(function(){

	var toc = function(converter) {
		return [
			{
				type: 'output', 
				filter: function(source) {
					var elements = $(source);
					var output = [];
					var headingLevel = null;
					var tocId = null;
					for (var i=0; i<elements.length; i++) {
						var element = $(elements[i]);
						var results = null;

						// Does the element consist only of [toc]?
						// If so, we can replace this element with out list.
						if (element.text().trim()=='[toc]') {
							element = $('<ol>',{'class':'showdown-toc'});
							headingLevel = null;
							tocId = output.length;
						}

						// Does this item contain a [toc] with other stuff?
						// If so, we'll split the element into two 
						else if (results = element.text().trim().match(/^([\s\S]*?)((?:\\)?\[toc\])([\s\S]*)$/)) {

							// If there was a \ before the [toc] they're trying to escape it,
							// so return the [toc] string without the \ and carry on. For
							// some reason (I'm guessing a bug in showdown) you actually
							// appear to need two \ (\\) in order to get this to show up for
							// the filter. Leaving this code here anyway for now because it's
							// "the right thing to do"(tm).
							if (results[2][0]=='\\') {
								element.text(results[1]+results[2].substr(1)+results[3]);
							}

							// Otherwise start building a new table of contents.
							else {
								var before = null;
								var after = null;

								// Create two of the same element.
								if (element.prop('tagName')) {
									if (results[1].trim().length>0) {
										before = $('<'+element.prop('tagName')+'>').text(results[1]);
									}
									if (results[3].trim().length>0) {
										after = $('<'+element.prop('tagName')+'>').text(results[3]);
									}
								}

								// Otherwise if there's no tagName assume it's a text node
								// and create two of those.
								else {
									if (results[1].trim().length>0) {
										before = document.createTextNode(results[1]);
									}
									if (results[3].trim().length>0) {
										after = document.createTextNode(results[3]);
									}
								}

								// Our new table of contents container.
								toc = $('<ol>',{'class':'showdown-toc'});

								// If there was text before our [toc], add that in
								if (before) {
									output.push(before);
								}

								// Keep track of where our current table is in the elements array.
								tocId = output.length;

								// If there was text after, push the contents onto the array and
								// use the after part as our current element.
								if (after) {
									output.push(toc);
									element = after;
								}

								// Otherwise use the contents as the current element.
								else {
									element = toc;
								}

								// Reset the heading level - we're going to start looking for new
								// headings again
								headingLevel = null;

							}
						}

						// If we've started a table of contents, but have nothing in it yet,
						// look for the first header tag we encounter (after the [toc]).
						// That's going to be what we use as contents entries for this table
						// of contents.
						else if (tocId && !headingLevel && element.prop("tagName")) {
							switch (element.prop("tagName")) {
								case 'H1':
								case 'H2':
								case 'H3':
								case 'H4':
								case 'H5':
								case 'H6':
									headingLevel = parseInt(element.prop('tagName').substr(1));
									break;
							}
						}

						// If we know what header level we're looking for (either we just
						// found it above, or we're continuing to look for more) then check to
						// see if this heading should be added to the contents.
						if (tocId && headingLevel) {
							switch (element.prop('tagName')) {
								case 'H1':
								case 'H2':
								case 'H3':
								case 'H4':
								case 'H5':
								case 'H6':
									var thisLevel = parseInt(element.prop('tagName').substr(1));
									if (thisLevel==headingLevel) {
										output[tocId] = $(output[tocId]).append($('<li>').append($('<a>',{href:'#'+element.attr('id'),text:element.text()})));
									}
									// If we move up in what would be the document tree
									// (eg: if we're looking for H2 and we suddenly find an
									// H1) then we can probably safely assume that we want
									// the table of contents to end for this section.
									else if (thisLevel<headingLevel) {
										toc = null
										tocId = null;
										headingLevel = null;
									}
									break;
							}
						}
						// Push whatever element we've been looking at onto the output array.
						output.push(element);
					}
					// Build some HTML to return
					// Return it.
					return $('<div>').append(output).html();
				}
			}

		];
	};

	// Client-side export
	if (typeof window !== 'undefined' && window.showdown && window.showdown.extensions) { window.showdown.extensions.toc = toc; }
	// Server-side export
	if (typeof module !== 'undefined') module.exports = toc;

}());