select.Pages.scala Maven / Gradle / Ivy
/*
* Copyright 2021 Kári Magnússon
*
* 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 kuzminki.select
import java.sql.SQLException
import zio._
import zio.blocking._
import zio.clock.Clock
import kuzminki.api.{Kuzminki, KuzminkiError}
import kuzminki.render.RenderedQuery
import kuzminki.api.db
object Pages {
def apply[R](query: RenderedQuery[R], limit: Int) = new Pages(query, limit)
}
class Pages[R](query: RenderedQuery[R], limit: Int) {
query.statement.split(' ').foreach {
case "OFFSET" | "LIMIT" =>
throw KuzminkiError("query for pages cannot contain OFFSET or LIMIT")
case _ =>
}
private var isDone = false
private var offset = 0
private val pageStatement = query.statement + " OFFSET ? LIMIT ?"
private def nextQuery = {
val args = query.args ++ Vector(offset, limit)
offset = offset + limit
new RenderedQuery(pageStatement, args, query.rowConv)
}
private def pageQuery = {
val args = query.args ++ Vector(offset, limit)
offset = offset + limit
new RenderedQuery(pageStatement, args, query.rowConv)
}
private val markDone: List[R] => List[R] = { rows =>
if (rows.size < limit) isDone = true
rows
}
def getOriginal = new Pages(query, limit)
def nextOpt: ZIO[Has[Kuzminki] with Blocking with Clock, SQLException, Option[List[R]]] =
next.map {
case Nil => None
case rows => Some(rows)
}
def next: ZIO[Has[Kuzminki] with Blocking with Clock, SQLException, List[R]] = {
if (isDone) db.query(nextQuery).map(markDone)
else ZIO.succeed(List.empty[R])
}
private def pageQuery(page: Int) = {
if (page < 1) throw KuzminkiError("page must be greater than 0")
val offset = (page - 1) * limit
val args = query.args ++ Vector(offset, limit)
new RenderedQuery(pageStatement, args, query.rowConv)
}
def pageOpt(num: Int): ZIO[Has[Kuzminki] with Blocking with Clock, SQLException, Option[List[R]]] =
page(num).map {
case Nil => None
case rows => Some(rows)
}
def page(num: Int): ZIO[Has[Kuzminki] with Blocking with Clock, SQLException, List[R]] =
db.query(pageQuery(num))
}