package eu.kanade.tachiyomi.extension

import android.content.Context
import android.graphics.drawable.Drawable
import com.jakewharton.rxrelay.BehaviorRelay
import eu.kanade.domain.source.model.SourceData
import eu.kanade.tachiyomi.R
import eu.kanade.tachiyomi.data.preference.PreferencesHelper
import eu.kanade.tachiyomi.extension.api.ExtensionGithubApi
import eu.kanade.tachiyomi.extension.model.Extension
import eu.kanade.tachiyomi.extension.model.InstallStep
import eu.kanade.tachiyomi.extension.model.LoadResult
import eu.kanade.tachiyomi.extension.util.ExtensionInstallReceiver
import eu.kanade.tachiyomi.extension.util.ExtensionInstaller
import eu.kanade.tachiyomi.extension.util.ExtensionLoader
import eu.kanade.tachiyomi.source.Source
import eu.kanade.tachiyomi.source.SourceManager
import eu.kanade.tachiyomi.util.lang.launchNow
import eu.kanade.tachiyomi.util.preference.plusAssign
import eu.kanade.tachiyomi.util.system.logcat
import eu.kanade.tachiyomi.util.system.toast
import kotlinx.coroutines.async
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.flow.asStateFlow
import logcat.LogPriority
import rx.Observable
import uy.kohesive.injekt.Injekt
import uy.kohesive.injekt.api.get

/**
 * The manager of extensions installed as another apk which extend the available sources. It handles
 * the retrieval of remotely available extensions as well as installing, updating and removing them.
 * To avoid malicious distribution, every extension must be signed and it will only be loaded if its
 * signature is trusted, otherwise the user will be prompted with a warning to trust it before being
 * loaded.
 *
 * @param context The application context.
 * @param preferences The application preferences.
 */
class ExtensionManager(
    private val context: Context,
    private val preferences: PreferencesHelper = Injekt.get(),
) {

    /**
     * API where all the available extensions can be found.
     */
    private val api = ExtensionGithubApi()

    /**
     * The installer which installs, updates and uninstalls the extensions.
     */
    private val installer by lazy { ExtensionInstaller(context) }

    /**
     * Relay used to notify the installed extensions.
     */
    private val installedExtensionsRelay = BehaviorRelay.create<List<Extension.Installed>>()

    private val iconMap = mutableMapOf<String, Drawable>()

    /**
     * List of the currently installed extensions.
     */
    var installedExtensions = emptyList<Extension.Installed>()
        private set(value) {
            field = value
            installedExtensionsFlow.value = field
            installedExtensionsRelay.call(value)
        }

    private val installedExtensionsFlow = MutableStateFlow(installedExtensions)

    fun getInstalledExtensionsFlow(): StateFlow<List<Extension.Installed>> {
        return installedExtensionsFlow.asStateFlow()
    }

    fun getAppIconForSource(source: Source): Drawable? {
        return getAppIconForSource(source.id)
    }

    fun getAppIconForSource(sourceId: Long): Drawable? {
        val pkgName = installedExtensions.find { ext -> ext.sources.any { it.id == sourceId } }?.pkgName
        if (pkgName != null) {
            return iconMap[pkgName] ?: iconMap.getOrPut(pkgName) { context.packageManager.getApplicationIcon(pkgName) }
        }
        return null
    }

    /**
     * Relay used to notify the available extensions.
     */
    private val availableExtensionsRelay = BehaviorRelay.create<List<Extension.Available>>()

    /**
     * List of the currently available extensions.
     */
    var availableExtensions = emptyList<Extension.Available>()
        private set(value) {
            field = value
            availableExtensionsRelay.call(value)
            updatedInstalledExtensionsStatuses(value)
            setupAvailableExtensionsSourcesDataMap(value)
        }

    private var availableExtensionsSourcesData: Map<Long, SourceData> = mapOf()

    private fun setupAvailableExtensionsSourcesDataMap(extensions: List<Extension.Available>) {
        if (extensions.isEmpty()) return
        availableExtensionsSourcesData = extensions
            .flatMap { ext -> ext.sources.map { it.toSourceData() } }
            .associateBy { it.id }
    }

    fun getSourceData(id: Long) = availableExtensionsSourcesData[id]

    /**
     * Relay used to notify the untrusted extensions.
     */
    private val untrustedExtensionsRelay = BehaviorRelay.create<List<Extension.Untrusted>>()

    /**
     * List of the currently untrusted extensions.
     */
    var untrustedExtensions = emptyList<Extension.Untrusted>()
        private set(value) {
            field = value
            untrustedExtensionsRelay.call(value)
        }

    /**
     * The source manager where the sources of the extensions are added.
     */
    private lateinit var sourceManager: SourceManager

    /**
     * Initializes this manager with the given source manager.
     */
    fun init(sourceManager: SourceManager) {
        this.sourceManager = sourceManager
        initExtensions()
        ExtensionInstallReceiver(InstallationListener()).register(context)
    }

    /**
     * Loads and registers the installed extensions.
     */
    private fun initExtensions() {
        val extensions = ExtensionLoader.loadExtensions(context)

        installedExtensions = extensions
            .filterIsInstance<LoadResult.Success>()
            .map { it.extension }
        installedExtensions
            .flatMap { it.sources }
            .forEach { sourceManager.registerSource(it) }

        untrustedExtensions = extensions
            .filterIsInstance<LoadResult.Untrusted>()
            .map { it.extension }
    }

    /**
     * Returns the relay of the installed extensions as an observable.
     */
    fun getInstalledExtensionsObservable(): Observable<List<Extension.Installed>> {
        return installedExtensionsRelay.asObservable()
    }

    /**
     * Returns the relay of the available extensions as an observable.
     */
    fun getAvailableExtensionsObservable(): Observable<List<Extension.Available>> {
        return availableExtensionsRelay.asObservable()
    }

    /**
     * Returns the relay of the untrusted extensions as an observable.
     */
    fun getUntrustedExtensionsObservable(): Observable<List<Extension.Untrusted>> {
        return untrustedExtensionsRelay.asObservable()
    }

    /**
     * Finds the available extensions in the [api] and updates [availableExtensions].
     */
    fun findAvailableExtensions() {
        launchNow {
            val extensions: List<Extension.Available> = try {
                api.findExtensions()
            } catch (e: Exception) {
                logcat(LogPriority.ERROR, e)
                context.toast(R.string.extension_api_error)
                emptyList()
            }

            availableExtensions = extensions
        }
    }

    /**
     * Sets the update field of the installed extensions with the given [availableExtensions].
     *
     * @param availableExtensions The list of extensions given by the [api].
     */
    private fun updatedInstalledExtensionsStatuses(availableExtensions: List<Extension.Available>) {
        if (availableExtensions.isEmpty()) {
            preferences.extensionUpdatesCount().set(0)
            return
        }

        val mutInstalledExtensions = installedExtensions.toMutableList()
        var changed = false

        for ((index, installedExt) in mutInstalledExtensions.withIndex()) {
            val pkgName = installedExt.pkgName
            val availableExt = availableExtensions.find { it.pkgName == pkgName }

            if (availableExt == null && !installedExt.isObsolete) {
                mutInstalledExtensions[index] = installedExt.copy(isObsolete = true)
                changed = true
            } else if (availableExt != null) {
                val hasUpdate = !installedExt.isUnofficial &&
                    availableExt.versionCode > installedExt.versionCode

                if (installedExt.hasUpdate != hasUpdate) {
                    mutInstalledExtensions[index] = installedExt.copy(hasUpdate = hasUpdate)
                    changed = true
                }
            }
        }
        if (changed) {
            installedExtensions = mutInstalledExtensions
        }
        updatePendingUpdatesCount()
    }

    /**
     * Returns an observable of the installation process for the given extension. It will complete
     * once the extension is installed or throws an error. The process will be canceled if
     * unsubscribed before its completion.
     *
     * @param extension The extension to be installed.
     */
    fun installExtension(extension: Extension.Available): Observable<InstallStep> {
        return installer.downloadAndInstall(api.getApkUrl(extension), extension)
    }

    /**
     * Returns an observable of the installation process for the given extension. It will complete
     * once the extension is updated or throws an error. The process will be canceled if
     * unsubscribed before its completion.
     *
     * @param extension The extension to be updated.
     */
    fun updateExtension(extension: Extension.Installed): Observable<InstallStep> {
        val availableExt = availableExtensions.find { it.pkgName == extension.pkgName }
            ?: return Observable.empty()
        return installExtension(availableExt)
    }

    fun cancelInstallUpdateExtension(extension: Extension) {
        installer.cancelInstall(extension.pkgName)
    }

    /**
     * Sets to "installing" status of an extension installation.
     *
     * @param downloadId The id of the download.
     */
    fun setInstalling(downloadId: Long) {
        installer.updateInstallStep(downloadId, InstallStep.Installing)
    }

    fun updateInstallStep(downloadId: Long, step: InstallStep) {
        installer.updateInstallStep(downloadId, step)
    }

    /**
     * Uninstalls the extension that matches the given package name.
     *
     * @param pkgName The package name of the application to uninstall.
     */
    fun uninstallExtension(pkgName: String) {
        installer.uninstallApk(pkgName)
    }

    /**
     * Adds the given signature to the list of trusted signatures. It also loads in background the
     * extensions that match this signature.
     *
     * @param signature The signature to whitelist.
     */
    fun trustSignature(signature: String) {
        val untrustedSignatures = untrustedExtensions.map { it.signatureHash }.toSet()
        if (signature !in untrustedSignatures) return

        ExtensionLoader.trustedSignatures += signature
        preferences.trustedSignatures() += signature

        val nowTrustedExtensions = untrustedExtensions.filter { it.signatureHash == signature }
        untrustedExtensions -= nowTrustedExtensions

        val ctx = context
        launchNow {
            nowTrustedExtensions
                .map { extension ->
                    async { ExtensionLoader.loadExtensionFromPkgName(ctx, extension.pkgName) }
                }
                .map { it.await() }
                .forEach { result ->
                    if (result is LoadResult.Success) {
                        registerNewExtension(result.extension)
                    }
                }
        }
    }

    /**
     * Registers the given extension in this and the source managers.
     *
     * @param extension The extension to be registered.
     */
    private fun registerNewExtension(extension: Extension.Installed) {
        installedExtensions += extension
        extension.sources.forEach { sourceManager.registerSource(it) }
    }

    /**
     * Registers the given updated extension in this and the source managers previously removing
     * the outdated ones.
     *
     * @param extension The extension to be registered.
     */
    private fun registerUpdatedExtension(extension: Extension.Installed) {
        val mutInstalledExtensions = installedExtensions.toMutableList()
        val oldExtension = mutInstalledExtensions.find { it.pkgName == extension.pkgName }
        if (oldExtension != null) {
            mutInstalledExtensions -= oldExtension
            extension.sources.forEach { sourceManager.unregisterSource(it) }
        }
        mutInstalledExtensions += extension
        installedExtensions = mutInstalledExtensions
        extension.sources.forEach { sourceManager.registerSource(it) }
    }

    /**
     * Unregisters the extension in this and the source managers given its package name. Note this
     * method is called for every uninstalled application in the system.
     *
     * @param pkgName The package name of the uninstalled application.
     */
    private fun unregisterExtension(pkgName: String) {
        val installedExtension = installedExtensions.find { it.pkgName == pkgName }
        if (installedExtension != null) {
            installedExtensions -= installedExtension
            installedExtension.sources.forEach { sourceManager.unregisterSource(it) }
        }
        val untrustedExtension = untrustedExtensions.find { it.pkgName == pkgName }
        if (untrustedExtension != null) {
            untrustedExtensions -= untrustedExtension
        }
    }

    /**
     * Listener which receives events of the extensions being installed, updated or removed.
     */
    private inner class InstallationListener : ExtensionInstallReceiver.Listener {

        override fun onExtensionInstalled(extension: Extension.Installed) {
            registerNewExtension(extension.withUpdateCheck())
            updatePendingUpdatesCount()
        }

        override fun onExtensionUpdated(extension: Extension.Installed) {
            registerUpdatedExtension(extension.withUpdateCheck())
            updatePendingUpdatesCount()
        }

        override fun onExtensionUntrusted(extension: Extension.Untrusted) {
            untrustedExtensions += extension
        }

        override fun onPackageUninstalled(pkgName: String) {
            unregisterExtension(pkgName)
            updatePendingUpdatesCount()
        }
    }

    /**
     * Extension method to set the update field of an installed extension.
     */
    private fun Extension.Installed.withUpdateCheck(): Extension.Installed {
        val availableExt = availableExtensions.find { it.pkgName == pkgName }
        if (isUnofficial.not() && availableExt != null && availableExt.versionCode > versionCode) {
            return copy(hasUpdate = true)
        }
        return this
    }

    private fun updatePendingUpdatesCount() {
        preferences.extensionUpdatesCount().set(installedExtensions.count { it.hasUpdate })
    }
}