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Fmodel provides just enough tactical Domain-Driven Design patterns, optimised for Event Sourcing and CQRS. The application library orchestrates the execution of the logic by loading state, executing domain components and storing new state. It is an Arrow (FP library for Kotlin) flavored implementation.

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/*
 * Copyright (c) 2021 Fraktalio D.O.O. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.fraktalio.fmodel.application.examples.numbers

import com.fraktalio.fmodel.application.EventRepository
import com.fraktalio.fmodel.domain.examples.numbers.api.NumberCommand
import com.fraktalio.fmodel.domain.examples.numbers.api.NumberEvent
import com.fraktalio.fmodel.domain.examples.numbers.api.NumberEvent.EvenNumberEvent
import com.fraktalio.fmodel.domain.examples.numbers.api.NumberEvent.OddNumberEvent
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.asFlow
import kotlinx.coroutines.flow.map

/**
 * A very simple event store ;)  It is initially empty.
 */
private var numberEventStorage: List = emptyList()

/**
 * Number (event) repository
 *
 * @constructor Creates Number repository
 */
class NumberRepository : EventRepository {


    override fun NumberCommand?.fetchEvents(): Flow =

        numberEventStorage.asFlow().map { numberEvent ->
            when (numberEvent) {
                is EvenNumberEvent -> numberEvent
                is OddNumberEvent -> numberEvent
                else -> throw UnsupportedOperationException("fetched null event from the event store")
            }
        }


    override suspend fun NumberEvent?.save(): NumberEvent? {

        numberEventStorage = numberEventStorage.plus(this)

        return this
    }

    fun deleteAll() {
        numberEventStorage = emptyList()

    }


}

/**
 * Number repository
 *
 * @return Number repository instance
 */
fun numberRepository(): EventRepository =
    NumberRepository()