/*
    fvlogger v1.0
    (c) 2005 davidfmiller
    http://www.fivevoltlogic.com/code/fvlogger/
    see readme.txt for documentation
*/

// version number
var FVLOGGER_VERSION = '1.0';

// turn logging on or off;
var FVL_LOG_ON = true;

// all logging statements that whose level is greater than or equal to FVL_DEFAULT_LOG_LEVEL will be processed;
// all others will be ignored
var FVL_DEFAULT_LOG_LEVEL = FVL_DEBUG;

// the id of the node that will have the logging statements appended to it
var FVL_LOG_ID = 'fvlogger';

// the element that should be wrapped around the log messages
var FVL_LOG_ELEMENT = 'p';

/* the code that follows is */

// constants for logging levels
var FVL_DEBUG = 0;
var FVL_INFO = 1;
var FVL_WARN = 2;
var FVL_ERROR = 3;
var FVL_FATAL = 4;

// the css classes that will be applied to the logging elements
var FVL_LOG_CLASSES = new Array("debug","info","warn","error","fatal");

/* */

// retrieves the element whose id is equal to FVL_LOG_ID
function getLogger(id) {
    if (arguments.length == 0) { id = FVL_LOG_ID; }
    return document.getElementById(id);
}

function showDebug() { FVL_showMessages(FVL_DEBUG); }
function showInfo() { FVL_showMessages(FVL_INFO); }
function showWarn() { FVL_showMessages(FVL_WARN); }
function showError() { FVL_showMessages(FVL_ERROR); }
function showFatal() { FVL_showMessages(FVL_FATAL); }
function showAll() { FVL_showMessages(); }

// removes all logging information from the logging element
function eraseLog(ask) {
    var debug = getLogger();
    if (! debug) { return false; }

    if (ask && ! confirm("Are you sure you wish to erase the log?")) {
        return false;
    }

    var ps = debug.getElementsByTagName(FVL_LOG_ELEMENT);
    var length = ps.length;
    for (var i = 0; i < length; i++) { debug.removeChild(ps[length - i - 1]); }
    return true;
}

function debug(message) { FVL_log("" + message, FVL_DEBUG); }
function warn(message) { FVL_log("" + message, FVL_WARN); }
function info(message) { FVL_log("" + message, FVL_INFO); }
function error(message) { FVL_log("" + message, FVL_ERROR);}
//function fatal(message) { FVL_log("" + message, FVL_FATAL);}

function windowError(message, url, line) {
    FVL_log('Error on line ' + line + ' of document ' + url + ': ' + message, FVL_FATAL);
    return true; //
}

// only override the window's error handler if we logging is turned on
if (FVL_LOG_ON) {
    window.onerror = windowError;
}

// 
function FVL_showMessages(level, hideOthers) {

  //alert('showing ' + level);

    var showAll = false;
    // if no level has been specified, use the default
    if (arguments.length == 0) { level = FVL_DEFAULT_LOG_LEVEL; showAll = true; }
    if (arguments.length < 2) { hideOthers = true; }

    // retrieve the element and current statements
    var debug = getLogger();
    if (! debug) { return false; }
    var ps = debug.getElementsByTagName("p");
    if (ps.length == 0) { return true; }

    // get the number of nodes in the list
    var l = ps.length; 

    // get the class name for the specified level
    var lookup = FVL_LOG_CLASSES[level]; 

    // loop through all logging statements/<p> elements...
    for (var i = l - 1; i >= 0; i--) {

        // hide all elements by default, if specified
        if (hideOthers) { hide(ps[i]); } 

        // get the class name for this <p>
        var c = getNodeClass(ps[i]);
//      alert(c);
//      alert("Node #" + i + "'s class is:" + c);
        if (c && c.indexOf(lookup) > -1 || showAll) { show(ps[i]); } 
    }
}

// appends a statement to the logging element if the threshold level is exceeded
function FVL_log(message, level) {

    // check to make sure logging is turned on
    if (! FVL_LOG_ON) { return false; } 

    // retrieve the infrastructure
    if (arguments.length == 1) { level = FVL_INFO;}
    if (level < FVL_DEFAULT_LOG_LEVEL) { return false; }
    var div = getLogger();
    if (! div) { return false; }

    // append the statement
    var p = document.createElement(FVL_LOG_ELEMENT);

    // this is a hack work around a bug in ie
    if (p.getAttributeNode("class")) {
        for (var i = 0; i < p.attributes.length; i++) {
            if (p.attributes[i].name.toUpperCase() == 'CLASS') {
                p.attributes[i].value = FVL_LOG_CLASSES[level];
            }
        }
    } else {
        p.setAttribute("class", FVL_LOG_CLASSES[level]);
    }
    var text = document.createTextNode(message);
    p.appendChild(text);
    div.appendChild(p);
    return true;
}

function exampleLogs() {
    // describe the four types of logging messages
    debug('Scatter debug messages throughout your code to provide a high-level overview of what your code is doing, such as which function is currently in scope and the values of loop counters.');
    info('Information messages are the meat and potatoes of logging messages; sprinkle them around to reveal more detailed information about your script\'s execution, such as the values of variables and function/method return values.');
    warn('Warning messages are used to indicate potentially hazardous situations, such as missing function arguments...');
    error('While error messages are used to indicate that something bad is about to happen; note that these kinds of errors are considered to be run-time errors, which are a different type of beast from the parse errors mentioned below.');

// generate an error to demonstrate the fatal error in ie and mozilla browsers
    a 
}

// show a node
function show(target) {
    target.style.display = "";
    return true;
}

// hide a node
function hide(target) {
    target.style.display = "none";
    return true;
}

// returns the class attribute of a node
function getNodeClass(obj) {
    var result = false;

    if (obj.getAttributeNode("class")) {
        result = obj.attributes.getNamedItem("class").value;
    }
    return result;
}