package net.pterodactylus.sone.web.pages

import com.google.common.base.Ticker
import com.google.common.cache.Cache
import com.google.common.cache.CacheBuilder
import freenet.support.Logger
import net.pterodactylus.sone.data.Post
import net.pterodactylus.sone.data.PostReply
import net.pterodactylus.sone.data.Sone
import net.pterodactylus.sone.utils.Pagination
import net.pterodactylus.sone.utils.emptyToNull
import net.pterodactylus.sone.utils.memoize
import net.pterodactylus.sone.utils.paginate
import net.pterodactylus.sone.utils.parameters
import net.pterodactylus.sone.web.WebInterface
import net.pterodactylus.sone.web.page.*
import net.pterodactylus.sone.web.pages.SearchPage.Optionality.FORBIDDEN
import net.pterodactylus.sone.web.pages.SearchPage.Optionality.OPTIONAL
import net.pterodactylus.sone.web.pages.SearchPage.Optionality.REQUIRED
import net.pterodactylus.util.template.Template
import net.pterodactylus.util.template.TemplateContext
import net.pterodactylus.util.text.StringEscaper
import net.pterodactylus.util.text.TextException
import java.util.concurrent.TimeUnit.MINUTES
import javax.inject.Inject

/**
 * This page lets the user search for posts and replies that contain certain
 * words.
 */
class SearchPage(template: Template, webInterface: WebInterface, ticker: Ticker = Ticker.systemTicker()) :
		SoneTemplatePage("search.html", webInterface, template, "Page.Search.Title") {

	@Inject constructor(template: Template, webInterface: WebInterface) :
			this(template, webInterface, Ticker.systemTicker())

	private val cache: Cache<Iterable<Phrase>, Pagination<Post>> = CacheBuilder.newBuilder().ticker(ticker).expireAfterAccess(5, MINUTES).build()

	override fun handleRequest(soneRequest: SoneRequest, templateContext: TemplateContext) {
		val startTime = System.currentTimeMillis()
		val phrases = try {
			soneRequest.parameters["query"].emptyToNull?.parse()
		} catch (te: TextException) {
			redirect("index.html")
		}
				?: redirect("index.html")

		when (phrases.size) {
			0 -> redirect("index.html")
			1 -> phrases.first().phrase.also { word ->
				when {
					word.removePrefix("sone://").let(soneRequest.core::getSone) != null -> redirect("viewSone.html?sone=${word.removePrefix("sone://")}")
					word.removePrefix("post://").let(soneRequest.core::getPost) != null -> redirect("viewPost.html?post=${word.removePrefix("post://")}")
					word.removePrefix("reply://").let(soneRequest.core::getPostReply) != null -> redirect("viewPost.html?post=${word.removePrefix("reply://").let(soneRequest.core::getPostReply)?.postId}")
					word.removePrefix("album://").let(soneRequest.core::getAlbum) != null -> redirect("imageBrowser.html?album=${word.removePrefix("album://")}")
					word.removePrefix("image://").let { soneRequest.core.getImage(it, false) } != null -> redirect("imageBrowser.html?image=${word.removePrefix("image://")}")
				}
			}
		}

		val soneNameCache = { sone: Sone -> sone.names() }.memoize()
		val sonePagination = soneRequest.core.sones
				.scoreAndPaginate(phrases, soneRequest.core.preferences.postsPerPage) { it.allText(soneNameCache) }
				.apply { page = soneRequest.parameters["sonePage"].emptyToNull?.toIntOrNull() ?: 0 }
		val postPagination = cache.get(phrases) {
			soneRequest.core.sones
					.flatMap(Sone::getPosts)
					.filter { Post.FUTURE_POSTS_FILTER.apply(it) }
					.scoreAndPaginate(phrases, soneRequest.core.preferences.postsPerPage) { it.allText(soneNameCache, soneRequest.core::getReplies) }
		}.apply { page = soneRequest.parameters["postPage"].emptyToNull?.toIntOrNull() ?: 0 }

		Logger.normal(SearchPage::class.java, "Finished search for “${soneRequest.parameters["query"]}” in ${System.currentTimeMillis() - startTime}ms.")
		templateContext["sonePagination"] = sonePagination
		templateContext["soneHits"] = sonePagination.items
		templateContext["postPagination"] = postPagination
		templateContext["postHits"] = postPagination.items
	}

	private fun <T> Iterable<T>.scoreAndPaginate(phrases: Iterable<Phrase>, postsPerPage: Int, texter: (T) -> String) =
			map { it to score(texter(it), phrases) }
					.filter { it.second > 0 }
					.sortedByDescending { it.second }
					.map { it.first }
					.paginate(postsPerPage)

	private fun Sone.names() =
			with(profile) {
				listOf(name, firstName, middleName, lastName)
						.filterNotNull()
						.joinToString("")
			}

	private fun Sone.allText(soneNameCache: (Sone) -> String) =
			(soneNameCache(this) + profile.fields.map { "${it.name} ${it.value}" }.joinToString(" ", " ")).toLowerCase()

	private fun Post.allText(soneNameCache: (Sone) -> String, getReplies: (String) -> Collection<PostReply>) =
			(text + recipient.orNull()?.let { " ${soneNameCache(it)}" } + getReplies(id)
					.filter { PostReply.FUTURE_REPLY_FILTER.apply(it) }
					.map { "${soneNameCache(it.sone)} ${it.text}" }.joinToString(" ", " ")).toLowerCase()

	private fun Iterable<Phrase>.indicesFor(text: String, predicate: (Phrase) -> Boolean) =
			filter(predicate).map(Phrase::phrase).map(String::toLowerCase).flatMap { text.findAll(it) }

	private fun score(text: String, phrases: Iterable<Phrase>): Double {
		val requiredPhrases = phrases.count { it.required }
		val requiredHits = phrases.indicesFor(text, Phrase::required)
				.map { Math.pow(1 - it / text.length.toDouble(), 2.0) }
				.sum()
		val optionalHits = phrases.indicesFor(text, Phrase::optional)
				.map { Math.pow(1 - it / text.length.toDouble(), 2.0) }
				.sum()
		val forbiddenHits = phrases.indicesFor(text, Phrase::forbidden)
				.count()
		return requiredHits * 3 + optionalHits + (requiredHits - requiredPhrases) * 5 - (forbiddenHits * 2)
	}

	private fun String.findAll(needle: String) =
			generateSequence(indexOf(needle).takeIf { it > -1 }) { lastPosition ->
				lastPosition
						.let { indexOf(needle, it + 1) }
						.takeIf { it > -1 }
			}.toList()

	private fun String.parse() =
			StringEscaper.parseLine(this)
					.map {
						when {
							it == "+" || it == "-" -> Phrase(it, OPTIONAL)
							it.startsWith("+") -> Phrase(it.drop(1), REQUIRED)
							it.startsWith("-") -> Phrase(it.drop(1), FORBIDDEN)
							else -> Phrase(it, OPTIONAL)
						}
					}

	private fun redirect(target: String): Nothing = throw RedirectException(target)

	enum class Optionality {
		OPTIONAL,
		REQUIRED,
		FORBIDDEN
	}

	private data class Phrase(val phrase: String, val optionality: Optionality) {
		val required = optionality == REQUIRED
		val forbidden = optionality == FORBIDDEN
		val optional = optionality == OPTIONAL
	}

}