/**
 * The reveal.js markdown plugin. Handles parsing of
 * markdown inside of presentations as well as loading
 * of external markdown documents.
 */
(function( root, factory ) {
    if( typeof exports === 'object' ) {
        module.exports = factory( require( './marked' ) );
    }
    else {
        // Browser globals (root is window)
        root.RevealMarkdown = factory( root.marked );
        root.RevealMarkdown.initialize();
    }
}( this, function( marked ) {

    if( typeof marked === 'undefined' ) {
        throw 'The reveal.js Markdown plugin requires marked to be loaded';
    }

    if( typeof hljs !== 'undefined' ) {
        marked.setOptions({
            highlight: function( lang, code ) {
                return hljs.highlightAuto( lang, code ).value;
            }
        });
    }

    var DEFAULT_SLIDE_SEPARATOR = '^\n---\n$',
        DEFAULT_NOTES_SEPARATOR = 'note:';


    /**
     * Retrieves the markdown contents of a slide section
     * element. Normalizes leading tabs/whitespace.
     */
    function getMarkdownFromSlide( section ) {

        var template = section.querySelector( 'script' );

        // strip leading whitespace so it isn't evaluated as code
        var text = ( template || section ).textContent;

        var leadingWs = text.match( /^\n?(\s*)/ )[1].length,
            leadingTabs = text.match( /^\n?(\t*)/ )[1].length;

        if( leadingTabs > 0 ) {
            text = text.replace( new RegExp('\\n?\\t{' + leadingTabs + '}','g'), '\n' );
        }
        else if( leadingWs > 1 ) {
            text = text.replace( new RegExp('\\n? {' + leadingWs + '}','g'), '\n' );
        }

        return text;

    }

    /**
     * Given a markdown slide section element, this will
     * return all arguments that aren't related to markdown
     * parsing. Used to forward any other user-defined arguments
     * to the output markdown slide.
     */
    function getForwardedAttributes( section ) {

        var attributes = section.attributes;
        var result = [];

        for( var i = 0, len = attributes.length; i < len; i++ ) {
            var name = attributes[i].name,
                value = attributes[i].value;

            // disregard attributes that are used for markdown loading/parsing
            if( /data\-(markdown|separator|vertical|notes)/gi.test( name ) ) continue;

            if( value ) {
                result.push( name + '=' + value );
            }
            else {
                result.push( name );
            }
        }

        return result.join( ' ' );

    }

    /**
     * Inspects the given options and fills out default
     * values for what's not defined.
     */
    function getSlidifyOptions( options ) {

        options = options || {};
        options.separator = options.separator || DEFAULT_SLIDE_SEPARATOR;
        options.notesSeparator = options.notesSeparator || DEFAULT_NOTES_SEPARATOR;
        options.attributes = options.attributes || '';

        return options;

    }

    /**
     * Helper function for constructing a markdown slide.
     */
    function createMarkdownSlide( content, options ) {

        options = getSlidifyOptions( options );

        var notesMatch = content.split( new RegExp( options.notesSeparator, 'mgi' ) );

        if( notesMatch.length === 2 ) {
            content = notesMatch[0] + '<aside class="notes" data-markdown>' + notesMatch[1].trim() + '</aside>';
        }

        return '<script type="text/template">' + content + '</script>';

    }

    /**
     * Parses a data string into multiple slides based
     * on the passed in separator arguments.
     */
    function slidify( markdown, options ) {

        options = getSlidifyOptions( options );

        var separatorRegex = new RegExp( options.separator + ( options.verticalSeparator ? '|' + options.verticalSeparator : '' ), 'mg' ),
            horizontalSeparatorRegex = new RegExp( options.separator );

        var matches,
            lastIndex = 0,
            isHorizontal,
            wasHorizontal = true,
            content,
            sectionStack = [];

        // iterate until all blocks between separators are stacked up
        while( matches = separatorRegex.exec( markdown ) ) {
            notes = null;

            // determine direction (horizontal by default)
            isHorizontal = horizontalSeparatorRegex.test( matches[0] );

            if( !isHorizontal && wasHorizontal ) {
                // create vertical stack
                sectionStack.push( [] );
            }

            // pluck slide content from markdown input
            content = markdown.substring( lastIndex, matches.index );

            if( isHorizontal && wasHorizontal ) {
                // add to horizontal stack
                sectionStack.push( content );
            }
            else {
                // add to vertical stack
                sectionStack[sectionStack.length-1].push( content );
            }

            lastIndex = separatorRegex.lastIndex;
            wasHorizontal = isHorizontal;
        }

        // add the remaining slide
        ( wasHorizontal ? sectionStack : sectionStack[sectionStack.length-1] ).push( markdown.substring( lastIndex ) );

        var markdownSections = '';

        // flatten the hierarchical stack, and insert <section data-markdown> tags
        for( var i = 0, len = sectionStack.length; i < len; i++ ) {
            // vertical
            if( sectionStack[i].propertyIsEnumerable( length ) && typeof sectionStack[i].splice === 'function' ) {
                markdownSections += '<section '+ options.attributes +'>';

                sectionStack[i].forEach( function( child ) {
                    markdownSections += '<section data-markdown>' +  createMarkdownSlide( child, options ) + '</section>';
                } );

                markdownSections += '</section>';
            }
            else {
                markdownSections += '<section '+ options.attributes +' data-markdown>' + createMarkdownSlide( sectionStack[i], options ) + '</section>';
            }
        }

        return markdownSections;

    }

    /**
     * Parses any current data-markdown slides, splits
     * multi-slide markdown into separate sections and
     * handles loading of external markdown.
     */
    function processSlides() {

        var sections = document.querySelectorAll( '[data-markdown]'),
            section;

        for( var i = 0, len = sections.length; i < len; i++ ) {

            section = sections[i];

            if( section.getAttribute( 'data-markdown' ).length ) {

                var xhr = new XMLHttpRequest(),
                    url = section.getAttribute( 'data-markdown' );

                datacharset = section.getAttribute( 'data-charset' );

                // see https://developer.mozilla.org/en-US/docs/Web/API/element.getAttribute#Notes
                if( datacharset != null && datacharset != '' ) {
                    xhr.overrideMimeType( 'text/html; charset=' + datacharset );
                }

                xhr.onreadystatechange = function() {
                    if( xhr.readyState === 4 ) {
                        if ( xhr.status >= 200 && xhr.status < 300 ) {

                            section.outerHTML = slidify( xhr.responseText, {
                                separator: section.getAttribute( 'data-separator' ),
                                verticalSeparator: section.getAttribute( 'data-vertical' ),
                                notesSeparator: section.getAttribute( 'data-notes' ),
                                attributes: getForwardedAttributes( section )
                            });

                        }
                        else {

                            section.outerHTML = '<section data-state="alert">' +
                                'ERROR: The attempt to fetch ' + url + ' failed with HTTP status ' + xhr.status + '.' +
                                'Check your browser\'s JavaScript console for more details.' +
                                '<p>Remember that you need to serve the presentation HTML from a HTTP server.</p>' +
                                '</section>';

                        }
                    }
                };

                xhr.open( 'GET', url, false );

                try {
                    xhr.send();
                }
                catch ( e ) {
                    alert( 'Failed to get the Markdown file ' + url + '. Make sure that the presentation and the file are served by a HTTP server and the file can be found there. ' + e );
                }

            }
            else if( section.getAttribute( 'data-separator' ) || section.getAttribute( 'data-vertical' ) || section.getAttribute( 'data-notes' ) ) {

                section.outerHTML = slidify( getMarkdownFromSlide( section ), {
                    separator: section.getAttribute( 'data-separator' ),
                    verticalSeparator: section.getAttribute( 'data-vertical' ),
                    notesSeparator: section.getAttribute( 'data-notes' ),
                    attributes: getForwardedAttributes( section )
                });

            }
            else {

                section.innerHTML = createMarkdownSlide( getMarkdownFromSlide( section ) );

            }
        }

    }

    /**
     * Converts any current data-markdown slides in the
     * DOM to HTML.
     */
    function convertSlides() {

        var sections = document.querySelectorAll( '[data-markdown]');

        for( var i = 0, len = sections.length; i < len; i++ ) {

            var section = sections[i];

            // Only parse the same slide once
            if( !section.getAttribute( 'data-markdown-parsed' ) ) {

                section.setAttribute( 'data-markdown-parsed', true )

                var notes = section.querySelector( 'aside.notes' );
                var markdown = getMarkdownFromSlide( section );

                section.innerHTML = marked( markdown );

                // If there were notes, we need to re-add them after
                // having overwritten the section's HTML
                if( notes ) {
                    section.appendChild( notes );
                }

            }

        }

    }

    // API
    return {

        initialize: function() {
            processSlides();
            convertSlides();
        },

        // TODO: Do these belong in the API?
        processSlides: processSlides,
        convertSlides: convertSlides,
        slidify: slidify

    };

}));
