From 268702fe266e56f5aa70673ee7b5cba034610c1a Mon Sep 17 00:00:00 2001
From: Matt Enlow <matt@novaugust.net>
Date: Tue, 12 Sep 2023 16:39:27 -0400
Subject: [PATCH] if/unless

---
 lib/style/single_node.ex        |  17 +++++
 test/style/single_node_test.exs | 125 ++++++++++++++++++++++++++++++++
 2 files changed, 142 insertions(+)

diff --git a/lib/style/single_node.ex b/lib/style/single_node.ex
index 997eac08..7cb9a3f9 100644
--- a/lib/style/single_node.ex
+++ b/lib/style/single_node.ex
@@ -212,6 +212,23 @@ defmodule Styler.Style.SingleNode do
   defp style({:case, cm, [head, [{do_, arrows}]]}), do: {:case, cm, [head, [{do_, rewrite_arrows(arrows)}]]}
   defp style({:fn, m, arrows}), do: {:fn, m, rewrite_arrows(arrows)}
 
+  # Credo.Check.Refactor.UnlessWithElse
+  # if adding a negation to the if is incorrect, we'll remove it on the recurse =)
+  defp style({:unless, m, [{_, hm, _} = head, [{do_block, do_body}, {else_block, else_body}]]}) do
+    style({:if, m, [{:!, hm, [head]}, [{do_block, else_body}, {else_block, do_body}]]})
+  end
+
+  # Credo.Check.Refactor.NegatedConditionsInUnless
+  defp style({:unless, m, [{negator, _, [expr]}, [{do_block, do_body}]]}) when negator in [:!, :not] do
+    style({:if, m, [expr, [{do_block, do_body}]]})
+  end
+
+  # Credo.Check.Refactor.NegatedConditionsWithElse
+  defp style({:if, m, [{negator, _, [expr]}, [{do_block, do_body}, {else_block, else_body}]]})
+       when negator in [:!, :not] do
+    style({:if, m, [expr, [{do_block, else_body}, {else_block, do_body}]]})
+  end
+
   defp style(node), do: node
 
   defp rewrite_arrows(arrows) when is_list(arrows),
diff --git a/test/style/single_node_test.exs b/test/style/single_node_test.exs
index 01b11b79..e9d60b7a 100644
--- a/test/style/single_node_test.exs
+++ b/test/style/single_node_test.exs
@@ -519,4 +519,129 @@ defmodule Styler.Style.SingleNodeTest do
       """)
     end
   end
+
+  describe "if/else" do
+    test "Credo.Check.Refactor.UnlessWithElse" do
+      for negator <- ["!", "not "] do
+        assert_style(
+          """
+          unless #{negator} a do
+            b
+          else
+            c
+          end
+          """,
+          """
+          if a do
+            c
+          else
+            b
+          end
+          """
+        )
+      end
+
+      assert_style(
+        """
+        unless a do
+          b
+        else
+          c
+        end
+        """,
+        """
+        if a do
+          b
+        else
+          c
+        end
+        """
+      )
+    end
+
+    test "Credo.Check.Refactor.NegatedConditionsInUnless" do
+      for negator <- ["!", "not "] do
+        assert_style("unless #{negator} foo, do: :bar", "if foo, do: :bar")
+
+        assert_style(
+          """
+          unless #{negator} foo do
+            bar
+          end
+          """,
+          """
+          if foo do
+            bar
+          end
+          """
+        )
+      end
+    end
+
+    test "Credo.Check.Refactor.NegatedConditionsWithElse" do
+      for negator <- ["!", "not "] do
+        assert_style("if #{negator}foo, do: :bar")
+        assert_style("if #{negator}foo, do: :bar, else: :baz", "if foo, do: :baz, else: :bar")
+
+        assert_style("""
+        if #{negator}foo do
+          bar
+        end
+        """)
+
+        assert_style(
+          """
+          if #{negator}foo do
+            bar
+          else
+            baz
+          end
+          """,
+          """
+          if foo do
+            baz
+          else
+            bar
+          end
+          """
+        )
+      end
+    end
+
+    test "recurses" do
+      assert_style(
+        """
+        if !!val do
+          a
+        else
+          b
+        end
+        """,
+        """
+        if val do
+          a
+        else
+          b
+        end
+        """
+      )
+
+      assert_style(
+        """
+        unless !! not true do
+          a
+        else
+          b
+        end
+        """,
+        """
+        if true do
+          b
+        else
+          a
+        end
+        """
+      )
+    end
+  end
 end