// ==UserScript==
// @name          Stack Exchange comments formatting shortcuts
// @namespace     stackexchange
// @version       1.3
// @description   Adds Ctrl+B (bold), Ctrl+I (italic), Ctrl+K (code), and Ctrl+L (link) keyboard shortcuts to comments.
// @icon          http://i.stack.imgur.com/6xzO1.png
// @homepage      http://stackapps.com/q/2103/5418
// @author        Kip Robinson - http://stackoverflow.com/users/18511/kip
// @contributor   Rodolfo Buaiz - http://stackapps.com/users/10590/brasofilo
// @match         *://*.askubuntu.com/*
// @match         *://*.mathoverflow.net/*
// @match         *://*.serverfault.com/*
// @match         *://*.stackapps.com/*
// @match         *://*.stackexchange.com/*
// @match         *://*.stackoverflow.com/*
// @match         *://*.superuser.com/*
// @exclude       *://chat.*
// @exclude       *://blog.*
// @exclude       *://api.*
// @exclude       *://data.*
// @updateURL     https://gist.github.com/raw/a539c1905608b253fcb6/CommentsFormattingShortcuts.user.js
// @downloadURL   https://gist.github.com/raw/a539c1905608b253fcb6/CommentsFormattingShortcuts.user.js
// @grant		  none
// ==/UserScript==

if( filter_so_check_page() ) {
	with_jquery( start_up );
}

/**
 * Check current page to determine if needs to run
 */
function filter_so_check_page() {
    var will_run = false;
    if( StackExchange ) {
        var routes = ['Review/Task', 'Questions/Show']; 
        var route = StackExchange.options.routeName;
        if( ( routes.indexOf(route) !== -1 ) ) {
            will_run = true;
        }
    }
    return will_run;
}

/**
 * Inject the script into the page
 */
function with_jquery( callback ) {
    var script = document.createElement("script");
    script.type = "text/javascript";
    script.textContent = "(" + callback.toString() + ")(jQuery)";
    document.body.appendChild( script );
}

/**
 * The real deal
 */
function start_up( $ ) {
    $(document).on( 'keydown', 'textarea[name=comment]', function(e) {
        //Ctrl+[BIKL]
        if( (e.ctrlKey||e.metaKey) && !e.altKey && (e.which == 66 || e.which == 73 || e.which == 75 || e.which == 76))
        {          
            //all text
            var text = $(this).val();
        
            //text before selection
            var before = text.substring(0,this.selectionStart);
        
            //selectect text
            var selected = text.substring(this.selectionStart,this.selectionEnd);
        
            //text after selection
            var after = text.substring(this.selectionEnd,text.length);
        
            //length of selection
            var selLen = selected.length;
        
            //markup character that will go before/after section. (Note: link is handled a bit differently.)
            var markup = '';
            var isLink = false;
            if(e.which == 66)
            markup = '**';
            else if(e.which == 73)
            markup = '*';
            else if(e.which == 75)
            markup = '`';
            else
            isLink = true;
        
            //markup length
            var mLen = markup.length;
        
            //replace is what the selected text will be replaced with
            var replace = '';
            if( selLen == 0 )
            {
                //nothing selected. just print the markup
                if(isLink)
                {
                    var url = prompt('Please input link URL');
                    var linkText = prompt('Please input link text');
                    replace = '[' + linkText + '](' + url + ')';
                }
                else
                {
                    replace = markup;
                }
            }
            else if( 
                !isLink && selLen > 2*mLen
                && selected.substring(0,mLen) == markup
                && selected.substring(selLen - mLen, selLen) == markup
            )
            {
                //We have selected something that starts and ends with the markup. We will remove the markup in
                //this case. For example, "*sometext*" becomes just "sometext". This is not available for links.
                replace = selected.substring(mLen, selLen - mLen);
            }
            else
            {
                //we have selected something. put the markup before and after it.
                if(isLink)
                {
                    var url = prompt('Please input link URL');
                    replace = '[' + selected + '](' + url + ')';
                }
                else
                {
                    replace = markup + selected + markup;
                }
            }
        
            //now update the text
            $(this).val(before + replace + after);
    
            if(selLen > 0)
            {
                //if something was selected, make the result selected too.
                this.selectionStart = before.length;
                this.selectionEnd = before.length + replace.length;
            }
            else
            {
                //nothign was selected, so put the cursor at the end of the updated text.
                this.selectionEnd = this.selectionStart = before.length + replace.length;
            }
    
            e.stopPropagation(); //prevent bubbling (new-school)
            return false; //prevent bubbling (old-school)
        }
    });
}