import sbt._

object SiteMap
{
	// represents the configurable aspects of a sitemap entry
	final case class Entry(changeFreq: String, priority: Double) {
		assert(priority >= 0.0 && priority <= 1.0, s"Priority must be between 0.0 and 1.0:, was $priority")
	}
	def generate(repoBase: File, remoteBase: URI, gzip: Boolean, entry: (File, String) => Option[Entry], log: Logger): (File, Seq[File]) =
	{
		def relativize(files: PathFinder): Seq[(File, String)] = files pair relativeTo(repoBase)
		def entries(files: PathFinder) =
			relativize(files) flatMap { case (f, path) =>
				entry(f, path).toList map { e =>
					entryXML(e, f, path)
				}
			}
		def entriesXML(entries: Seq[xml.Node]): xml.Elem =
		{
			assert(entries.size <= 50000, "A site map cannot contain more than 50,000 entries.")
			<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
				{entries}
			</urlset>
		}

		def entryXML(e: Entry, f: File, relPath: String) =
			<url>
				<loc>{remoteBase.resolve(relPath).toString}</loc>
				<lastmod>{lastModifiedString(f)}</lastmod>
				<changefreq>{e.changeFreq}</changefreq>
				<priority>{e.priority.toString}</priority>
			</url>

		def singleSiteMap(dir: File, files: PathFinder): Option[File] = {
			val es = entries(files)
			if(es.isEmpty) None else Some( writeXMLgz(dir / "sitemap.xml", dir / "sitemap.xml.gz", gzip, entriesXML(es)) )
		}
		def indexEntryXML(sub: File, relPath: String): xml.Elem =
			<sitemap>
				<loc>{remoteBase.resolve(relPath).toString}</loc>
				<lastmod>{lastModifiedString(sub)}</lastmod>
			</sitemap>
		def indexEntriesXML(entries: Seq[xml.Node]): xml.Elem =
			<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
				{entries}
			</sitemapindex>
		def indexEntries(subs: Seq[File]) =
			relativize(subs) map { case (f, path) => indexEntryXML(f, path) }
		def siteMapIndex(dir: File, subs: Seq[File]): File =
		{
			val xml = indexEntriesXML(indexEntries(subs))
			writeXMLgz(dir / "sitemap_index.xml", dir / "sitemap_index.xml.gz", gzip, xml)
		}
		def isSymlink(f: File) = f.getCanonicalFile != f.getAbsoluteFile

		val (symlinks, normal) = (repoBase * DirectoryFilter).get.partition(dir => isSymlink(dir))
		log.debug("Detected symlinks: " + symlinks.mkString("\n\t", "\n\t", ""))
		val subMaps =
			singleSiteMap(repoBase, (repoBase * "*.html") +++ (symlinks ** "*.html") ).toList ++
			normal.flatMap( dir =>
				singleSiteMap(dir, dir ** "*.html").toList
			)
		val index = siteMapIndex(repoBase, subMaps)
		(index, subMaps)
	}
	// generates a string suitable for a sitemap file representing the last modified time of the given File
	private[this] def lastModifiedString(f: File): String =
	{
		val formatter = new java.text.SimpleDateFormat("yyyy-MM-dd")
		formatter.format(new java.util.Date(f.lastModified))
	}
	// writes the provided XML node to `output` and then gzips it to `gzipped` if `gzip` is true
	private[this] def writeXMLgz(output: File, gzipped: File, gzip: Boolean, node: xml.Node): File =
	{
		writeXML(output, node)
		if(gzip) {
			IO.gzip(output, gzipped)
			gzipped
		} else
			output
	}
	private[this] def writeXML(output: File, node: xml.Node): Unit =
		write(output, new xml.PrettyPrinter(1000, 4).format(node))

	private[this] def write(output: File, xmlString: String)
	{
		// use \n as newline because toString uses PrettyPrinter, which hard codes line endings to be \n
		IO.write(output, s"<?xml version='1.0' encoding='${IO.utf8.name}'?>\n")
		IO.append(output, xmlString)
	}
}