defmodule Microwaveprop.ApplicationTest do
  use ExUnit.Case, async: false

  describe "build_timestamp/0" do
    test "returns the compile-time fallback when file and env are absent" do
      prev_file = Application.get_env(:microwaveprop, :build_timestamp_file, :__unset)
      prev_env = System.get_env("DEPLOY_TIMESTAMP")

      Application.put_env(:microwaveprop, :build_timestamp_file, "/nonexistent/path")
      System.delete_env("DEPLOY_TIMESTAMP")

      on_exit(fn ->
        if prev_file == :__unset do
          Application.delete_env(:microwaveprop, :build_timestamp_file)
        else
          Application.put_env(:microwaveprop, :build_timestamp_file, prev_file)
        end

        if prev_env, do: System.put_env("DEPLOY_TIMESTAMP", prev_env)
      end)

      assert %DateTime{} = Microwaveprop.Application.build_timestamp()
    end

    test "reads ISO 8601 timestamp from the configured file" do
      tmp = Path.join(System.tmp_dir!(), "build_ts_test_#{System.unique_integer([:positive])}")
      ts = "2026-04-17T18:30:00Z"
      File.write!(tmp, ts)

      prev_file = Application.get_env(:microwaveprop, :build_timestamp_file)
      Application.put_env(:microwaveprop, :build_timestamp_file, tmp)

      on_exit(fn ->
        File.rm(tmp)
        if prev_file, do: Application.put_env(:microwaveprop, :build_timestamp_file, prev_file)
      end)

      assert Microwaveprop.Application.build_timestamp() == ~U[2026-04-17 18:30:00Z]
    end

    test "falls back to DEPLOY_TIMESTAMP env when file is missing" do
      prev_file = Application.get_env(:microwaveprop, :build_timestamp_file)
      Application.put_env(:microwaveprop, :build_timestamp_file, "/nonexistent/path")

      prev_env = System.get_env("DEPLOY_TIMESTAMP")
      System.put_env("DEPLOY_TIMESTAMP", "2026-05-01T12:00:00Z")

      on_exit(fn ->
        if prev_file, do: Application.put_env(:microwaveprop, :build_timestamp_file, prev_file)
        if prev_env, do: System.put_env("DEPLOY_TIMESTAMP", prev_env)
      end)

      assert Microwaveprop.Application.build_timestamp() == ~U[2026-05-01 12:00:00Z]
    end

    test "ignores file contents that are not valid ISO 8601" do
      tmp = Path.join(System.tmp_dir!(), "build_ts_bad_#{System.unique_integer([:positive])}")
      File.write!(tmp, "not-a-timestamp")

      prev_file = Application.get_env(:microwaveprop, :build_timestamp_file)
      Application.put_env(:microwaveprop, :build_timestamp_file, tmp)

      prev_env = System.get_env("DEPLOY_TIMESTAMP")
      System.delete_env("DEPLOY_TIMESTAMP")

      on_exit(fn ->
        File.rm(tmp)
        if prev_file, do: Application.put_env(:microwaveprop, :build_timestamp_file, prev_file)
        if prev_env, do: System.put_env("DEPLOY_TIMESTAMP", prev_env)
      end)

      assert %DateTime{} = Microwaveprop.Application.build_timestamp()
    end
  end
end