/* 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 org.mozilla.fenix.components.searchengine

import android.content.Context
import android.content.SharedPreferences
import androidx.annotation.VisibleForTesting
import mozilla.components.browser.icons.IconRequest
import mozilla.components.browser.search.SearchEngine
import mozilla.components.browser.search.SearchEngineParser
import mozilla.components.browser.search.provider.SearchEngineList
import mozilla.components.browser.search.provider.SearchEngineProvider
import mozilla.components.support.ktx.android.content.PreferencesHolder
import mozilla.components.support.ktx.android.content.stringSetPreference
import org.mozilla.fenix.ext.components
import java.lang.Exception

/**
 * SearchEngineProvider implementation to load user entered custom search engines.
 */
class CustomSearchEngineProvider : SearchEngineProvider {
    override suspend fun loadSearchEngines(context: Context): SearchEngineList {
        return SearchEngineList(CustomSearchEngineStore.loadCustomSearchEngines(context), null)
    }
}

/**
 * Object to handle storing custom search engines
 */
object CustomSearchEngineStore {
    class EngineNameAlreadyExists : Exception()

    /**
     * Add a search engine to the store.
     * @param context [Context] used for various Android interactions.
     * @param engineName The name of the search engine
     * @param searchQuery The templated search string for the search engine
     * @throws EngineNameAlreadyExists if you try to add a search engine that already exists
     */
    suspend fun addSearchEngine(context: Context, engineName: String, searchQuery: String) {
        val storage = engineStorage(context)
        if (storage.customSearchEngineIds.contains(engineName)) { throw EngineNameAlreadyExists() }

        val icon = context.components.core.icons.loadIcon(IconRequest(searchQuery)).await()
        val searchEngineXml = SearchEngineWriter.buildSearchEngineXML(engineName, searchQuery, icon.bitmap)
        val engines = storage.customSearchEngineIds.toMutableSet()
        engines.add(engineName)
        storage.customSearchEngineIds = engines
        storage[engineName] = searchEngineXml
    }

    /**
     * Updates an existing search engine.
     * To prevent duplicate search engines we want to remove the old engine before adding the new one
     * @param context [Context] used for various Android interactions.
     * @param oldEngineName the name of the engine you want to replace
     * @param newEngineName the name of the engine you want to save
     * @param searchQuery The templated search string for the search engine
     */
    suspend fun updateSearchEngine(
        context: Context,
        oldEngineName: String,
        newEngineName: String,
        searchQuery: String
    ) {
        removeSearchEngine(context, oldEngineName)
        addSearchEngine(context, newEngineName, searchQuery)
    }

    /**
     * Removes a search engine from the store
     * @param context [Context] used for various Android interactions.
     * @param engineId the id of the engine you want to remove
     */
    fun removeSearchEngine(context: Context, engineId: String) {
        val storage = engineStorage(context)
        val customEngines = storage.customSearchEngineIds
        storage.customSearchEngineIds = customEngines.filterNot { it == engineId }.toSet()
        storage[engineId] = null
    }

    /**
     * Checks the store to see if it contains a search engine
     * @param context [Context] used for various Android interactions.
     * @param engineId The name of the engine to check
     */
    fun isCustomSearchEngine(context: Context, engineId: String): Boolean {
        val storage = engineStorage(context)
        return storage.customSearchEngineIds.contains(engineId)
    }

    /**
     * Creates a list of [SearchEngine] from the store
     * @param context [Context] used for various Android interactions.
     */
    fun loadCustomSearchEngines(context: Context): List<SearchEngine> {
        val storage = engineStorage(context)
        val parser = SearchEngineParser()
        val engines = storage.customSearchEngineIds

        return engines.mapNotNull {
            val engineXml = storage[it] ?: return@mapNotNull null
            val engineInputStream = engineXml.byteInputStream().buffered()
            parser.load(it, engineInputStream)
        }
    }

    /**
     * Creates a helper object to help interact with [SharedPreferences]
     * @param context [Context] used for various Android interactions.
     */
    private fun engineStorage(context: Context) = object : PreferencesHolder {
        override val preferences: SharedPreferences
            get() = context.getSharedPreferences(PREF_FILE_SEARCH_ENGINES, Context.MODE_PRIVATE)

        var customSearchEngineIds by stringSetPreference(PREF_KEY_CUSTOM_SEARCH_ENGINES, emptySet())

        operator fun get(engineId: String): String? {
            return preferences.getString(engineId, null)
        }

        operator fun set(engineId: String, value: String?) {
            preferences.edit().putString(engineId, value).apply()
        }
    }

    private const val PREF_KEY_CUSTOM_SEARCH_ENGINES = "pref_custom_search_engines"
    @VisibleForTesting
    const val PREF_FILE_SEARCH_ENGINES = "custom-search-engines"
}