fun undoEscaping(src: String) {
	assert(src[0] == "%");
	x = src[1];
	y = src[2];
	if not isHex(x)
	or not isHex(y):
		return none, "Invalid %xx token";
	x = hexToInt(x);
	y = hexToInt(y);
	byte = x * 16 + y;
	char = chr(byte);
	return char, i;
}

fun getStringToken(src: String, i: int)
{
	token = "";
	while i < count(src) 
	  and src[i] != "=" 
	  and src[i] != "&": {
	
		char = src[i];
		
		if char == "%": {

			# Slice the "%xx" token
			if i+2 >= count(src):
				return none, none, "Invalid %xx escape token";
			slice = string.slice(src, i, 3);

			# Convert it to a character
			char, error = undoEscaping(slice);
			if error != none:
				return none, none, error;

			i = i+3;
		} else {
			if char == "+":
				char = " ";
			i = i+1;
		}
		
		token = string.cat(token, char);
	}
	return token, i;
}

fun parse(src: String) {

	result = {};

	i = 0;
	while i < count(src): {

		name, i, error = getStringToken(src, i);
		if error != none:
			return none, error;

		if i < count(src) and src[i] == "=": {
			i = i+1; # Skip the "="
			value, i, error = getStringToken(src, i);
			if error != none:
				return error;
		} else
			value = none;
		
		result[name] = value;

		if i < count(src) and src[i] == "&":
			i = i+1;
	}

	return result;
}

return {parse: parse};