package com.remek.rosettapos.common.storage

import android.app.Application
import android.content.Context
import com.google.gson.Gson

/**
 * Storage implementation that tries to serialize the objects and store the serialized form in
 * shared preferences.
 */
abstract class SerializedSharedPreferenceStorage<T>(
        application: Application,
        preferenceName: String,
        private val typeOfItem: Class<T>) : PersistentStorage<T> {

    companion object {
        /**
         * Key used for storing the shared preference item.
         */
        const val PREFERENCE_ITEM_KEY = "SerializedSharedPreferenceStorage:Item"
    }

    /**
     * The shared preference containing the serialized item.
     */
    private val preferences = application.getSharedPreferences(preferenceName, Context.MODE_PRIVATE)

    private val gson = Gson()

    override fun store(item: T) {
        preferences.edit().clear().putString(PREFERENCE_ITEM_KEY, Gson().toJson(item)).apply()
    }

    override fun retrieve(): T? {
        return if (preferences.contains(PREFERENCE_ITEM_KEY)) gson.fromJson(
                preferences.getString(PREFERENCE_ITEM_KEY, "{}"), typeOfItem) else null
    }

}