From 0a3ac9f121c761f7c1b6cda591b5bb3cbd510bc3 Mon Sep 17 00:00:00 2001
From: eikek <eike.kettner@posteo.de>
Date: Fri, 12 Aug 2022 16:26:20 +0200
Subject: [PATCH] Add anonymous subselects to query builder

---
 .../main/scala/docspell/store/qb/Select.scala | 21 ++++++++++++-------
 .../scala/docspell/store/qb/SelectExpr.scala  |  2 ++
 .../store/qb/impl/SelectBuilder.scala         |  2 +-
 .../docspell/store/qb/QueryBuilderTest.scala  |  6 ++++--
 4 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/modules/store/src/main/scala/docspell/store/qb/Select.scala b/modules/store/src/main/scala/docspell/store/qb/Select.scala
index 65ec0c6e..7f2e6916 100644
--- a/modules/store/src/main/scala/docspell/store/qb/Select.scala
+++ b/modules/store/src/main/scala/docspell/store/qb/Select.scala
@@ -7,6 +7,7 @@
 package docspell.store.qb
 
 import cats.data.{NonEmptyList => Nel}
+import cats.syntax.option._
 
 import docspell.store.qb.impl.SelectBuilder
 
@@ -23,6 +24,9 @@ sealed trait Select {
   def as(alias: String): SelectExpr.SelectQuery =
     SelectExpr.SelectQuery(this, Some(alias))
 
+  def asSubSelect: SelectExpr.SelectQuery =
+    SelectExpr.SelectQuery(this, None)
+
   /** Adds one or more order-by definitions */
   def orderBy(ob: OrderBy, obs: OrderBy*): Select
 
@@ -71,35 +75,38 @@ sealed trait Select {
 }
 
 object Select {
+  def apply(projection: SelectExpr) =
+    SimpleSelect(false, Nel.of(projection), None, Condition.unit, None)
+
   def apply(projection: Nel[SelectExpr], from: FromExpr) =
-    SimpleSelect(false, projection, from, Condition.unit, None)
+    SimpleSelect(false, projection, from.some, Condition.unit, None)
 
   def apply(projection: SelectExpr, from: FromExpr) =
-    SimpleSelect(false, Nel.of(projection), from, Condition.unit, None)
+    SimpleSelect(false, Nel.of(projection), from.some, Condition.unit, None)
 
   def apply(
       projection: Nel[SelectExpr],
       from: FromExpr,
       where: Condition
-  ) = SimpleSelect(false, projection, from, where, None)
+  ) = SimpleSelect(false, projection, from.some, where, None)
 
   def apply(
       projection: SelectExpr,
       from: FromExpr,
       where: Condition
-  ) = SimpleSelect(false, Nel.of(projection), from, where, None)
+  ) = SimpleSelect(false, Nel.of(projection), from.some, where, None)
 
   def apply(
       projection: Nel[SelectExpr],
       from: FromExpr,
       where: Condition,
       groupBy: GroupBy
-  ) = SimpleSelect(false, projection, from, where, Some(groupBy))
+  ) = SimpleSelect(false, projection, from.some, where, Some(groupBy))
 
   case class SimpleSelect(
       distinctFlag: Boolean,
       projection: Nel[SelectExpr],
-      from: FromExpr,
+      from: Option[FromExpr],
       where: Condition,
       groupBy: Option[GroupBy]
   ) extends Select {
@@ -125,7 +132,7 @@ object Select {
       copy(projection = es)
 
     def changeFrom(f: FromExpr => FromExpr): SimpleSelect =
-      copy(from = f(from))
+      copy(from = from.map(f))
 
     def changeWhere(f: Condition => Condition): SimpleSelect =
       copy(where = f(where))
diff --git a/modules/store/src/main/scala/docspell/store/qb/SelectExpr.scala b/modules/store/src/main/scala/docspell/store/qb/SelectExpr.scala
index 8c922522..1bba08ae 100644
--- a/modules/store/src/main/scala/docspell/store/qb/SelectExpr.scala
+++ b/modules/store/src/main/scala/docspell/store/qb/SelectExpr.scala
@@ -33,6 +33,8 @@ object SelectExpr {
   case class SelectLiteral(value: String, alias: Option[String]) extends SelectExpr {
     def as(a: String): SelectLiteral =
       copy(alias = Some(a))
+    def as(otherCol: Column[_]): SelectExpr =
+      copy(alias = Some(otherCol.name))
   }
 
   case class SelectQuery(query: Select, alias: Option[String]) extends SelectExpr {
diff --git a/modules/store/src/main/scala/docspell/store/qb/impl/SelectBuilder.scala b/modules/store/src/main/scala/docspell/store/qb/impl/SelectBuilder.scala
index e77bfe6f..2f6641dc 100644
--- a/modules/store/src/main/scala/docspell/store/qb/impl/SelectBuilder.scala
+++ b/modules/store/src/main/scala/docspell/store/qb/impl/SelectBuilder.scala
@@ -52,7 +52,7 @@ object SelectBuilder {
 
   def buildSimple(sq: Select.SimpleSelect): Fragment = {
     val f0 = sq.projection.map(selectExpr).reduceLeft(_ ++ comma ++ _)
-    val f1 = fromExpr(sq.from)
+    val f1 = sq.from.map(fromExpr).getOrElse(Fragment.empty)
     val f2 = cond(sq.where)
     val f3 = sq.groupBy.map(groupBy).getOrElse(Fragment.empty)
     f0 ++ f1 ++ f2 ++ f3
diff --git a/modules/store/src/test/scala/docspell/store/qb/QueryBuilderTest.scala b/modules/store/src/test/scala/docspell/store/qb/QueryBuilderTest.scala
index a36afeff..69a63410 100644
--- a/modules/store/src/test/scala/docspell/store/qb/QueryBuilderTest.scala
+++ b/modules/store/src/test/scala/docspell/store/qb/QueryBuilderTest.scala
@@ -50,9 +50,11 @@ class QueryBuilderTest extends FunSuite with TestLoggingConfig {
         )
         assertEquals(11, proj.size)
         from match {
-          case FromExpr.From(_) =>
+          case None =>
             fail("Unexpected from value")
-          case FromExpr.Joined(f, joins) =>
+          case Some(FromExpr.From(_)) =>
+            fail("Unexpected from value")
+          case Some(FromExpr.Joined(f, joins)) =>
             assertEquals(f, FromExpr.From(c))
             assertEquals(2, joins.size)
             joins.head match {