package ca.allanwang.kau.kpref

import ca.allanwang.kau.kotlin.ILazyResettable

fun KPref.kprefSingle(key: String) = KPrefSingleDelegate(key, this)

/**
 * Created by Allan Wang on 2017-06-07.
 *
 * Singular KPref Delegate for booleans
 * When the shared pref is not initialized, it will return [true] then set the pref to [false]
 * All subsequent retrievals will be [false]
 * This is useful for one time toggles such as showcasing items
 */
class KPrefSingleDelegate internal constructor(private val key: String, private val pref: KPref, lock: Any? = null) : ILazyResettable<Boolean> {

    @Volatile
    private var _value: Boolean? = null
    private val lock = lock ?: this

    init {
        if (pref.prefMap.containsKey(key))
            throw KPrefException("$key is already used elsewhere in preference ${pref.PREFERENCE_NAME}")
        pref.prefMap.put(key, this@KPrefSingleDelegate)
    }

    override fun invalidate() {
        _value = null
    }

    override val value: Boolean
        get() {
            val _v1 = _value
            if (_v1 != null)
                return _v1

            return synchronized(lock) {
                val _v2 = _value
                if (_v2 != null) {
                    _v2
                } else {
                    _value = pref.sp.getBoolean(key, true)
                    if (_value!!) {
                        pref.sp.edit().putBoolean(key, false).apply()
                        _value = false
                        true
                    } else false
                }
            }
        }

    override fun isInitialized(): Boolean = _value != null

    override fun toString(): String = if (isInitialized()) value.toString() else "Lazy kPref $key not initialized yet."

}