var isNav4, isNav6, isIE4;

// Browser version snooper; determines your browser
// (Navigator 4, Navigator 6, or Internet Explorer 4/5)

function setBrowser() {
	if (navigator.appVersion.charAt(0) == "4") {
		if (navigator.appName.indexOf("Explorer") >= 0) {
			isIE4 = true;
		} else {
			isNav4 = true;
		}
	} else if (navigator.appVersion.charAt(0) > "4") {
		isNav6 = true;
	}
}

// Given a selector string, return a style object
// by searching through stylesheets. Return null if
// none found

function getStyleBySelector(selector) {
	if (!isNav6) {
		return null;
	}
	var sheetList = document.styleSheets;
	var ruleList;
	var i, j;

	// look through stylesheets in reverse order that
	// they appear in the document

	for (i=sheetList.length-1; i >= 0; i--) {
		ruleList = sheetList[i].cssRules;
		for (j=0; j<ruleList.length; j++) {
			if (ruleList[j].type == CSSRule.STYLE_RULE && ruleList[j].selectorText == selector) {
				return ruleList[j].style;
			}   
		}
	}
	return null;
}

// Given an id and a property (as strings), return
// the given property of that id.  Navigator 6 will
// first look for the property in a tag; if not found,
// it will look through the stylesheet.
//
// Note: do not precede the id with a # -- it will be
// appended when searching the stylesheets

function getIdProperty(id, property) {
	if (isNav6) {
		var styleObject = document.getElementById(id);
		if (styleObject != null) {
			styleObject = styleObject.style;
			if (styleObject[property]) {
				return styleObject[property];
			}
		}
		styleObject = getStyleBySelector("#" + id);
		return (styleObject != null) ?
			styleObject[property] : 
			null;
	} else if (isNav4) {
		return document[id][property];
	} else {
		return document.all[id].style[property];
	}
}

// Given an id and a property (as strings), set
// the given property of that id to the value provided.
//
// The property is set directly on the tag, not in the
// stylesheet.

function setIdProperty(id, property, value) {
	if (isNav6) {
		var styleObject = document.getElementById( id );
		if (styleObject != null) {
			styleObject = styleObject.style;
			styleObject[property] = value;
		}
		
	} else if (isNav4) {
		document[id][property] = value;
	} else if (isIE4) {
		 document.all[id].style[property] = value;
	}
}

// Move a given id.  If additive is true,
// then move it by xValue dots horizontally and
// yValue units vertically.  If additive is
// false, then move it to (xValue, yValue)
//
// Note: do not precede the id with a # -- it will be
// appended when searching the stylesheets
//
// Note also: length units are preserved in Navigator 6
// and Internet Explorer. That is, if left is 2cm and
// top is 3cm, and you move to (4, 5), the left will
// become 4cm and the top 5cm.

function generic_move(id, xValue, yValue, additive) {
	var left = getIdProperty(id, "left");
	var top = getIdProperty(id, "top");
	var leftMatch, topMatch;

	if (isNav4) {
		leftMatch = new Array(0, left, "");
		topMatch = new Array(0, top, "");
	} else if (isNav6 || isIE4) {
		var splitexp = /([-0-9.]+)(\w+)/;
		leftMatch = splitexp.exec(left);
		topMatch = splitexp.exec(top);
		if (leftMatch == null || topMatch == null) {
			leftMatch = new Array(0, 0, "px");
			topMatch = new Array(0, 0, "px");
		}
	}
	left = ((additive) ? parseFloat(leftMatch[1]) : 0) + xValue;
	top = ((additive) ? parseFloat(topMatch[1]) : 0) + yValue;
	setIdProperty( id, "left", left + leftMatch[2]);
	setIdProperty( id, "top", top + topMatch[2]);
}

// Move a given id to position (xValue, yValue)

function moveIdTo(id, x, y) {
	generic_move(id, x, y, false);
}

// Move a given id to (currentX + xValue, currentY + yValue)

function moveIdBy(id, x, y) {
	generic_move(id, x, y, true);
}

// Function used when converting rgb format colors
// from Navigator 6 to a hex format

function hex(n) {
	var hexdigits = "0123456789abcdef";
	return (hexdigits.charAt(n >> 4) + hexdigits.charAt(n & 0x0f));
}

// Retrieve background color for a given id.
// The value returned will be in hex format (#rrggbb)

function getBackgroundColor(id) {
	var color;

	if (isNav4) {
		color = document[id].bgColor;
	} else if (isNav6) {
		var parseExp = /rgb.(\d+),(\d+),(\d+)./;
		var rgbvals;
		color = getIdProperty(id, "backgroundColor");
		if (color) {
			rgbvals = parseExp.exec(color);
			if (rgbvals) {
				color = "#" + hex(rgbvals[1]) + hex(rgbvals[2]) +
					hex(rgbvals[3]);
			}
		}
		return color;
	} else if (isIE4) {
		return document.all[id].backgroundColor;
	}
	return "";
}

// Return a division's document

function getDocument(divName) {
	var doc;

	if (isNav4) {
		doc = window.document[divName].document;
	} else if (isNav6) {
		doc = document;
	} else if (isIE4) {
		doc = document;
	}
	return doc;
}