From e41fbea5438c80e7be8cbb12eecae656afe525ed Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lars=20G=C3=B6ttgens?= <lars.goettgens@rwth-aachen.de>
Date: Wed, 31 Jul 2024 15:48:19 +0200
Subject: [PATCH] Add serialization of weyl groups

---
 experimental/LieAlgebras/src/serialization.jl | 42 ++++++++++++++
 .../LieAlgebras/test/WeylGroup-test.jl        | 58 +++++++++++++++++++
 2 files changed, 100 insertions(+)

diff --git a/experimental/LieAlgebras/src/serialization.jl b/experimental/LieAlgebras/src/serialization.jl
index 91f14410fe33..f630772da5b6 100644
--- a/experimental/LieAlgebras/src/serialization.jl
+++ b/experimental/LieAlgebras/src/serialization.jl
@@ -193,3 +193,45 @@ function load_type_params(
 )
   return load_typed_object(s)
 end
+
+###############################################################################
+#
+#   Weyl groups
+#
+###############################################################################
+
+@register_serialization_type WeylGroup uses_id
+
+function save_object(s::SerializerState, W::WeylGroup)
+  save_data_dict(s) do
+    save_typed_object(s, root_system(W), :root_system)
+  end
+end
+
+function load_object(s::DeserializerState, ::Type{WeylGroup})
+  R = load_typed_object(s, :root_system)
+  return weyl_group(R)
+end
+
+@register_serialization_type WeylGroupElem uses_params
+
+function save_object(s::SerializerState, x::WeylGroupElem)
+  save_object(s, word(x))
+end
+
+function load_object(s::DeserializerState, ::Type{WeylGroupElem}, W::WeylGroup)
+  return W(load_object(s, Vector, UInt8); normalize=false)
+end
+
+function save_type_params(s::SerializerState, x::WeylGroupElem)
+  save_data_dict(s) do
+    save_object(s, encode_type(typeof(x)), :name)
+    parent_x = parent(x)
+    parent_ref = save_as_ref(s, parent_x)
+    save_object(s, parent_ref, :params)
+  end
+end
+
+function load_type_params(s::DeserializerState, ::Type{WeylGroupElem})
+  return load_typed_object(s)
+end
diff --git a/experimental/LieAlgebras/test/WeylGroup-test.jl b/experimental/LieAlgebras/test/WeylGroup-test.jl
index 375cbb4b5569..da8ae8a26d44 100644
--- a/experimental/LieAlgebras/test/WeylGroup-test.jl
+++ b/experimental/LieAlgebras/test/WeylGroup-test.jl
@@ -431,4 +431,62 @@ include(
       @test allunique(orb)
     end
   end
+
+  @testset "Serialization" begin
+    mktempdir() do path
+      @testset "simple saving and loading" begin
+        W = weyl_group((:A, 2), (:B, 4))
+
+        test_save_load_roundtrip(path, W) do loaded
+          # nothing, cause `W === loaded` anyway
+        end
+
+        x = rand(W)
+        test_save_load_roundtrip(path, x) do loaded
+          @test parent(loaded) === W
+          @test word(loaded) == word(x)
+        end
+
+        test_save_load_roundtrip(path, gens(W)) do loaded
+          @test length(loaded) == ngens(W)
+          @test all(
+            word(loaded[i]) == word(gen(W, i)) for i in 1:ngens(W)
+          )
+        end
+      end
+
+      @testset "cyclic reference between R and W survives" begin
+        Oscar.reset_global_serializer_state()
+
+        R_filename = joinpath(path, "R.mrdi")
+        W_filename = joinpath(path, "W.mrdi")
+
+        R = root_system(:D, 5)
+        W = weyl_group(R)
+
+        save(R_filename, R)
+        save(W_filename, W)
+
+        Oscar.reset_global_serializer_state()
+
+        loaded_R = load(R_filename)
+        loaded_W = load(W_filename)
+
+        @test loaded_R === root_system(loaded_W)
+        @test loaded_W === weyl_group(loaded_R)
+
+        loaded_R = loaded_W = nothing # unset all references
+
+        Oscar.reset_global_serializer_state()
+
+        loaded_W = load(W_filename)
+        loaded_R = load(R_filename)
+
+        @test loaded_R === root_system(loaded_W)
+        @test loaded_W === weyl_group(loaded_R)
+
+        loaded_R = loaded_W = nothing # unset all references        
+      end
+    end
+  end
 end