/*
 * Copyright 2018 Allan Wang
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package com.pitchedapps.frost.debugger

import ca.allanwang.kau.logging.KauLoggerExtension
import com.pitchedapps.frost.facebook.FB_CSS_URL_MATCHER
import com.pitchedapps.frost.facebook.USER_AGENT_BASIC
import com.pitchedapps.frost.facebook.get
import com.pitchedapps.frost.facebook.requests.call
import com.pitchedapps.frost.facebook.requests.zip
import com.pitchedapps.frost.utils.createFreshDir
import com.pitchedapps.frost.utils.createFreshFile
import com.pitchedapps.frost.utils.frostJsoup
import com.pitchedapps.frost.utils.unescapeHtml
import io.reactivex.disposables.CompositeDisposable
import io.reactivex.rxkotlin.addTo
import okhttp3.Request
import okhttp3.ResponseBody
import org.jsoup.Jsoup
import org.jsoup.nodes.Document
import org.jsoup.nodes.Element
import org.jsoup.nodes.Entities
import java.io.File
import java.io.FileOutputStream
import java.util.concurrent.ConcurrentHashMap
import java.util.concurrent.atomic.AtomicInteger
import java.util.zip.ZipEntry
import java.util.zip.ZipOutputStream

/**
 * Created by Allan Wang on 04/01/18.
 *
 * Helper to download html files and assets for offline viewing
 *
 * Inspired by <a href="https://github.com/JonasCz/save-for-offline">Save for Offline</a>
 */
class OfflineWebsite(
    private val url: String,
    private val cookie: String = "",
    baseUrl: String? = null,
    private val html: String? = null,
    /**
     * Directory that holds all the files
     */
    val baseDir: File,
    private val userAgent: String = USER_AGENT_BASIC
) {

    /**
     * Supplied url without the queries
     */
    private val baseUrl = (baseUrl ?: url.substringBefore("?")
        .substringBefore(".com")).trim('/')

    private val mainFile = File(baseDir, "index.html")
    private val assetDir = File(baseDir, "assets")

    private var cancelled = false
    private val urlMapper = ConcurrentHashMap<String, String>()
    private val atomicInt = AtomicInteger()

    private val L = KauLoggerExtension("Offline", com.pitchedapps.frost.utils.L)

    init {
        if (!this.baseUrl.startsWith("http"))
            throw IllegalArgumentException("Base Url must start with http")
    }

    private val fileQueue = mutableSetOf<String>()

    private val cssQueue = mutableSetOf<String>()

    private fun request(url: String) = Request.Builder()
        .header("Cookie", cookie)
        .header("User-Agent", userAgent)
        .url(url)
        .get()
        .call()

    private val compositeDisposable = CompositeDisposable()

    /**
     * Caller to bind callbacks and start the load
     * Callback is guaranteed to be called unless the load is cancelled
     */
    fun load(progress: (Int) -> Unit = {}, callback: (Boolean) -> Unit) {
        reset()

        L.v { "Saving $url to ${baseDir.absolutePath}" }

        if (!baseDir.exists() && !baseDir.mkdirs()) {
            L.e { "Could not make directory" }
            return callback(false)
        }

        if (!mainFile.createNewFile()) {
            L.e { "Could not create ${mainFile.absolutePath}" }
            return callback(false)
        }

        if (!assetDir.createFreshDir()) {
            L.e { "Could not create ${assetDir.absolutePath}" }
            return callback(false)
        }

        progress(10)

        if (cancelled) return

        val doc: Document
        if (html == null || html.length < 100) {
            doc = frostJsoup(cookie, url)
        } else {
            doc = Jsoup.parse("<html>${html.unescapeHtml()}</html>")
            L.d { "Building data from supplied content of size ${html.length}" }
        }
        doc.setBaseUri(baseUrl)
        doc.outputSettings().escapeMode(Entities.EscapeMode.extended)
        if (doc.childNodeSize() == 0) {
            L.e { "No content found" }
            return callback(false)
        }

        if (cancelled) return

        progress(35)

        doc.collect("link[href][rel=stylesheet]", "href", cssQueue)
        doc.collect("link[href]:not([rel=stylesheet])", "href", fileQueue)
        doc.collect("img[src]", "src", fileQueue)
        doc.collect("img[data-canonical-src]", "data-canonical-src", fileQueue)
        doc.collect("script[src]", "src", fileQueue)

        // make links absolute
        doc.select("a[href]").forEach {
            val absLink = it.attr("abs:href")
            it.attr("href", absLink)
        }

        if (cancelled) return

        mainFile.writeText(doc.html())

        progress(50)

        downloadCss().subscribe { cssLinks, cssThrowable ->

            if (cssThrowable != null) {
                L.e { "CSS parsing failed: ${cssThrowable.message} $cssThrowable" }
                callback(false)
                return@subscribe
            }

            progress(70)

            fileQueue.addAll(cssLinks)

            if (cancelled) return@subscribe

            downloadFiles().subscribe { success, throwable ->
                L.v { "All files downloaded: $success with throwable $throwable" }
                progress(100)
                callback(true)
            }
        }.addTo(compositeDisposable)
    }

    fun zip(name: String): Boolean {
        try {
            val zip = File(baseDir, "$name.zip")
            if (!zip.createFreshFile()) {
                L.e { "Failed to create zip at ${zip.absolutePath}" }
                return false
            }

            ZipOutputStream(FileOutputStream(zip)).use { out ->

                fun File.zip(name: String = this.name) {
                    if (!isFile) return
                    inputStream().use { file ->
                        out.putNextEntry(ZipEntry(name))
                        file.copyTo(out)
                    }
                    out.closeEntry()
                    delete()
                }

                baseDir.listFiles { _, n -> n != "$name.zip" }.forEach { it.zip() }
                assetDir.listFiles().forEach {
                    it.zip("assets/${it.name}")
                }
            }
            return true
        } catch (e: Exception) {
            L.e { "Zip failed: ${e.message}" }
            return false
        }
    }

    fun loadAndZip(name: String, progress: (Int) -> Unit = {}, callback: (Boolean) -> Unit) {

        load({ progress((it * 0.85f).toInt()) }) {
            if (cancelled) return@load
            if (!it) callback(false)
            else {
                val result = zip(name)
                progress(100)
                callback(result)
            }
        }
    }

    private fun downloadFiles() = fileQueue.clean().toTypedArray().zip<String, Boolean, Boolean>({
        it.all { self -> self }
    }, {
        it.downloadUrl({ false }) { file, body ->
            body.byteStream().use { input ->
                file.outputStream().use { output ->
                    input.copyTo(output)
                    return@downloadUrl true
                }
            }
        }
    })

    private fun downloadCss() = cssQueue.clean().toTypedArray().zip<String, Set<String>, Set<String>>({
        it.flatMap { l -> l }.toSet()
    }, { cssUrl ->
        cssUrl.downloadUrl({ emptySet() }) { file, body ->
            var content = body.string()
            val links = FB_CSS_URL_MATCHER.findAll(content).mapNotNull { it[1] }
            val absLinks = links.mapNotNull {
                val url = when {
                    it.startsWith("http") -> it
                    it.startsWith("/") -> "$baseUrl$it"
                    else -> return@mapNotNull null
                }
                // css files are already in the asset folder,
                // so the url does not point to another subfolder
                content = content.replace(it, url.fileName())
                url
            }.toSet()

            L.v { "Abs links $absLinks" }

            file.writeText(content)
            return@downloadUrl absLinks
        }
    })

    private inline fun <T> String.downloadUrl(
        fallback: () -> T,
        action: (file: File, body: ResponseBody) -> T
    ): T {

        val file = File(assetDir, fileName())
        if (!file.createNewFile()) {
            L.e { "Could not create path for ${file.absolutePath}" }
            return fallback()
        }

        val body = request(this).execute().body() ?: return fallback()

        try {
            body.use {
                return action(file, it)
            }
        } catch (e: Exception) {
            return fallback()
        }
    }

    private fun Element.collect(query: String, key: String, collector: MutableSet<String>) {
        val data = select(query)
        L.v { "Found ${data.size} elements with $query" }
        data.forEach {
            val absLink = it.attr("abs:$key")
            if (!absLink.isValid) return@forEach
            collector.add(absLink)
            it.attr(key, "assets/${absLink.fileName()}")
        }
    }

    private inline val String.isValid
        get() = startsWith("http")

    /**
     * Fetch the previously discovered filename
     * or create a new one
     * This is thread-safe
     */
    private fun String.fileName(): String {
        val mapped = urlMapper[this]
        if (mapped != null) return mapped

        val candidate = substringBefore("?").trim('/')
            .substringAfterLast("/").shorten()

        val index = atomicInt.getAndIncrement()

        var newUrl = "a${index}_$candidate"

        /**
         * This is primarily for zipping up and sending via emails
         * As .js files typically aren't allowed, we'll simply make everything txt files
         */
        if (newUrl.endsWith(".js"))
            newUrl = "$newUrl.txt"

        urlMapper[this] = newUrl
        return newUrl
    }

    private fun String.shorten() =
        if (length <= 10) this else substring(length - 10)

    private fun Set<String>.clean(): List<String> =
        filter(String::isNotBlank).filter { it.startsWith("http") }

    private fun reset() {
        cancelled = false
        urlMapper.clear()
        atomicInt.set(0)
        fileQueue.clear()
        cssQueue.clear()
    }

    fun cancel() {
        cancelled = true
        compositeDisposable.dispose()
        L.v { "Request cancelled" }
    }
}