Allow getting a tree entry by position

c_src/geef.c

@@ -163,6 +163,7 @@ static ErlNifFunc geef_funcs[] =
 	{"commit_tree", 1, geef_commit_tree},
 	{"commit_tree_id", 1, geef_commit_tree_id},
 	{"tree_bypath", 2, geef_tree_bypath},
+	{"tree_nth",     2, geef_tree_nth},
 	{"blob_size", 1, geef_blob_size},
 	{"blob_content", 1, geef_blob_content},
 	{"tag_peel", 1, geef_tag_peel},

c_src/tree.c

@@ -59,3 +59,24 @@ geef_tree_bypath(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
 	enif_release_binary(&bin);
 	return tree_entry_to_term(env, entry);
 }
+
+ERL_NIF_TERM
+geef_tree_nth(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
+{
+	geef_object *obj;
+	const git_tree_entry *entry;
+	unsigned int nth;
+
+	if (!enif_get_resource(env, argv[0], geef_object_type, (void **) &obj))
+		return enif_make_badarg(env);
+
+	if (!enif_get_uint(env, argv[1], &nth))
+		return enif_make_badarg(env);
+
+	entry = git_tree_entry_byindex((git_tree *)obj->obj, nth);
+
+	if (!entry)
+		return geef_error(env);
+
+	return tree_entry_to_term(env, entry);
+}

c_src/tree.h

@@ -4,5 +4,6 @@
 #include "object.h"
 
 ERL_NIF_TERM geef_tree_bypath(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]);
+ERL_NIF_TERM geef_tree_nth(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]);
 
 #endif

lib/geef/tree.ex

@@ -15,21 +15,26 @@ defrecord Geef.Tree, Record.extract(:geef_object, from: "src/geef_records.hrl")
     end
   end
 
-  def get(tree, path) do
-    case :geef_tree.get(rebind(tree), path) do
-      {:ok, entry} ->
-        {:ok, TreeEntry.new entry}
-      error ->
-        error
-    end
-  end
+  defp maybe_entry({:ok, entry}), do: {:ok, TreeEntry.new entry}
+  defp maybe_entry(error = {:error, _}), do: error
+
+  def get(tree, path), do: :geef_tree.get(rebind(tree), path) |> maybe_entry
+  def nth(tree, pos), do: :geef_tree.nth(rebind(tree), pos) |> maybe_entry
 
 end
 
 defimpl Access, for: Geef.Tree do
+  alias Geef.Tree
+
+  def access(tree, key) when is_number(key) do
+    case Tree.nth(tree, key) do
+      {:ok, entry} -> entry
+      {:error, _} -> nil
+    end
+  end
 
   def access(tree, key) do
-    case Geef.Tree.get(tree, key) do
+    case Tree.get(tree, key) do
       {:ok, entry} -> entry
       {:error, _} -> nil
     end

src/geef_nif.erl

@@ -96,6 +96,10 @@ commit_tree(_Handle) ->
 tree_bypath(_TreeHandle, _Path) ->
     nif_error(?LINE).
 
+-spec tree_nth(term, non_neg_integer()) -> term().
+tree_nth(_TreeHandle, _Nth) ->
+    ?NIF_FN.
+
 -spec blob_size(term) -> {ok, integer()} | error.
 blob_size(_ObjHandle) ->
     nif_error(?LINE).

src/geef_tree.erl

@@ -4,19 +4,22 @@
 -include_lib("eunit/include/eunit.hrl").
 -endif.
 
--export([get/2, lookup/2]).
+-export([get/2, nth/2, lookup/2]).
 
 -include("geef_records.hrl").
 
+from_nif({ok, Mode, Type, Oid, Name}) ->
+    {ok, #geef_tree_entry{mode=Mode, type=Type, id=#geef_oid{oid=Oid}, name=Name}};
+from_nif(Err = {error, _}) ->
+    Err.
+
 -spec get(geef_object(), iolist()) -> {ok, geef_tree_entry()} | {error, term()}.
 get(#geef_object{type=tree,handle=Handle}, Path) ->
-    case geef_nif:tree_bypath(Handle, Path) of
-	{ok, Mode, Type, Geef_Oid, Name} ->
-	    {ok, #geef_tree_entry{mode=Mode, type=Type,
-				  id=#geef_oid{oid=Geef_Oid}, name=Name}};
-	Other ->
-	    Other
-    end.
+    from_nif(geef_nif:tree_bypath(Handle, Path)).
+
+-spec nth(geef_object(), non_neg_integer()) -> {ok, geef_tree_entry()} | {error, term()}.
+nth(#geef_object{type=tree,handle=Handle}, Nth) ->
+    from_nif(geef_nif:tree_nth(Handle, Nth)).
 
 -spec lookup(pid(), geef_oid() | iolist()) -> {ok, geef_object()} | {error, term()}.
 lookup(Repo, Id) ->
@@ -26,11 +29,13 @@ lookup(Repo, Id) ->
 
 %% This is somewhat hacky, assuming that this is running under .eunit,
 %% but it's good enough for now
-bypath_test() ->
+access_test() ->
     {ok, Repo} = geef_repo:open(".."),
     {ok, Tree} = geef_obj:lookup(Repo, geef_oid:parse("395e1c39cb203640b78da8458a42afdb92bef7aa")),
     Id = geef_oid:parse("80d5c15a040c93a4f98f4496a05ebf30cdd58650"),
     Expected = #geef_tree_entry{mode=8#100644, type=blob, id=Id, name = <<"README.md">>},
-    {ok, Actual}= geef_tree:get(Tree, "README.md"),
-    ?assertEqual(Expected, Actual).
+    {ok, ActualByPath}= geef_tree:get(Tree, "README.md"),
+    {ok, ActualNth} = geef_tree:nth(Tree, 2),
+    ?assertEqual(Expected, ActualByPath),
+    ?assertEqual(Expected, ActualNth).
 -endif.