/*
* toc.js : 根据文档内容生成table
*
*    本模块注册一个当文档加载完成后会自动运行的匿名函数。
*    改函数运行时首先查看文档中id为TOC的元素，如果没有找到
*    则在文档开头创建它
*
*    接下来，函数寻找文档中所有的<h1>到<h6>标签，并将其当做章节标题，
*    然后以此为内容在TOC元素中创建一个table。该函数为每一个章节标题编号
*    并且为每一个h标签添加命名的描点，这样就可以通过点击TOC中table连接到对应章节。
*    生成的锚点一TOC作为前缀，所以你应该在自己的HTML代码中避免使用这个前缀
*
*    生成的目录入口可以用css进行格式。所有的入口具有类标识"TOCEntry"，入口同时根据<h>
*    的级别拥有对应的类标志，如<h1>对应类标识为"TOCLevel1",<h2>对应类标志为"TOCLevel2"。
*    插入到头部的章节编号具有类标志"TOCSectNum"
*
*    你可以在本模块中使用如下样式表(我定义在HomGH.css里)
*    #TOC { border: solid black 1px; margin: 10px; padding: 10px; }
*    .TOCEntry { font-family: sans-serif; }
*    .TOCEntry a { text-decoration: none; }
*    .TOCLevel1 { font-size: 16pt; font-weight: bold; }
*    .TOCLevel2 { font-size: 12pt; margin-left: .5in; }
*    .TOCSecNum:after { content: ": "; }
*/

function toc() {
	// Find the TOC container element.
	// If there isn't one, create one at the start of the document.
	var toc = document.getElementById("TOC");
	if (!toc) {
		toc = document.createElement("div");
		toc.id = "TOC";
		document.body.insertBefore(toc, document.body.firstChild);
	}
	// Find all section heading elements
	var headings;
	if (document.querySelectorAll) // Can we do it the easy way?
		headings = document.querySelectorAll("h1,h2,h3,h4,h5,h6");
	else   // Otherwise, find the headings the hard way
		headings = findHeadings(document.body, []);
	// Recursively traverse the document body looking for headings
	function findHeadings(root, sects) {
		for(var c = root.firstChild; c != null; c = c.nextSibling) {
			if (c.nodeType !== 1) continue;
			if (c.tagName.length == 2 && c.tagName.charAt(0) == "H")
				sects.push(c);
			else
				findHeadings(c, sects);
		}
		return sects;
	}
	// Initialize an array that keeps track of section numbers.
	var sectionNumbers = [0,0,0,0,0,0];
	// Now loop through the section header elements we found.
	for(var h = 0; h < headings.length; h++) {
		var heading = headings[h];
		// Skip the section heading if it is inside the TOC container.
		if (heading.parentNode == toc) continue;
		// Figure out what level heading it is.
		var level = parseInt(heading.tagName.charAt(1));
		if (isNaN(level) || level < 1 || level > 6) continue;
		// Increment the section number for this heading level
		// and reset all lower heading level numbers to zero.
		sectionNumbers[level-1]++;
		for(var i = level; i < 6; i++) sectionNumbers[i] = 0;
		// Now combine section numbers for all heading levels
		// to produce a section number like 2.3.1.
		var sectionNumber = sectionNumbers.slice(0,level).join(".")
		// Add the section number to the section header title.
		// We place the number in a <span> to make it styleable.
		var span = document.createElement("span");
		span.className = "TOCSectNum";
		//span.innerHTML = sectionNumber;
		heading.insertBefore(span, heading.firstChild);
		// Wrap the heading in a named anchor so we can link to it.
		var anchor = document.createElement("a");
		anchor.name = "TOC"+sectionNumber;
		heading.parentNode.insertBefore(anchor, heading);
		//Don't need to append.
		//anchor.appendChild(heading);
		// Now create a link to this section.
		var link = document.createElement("a");
		link.href = "#TOC" + sectionNumber; // Link destination
		//may get wrong when header content is a link
		link.innerHTML = heading.innerHTML; // Link text is same as heading
		// Place the link in a div that is styleable based on the level.
		var entry = document.createElement("div");
		entry.className = "TOCEntry TOCLevel" + level;
		entry.appendChild(link);
		// And add the div to the TOC container.
		toc.appendChild(entry);
	}
}

window.onload=function(){ toc()}