package net.pterodactylus.sone.core

import com.google.common.base.Ticker
import com.google.common.cache.Cache
import com.google.common.cache.CacheBuilder
import freenet.keys.FreenetURI
import org.jsoup.Jsoup
import org.jsoup.nodes.Document
import java.io.ByteArrayInputStream
import java.net.URLDecoder
import java.nio.charset.Charset
import java.text.Normalizer
import java.util.concurrent.TimeUnit.MINUTES
import javax.activation.MimeType
import javax.imageio.ImageIO
import javax.inject.Inject

/**
 * [ElementLoader] implementation that uses a simple Guava [com.google.common.cache.Cache].
 */
class DefaultElementLoader(private val freenetInterface: FreenetInterface, ticker: Ticker): ElementLoader {

	@Inject constructor(freenetInterface: FreenetInterface): this(freenetInterface, Ticker.systemTicker())

	private val loadingLinks: Cache<String, Boolean> = CacheBuilder.newBuilder().build()
	private val failureCache: Cache<String, Boolean> = CacheBuilder.newBuilder().ticker(ticker).expireAfterWrite(30, MINUTES).build()
	private val elementCache: Cache<String, LinkedElement> = CacheBuilder.newBuilder().build()
	private val callback = object: FreenetInterface.BackgroundFetchCallback {
		override fun shouldCancel(uri: FreenetURI, mimeType: String, size: Long): Boolean {
			return (size > 2097152) || (!mimeType.startsWith("image/") && !mimeType.startsWith("text/html"))
		}

		override fun loaded(uri: FreenetURI, mimeTypeText: String, data: ByteArray) {
			MimeType(mimeTypeText).also { mimeType ->
				when {
					mimeType.primaryType == "image" -> {
						ByteArrayInputStream(data).use {
							ImageIO.read(it)
						}?.let {
							elementCache.get(uri.toString().decode().normalize()) {
								LinkedElement(uri.toString(), properties = mapOf("type" to "image", "size" to data.size, "sizeHuman" to data.size.human))
							}
						}
					}
					mimeType.baseType == "text/html" -> {
						val document = Jsoup.parse(data.toString(Charset.forName(mimeType.getParameter("charset") ?: "UTF-8")))
						elementCache.get(uri.toString().decode().normalize()) {
							LinkedElement(uri.toString(), properties = mapOf(
									"type" to "html", "size" to data.size, "sizeHuman" to data.size.human,
									"title" to document.title().emptyToNull,
									"description" to (document.metaDescription ?: document.firstNonHeadingParagraph)
							))
						}
					}
				}
				removeLoadingLink(uri)
			}
		}

		override fun failed(uri: FreenetURI) {
			failureCache.put(uri.toString().decode().normalize(), true)
			removeLoadingLink(uri)
		}

		private fun removeLoadingLink(uri: FreenetURI) {
			synchronized(loadingLinks) {
				loadingLinks.invalidate(uri.toString().decode().normalize())
			}
		}
	}

	override fun loadElement(link: String): LinkedElement {
		val normalizedLink = link.decode().normalize()
		synchronized(loadingLinks) {
			elementCache.getIfPresent(normalizedLink)?.run {
				return this
			}
			failureCache.getIfPresent(normalizedLink)?.run {
				return LinkedElement(link, failed = true)
			}
			if (loadingLinks.getIfPresent(normalizedLink) == null) {
				loadingLinks.put(normalizedLink, true)
				freenetInterface.startFetch(FreenetURI(link), callback)
			}
		}
		return LinkedElement(link, loading = true)
	}

}

private fun String.decode() = URLDecoder.decode(this, "UTF-8")!!
private fun String.normalize() = Normalizer.normalize(this, Normalizer.Form.NFC)!!
private val String?.emptyToNull get() = if (this == "") null else this

private val Document.metaDescription: String?
	get() = head().getElementsByTag("meta")
		.map { it.attr("name") to it.attr("content") }
		.firstOrNull { it.first == "description" }
		?.second

private val Document.firstNonHeadingParagraph: String?
	get() = body().children()
		.map { it to it.text() }
		.filterNot { it.second == "" }
		.firstOrNull { !it.first.tagName().startsWith("h", ignoreCase = true) }
		?.second

private val Int.human get() = when (this) {
	in 0..1023 -> "$this B"
	in 1024..1048575 -> "${this / 1024} KiB"
	in 1048576..1073741823 -> "${this / 1048576} MiB"
	else -> "${this / 1073741824} GiB"
}