codenothing/CSSTree

window.jQuery(function( jQuery ) {
    var alert = window.alert,
        textbox = jQuery( 'textarea' ),
        selectStart = jQuery( 'input[name=start]' ),
        selectEnd = jQuery( 'input[name=end]' ),
        positionInfo = jQuery( '#position' );

    // Highlighting input ranges
    function select( start, end ) {
        var element = textbox[ 0 ], range;

        if ( start >= end ) {
            alert( 'Start Must Be Less Than End' );
            return;
        }
        else if ( element.createTextRange ) {
            range = element.createTextRange();
            range.collapse( true );
            range.moveStart( 'character', start );
            range.moveEnd( 'character', end );
            range.select();
        }
        else if ( element.setSelectionRange ) {
            element.setSelectionRange( start, end );
        }
        else if ( element.selectionStart ) {
            element.selectionStart = start;
            element.selectionEnd = end;
        }
    }

    // Scroll text area to highlighted section (centered if possible)
    function scroll(){
        var current = textbox.scrollTop(),
            caret = textbox.textareaHelper( 'caretPos' ).top,
            height = textbox.height(),
            ypos = current + caret - parseInt( height / 2, 10 );

        if ( ypos < 0 ) {
            ypos = 0;
        }

        textbox.scrollTop( ypos );
    }

    // Greps the current caret position in relation to the string in the textbox (not x,y coord)
    function caretPos(){
        var element = textbox[ 0 ], pos = 0;

        if ( element.selectionStart ) {
            pos = element.selectionStart;
        }

        return pos;
    }

    // Update character position info
    function updatePosition(){
        positionInfo.html( caretPos() );
    }

    // Update caret position on any user action
    textbox.on( 'keyup', updatePosition )
        .on( 'click', updatePosition )
        .on( 'focus', updatePosition );

    // Watch for highlight trigger
    jQuery( 'form' ).on( 'submit', function( event ) {
        select(
            parseInt( selectStart.val() || '0', 10 ),
            parseInt( selectEnd.val() || '0', 10 ) + 1
        );

        scroll();
        return false;
    });
});