From 7158fccf2f6405e1b0ce480aa3870196a79b5def Mon Sep 17 00:00:00 2001
From: Albert Latacz <albert.latacz@gmail.com>
Date: Wed, 3 Jan 2024 11:04:43 +0000
Subject: [PATCH] object field

---
 .../kotlin/dev/forkhandles/lens/MapWrapper.kt    | 16 ++++++++++++----
 .../dev/forkhandles/lens/MapWrapperTest.kt       |  8 ++++++++
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/lens4k/src/main/kotlin/dev/forkhandles/lens/MapWrapper.kt b/lens4k/src/main/kotlin/dev/forkhandles/lens/MapWrapper.kt
index bb47c64..f8b986e 100644
--- a/lens4k/src/main/kotlin/dev/forkhandles/lens/MapWrapper.kt
+++ b/lens4k/src/main/kotlin/dev/forkhandles/lens/MapWrapper.kt
@@ -1,9 +1,17 @@
 package dev.forkhandles.lens
 
+@Suppress("UNCHECKED_CAST")
 abstract class MapWrapper(private val map: Map<String, Any?>) {
     class Field<OUT> : AbstractLensProp<MapWrapper, OUT>({ map.containsKey(it) }, { map[it] })
-    class ListField<IN, OUT>(mapFn: (IN) -> OUT) : AbstractLensProp<MapWrapper, List<OUT>>({ map.containsKey(it) }, {
-        @Suppress("UNCHECKED_CAST")
-        (map[it] as List<IN>).map(mapFn)
-    })
+    class ListField<IN : Any, OUT>(mapFn: (IN) -> OUT) : AbstractLensProp<MapWrapper, List<OUT>>(
+        { map.containsKey(it) },
+        { (map[it] as List<IN>).map(mapFn) }
+    )
+
+    class ObjectField<OUT : MapWrapper>(wrapper: (Map<String, Any?>) -> OUT) :
+        AbstractLensProp<MapWrapper, OUT>(
+            { map.containsKey(it) },
+            { wrapper(map[it] as Map<String, Any?>) }
+        )
+
 }
diff --git a/lens4k/src/test/kotlin/dev/forkhandles/lens/MapWrapperTest.kt b/lens4k/src/test/kotlin/dev/forkhandles/lens/MapWrapperTest.kt
index 890e2ae..dbc400b 100644
--- a/lens4k/src/test/kotlin/dev/forkhandles/lens/MapWrapperTest.kt
+++ b/lens4k/src/test/kotlin/dev/forkhandles/lens/MapWrapperTest.kt
@@ -21,6 +21,8 @@ class MapWrapperTest {
         val notAStringField by Field<String>()
         val noSuchField by Field<String>()
         val listField by ListField(::SubMap)
+        val listField2 by ListField(Any::toString)
+        val objectField by ObjectField(::SubMap)
     }
 
     @Test
@@ -36,6 +38,10 @@ class MapWrapperTest {
                 "listField" to listOf(
                     mapOf("stringField" to "string1"),
                     mapOf("stringField" to "string2"),
+                ),
+                "listField2" to listOf("string1", "string2"),
+                "objectField" to mapOf(
+                    "stringField" to "string"
                 )
             )
         )
@@ -46,6 +52,8 @@ class MapWrapperTest {
         expectThat(mapBacked.longField).isEqualTo(Long.MAX_VALUE)
         expectThat(mapBacked.decimalField).isEqualTo(1.1234)
         expectThat(mapBacked.listField.map { it.stringField }).isEqualTo(listOf("string1", "string2"))
+        expectThat(mapBacked.listField2).isEqualTo(listOf("string1", "string2"))
+        expectThat(mapBacked.objectField.stringField).isEqualTo("string")
         expectThrows<NoSuchElementException> { mapBacked.notAStringField }.message.isEqualTo("Value for field <notAStringField> is not a class kotlin.String but class kotlin.Int")
         expectThrows<NoSuchElementException> { mapBacked.noSuchField }.message.isEqualTo("Field <noSuchField> is missing")
     }