bikoret/vav_pipeline/test/machtzit_ha_shekel_test.exs

defmodule VavPipeline.MachtzitHaShekelTest do
  @moduledoc """
  Tests for the half-shekel counting protocol — Form 3 of avodah
  zarah realized as architecture (vehaya §3.2). Verifies the six
  positive Torah-anchored properties from Shemot 30:11-16,
  Devarim 23:16-17, Vayikra 19:14, and Shemot 5:6-8.
  """

  use ExUnit.Case, async: false

  alias VavPipeline.MachtzitHaShekel

  setup do
    # MachtzitHaShekel runs in the supervision tree, so it's already
    # alive. Reset between tests.
    MachtzitHaShekel.reset()
    :ok
  end

  # ============================================================
  # Property 1 — KOFER PROTOCOL (Shemot 30:12)
  # ============================================================

  test "increment/0 takes no argument — no caller distinction is even expressible" do
    # Structural test: the function arity is 0. There is no place to
    # pass a caller identifier. The Shemot 30:15 uniformity property
    # is enforced at the type level: there's no slot for non-uniform
    # input.
    assert function_exported?(MachtzitHaShekel, :increment, 0)
  end

  test "increment/0 advances the count by exactly 1" do
    MachtzitHaShekel.increment()
    assert MachtzitHaShekel.count() == 1
  end

  test "increment/1 advances the count by N" do
    MachtzitHaShekel.increment(5)
    assert MachtzitHaShekel.count() == 5
  end

  # ============================================================
  # Property 2 — UNIFORM PROTOCOL (Shemot 30:15)
  # ============================================================

  test "every increment is the same size — rich don't give more, poor don't give less" do
    Enum.each(1..100, fn _ -> MachtzitHaShekel.increment() end)
    assert MachtzitHaShekel.count() == 100
  end

  test "no per-caller weighting function exists" do
    # Negative structural assertion: no `increment_with_weight` or
    # similar function. The uniform property is enforced by absence.
    public = MachtzitHaShekel.__info__(:functions)
    weight_shaped = Enum.filter(public, fn {name, _arity} ->
      name_str = to_string(name)
      String.contains?(name_str, "weight") or
        String.contains?(name_str, "tier") or
        String.contains?(name_str, "premium")
    end)

    assert weight_shaped == []
  end

  # ============================================================
  # Property 3 — ZIKARON PROTOCOL (Shemot 30:16)
  # ============================================================

  test "count/0 returns a single integer, not a list or map of contributions" do
    Enum.each(1..3, fn _ -> MachtzitHaShekel.increment() end)
    result = MachtzitHaShekel.count()

    assert is_integer(result)
    refute is_list(result)
    refute is_map(result)
  end

  test "no per-caller breakdown function exists" do
    public = MachtzitHaShekel.__info__(:functions)

    forbidden = Enum.filter(public, fn {name, _arity} ->
      name_str = to_string(name)
      Enum.any?(
        ~w(callers list_who breakdown by_caller per_caller histogram top who),
        &String.contains?(name_str, &1)
      )
    end)

    assert forbidden == [], (
      "MachtzitHaShekel exposes per-caller breakdown function(s): " <>
        "#{inspect(forbidden)}. Their absence IS the architectural " <>
        "commitment (Shemot 30:16 — zikaron, not roster)."
    )
  end

  # ============================================================
  # Property 5 — REFUSAL PROTOCOL (Devarim 23:16-17)
  # ============================================================

  test "no identify/locate/deanonymize function exists" do
    public = MachtzitHaShekel.__info__(:functions)

    forbidden = Enum.filter(public, fn {name, _arity} ->
      name_str = to_string(name)
      Enum.any?(
        ~w(identify locate deanonymize lookup find_caller),
        &String.contains?(name_str, &1)
      )
    end)

    assert forbidden == [], (
      "MachtzitHaShekel exposes caller-identification function(s): " <>
        "#{inspect(forbidden)}. The system does not deliver " <>
        "caller-state to authorities (Devarim 23:16, lo tasgir)."
    )
  end

  # ============================================================
  # Property 6 — ANTI-QUOTA PROTOCOL (Shemot 5:6-8)
  # ============================================================

  test "no per-caller productivity tracking function exists" do
    public = MachtzitHaShekel.__info__(:functions)

    forbidden = Enum.filter(public, fn {name, _arity} ->
      name_str = to_string(name)
      Enum.any?(
        ~w(quota productivity throughput per_caller_count),
        &String.contains?(name_str, &1)
      )
    end)

    assert forbidden == [], (
      "MachtzitHaShekel exposes quota/productivity function(s): " <>
        "#{inspect(forbidden)}. Per-caller productivity tracking is " <>
        "Pharaoh's straw quota (Shemot 5:6-8) — refused by absence."
    )
  end

  # ============================================================
  # Reset semantics
  # ============================================================

  test "reset/0 brings the count to zero" do
    MachtzitHaShekel.increment(50)
    assert MachtzitHaShekel.count() == 50
    MachtzitHaShekel.reset()
    assert MachtzitHaShekel.count() == 0
  end

  test "increment after reset starts from zero" do
    MachtzitHaShekel.increment(10)
    MachtzitHaShekel.reset()
    MachtzitHaShekel.increment(3)
    assert MachtzitHaShekel.count() == 3
  end

  # ============================================================
  # The ENTIRE public surface — explicit enumeration
  # ============================================================

  test "the module's public surface is exactly the documented six functions" do
    # An exhaustive list. Any added function must be reviewed for
    # whether it weakens the Form 3 architectural commitment.
    expected = [
      {:start_link, 0},
      {:start_link, 1},
      {:increment, 0},
      {:increment, 1},
      {:count, 0},
      {:reset, 0},
      # Agent-derived defaults — not part of the surveillance surface
      {:child_spec, 1}
    ]

    actual =
      MachtzitHaShekel.__info__(:functions)
      |> Enum.filter(fn {name, _} ->
        not String.starts_with?(to_string(name), "__")
      end)
      |> Enum.sort()

    extras = actual -- expected
    missing = expected -- actual

    assert extras == [], "MachtzitHaShekel exposed unexpected function(s): #{inspect(extras)}"
    assert missing == [], "MachtzitHaShekel missing expected function(s): #{inspect(missing)}"
  end
end