/*
 * This is a modified version of jquery.numeric.js from
 * http://www.texotela.co.uk/code/jquery/numeric/
 * Allows only valid characters to be entered into input boxes.
 * Note: does not validate that the final text is a valid number
 * (that could be done by another script, or server-side)
 * 
 * Options:
 * decimal - Decimal character
 * posNumber - true if only positive numbers is allowed
 * successCallback - A callback function to call when a valid value was inserted
 * errorCallback - A callback function to call when an invalid value was inserted
 *
 */
jQuery.fn.numeric = function(options) {
	var decimal = options.decimal || '.';
    var posNumber = options.posNumber ? options.posNumber : false;
    var errorCallback = options.errorCallback || function(key) {};
    var successCallback = options.successCallback || function(key) {};
    
	this.keypress(function(e) {
        var key = e.charCode ? e.charCode : e.keyCode ? e.keyCode : 0;
        var allow = false;
        // allow enter/return key (only when in an input box)
        if(key == 13 && this.nodeName.toLowerCase() == "input") {
            allow = true;
        }
        
        // allow Ctrl+A
        if((e.ctrlKey && key == 97 /* firefox */) || (e.ctrlKey && key == 65) /* opera */) return true;
        // allow Ctrl+X (cut)
        if((e.ctrlKey && key == 120 /* firefox */) || (e.ctrlKey && key == 88) /* opera */) return true;
        // allow Ctrl+C (copy)
        if((e.ctrlKey && key == 99 /* firefox */) || (e.ctrlKey && key == 67) /* opera */) return true;
        // allow Ctrl+Z (undo)
        if((e.ctrlKey && key == 122 /* firefox */) || (e.ctrlKey && key == 90) /* opera */) return true;
        // allow or deny Ctrl+V (paste), Shift+Ins
        if((e.ctrlKey && key == 118 /* firefox */) || (e.ctrlKey && key == 86) /* opera */
        || (e.shiftKey && key == 45)) return true;
        
        // if a number was not pressed
        if(key < 48 || key > 57) {
            /* '-' only allowed at start */
            if(key == 45 && this.value.length == 0) {
                allow = posNumber ? false : true;
            }
            //if(key == 45 && this.value.length == 0) return true;
            
            /* only one decimal separator allowed */
            if(key == decimal.charCodeAt(0) && this.value.indexOf(decimal) != -1) {
                allow = false;
            }
            // check for other keys that have special purposes
            if(
                key == 8 /* backspace */ ||
                key == 9 /* tab */ ||
                key == 13 /* enter */ ||
                key == 35 /* end */ ||
                key == 36 /* home */ ||
                key == 37 /* left */ ||
                key == 39 /* right */ ||
                key == 46 /* del */
            ) {
                // for detecting special keys (listed above)
                // IE does not support 'charCode' and ignores them in keypress anyway
                if(typeof e.charCode != "undefined") {
                    // special keys have 'keyCode' and 'which' the same (e.g. backspace)
                    if(e.keyCode == e.which && e.which != 0) {
                        allow = true;
                    }
                    // or keyCode != 0 and 'charCode'/'which' = 0
                    else if(e.keyCode != 0 && e.charCode == 0 && e.which == 0) {
                        allow = true;
                    }
                }
            }
            // space is ok
            else if(e.charCode == 32) {
            	allow = true;
            } else {
                allow = false;
            }
            // if key pressed is the decimal and it is not already in the field
            if(key == decimal.charCodeAt(0) && this.value.indexOf(decimal) == -1) {
                allow = true;
            }
        } else {
            allow = true;
        }
                
        if (allow) {
            successCallback(key);
        } else {
       	    errorCallback(key);
        }
        
        return allow;
    });
    
	return this;
};