/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

package mozilla.components.feature.addons.amo

import android.content.Context
import android.graphics.Bitmap
import android.graphics.BitmapFactory
import android.util.AtomicFile
import androidx.annotation.VisibleForTesting
import mozilla.components.concept.fetch.Client
import mozilla.components.concept.fetch.Request
import mozilla.components.concept.fetch.isSuccess
import mozilla.components.feature.addons.Addon
import mozilla.components.feature.addons.AddonsProvider
import mozilla.components.support.base.log.logger.Logger
import mozilla.components.support.ktx.kotlin.sanitizeFileName
import mozilla.components.support.ktx.kotlin.sanitizeURL
import mozilla.components.support.ktx.util.readAndDeserialize
import mozilla.components.support.ktx.util.writeString
import org.json.JSONArray
import org.json.JSONException
import org.json.JSONObject
import java.io.File
import java.io.IOException
import java.text.SimpleDateFormat
import java.util.concurrent.TimeUnit
import java.util.Date
import java.util.Locale

internal const val API_VERSION = "api/v4"
internal const val DEFAULT_SERVER_URL = "https://services.addons.mozilla.org"
internal const val DEFAULT_COLLECTION_USER = "mozilla"
internal const val DEFAULT_COLLECTION_NAME = "7e8d6dc651b54ab385fb8791bf9dac"
internal const val COLLECTION_FILE_NAME_PREFIX = "mozilla_components_addon_collection"
internal const val COLLECTION_FILE_NAME = "${COLLECTION_FILE_NAME_PREFIX}_%s.json"
internal const val COLLECTION_FILE_NAME_WITH_LANGUAGE = "${COLLECTION_FILE_NAME_PREFIX}_%s_%s.json"
internal const val REGEX_FILE_NAMES = "$COLLECTION_FILE_NAME_PREFIX(_\\w+)?_%s.json"
internal const val MINUTE_IN_MS = 60 * 1000
internal const val DEFAULT_READ_TIMEOUT_IN_SECONDS = 20L
internal const val PAGE_SIZE = 50

/**
 * Provide access to the AMO collections API.
 * https://addons-server.readthedocs.io/en/latest/topics/api/collections.html
 *
 * @property context A reference to the application context.
 * @property client A [Client] for interacting with the AMO HTTP api.
 * @property serverURL The url of the endpoint to interact with e.g production, staging
 * or testing. Defaults to [DEFAULT_SERVER_URL].
 * @property collectionUser The id or name of the user owning the collection specified in
 * [collectionName], defaults to [DEFAULT_COLLECTION_USER].
 * @property collectionName The name of the collection to access, defaults
 * to [DEFAULT_COLLECTION_NAME].
 * @property maxCacheAgeInMinutes maximum time (in minutes) the collection cache
 * should remain valid before a refresh is attempted. Defaults to -1, meaning no
 * cache is being used by default
 */
@Suppress("LongParameterList")
open class AddonCollectionProvider(
    private val context: Context,
    private val client: Client,
    private val serverURL: String = DEFAULT_SERVER_URL,
    private val collectionUser: String = DEFAULT_COLLECTION_USER,
    private val collectionName: String = DEFAULT_COLLECTION_NAME,
    private val sortOption: SortOption = SortOption.POPULARITY_DESC,
    private val maxCacheAgeInMinutes: Long = -1
) : AddonsProvider {

    private val logger = Logger("AddonCollectionProvider")

    private val diskCacheLock = Any()

    /**
     * Interacts with the collections endpoint to provide a list of available
     * add-ons. May return a cached response, if [allowCache] is true, and the
     * cache is not expired (see [maxCacheAgeInMinutes]) or fetching from
     * AMO failed.
     *
     * @param allowCache whether or not the result may be provided
     * from a previously cached response, defaults to true. Note that
     * [maxCacheAgeInMinutes] must be set for the cache to be active.
     * @param readTimeoutInSeconds optional timeout in seconds to use when fetching
     * available add-ons from a remote endpoint. If not specified [DEFAULT_READ_TIMEOUT_IN_SECONDS]
     * will be used.
     * @param language indicates in which language the translatable fields should be in, if no
     * matching language is found then a fallback translation is returned using the default language.
     * When it is null all translations available will be returned.
     * @throws IOException if the request failed, or could not be executed due to cancellation,
     * a connectivity problem or a timeout.
     */
    @Throws(IOException::class)
    @Suppress("NestedBlockDepth")
    override suspend fun getAvailableAddons(
        allowCache: Boolean,
        readTimeoutInSeconds: Long?,
        language: String?
    ): List<Addon> {
        // We want to make sure we always use useFallbackFile = false here, as it warranties
        // that we are trying to fetch the latest localized add-ons when the user changes
        // language from the previous one.
        val cachedAvailableAddons = if (allowCache && !cacheExpired(context, language, useFallbackFile = false)) {
            readFromDiskCache(language, useFallbackFile = false)
        } else {
            null
        }

        if (cachedAvailableAddons != null) {
            return cachedAvailableAddons
        }

        return try {
            fetchAvailableAddons(readTimeoutInSeconds, language)
        } catch (e: IOException) {
            logger.error("Failed to fetch available add-ons", e)
            if (allowCache) {
                val cacheLastUpdated = getCacheLastUpdated(context, language, useFallbackFile = true)
                if (cacheLastUpdated > -1) {
                    val cache = readFromDiskCache(language, useFallbackFile = true)
                    cache?.let {
                        logger.info("Falling back to available add-ons cache from ${
                            SimpleDateFormat("yyyy-MM-dd'T'HH:mm'Z'", Locale.US).format(cacheLastUpdated)
                        }")
                        return it
                    }
                }
            }
            throw e
        }
    }

    private fun fetchAvailableAddons(readTimeoutInSeconds: Long?, language: String?): List<Addon> {
        val langParam = if (!language.isNullOrEmpty()) {
            "&lang=$language"
        } else {
            ""
        }
        client.fetch(
            Request(
                // NB: The trailing slash after addons is important to prevent a redirect and additional request
                url = "$serverURL/$API_VERSION/accounts/account/$collectionUser/collections/$collectionName/addons/" +
                    "?page_size=$PAGE_SIZE" +
                    "&sort=${sortOption.value}" +
                    langParam,
                readTimeout = Pair(readTimeoutInSeconds ?: DEFAULT_READ_TIMEOUT_IN_SECONDS, TimeUnit.SECONDS)
            )
        )
        .use { response ->
            if (response.isSuccess) {
                val responseBody = response.body.string(Charsets.UTF_8)
                return try {
                    JSONObject(responseBody).getAddons(language).also {
                        if (maxCacheAgeInMinutes > 0) {
                            writeToDiskCache(responseBody, language)
                        }
                        deleteUnusedCacheFiles(language)
                    }
                } catch (e: JSONException) {
                    throw IOException(e)
                }
            } else {
                val errorMessage = "Failed to fetch add-on collection. Status code: ${response.status}"
                logger.error(errorMessage)
                throw IOException(errorMessage)
            }
        }
    }

    /**
     * Fetches given Addon icon from the url and returns a decoded Bitmap
     * @throws IOException if the request could not be executed due to cancellation,
     * a connectivity problem or a timeout.
     */
    @Throws(IOException::class)
    open suspend fun getAddonIconBitmap(addon: Addon): Bitmap? {
        var bitmap: Bitmap? = null
        if (addon.iconUrl != "") {
            client.fetch(
                    Request(url = addon.iconUrl.sanitizeURL())
            ).use { response ->
                if (response.isSuccess) {
                    response.body.useStream {
                        bitmap = BitmapFactory.decodeStream(it)
                    }
                }
            }
        }

        return bitmap
    }

    @VisibleForTesting
    protected fun writeToDiskCache(collectionResponse: String, language: String?) {
        synchronized(diskCacheLock) {
            getCacheFile(context, language, useFallbackFile = false).writeString { collectionResponse }
        }
    }

    @VisibleForTesting
    internal fun readFromDiskCache(language: String?, useFallbackFile: Boolean): List<Addon>? {
        synchronized(diskCacheLock) {
            return getCacheFile(context, language, useFallbackFile).readAndDeserialize {
                JSONObject(it).getAddons(language)
            }
        }
    }

    /**
     * Deletes cache files from previous (now unused) collections.
     */
    @VisibleForTesting
    internal fun deleteUnusedCacheFiles(language: String?) {
        val currentCacheFileName = getBaseCacheFile(context, language, useFallbackFile = true).name

        context.filesDir
            .listFiles {
                _, s -> s.startsWith(COLLECTION_FILE_NAME_PREFIX) && s != currentCacheFileName
            }
            ?.forEach {
                logger.debug("Deleting unused collection cache: " + it.name)
                it.delete()
            }
    }

    @VisibleForTesting
    internal fun cacheExpired(context: Context, language: String?, useFallbackFile: Boolean): Boolean {
        return getCacheLastUpdated(
            context,
            language,
            useFallbackFile
        ) < Date().time - maxCacheAgeInMinutes * MINUTE_IN_MS
    }

    @VisibleForTesting
    internal fun getCacheLastUpdated(context: Context, language: String?, useFallbackFile: Boolean): Long {
        val file = getBaseCacheFile(context, language, useFallbackFile)
        return if (file.exists()) file.lastModified() else -1
    }

    private fun getCacheFile(context: Context, language: String?, useFallbackFile: Boolean): AtomicFile {
        return AtomicFile(getBaseCacheFile(context, language, useFallbackFile))
    }

    @VisibleForTesting
    internal fun getBaseCacheFile(context: Context, language: String?, useFallbackFile: Boolean): File {
        var file = File(context.filesDir, getCacheFileName(language))
        if (!file.exists() && useFallbackFile) {
            // In situations, where users change languages and we can't retrieve the new one,
            // we always want to fallback to the previous localized file.
            // Try to find first available localized file.
            val regex = Regex(REGEX_FILE_NAMES.format(getCollectionName()))
            val fallbackFile = context.filesDir.listFiles()?.find { it.name.matches(regex) }

            if (fallbackFile?.exists() == true) {
                file = fallbackFile
            }
        }
        return file
    }

    @VisibleForTesting
    internal fun getCacheFileName(language: String? = ""): String {
        val collection = getCollectionName()

        val fileName = if (language.isNullOrEmpty()) {
            COLLECTION_FILE_NAME.format(collection)
        } else {
            COLLECTION_FILE_NAME_WITH_LANGUAGE.format(language, collection)
        }
        return fileName.sanitizeFileName()
    }

    @VisibleForTesting
    internal fun getCollectionName(): String {
        val collectionUser = collectionUser.sanitizeFileName()
        val collectionName = collectionName.sanitizeFileName()

        // Prefix with collection user in case it was customized. We don't want
        // to do this for the default "mozilla" user so we don't break out of
        // the existing cache when we're introducing this. Plus mozilla is
        // already in the file name anyway.
        return if (collectionUser != DEFAULT_COLLECTION_USER) {
            "${collectionUser}_$collectionName"
        } else {
            collectionName
        }
    }
}

/**
 * Represents possible sort options for the recommended add-ons from
 * the configured add-on collection.
 */
enum class SortOption(val value: String) {
    POPULARITY("popularity"),
    POPULARITY_DESC("-popularity"),
    NAME("name"),
    NAME_DESC("-name"),
    DATE_ADDED("added"),
    DATE_ADDED_DESC("-added")
}

internal fun JSONObject.getAddons(language: String? = null): List<Addon> {
    val addonsJson = getJSONArray("results")
    return (0 until addonsJson.length()).map { index ->
        addonsJson.getJSONObject(index).toAddons(language)
    }
}

internal fun JSONObject.toAddons(language: String? = null): Addon {
    return with(getJSONObject("addon")) {
        val download = getDownload()
        val safeLanguage = language?.toLowerCase(Locale.getDefault())
        val summary = getSafeTranslations("summary", safeLanguage)
        val isLanguageInTranslations = summary.containsKey(safeLanguage)
        Addon(
            id = getSafeString("guid"),
            authors = getAuthors(),
            categories = getCategories(),
            createdAt = getSafeString("created"),
            updatedAt = getSafeString("last_updated"),
            downloadId = download?.getDownloadId() ?: "",
            downloadUrl = download?.getDownloadUrl() ?: "",
            version = getCurrentVersion(),
            permissions = getPermissions(),
            translatableName = getSafeTranslations("name", safeLanguage),
            translatableDescription = getSafeTranslations("description", safeLanguage),
            translatableSummary = summary,
            iconUrl = getSafeString("icon_url"),
            siteUrl = getSafeString("url"),
            rating = getRating(),
            defaultLocale = (if (!safeLanguage.isNullOrEmpty() && isLanguageInTranslations) {
                safeLanguage
            } else {
                getSafeString("default_locale").ifEmpty { Addon.DEFAULT_LOCALE }
            }).toLowerCase(Locale.ROOT)
        )
    }
}

internal fun JSONObject.getRating(): Addon.Rating? {
    val jsonRating = optJSONObject("ratings")
    return if (jsonRating != null) {
        Addon.Rating(
            reviews = jsonRating.optInt("count"),
            average = jsonRating.optDouble("average").toFloat()
        )
    } else {
        null
    }
}

internal fun JSONObject.getCategories(): List<String> {
    val jsonCategories = optJSONObject("categories")
    return if (jsonCategories == null) {
        emptyList()
    } else {
        val jsonAndroidCategories = jsonCategories.getSafeJSONArray("android")
        (0 until jsonAndroidCategories.length()).map { index ->
            jsonAndroidCategories.getString(index)
        }
    }
}

internal fun JSONObject.getPermissions(): List<String> {
    val fileJson = getJSONObject("current_version")
        .getSafeJSONArray("files")
        .getJSONObject(0)

    val permissionsJson = fileJson.getSafeJSONArray("permissions")
    return (0 until permissionsJson.length()).map { index ->
        permissionsJson.getString(index)
    }
}

internal fun JSONObject.getCurrentVersion(): String {
    return optJSONObject("current_version")?.getSafeString("version") ?: ""
}

internal fun JSONObject.getDownload(): JSONObject? {
    return (getJSONObject("current_version")
        .optJSONArray("files")
        ?.getJSONObject(0))
}

internal fun JSONObject.getDownloadId(): String {
    return getSafeString("id")
}

internal fun JSONObject.getDownloadUrl(): String {
    return getSafeString("url")
}

internal fun JSONObject.getAuthors(): List<Addon.Author> {
    val authorsJson = getSafeJSONArray("authors")
    return (0 until authorsJson.length()).map { index ->
        val authorJson = authorsJson.getJSONObject(index)

        Addon.Author(
            id = authorJson.getSafeString("id"),
            name = authorJson.getSafeString("name"),
            username = authorJson.getSafeString("username"),
            url = authorJson.getSafeString("url")
        )
    }
}

internal fun JSONObject.getSafeString(key: String): String {
    return if (isNull(key)) {
        ""
    } else {
        getString(key)
    }
}

internal fun JSONObject.getSafeJSONArray(key: String): JSONArray {
    return if (isNull(key)) {
        JSONArray("[]")
    } else {
        getJSONArray(key)
    }
}
internal fun JSONObject.getSafeTranslations(valueKey: String, language: String?): Map<String, String> {
    // We can have two different versions of the JSON structure for translatable fields:
    // 1) A string with only one language, when we provide a language parameter.
    // 2) An object containing all the languages available when a language parameter is NOT present.
    // For this reason, we have to be specific about how we parse the JSON.
    return if (get(valueKey) is String) {
        val safeLanguage = (language ?: Addon.DEFAULT_LOCALE).toLowerCase(Locale.ROOT)
        mapOf(safeLanguage to getSafeString(valueKey))
    } else {
        getSafeMap(valueKey)
    }
}
internal fun JSONObject.getSafeMap(valueKey: String): Map<String, String> {
    return if (isNull(valueKey)) {
        emptyMap()
    } else {
        val map = mutableMapOf<String, String>()
        val jsonObject = getJSONObject(valueKey)

        jsonObject.keys()
            .forEach { key ->
                map[key.toLowerCase(Locale.ROOT)] = jsonObject.getSafeString(key)
            }
        map
    }
}
