parsec3/src/commonMain/kotlin/net.sergeych.parsec3/KVStorage.kt

package net.sergeych.parsec3

import net.sergeych.boss_serialization.BossDecoder
import net.sergeych.boss_serialization_mp.BossEncoder
import net.sergeych.mp_logger.LogTag
import net.sergeych.mp_logger.exception
import net.sergeych.mp_logger.info
import net.sergeych.mptools.encodeToHex
import net.sergeych.mptools.toDump
import kotlin.reflect.KProperty
import kotlin.reflect.KType
import kotlin.reflect.typeOf


/**
 * Generic storage of binary content. PArsec uses boss encoding to store everything in it
 * in te convenient way. See [KVStorage.stored] delegate. The [MemoryKVStorage] allows to
 * store values in-memory and then connect some permanent stprage to it in a transparent way.
 */
interface KVStorage {
    operator fun get(key: String): ByteArray?
    operator fun set(key: String, value: ByteArray?)

    /**
     * Check whether key is in storage.
     * Default implementation uses [keys]. You may override it for performance
     */
    operator fun contains(key: String): Boolean = key in keys

    val keys: Set<String>


    /**
     * Get number of object in the storage
     * Default implementation uses [keys]. You may override it for performance
     */
    val size: Int get() = keys.size

    /**
     * Clears all objects in the storage
     * Default implementation uses [keys]. You may override it for performance
     */
    fun clear() {
        for (k in keys) this[k] = null
    }

    /**
     * Default implementation uses [keys]. You may override it for performance
     */
    fun isEmpty() = size == 0

    /**
     * Default implementation uses [keys]. You may override it for performance
     */
    fun isNotEmpty() = size != 0

    fun addAll(other: KVStorage) {
        for (k in other.keys) {
            this[k] = other[k]
        }
    }

}

inline operator fun <reified T> KVStorage.invoke(defaultValue: T, overrideName: String? = null) =
    KVStorageDelegate<T>(this, typeOf<T>(), defaultValue, overrideName)

inline fun <reified T> KVStorage.stored(defaultValue: T, overrideName: String? = null) =
    KVStorageDelegate<T>(this, typeOf<T>(), defaultValue, overrideName)

inline fun <reified T> KVStorage.optStored(defaultValue: T? = null, overrideName: String? = null) =
    KVStorageDelegate<T?>(this, typeOf<T>(), defaultValue, overrideName)

class KVStorageDelegate<T>(
    private val storage: KVStorage,
    private val type: KType,
    private val defaultValue: T,
    private val overrideName: String? = null,
): LogTag("KVSD") {

    private fun name(property: KProperty<*>): String = overrideName ?: property.name

    private var cachedValue: T = defaultValue
    private var cacheReady = false

    operator fun getValue(thisRef: Any?, property: KProperty<*>): T {
        if (cacheReady) return cachedValue
        val data = storage.get(name(property))
        if (data == null)
            cachedValue = defaultValue
        else
            cachedValue = try {
                info { " get ${name(property)}: ${type} [{${data.encodeToHex()}" }
                BossDecoder.decodeFrom<T>(type, data)
                    .also { println("decoded as $it") }
            } catch (e: Exception) {
                exception {  "failed to decode ${name(property)}: ${type}" to e }
                defaultValue
            }
        cacheReady = true
        return cachedValue
    }

    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
//        if (!cacheReady || value != cachedValue) {
        cachedValue = value
        cacheReady = true
        println("set ${name(property)} to ${BossEncoder.encode(type, value).toDump()}")
        storage[name(property)] = BossEncoder.encode(type, value)
//        }
    }
}

/**
 * Memory storage allows to connect existing in-memory content to some permanent storage on the fly
 */
class MemoryKVStorage(copyFrom: KVStorage? = null) : KVStorage {

    // is used when connected:
    private var underlying: KVStorage? = null

    // is used while underlying is null:
    private val data = mutableMapOf<String, ByteArray>()

    @Suppress("unused")
    fun connectToStorage(other: KVStorage) {
        other.addAll(this)
        underlying = other
        data.clear()
    }


    override fun get(key: String): ByteArray? {
        underlying?.let {
            return it[key]
        }
        return data[key]
    }

    override fun set(key: String, value: ByteArray?) {
        underlying?.let { it[key] = value } ?: run {
            if (value != null) data[key] = value
            else data.remove(key)
        }
    }

    override fun contains(key: String): Boolean {
        underlying?.let { return key in it }
        return key in data
    }

    override val keys: Set<String>
        get() = underlying?.keys ?: data.keys

    override fun clear() {
        underlying?.clear() ?: data.clear()
    }

    init {
        copyFrom?.let { addAll(it) }
    }
}

expect fun defaultNamedStorage(name: String): KVStorage