package eu.kanade.tachiyomi.extension

import android.content.Context
import android.graphics.drawable.Drawable
import eu.kanade.domain.source.service.SourcePreferences
import eu.kanade.tachiyomi.R
import eu.kanade.tachiyomi.extension.api.ExtensionGithubApi
import eu.kanade.tachiyomi.extension.model.AvailableSources
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.util.preference.plusAssign
import eu.kanade.tachiyomi.util.system.toast
import kotlinx.coroutines.async
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.asStateFlow
import logcat.LogPriority
import rx.Observable
import tachiyomi.core.util.lang.launchNow
import tachiyomi.core.util.lang.withUIContext
import tachiyomi.core.util.system.logcat
import tachiyomi.domain.source.model.SourceData
import uy.kohesive.injekt.Injekt
import uy.kohesive.injekt.api.get
import java.util.Locale

/**
 * 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: SourcePreferences = Injekt.get(),
) {

    var isInitialized = false
        private set

    /**
     * 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) }

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

    private val _installedExtensionsFlow = MutableStateFlow(emptyList<Extension.Installed>())
    val installedExtensionsFlow = _installedExtensionsFlow.asStateFlow()

    private var subLanguagesEnabledOnFirstRun = preferences.enabledLanguages().isSet()

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

    private val _availableExtensionsFlow = MutableStateFlow(emptyList<Extension.Available>())
    val availableExtensionsFlow = _availableExtensionsFlow.asStateFlow()

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

    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]

    private val _untrustedExtensionsFlow = MutableStateFlow(emptyList<Extension.Untrusted>())
    val untrustedExtensionsFlow = _untrustedExtensionsFlow.asStateFlow()

    init {
        initExtensions()
        ExtensionInstallReceiver(InstallationListener()).register(context)
    }

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

        _installedExtensionsFlow.value = extensions
            .filterIsInstance<LoadResult.Success>()
            .map { it.extension }

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

        isInitialized = true
    }

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

        enableAdditionalSubLanguages(extensions)

        _availableExtensionsFlow.value = extensions
        updatedInstalledExtensionsStatuses(extensions)
        setupAvailableExtensionsSourcesDataMap(extensions)
    }

    /**
     * Enables the additional sub-languages in the app first run. This addresses
     * the issue where users still need to enable some specific languages even when
     * the device language is inside that major group. As an example, if a user
     * has a zh device language, the app will also enable zh-Hans and zh-Hant.
     *
     * If the user have already changed the enabledLanguages preference value once,
     * the new languages will not be added to respect the user enabled choices.
     */
    private fun enableAdditionalSubLanguages(extensions: List<Extension.Available>) {
        if (subLanguagesEnabledOnFirstRun || extensions.isEmpty()) {
            return
        }

        // Use the source lang as some aren't present on the extension level.
        val availableLanguages = extensions
            .flatMap(Extension.Available::sources)
            .distinctBy(AvailableSources::lang)
            .map(AvailableSources::lang)

        val deviceLanguage = Locale.getDefault().language
        val defaultLanguages = preferences.enabledLanguages().defaultValue()
        val languagesToEnable = availableLanguages.filter {
            it != deviceLanguage && it.startsWith(deviceLanguage)
        }

        preferences.enabledLanguages().set(defaultLanguages + languagesToEnable)
        subLanguagesEnabledOnFirstRun = true
    }

    /**
     * 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 = _installedExtensionsFlow.value.toMutableList()
        var changed = false

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

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

                if (installedExt.hasUpdate != hasUpdate) {
                    mutInstalledExtensions[index] = installedExt.copy(hasUpdate = hasUpdate)
                    changed = true
                }
            }
        }
        if (changed) {
            _installedExtensionsFlow.value = 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 = _availableExtensionsFlow.value.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 = _untrustedExtensionsFlow.value.map { it.signatureHash }.toSet()
        if (signature !in untrustedSignatures) return

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

        val nowTrustedExtensions = _untrustedExtensionsFlow.value.filter { it.signatureHash == signature }
        _untrustedExtensionsFlow.value -= 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) {
        _installedExtensionsFlow.value += extension
    }

    /**
     * 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 = _installedExtensionsFlow.value.toMutableList()
        val oldExtension = mutInstalledExtensions.find { it.pkgName == extension.pkgName }
        if (oldExtension != null) {
            mutInstalledExtensions -= oldExtension
        }
        mutInstalledExtensions += extension
        _installedExtensionsFlow.value = mutInstalledExtensions
    }

    /**
     * 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 = _installedExtensionsFlow.value.find { it.pkgName == pkgName }
        if (installedExtension != null) {
            _installedExtensionsFlow.value -= installedExtension
        }
        val untrustedExtension = _untrustedExtensionsFlow.value.find { it.pkgName == pkgName }
        if (untrustedExtension != null) {
            _untrustedExtensionsFlow.value -= 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) {
            _untrustedExtensionsFlow.value += 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 {
        return if (updateExists()) {
            copy(hasUpdate = true)
        } else {
            this
        }
    }

    private fun Extension.Installed.updateExists(availableExtension: Extension.Available? = null): Boolean {
        val availableExt = availableExtension ?: _availableExtensionsFlow.value.find { it.pkgName == pkgName }
        if (isUnofficial || availableExt == null) return false

        return (availableExt.versionCode > versionCode || availableExt.libVersion > libVersion)
    }

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