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reads.scala
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reads.scala
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/*
* Copyright 2020 Scala EventStoreDB Client
*
* 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 sec
package api
package streams
import cats.syntax.all._
import cats.effect.Temporal
import fs2.Stream
import com.eventstore.dbclient.proto.streams._
import sec.api.mapping.streams.{incoming => mi}
import sec.api.mapping.streams.{outgoing => mo}
/** Low-level API for reading streams that exposes more detailed messages than the [[Streams]] API.
*
* @tparam F
* the effect type in which [[Reads]] operates.
*/
trait Reads[F[_]] {
/** Read [[AllMessage]] messages from the global stream, [[sec.StreamId.All]].
*
* @param from
* log position to read from.
* @param direction
* whether to read forwards or backwards.
* @param maxCount
* limits maximum events returned.
* @param resolveLinkTos
* whether to resolve [[EventType.LinkTo]] events automatically.
* @return
* a [[Stream]] that emits [[AllMessage]] values.
*/
def readAllMessages(
from: LogPosition,
direction: Direction,
maxCount: Long,
resolveLinkTos: Boolean
): Stream[F, AllMessage]
/** Read [[StreamMessage]] messages from an individual stream.
*
* @param streamId
* the id of the stream to subscribe to.
* @param from
* stream position to read from.
* @param direction
* whether to read forwards or backwards.
* @param maxCount
* limits maximum events returned.
* @param resolveLinkTos
* whether to resolve [[EventType.LinkTo]] events automatically.
* @return
* a [[Stream]] that emits [[StreamMessage]] values.
*/
def readStreamMessages(
streamId: StreamId,
from: StreamPosition,
direction: Direction,
maxCount: Long,
resolveLinkTos: Boolean
): Stream[F, StreamMessage]
}
object Reads {
private[sec] def apply[F[_]: Temporal, C](
client: StreamsFs2Grpc[F, C],
mkCtx: Option[UserCredentials] => C
): Reads[F] = new Reads[F] {
val readAll: ReadReq => Stream[F, mi.AllResult] =
client.read(_, mkCtx(None)).evalMap(mi.AllResult.fromWire[F])
val readStream: ReadReq => Stream[F, mi.StreamResult] =
client.read(_, mkCtx(None)).evalMap(mi.StreamResult.fromWire[F])
def readAllMessages(
from: LogPosition,
direction: Direction,
maxCount: Long,
resolveLinkTos: Boolean
): Stream[F, AllMessage] =
ReadAll(from, direction, maxCount, resolveLinkTos, readAll).run
.mapFilter(_.toAllMessage)
def readStreamMessages(
streamId: StreamId,
from: StreamPosition,
direction: Direction,
maxCount: Long,
resolveLinkTos: Boolean
): Stream[F, StreamMessage] =
ReadStream(streamId, from, direction, maxCount, resolveLinkTos, readStream).run
.mapFilter(_.toStreamMessage)
}
}
// ====================================================================================================================
final private[api] case class ReadAll[F[_]](
from: LogPosition,
direction: Direction,
maxCount: Long,
resolveLinkTos: Boolean,
handle: ReadReq => Stream[F, mi.AllResult]
)
private[api] object ReadAll {
implicit final class ReadAllOps[F[_]](val ra: ReadAll[F]) extends AnyVal {
def withFrom(lp: LogPosition): ReadAll[F] =
ra.copy(from = lp)
def run: Stream[F, mi.AllResult] = {
val valid = ra.maxCount > 0L
val req = mo.mkReadAllReq(ra.from, ra.direction, ra.maxCount, ra.resolveLinkTos)
if (valid) ra.handle(req) else Stream.empty
}
}
}
final private[api] case class ReadStream[F[_]](
streamId: StreamId,
from: StreamPosition,
direction: Direction,
maxCount: Long,
resolveLinkTos: Boolean,
handle: ReadReq => Stream[F, mi.StreamResult]
)
private[api] object ReadStream {
implicit final class ReadStreamOps[F[_]](val rs: ReadStream[F]) extends AnyVal {
def withFrom(sp: StreamPosition): ReadStream[F] =
rs.copy(from = sp)
def run: Stream[F, mi.StreamResult] = {
val valid = rs.direction.fold(rs.from =!= StreamPosition.End, true) && rs.maxCount > 0L
val req = mo.mkReadStreamReq(rs.streamId, rs.from, rs.direction, rs.maxCount, rs.resolveLinkTos)
if (valid) rs.handle(req) else Stream.empty
}
}
}