From 570bb25eb56603bf947de60dadb3f2bbb9e5cd4c Mon Sep 17 00:00:00 2001
From: Daniel Slapman <danslapman@gmail.com>
Date: Sun, 19 Nov 2023 14:15:08 +0100
Subject: [PATCH] Add chained test & usage example

---
 readme.md                                     | 19 +++++++++++++++++++
 .../ChainedOpticTests.cs                      | 13 +++++++++++++
 src/LeviySoft.Visor.Gen.Tests/Sample.cs       |  4 +++-
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/readme.md b/readme.md
index 2522da1..d501977 100644
--- a/readme.md
+++ b/readme.md
@@ -62,6 +62,25 @@ var id = Sample.IdLens.Get(...);
 Sample.DescriptionLens.Set("replaced")(...);
 ```
 
+## Dealing with immutable collections & nullable properties
+
+`Visor` comes with a useful set of optics for manipulating values at nullable anr/or collection properties.
+Although `System.Collections.Immutable` is supported I strongly recommend using language-ext's immutable collections
+because standart ones breaks value equality of records.
+
+Here is a brief example of using build-in optics:
+
+```csharp
+[Optics] internal partial record InnerItem(int Id, string Name);
+[Optics] internal partial record Aux(string Comment, IImmutableList<string> Tags);
+[Optics(withNested: true)] internal partial record ItemWrapper(InnerItem Item, Aux? Aux);
+[Optics(withNested: true)] internal partial record Warehouse(ItemWrapper Main);
+
+var warehouse = new Warehouse(new ItemWrapper(new InnerItem(1, "Default"), new Aux("test", ImmutableList.Create("tag1", "tag2"))));
+var telescope = Warehouse.FocusMain.AuxLens.NotNull().Compose(Aux.TagsLens).Compose(Property.IImmutableList.First<string>());
+var warehouse2 = telescope.Set("updated_tag")(warehouse); //Now warehouse2.Main.Aux?.Tags is ("updated_tag", "tag2")
+```
+
 ## Coming soon
 - Prism
 - Traverse
diff --git a/src/LeviySoft.Visor.Gen.Tests/ChainedOpticTests.cs b/src/LeviySoft.Visor.Gen.Tests/ChainedOpticTests.cs
index 463e88d..46eca31 100644
--- a/src/LeviySoft.Visor.Gen.Tests/ChainedOpticTests.cs
+++ b/src/LeviySoft.Visor.Gen.Tests/ChainedOpticTests.cs
@@ -1,5 +1,7 @@
 using Shouldly;
 using Xunit;
+using System.Collections.Immutable;
+using LeviySoft.Visor.Collections.Immutable;
 
 namespace LeviySoft.Visor.Gen.Tests;
 
@@ -14,4 +16,15 @@ public void SetIdTest()
 
         warehouse2.Main.Item.Id.ShouldBe(42);
     }
+
+    [Fact]
+    public void UpdateTagTest()
+    {
+        var warehouse = new Warehouse(new ItemWrapper(new InnerItem(1, "Default"), new Aux("test", ImmutableList.Create("tag1", "tag2"))));
+
+        var telescope = Warehouse.FocusMain.AuxLens.NotNull().Compose(Aux.TagsLens).Compose(Property.IImmutableList.First<string>());
+
+        var warehouse2 = telescope.Set("updated_tag")(warehouse);
+        warehouse2.Main.Aux?.Tags.ShouldBe(ImmutableList.Create("updated_tag", "tag2"));
+    }
 }
\ No newline at end of file
diff --git a/src/LeviySoft.Visor.Gen.Tests/Sample.cs b/src/LeviySoft.Visor.Gen.Tests/Sample.cs
index 7ab0681..7842061 100644
--- a/src/LeviySoft.Visor.Gen.Tests/Sample.cs
+++ b/src/LeviySoft.Visor.Gen.Tests/Sample.cs
@@ -1,3 +1,5 @@
+using System.Collections.Immutable;
+
 namespace LeviySoft.Visor.Gen.Tests;
 
 [Optics]
@@ -8,7 +10,7 @@ internal partial record Sample(int Id, string Description, Inner Inner);
 
 [Optics] internal partial record InnerItem(int Id, string Name);
 
-[Optics] internal partial record Aux(string Comment);
+[Optics] internal partial record Aux(string Comment, IImmutableList<string> Tags);
 
 [Optics(withNested: true)] internal partial record ItemWrapper(InnerItem Item, Aux? Aux);