/*
* This is the function that actually highlights a text string by
* adding HTML tags before and after all occurrences of the search
* term. You can pass your own tags if you'd like, or if the
* highlightStartTag or highlightEndTag parameters are omitted or
* are empty strings then the default <font> tags will be used.
*/
function doHighlight(bodyText, searchTerm, highlightStartTag, highlightEndTag) {
	// the highlightStartTag and highlightEndTag parameters are optional
	if ((!highlightStartTag) || (!highlightEndTag)) {
		highlightStartTag = "<font style='color:blue; background-color:yellow;'>";
		highlightEndTag = "</font>";
	}

	// find all occurences of the search term in the given text,
	// and add some "highlight" tags to them (we're not using a
	// regular expression search, because we want to filter out
	// matches that occur within HTML tags and script blocks, so
	// we have to do a little extra validation)
	var newText = "";
	var i = -1;
	var lcSearchTerm = searchTerm.toLowerCase();
	var lcBodyText = bodyText.toLowerCase();

	while (bodyText.length > 0) {
		i = lcBodyText.indexOf(lcSearchTerm, i + 1);
		if (i < 0) {
			newText += bodyText;
			bodyText = "";
		} else {
			// skip anything inside an HTML tag
			if (bodyText.lastIndexOf(">", i) >= bodyText.lastIndexOf("<", i)) {
				// skip anything inside a <script> block
				if (lcBodyText.lastIndexOf("/script>", i) >= lcBodyText.lastIndexOf("<script", i)) {
					newText += bodyText.substring(0, i) + highlightStartTag + bodyText.substr(i, searchTerm.length) + highlightEndTag;
					bodyText = bodyText.substr(i + searchTerm.length);
					lcBodyText = bodyText.toLowerCase();
					i = -1;
				}
			}
		}
	}

	return newText;
}


/*
* This is sort of a wrapper function to the doHighlight function.
* It takes the searchText that you pass, optionally splits it into
* separate words, and transforms the text on the current web page.
* Only the "searchText" parameter is required; all other parameters
* are optional and can be omitted.
*/
function highlightTextSearchTerms(Text, searchText, treatAsPhrase) {
	// if the treatAsPhrase parameter is true, then we should search for 
	// the entire phrase that was entered; otherwise, we will split the
	// search string so that each word is searched for and highlighted
	// individually
	if (treatAsPhrase) {
		searchArray = [searchText];
	} else {
		
		searchText = searchText.replace(',', ' ');
		while (searchText.indexOf("  ") != -1) {
			searchText = searchText.replace("  ", " ");
		}
		searchArray = searchText.split(" ");
	}

	var bodyText = Text; 
	for (var i = 0; i < searchArray.length; i++) {
		if (searchArray[i] != "") {
			bodyText = doHighlight(bodyText, searchArray[i]);
		}
	}

	return bodyText;
}

/*
* This is sort of a wrapper function to the doHighlight function.
* It takes the searchText that you pass, optionally splits it into
* separate words, and transforms the text on the current web page.
* Only the "searchText" parameter is required; all other parameters
* are optional and can be omitted.
*/
function highlightSearchTerms(searchText, treatAsPhrase, warnOnFailure, highlightStartTag, highlightEndTag) {
	// if the treatAsPhrase parameter is true, then we should search for 
	// the entire phrase that was entered; otherwise, we will split the
	// search string so that each word is searched for and highlighted
	// individually
	if (treatAsPhrase) {
		searchArray = [searchText];
	} else {
		searchArray = searchText.split(" ");
	}

	if (!document.body || typeof (document.body.innerHTML) == "undefined") {
		if (warnOnFailure) {
			alert("Sorry, for some reason the text of this page is unavailable. Searching will not work.");
		}
		return false;
	}

	var bodyText = document.body.innerHTML;
	for (var i = 0; i < searchArray.length; i++) {
		bodyText = doHighlight(bodyText, searchArray[i], highlightStartTag, highlightEndTag);
	}

	document.body.innerHTML = bodyText;
	return true;
}


/*
* This displays a dialog box that allows a user to enter their own
* search terms to highlight on the page, and then passes the search
* text or phrase to the highlightSearchTerms function. All parameters
* are optional.
*/
function searchPrompt(defaultText, treatAsPhrase, textColor, bgColor) {
	// This function prompts the user for any words that should
	// be highlighted on this web page
	if (!defaultText) {
		defaultText = "";
	}

	// we can optionally use our own highlight tag values
	if ((!textColor) || (!bgColor)) {
		highlightStartTag = "";
		highlightEndTag = "";
	} else {
		highlightStartTag = "<font style='color:" + textColor + "; background-color:" + bgColor + ";'>";
		highlightEndTag = "</font>";
	}

	if (treatAsPhrase) {
		promptText = "Please enter the phrase you'd like to search for:";
	} else {
		promptText = "Please enter the words you'd like to search for, separated by spaces:";
	}

	searchText = prompt(promptText, defaultText);

	if (!searchText) {
		alert("No search terms were entered. Exiting function.");
		return false;
	}

	return highlightSearchTerms(searchText, treatAsPhrase, true, highlightStartTag, highlightEndTag);
}