Add support for Zipper.find_all/3 (#163)

lib/sourceror/zipper.ex

@@ -726,6 +726,29 @@ defmodule Sourceror.Zipper do
     end
   end
 
+  @doc """
+  Returns a list of `zippers` to each `node` that satisfies the `predicate` function, or
+  an empty list if none are found.
+
+  The optional second parameters specifies the `direction`, defaults to
+  `:next`.
+  """
+  @spec find_all(t, direction :: :prev | :next, predicate :: (tree -> any)) :: t | []
+  def find_all(%Z{} = zipper, direction \\ :next, predicate)
+      when direction in [:next, :prev] and is_function(predicate, 1) do
+    do_find_all(zipper, move(direction), predicate, [])
+  end
+
+  defp do_find_all(nil, _move, _predicate, buffer), do: Enum.reverse(buffer)
+
+  defp do_find_all(%Z{node: tree} = zipper, move, predicate, buffer) do
+    if predicate.(tree) do
+      zipper |> move.() |> do_find_all(move, predicate, [zipper | buffer])
+    else
+      zipper |> move.() |> do_find_all(move, predicate, buffer)
+    end
+  end
+
   @spec find_value(t, (tree -> any)) :: any | nil
   def find_value(%Z{} = zipper, direction \\ :next, fun)
       when direction in [:next, :prev] and is_function(fun, 1) do

test/zipper_test.exs

@@ -571,6 +571,72 @@ defmodule SourcerorTest.ZipperTest do
     end
   end
 
+  describe "find_all/3" do
+    test "finds zippers with a predicate" do
+      zipper = Z.zip([1, [2, [3, 4], 5]])
+
+      assert Z.find_all(zipper, fn
+               x when is_integer(x) -> rem(x, 2) == 0
+               _other -> false
+             end)
+             |> Enum.map(&Z.node(&1)) == [2, 4]
+
+      assert Z.find_all(zipper, :next, fn
+               x when is_integer(x) -> rem(x, 2) == 0
+               _other -> false
+             end)
+             |> Enum.map(&Z.node(&1)) == [2, 4]
+    end
+
+    test "returns empty list if nothing was found" do
+      zipper = Z.zip([1, [2, [3, 4], 5]])
+
+      assert Z.find_all(zipper, fn
+               x when is_integer(x) -> x == 9
+               _other -> false
+             end) == []
+
+      assert Z.find_all(zipper, :prev, fn
+               x when is_integer(x) -> x == 9
+               _other -> false
+             end) == []
+    end
+
+    test "finds a zippers with a predicate in direction :prev" do
+      zipper =
+        [1, [2, [3, 4], 5]]
+        |> Z.zip()
+        |> Z.next()
+        |> Z.next()
+        |> Z.next()
+        |> Z.next()
+        |> Z.next()
+        |> Z.next()
+        |> Z.next()
+
+      assert Z.find_all(zipper, :prev, fn
+               x when is_integer(x) -> rem(x, 2) == 0
+               _other -> false
+             end)
+             |> Enum.map(&Z.node(&1)) == [4, 2]
+    end
+
+    test "retruns empty list if nothing was found in direction :prev" do
+      zipper =
+        [1, [2, [3, 4], 5]]
+        |> Z.zip()
+        |> Z.next()
+        |> Z.next()
+        |> Z.next()
+        |> Z.next()
+        |> Z.next()
+        |> Z.next()
+        |> Z.next()
+
+      assert Z.find_all(zipper, :prev, fn x -> x == 9 end) == []
+    end
+  end
+
   describe "find_value/3" do
     test "finds a zipper and returns the value" do
       zipper = Z.zip([1, [2, [3, 4], 5]])