgba(0, 255, 255, 0.5)';
				ctx2.fillRect(0, 0, 1, 1);
				var data2 = ctx2.getImageData(0, 0, 1, 1).data;

				// Firefox returns premultiplied alpha

				if (data2[1] > 100 && data2[1] < 150)
					_getImageDataIsPremul = true;
				else
					_getImageDataIsPremul = false;

				// Opera Mini 4 Beta returns BGRA instead of RGBA

				if (data2[0] > 250 && data2[2] < 5)
					_getImageDataIsBGRA = true;
				else
					_getImageDataIsBGRA = false;

				_getImageDataCalibrated = true;
			}

			// Undo the BGRA flipping
			var rgba = (_getImageDataIsBGRA
				? [ imgdata.data[2], imgdata.data[1], imgdata.data[0], imgdata.data[3] ]
				: [ imgdata.data[0], imgdata.data[1], imgdata.data[2], imgdata.data[3] ]);

			if (! _getImageDataIsPremul)
				return rgba;

			// Undo the premultiplying
			if (rgba[3] == 0)
				return [ 0, 0, 0, 0 ];
			else
			{
				var a = rgba[3] / 255;
				return [
					Math.round(rgba[0]/a),
					Math.round(rgba[1]/a),
					Math.round(rgba[2]/a),
					rgba[3]
				];
			}
		}
	}

	try { ctx = canvas.getContext('opera-2dgame'); } catch (e) { /* Firefox throws */ }
	if (ctx && typeof(ctx.getPixel) != 'undefined')
	{
		try {
			var c = ctx.getPixel(x, y);
		} catch (e) {
			// probably a security exception caused by having drawn
			// data: URLs onto the canvas
			c = null;
		}
		if (c)
		{
			var matches = /^rgba\((\d+), (\d+), (\d+), ([\d\.]+)\)$/.exec(c);
			if (matches)
				return [ matches[1], matches[2], matches[3], Math.round(matches[4]*255) ];
			matches = /^#(..)(..)(..)$/.exec(c);
			if (matches)
				return [ _hex2dec(matches[1]), _hex2dec(matches[2]), _hex2dec(matches[3]), 255 ];
		}
	}
	//_warn("(Can't test pixel value)");
	_manual_check = true;
	return undefined;
}

function _assertPixel(canvas, x,y, r,g,b,a, pos, colour)
{
	_asserted = true;
	var c = _getPixel(canvas, x,y);
	if (c && ! (c[0] == r && c[1] == g && c[2] == b && c[3] == a))
		_fail('Failed assertion: got pixel [' + c + '] at ('+x+','+y+'), expected ['+r+','+g+','+b+','+a+']');
}

function _assertPixelApprox(canvas, x,y, r,g,b,a, pos, colour, tolerance)
{
	_asserted = true;
	var c = _getPixel(canvas, x,y);
	if (c)
	{
		var diff = Math.max(Math.abs(c[0]-r), Math.abs(c[1]-g), Math.abs(c[2]-b), Math.abs(c[3]-a));
		if (diff > tolerance)
			_fail('Failed assertion: got pixel [' + c + '] at ('+x+','+y+'), expected ['+r+','+g+','+b+','+a+'] +/- '+tolerance);
	}
}

function _addTest(test)
{
	var deferred = false;
	window.deferTest = function () { deferred = true; };
	function endTest()
	{
		if (_failed) // test failed
		{
			document.documentElement.className += ' fail';
			window._testStatus = ['fail', document.getElementById('d').innerHTML];
		}
		else if (_manual_check || !_asserted)
		{ // test case explicitly asked for a manual check, or no automatic assertions were performed
			document.getElementById('d').innerHTML += '<li>Cannot automatically verify result';
			document.documentElement.className += ' needs_check';
			window._testStatus = ['check', document.getElementById('d').innerHTML];
		}
		else // test succeeded
		{
			document.getElementById('d').innerHTML += '<li>Passed';
			document.documentElement.className += ' pass';
			window._testStatus = ['pass', document.getElementById('d').innerHTML];
		}
	}
	window.endTest = endTest;
	window.wrapFunction = function (f)
	{
		return function()
		{
			try
			{
				f.apply(null, arguments);
			}
			catch (e)
			{
				_fail('Aborted with exception: ' + e.message);
			}
			endTest();
		}
	}

	window.onload = function ()
	{
		try
		{
			var canvas = document.getElementById('c');
			var ctx = canvas.getContext('2d');
			test(canvas, ctx);
		}
		catch (e)
		{
			_fail('Aborted with exception: ' + e.message);
			deferred = false; // cancel any deference
		}

		if (! deferred)
			endTest();
	};
}