From 3e07adebc96eb8dff0170d80c297179226ce6924 Mon Sep 17 00:00:00 2001
From: Jesse Stimpson <jesse.stimpson@gmail.com>
Date: Sun, 26 Apr 2026 21:32:53 -0400
Subject: [PATCH] Add mix.exs for Elixir project compilation

---
 CHANGELOG.md        |   7 ++-
 mix.exs             | 126 ++++++++++++++++++++++++++++++++++++++++++++
 rebar.config.script |   1 -
 3 files changed, 132 insertions(+), 2 deletions(-)
 create mode 100644 mix.exs

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8a8611a..4bbf70e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,7 +4,12 @@
 
 ### Enhancements
 
- * Added `erlfdb_directory_cache`: a simple ETS-driven cache for storing open directories.
+ * (#75) Added `erlfdb_directory_cache`: a simple ETS-driven cache for storing open directories.
+ * (#76) Added `mix.exs` for proper compilation using Mix in Elixir projects
+ 
+### Bug fixes
+
+ * (#76) Removed extraneous log message "===> [erlfdb] Compiling with FDB_API_VERSION=730" from rebar output
 
 ## v1.1.0 (2026-03-07)
 
diff --git a/mix.exs b/mix.exs
new file mode 100644
index 0000000..27ae3d1
--- /dev/null
+++ b/mix.exs
@@ -0,0 +1,126 @@
+defmodule Erlfdb.MixProject do
+  use Mix.Project
+
+  @script_path Path.join(__DIR__, "rebar.config.script")
+
+  # Evaluate rebar.config.script once at load time. The script already detects
+  # Mix vs rebar3 via code:ensure_loaded(rebar_api) and uses Mix.shell() for
+  # logging, so it runs correctly in both environments.
+  @rebar_config (case :file.script(String.to_charlist(@script_path), [{:CONFIG, []}]) do
+                   {:ok, result} ->
+                     result
+
+                   {:error, %Mix.Error{} = err} ->
+                     raise err
+
+                   {:error, reason} ->
+                     Mix.raise("rebar.config.script error: #{inspect(reason)}")
+                 end)
+
+  @version (case :file.consult(String.to_charlist(Path.join(__DIR__, "src/erlfdb.app.src"))) do
+              {:ok, [{:application, :erlfdb, props}]} ->
+                props |> Keyword.fetch!(:vsn) |> List.to_string()
+
+              {:error, reason} ->
+                Mix.raise("Failed to read erlfdb.app.src: #{inspect(reason)}")
+            end)
+
+  def project do
+    [
+      app: :erlfdb,
+      version: @version,
+      language: :erlang,
+      compilers: [:erlfdb_nif, :erlang, :app],
+      erlc_options: rebar_erl_opts(),
+      deps: deps()
+    ]
+  end
+
+  def rebar_erl_opts do
+    :proplists.get_value(:erl_opts, @rebar_config, [])
+  end
+
+  defp deps, do: []
+end
+
+defmodule Mix.Tasks.Compile.ErlfdbNif do
+  use Mix.Task.Compiler
+
+  @impl true
+  def run(_args) do
+    erl_opts = Erlfdb.MixProject.rebar_erl_opts()
+
+    api_version =
+      Enum.find_value(erl_opts, fn
+        {:d, :erlfdb_compile_time_api_version, v} -> v
+        _ -> nil
+      end) || raise "`:erlfdb_compile_time_api_version` not found"
+
+    lib =
+      Enum.find_value(erl_opts, fn
+        {:d, :erlfdb_compile_time_external_client_library, v} -> List.to_string(v)
+        _ -> nil
+      end) || raise "`:erlfdb_compile_time_external_client_library` not found"
+
+    lib_dir = Path.dirname(lib)
+    include_dir = System.get_env("ERLFDB_INCLUDE_DIR", "/usr/local/include")
+
+    project_root = Mix.Project.project_file() |> Path.dirname()
+    priv_dir = Path.join(Mix.Project.app_path(), "priv")
+    File.mkdir_p!(priv_dir)
+
+    sources = Path.wildcard(Path.join(project_root, "c_src/*.c"))
+    output = Path.join(priv_dir, "erlfdb_nif.so")
+
+    if stale?(sources, output) do
+      compile(api_version, include_dir, lib_dir, sources, output)
+    else
+      {:noop, []}
+    end
+  end
+
+  defp stale?(sources, output) do
+    case File.stat(output) do
+      {:error, _} ->
+        true
+
+      {:ok, %{mtime: out_mtime}} ->
+        Enum.any?(sources, fn src ->
+          case File.stat(src) do
+            {:ok, %{mtime: src_mtime}} -> src_mtime > out_mtime
+            _ -> true
+          end
+        end)
+    end
+  end
+
+  defp compile(api_version, include_dir, lib_dir, sources, output) do
+    cflags_version =
+      if is_integer(api_version),
+        do: "-DFDB_API_VERSION=#{api_version}",
+        else: "-DFDB_USE_LATEST_API_VERSION=1"
+
+    erts_include = Path.join([:code.root_dir(), "usr", "include"])
+    cflags = "-I#{include_dir} -I#{erts_include} -Ic_src/ -g -Wall -Werror #{cflags_version}"
+
+    ldflags =
+      case :os.type() do
+        {:unix, :darwin} ->
+          "-undefined dynamic_lookup -rpath @loader_path -rpath #{lib_dir} -L#{lib_dir} -lfdb_c"
+
+        _ ->
+          "-Wl,-rpath,\\$ORIGIN -Wl,-rpath,#{lib_dir} -L#{lib_dir} -lfdb_c"
+      end
+
+    cmd = "cc -shared -fPIC #{cflags} #{Enum.join(sources, " ")} -o #{output} #{ldflags}"
+
+    case System.cmd("sh", ["-c", cmd], stderr_to_stdout: true) do
+      {_, 0} ->
+        {:ok, []}
+
+      {out, code} ->
+        Mix.shell().error("===> [erlfdb] NIF compilation failed (exit #{code}):\n#{out}")
+        {:error, []}
+    end
+  end
+end
diff --git a/rebar.config.script b/rebar.config.script
index 8968220..d899cfa 100644
--- a/rebar.config.script
+++ b/rebar.config.script
@@ -223,7 +223,6 @@ case CompileAPIVersion of
                 Log(error, "FDB API version could not be determined. Continuing anyway...", [])
         end;
     _ ->
-        Log(info, "Compiling with FDB_API_VERSION=~p", [CompileAPIVersion]),
         ok
 end.