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package io.fluidsonic.raptor.domain.mongo

import com.mongodb.*
import com.mongodb.client.model.*
import com.mongodb.client.model.Sorts.*
import io.fluidsonic.mongo.*
import io.fluidsonic.raptor.domain.*
import io.fluidsonic.raptor.domain.mongo.RaptorAggregateEventBson.Fields
import io.fluidsonic.raptor.mongo.*
import io.fluidsonic.time.Timestamp
import kotlinx.coroutines.*
import kotlinx.coroutines.flow.*


// TODO Support horizontal scaling.
private class MongoAggregateStore(
	private val client: MongoClient,
	private val collection: MongoCollection>,
	private val transactionOptions: TransactionOptions,
) : RaptorAggregateStore {

	override suspend fun add(events: List>) {
		// TODO Batch in case the number of events is large.
		try {
			client.transaction(transactionOptions) { session ->
				collection.insertMany(session, events, InsertManyOptions().ordered(false))
			}
		}
		catch (e: MongoBulkWriteException) {
			// FIXME Check for duplicate key errors.
			// throw RaptorAggregateVersionConflict(e)

			// FIXME We actually cannot recover from this without stopping Raptor & starting a new one.
			//       We only support a single instance for now.
			throw e
		}
	}

	override suspend fun lastEventTimestampOrNull(): Timestamp? =
		collection.find()
			.sort(descending(Fields.id))
			.firstOrNull()
			?.timestamp


	override fun load(after: RaptorAggregateEventId?): Flow> =
		collection.find()
			// Any significantly large batch size is fine. We max out what MongoDB allows. 4-6x speed increase until here.
			.batchSize(1_000_000)
			.let { events ->
				when (after) {
					null -> events
					else -> events.filter(Filters.gt(Fields.id, after))
				}
			}
			.sort(ascending(Fields.id))


	override suspend fun start() {
		coroutineScope {
			launch {
				collection.createIndex(
					Indexes.ascending(Fields.aggregateType, Fields.aggregateId, Fields.version),
					IndexOptions().unique(true),
				)
			}
		}
	}
}


public fun RaptorAggregateStore.Companion.mongo(
	client: MongoClient,
	databaseName: String,
	collectionName: String,
	transactionOptions: TransactionOptions = TransactionOptions.builder().build(),
): RaptorAggregateStore =
	MongoAggregateStore(
		client = client,
		collection = client.getDatabase(databaseName).getCollectionOf(collectionName),
		transactionOptions = transactionOptions,
	)