defmodule Tilly.BDDTest do
  use ExUnit.Case, async: true

  alias Tilly.BDD.Node

  describe "init_bdd_store/1" do
    test "initializes bdd_store in typing_ctx with predefined false and true nodes" do
      typing_ctx = %{}
      new_ctx = Tilly.BDD.init_bdd_store(typing_ctx)

      assert %{bdd_store: bdd_store} = new_ctx
      assert is_map(bdd_store.nodes_by_structure)
      assert is_map(bdd_store.structures_by_id)
      assert bdd_store.next_node_id == 2 # 0 for false, 1 for true
      assert bdd_store.ops_cache == %{}

      # Check false node
      false_id = Tilly.BDD.false_node_id()
      false_ops_module = Tilly.BDD.universal_ops_module()
      assert bdd_store.nodes_by_structure[{Node.mk_false(), false_ops_module}] == false_id
      assert bdd_store.structures_by_id[false_id] == %{structure: Node.mk_false(), ops_module: false_ops_module}

      # Check true node
      true_id = Tilly.BDD.true_node_id()
      true_ops_module = Tilly.BDD.universal_ops_module()
      assert bdd_store.nodes_by_structure[{Node.mk_true(), true_ops_module}] == true_id
      assert bdd_store.structures_by_id[true_id] == %{structure: Node.mk_true(), ops_module: true_ops_module}
    end
  end

  describe "get_or_intern_node/3" do
    setup do
      typing_ctx = Tilly.BDD.init_bdd_store(%{})
      %{initial_ctx: typing_ctx}
    end

    test "interning Node.mk_false() returns predefined false_id and doesn't change store", %{initial_ctx: ctx} do
      false_ops_module = Tilly.BDD.universal_ops_module()
      {new_ctx, node_id} = Tilly.BDD.get_or_intern_node(ctx, Node.mk_false(), false_ops_module)
      assert node_id == Tilly.BDD.false_node_id()
      assert new_ctx.bdd_store == ctx.bdd_store
    end

    test "interning Node.mk_true() returns predefined true_id and doesn't change store", %{initial_ctx: ctx} do
      true_ops_module = Tilly.BDD.universal_ops_module()
      {new_ctx, node_id} = Tilly.BDD.get_or_intern_node(ctx, Node.mk_true(), true_ops_module)
      assert node_id == Tilly.BDD.true_node_id()
      assert new_ctx.bdd_store == ctx.bdd_store
    end

    test "interning a new leaf node returns a new ID and updates the store", %{initial_ctx: ctx} do
      leaf_structure = Node.mk_leaf("test_leaf")
      ops_mod = :my_ops

      {ctx_after_intern, node_id} = Tilly.BDD.get_or_intern_node(ctx, leaf_structure, ops_mod)

      assert node_id == 2 # Initial next_node_id
      assert ctx_after_intern.bdd_store.next_node_id == 3
      assert ctx_after_intern.bdd_store.nodes_by_structure[{leaf_structure, ops_mod}] == node_id
      assert ctx_after_intern.bdd_store.structures_by_id[node_id] == %{structure: leaf_structure, ops_module: ops_mod}
    end

    test "interning the same leaf node again returns the same ID and doesn't change store", %{initial_ctx: ctx} do
      leaf_structure = Node.mk_leaf("test_leaf")
      ops_mod = :my_ops

      {ctx_after_first_intern, first_node_id} = Tilly.BDD.get_or_intern_node(ctx, leaf_structure, ops_mod)
      {ctx_after_second_intern, second_node_id} = Tilly.BDD.get_or_intern_node(ctx_after_first_intern, leaf_structure, ops_mod)

      assert first_node_id == second_node_id
      assert ctx_after_first_intern.bdd_store == ctx_after_second_intern.bdd_store
    end

    test "interning a new split node returns a new ID and updates the store", %{initial_ctx: ctx} do
      split_structure = Node.mk_split(:el, Tilly.BDD.true_node_id(), Tilly.BDD.false_node_id(), Tilly.BDD.true_node_id())
      ops_mod = :split_ops

      {ctx_after_intern, node_id} = Tilly.BDD.get_or_intern_node(ctx, split_structure, ops_mod)

      assert node_id == 2 # Initial next_node_id
      assert ctx_after_intern.bdd_store.next_node_id == 3
      assert ctx_after_intern.bdd_store.nodes_by_structure[{split_structure, ops_mod}] == node_id
      assert ctx_after_intern.bdd_store.structures_by_id[node_id] == %{structure: split_structure, ops_module: ops_mod}
    end

    test "interning structurally identical nodes with different ops_modules results in different IDs", %{initial_ctx: ctx} do
      leaf_structure = Node.mk_leaf("shared_leaf")
      ops_mod1 = :ops1
      ops_mod2 = :ops2

      {ctx1, id1} = Tilly.BDD.get_or_intern_node(ctx, leaf_structure, ops_mod1)
      {_ctx2, id2} = Tilly.BDD.get_or_intern_node(ctx1, leaf_structure, ops_mod2)

      assert id1 != id2
      assert id1 == 2
      assert id2 == 3
    end

    test "raises ArgumentError if bdd_store is not initialized" do
      assert_raise ArgumentError, ~r/BDD store not initialized/, fn ->
        Tilly.BDD.get_or_intern_node(%{}, Node.mk_leaf("foo"), :ops)
      end
    end
  end

  describe "get_node_data/2" do
    setup do
      ctx = Tilly.BDD.init_bdd_store(%{})
      leaf_structure = Node.mk_leaf("data")
      ops_mod = :leaf_ops
      {new_ctx, leaf_id_val} = Tilly.BDD.get_or_intern_node(ctx, leaf_structure, ops_mod)
      %{ctx: new_ctx, leaf_structure: leaf_structure, ops_mod: ops_mod, leaf_id: leaf_id_val}
    end

    test "returns correct data for false node", %{ctx: ctx} do
      false_id = Tilly.BDD.false_node_id()
      false_ops_module = Tilly.BDD.universal_ops_module()
      assert Tilly.BDD.get_node_data(ctx, false_id) == %{structure: Node.mk_false(), ops_module: false_ops_module}
    end

    test "returns correct data for true node", %{ctx: ctx} do
      true_id = Tilly.BDD.true_node_id()
      true_ops_module = Tilly.BDD.universal_ops_module()
      assert Tilly.BDD.get_node_data(ctx, true_id) == %{structure: Node.mk_true(), ops_module: true_ops_module}
    end

    test "returns correct data for a custom interned leaf node", %{ctx: ctx, leaf_structure: ls, ops_mod: om, leaf_id: id} do
      assert Tilly.BDD.get_node_data(ctx, id) == %{structure: ls, ops_module: om}
    end

    test "returns nil for an unknown node ID", %{ctx: ctx} do
      assert Tilly.BDD.get_node_data(ctx, 999) == nil
    end

    test "returns nil if bdd_store not in ctx" do
      assert Tilly.BDD.get_node_data(%{}, 0) == nil
    end
  end

  describe "is_false_node?/2 and is_true_node?/2" do
    setup do
      ctx = Tilly.BDD.init_bdd_store(%{})
      leaf_structure = Node.mk_leaf("data")
      ops_mod = :leaf_ops
      {new_ctx, leaf_id_val} = Tilly.BDD.get_or_intern_node(ctx, leaf_structure, ops_mod)
      %{ctx: new_ctx, leaf_id: leaf_id_val}
    end

    test "is_false_node?/2", %{ctx: ctx, leaf_id: id} do
      assert Tilly.BDD.is_false_node?(ctx, Tilly.BDD.false_node_id()) == true
      assert Tilly.BDD.is_false_node?(ctx, Tilly.BDD.true_node_id()) == false
      assert Tilly.BDD.is_false_node?(ctx, id) == false
      assert Tilly.BDD.is_false_node?(ctx, 999) == false # Unknown ID
    end

    test "is_true_node?/2", %{ctx: ctx, leaf_id: id} do
      assert Tilly.BDD.is_true_node?(ctx, Tilly.BDD.true_node_id()) == true
      assert Tilly.BDD.is_true_node?(ctx, Tilly.BDD.false_node_id()) == false
      assert Tilly.BDD.is_true_node?(ctx, id) == false
      assert Tilly.BDD.is_true_node?(ctx, 999) == false # Unknown ID
    end
  end
end