/*
 * Copyright © 2020 WireGuard LLC. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0
 */

package com.wireguard.android.util

import android.content.ContentResolver
import android.net.Uri
import android.provider.OpenableColumns
import android.util.Log
import androidx.fragment.app.FragmentManager
import com.wireguard.android.Application
import com.wireguard.android.R
import com.wireguard.android.fragment.ConfigNamingDialogFragment
import com.wireguard.android.model.ObservableTunnel
import com.wireguard.config.Config
import kotlinx.coroutines.Deferred
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.SupervisorJob
import kotlinx.coroutines.async
import kotlinx.coroutines.withContext
import java.io.BufferedReader
import java.io.ByteArrayInputStream
import java.io.InputStreamReader
import java.nio.charset.StandardCharsets
import java.util.ArrayList
import java.util.zip.ZipEntry
import java.util.zip.ZipInputStream

object TunnelImporter {
    suspend fun importTunnel(contentResolver: ContentResolver, uri: Uri, messageCallback: (CharSequence) -> Unit) = withContext(Dispatchers.IO) {
        val context = Application.get().applicationContext
        val futureTunnels = ArrayList<Deferred<ObservableTunnel>>()
        val throwables = ArrayList<Throwable>()
        try {
            val columns = arrayOf(OpenableColumns.DISPLAY_NAME)
            var name = ""
            contentResolver.query(uri, columns, null, null, null)?.use { cursor ->
                if (cursor.moveToFirst() && !cursor.isNull(0)) {
                    name = cursor.getString(0)
                }
            }
            if (name.isEmpty()) {
                name = Uri.decode(uri.lastPathSegment)
            }
            var idx = name.lastIndexOf('/')
            if (idx >= 0) {
                require(idx < name.length - 1) { context.getString(R.string.illegal_filename_error, name) }
                name = name.substring(idx + 1)
            }
            val isZip = name.lowercase().endsWith(".zip")
            if (name.lowercase().endsWith(".conf")) {
                name = name.substring(0, name.length - ".conf".length)
            } else {
                require(isZip) { context.getString(R.string.bad_extension_error) }
            }

            if (isZip) {
                ZipInputStream(contentResolver.openInputStream(uri)).use { zip ->
                    val reader = BufferedReader(InputStreamReader(zip, StandardCharsets.UTF_8))
                    var entry: ZipEntry?
                    while (true) {
                        entry = zip.nextEntry ?: break
                        name = entry.name
                        idx = name.lastIndexOf('/')
                        if (idx >= 0) {
                            if (idx >= name.length - 1) {
                                continue
                            }
                            name = name.substring(name.lastIndexOf('/') + 1)
                        }
                        if (name.lowercase().endsWith(".conf")) {
                            name = name.substring(0, name.length - ".conf".length)
                        } else {
                            continue
                        }
                        try {
                            Config.parse(reader)
                        } catch (e: Throwable) {
                            throwables.add(e)
                            null
                        }?.let {
                            val nameCopy = name
                            futureTunnels.add(async(SupervisorJob()) { Application.getTunnelManager().create(nameCopy, it) })
                        }
                    }
                }
            } else {
                futureTunnels.add(async(SupervisorJob()) { Application.getTunnelManager().create(name, Config.parse(contentResolver.openInputStream(uri)!!)) })
            }

            if (futureTunnels.isEmpty()) {
                if (throwables.size == 1) {
                    throw throwables[0]
                } else {
                    require(throwables.isNotEmpty()) { context.getString(R.string.no_configs_error) }
                }
            }
            val tunnels = futureTunnels.mapNotNull {
                try {
                    it.await()
                } catch (e: Throwable) {
                    throwables.add(e)
                    null
                }
            }
            withContext(Dispatchers.Main.immediate) { onTunnelImportFinished(tunnels, throwables, messageCallback) }
        } catch (e: Throwable) {
            withContext(Dispatchers.Main.immediate) { onTunnelImportFinished(emptyList(), listOf(e), messageCallback) }
        }
    }

    fun importTunnel(parentFragmentManager: FragmentManager, configText: String, messageCallback: (CharSequence) -> Unit) {
        try {
            // Ensure the config text is parseable before proceeding…
            Config.parse(ByteArrayInputStream(configText.toByteArray(StandardCharsets.UTF_8)))

            // Config text is valid, now create the tunnel…
            ConfigNamingDialogFragment.newInstance(configText).show(parentFragmentManager, null)
        } catch (e: Throwable) {
            onTunnelImportFinished(emptyList(), listOf<Throwable>(e), messageCallback)
        }
    }

    private fun onTunnelImportFinished(tunnels: List<ObservableTunnel>, throwables: Collection<Throwable>, messageCallback: (CharSequence) -> Unit) {
        val context = Application.get().applicationContext
        var message = ""
        for (throwable in throwables) {
            val error = ErrorMessages[throwable]
            message = context.getString(R.string.import_error, error)
            Log.e(TAG, message, throwable)
        }
        if (tunnels.size == 1 && throwables.isEmpty())
            message = context.getString(R.string.import_success, tunnels[0].name)
        else if (tunnels.isEmpty() && throwables.size == 1)
        else if (throwables.isEmpty())
            message = context.resources.getQuantityString(R.plurals.import_total_success,
                    tunnels.size, tunnels.size)
        else if (!throwables.isEmpty())
            message = context.resources.getQuantityString(R.plurals.import_partial_success,
                    tunnels.size + throwables.size,
                    tunnels.size, tunnels.size + throwables.size)

        messageCallback(message)
    }

    private const val TAG = "WireGuard/TunnelImporter"
}