defmodule VavPipeline.Tablet38L1IntegrityTest do
  @moduledoc """
  Tablet 38 (2026-10-04) — the integrity check did not check integrity.

  `L1Reader.verify_integrity/0` compared the hash recorded in
  `integrity.sha256` with the hash compiled into the module. It never read
  a verse. Every test of it passed, because every test asked it about an
  untouched L1 — the one question a check that checks nothing answers
  correctly.

  These tests change the scroll and ask again.
  """

  use ExUnit.Case, async: false

  import Plug.Test
  import Plug.Conn

  alias VavPipeline.{HaltMonitor, L1Integrity, L1Reader, MannaLedger}
  alias VavPipeline.BigdeiKodesh.Router

  @opts Router.init([])

  # ============================================================
  # The hash itself
  # ============================================================
  describe "compute_tree_hash/1" do
    test "of the real scroll is the pinned hash, and the hash build_l1.py recorded" do
      assert {:ok, hash} = L1Reader.compute_tree_hash()
      assert hash == L1Reader.expected_hash()

      recorded = L1Reader.l1_root() |> Path.join("integrity.sha256") |> File.read!() |> String.trim()
      assert hash == recorded
    end

    test "hashes path then bytes, directories then files, in plain string order" do
      root = small_scroll()

      # The order build_l1.py walks: the torah root's own files, then each
      # directory by path; within a directory, names as strings — so
      # 10.json comes before 2.json.
      expected =
        [
          {"index.json", "INDEX"},
          {"alef/1/1.json", "one"},
          {"alef/1/10.json", "ten"},
          {"alef/1/2.json", "two"},
          {"alef/2/1.json", "second chapter"}
        ]
        |> Enum.reduce(:crypto.hash_init(:sha256), fn {rel, bytes}, ctx ->
          ctx |> :crypto.hash_update(rel) |> :crypto.hash_update(bytes)
        end)
        |> :crypto.hash_final()
        |> Base.encode16(case: :lower)

      assert {:ok, ^expected} = L1Reader.compute_tree_hash(root)
    end

    test "one changed byte, one added file, one renamed file — each changes the hash" do
      root = small_scroll()
      {:ok, original} = L1Reader.compute_tree_hash(root)
      verse = Path.join([root, "torah", "alef", "1", "2.json"])

      File.write!(verse, "twO")
      assert {:ok, changed} = L1Reader.compute_tree_hash(root)
      assert changed != original

      File.write!(verse, "two")
      assert {:ok, ^original} = L1Reader.compute_tree_hash(root)

      File.write!(Path.join([root, "torah", "alef", "1", "3.json"]), "an added verse")
      assert {:ok, added} = L1Reader.compute_tree_hash(root)
      assert added != original
      File.rm!(Path.join([root, "torah", "alef", "1", "3.json"]))

      File.rename!(verse, Path.join([root, "torah", "alef", "1", "20.json"]))
      assert {:ok, renamed} = L1Reader.compute_tree_hash(root)
      assert renamed != original
    end

    test "a scroll that is not there is an error, not a hash" do
      assert {:error, reason} = L1Reader.compute_tree_hash("/nonexistent/l1")
      assert reason =~ "not a directory"
    end
  end

  # ============================================================
  # The witness
  # ============================================================
  describe "L1Integrity" do
    test "reads the scroll when it starts, and again when asked" do
      root = small_scroll()
      {:ok, pinned} = L1Reader.compute_tree_hash(root)

      {:ok, pid} =
        L1Integrity.start_link(name: :tablet38_witness, l1_root: root, expected_hash: pinned, interval: :never)

      on_exit(fn -> if Process.alive?(pid), do: GenServer.stop(pid) end)

      assert :ok = L1Integrity.status(:tablet38_witness)
      assert %{computed: ^pinned, expected: ^pinned} = L1Integrity.reading(:tablet38_witness)

      # Someone alters a verse. The last reading still says tov — it is a
      # reading, not a guard — until the scroll is read again.
      File.write!(Path.join([root, "torah", "alef", "1", "1.json"]), "0ne")
      assert {:error, reason} = L1Integrity.recheck(:tablet38_witness)
      assert reason =~ "L1_INTEGRITY_FAILED"
      assert reason =~ "expected #{pinned}"
      assert {:error, _} = L1Integrity.status(:tablet38_witness)

      # Restored, it is tov again.
      File.write!(Path.join([root, "torah", "alef", "1", "1.json"]), "one")
      assert :ok = L1Integrity.recheck(:tablet38_witness)
    end

    test "re-reads on its own at the interval" do
      root = small_scroll()
      {:ok, pinned} = L1Reader.compute_tree_hash(root)

      {:ok, pid} =
        L1Integrity.start_link(name: :tablet38_periodic, l1_root: root, expected_hash: pinned, interval: 50)

      on_exit(fn -> if Process.alive?(pid), do: GenServer.stop(pid) end)

      assert :ok = L1Integrity.status(:tablet38_periodic)
      File.write!(Path.join([root, "torah", "index.json"]), "INDEX, altered")

      assert eventually(fn -> match?({:error, _}, L1Integrity.status(:tablet38_periodic)) end)

      # And it keeps re-reading: restored, it is tov again without being asked.
      File.write!(Path.join([root, "torah", "index.json"]), "INDEX")
      assert eventually(fn -> L1Integrity.status(:tablet38_periodic) == :ok end)
    end

    test "answers from the last reading while a periodic re-reading is under way" do
      root = small_scroll()
      {:ok, pinned} = L1Reader.compute_tree_hash(root)

      {:ok, pid} =
        L1Integrity.start_link(name: :tablet38_busy, l1_root: root, expected_hash: pinned, interval: :never)

      on_exit(fn -> if Process.alive?(pid), do: GenServer.stop(pid) end)

      # Trigger a periodic reading by hand; the process must not be busy
      # with it — a status call is answered at once, from the last reading.
      send(pid, :read)
      {micros, status} = :timer.tc(fn -> L1Integrity.status(:tablet38_busy) end)
      assert status == :ok
      assert micros < 50_000
    end
  end

  # ============================================================
  # The whole path: an altered scroll stops the vessel
  # ============================================================
  describe "with a scroll that does not match its pin" do
    setup do
      if HaltMonitor.halted?(), do: HaltMonitor.resolve("tablet38 test setup")
      MannaLedger.reset()
      write_provision(20)

      # Sanity: with the real scroll, all is well.
      assert :ok = L1Reader.verify_integrity()

      # Replace the supervised witness with one that reads an altered
      # copy — the recorded hash file is untouched and still "matches",
      # which is exactly the case the old check could not see.
      root = small_scroll()
      :ok = Supervisor.terminate_child(VavPipeline.Supervisor, L1Integrity)

      {:ok, pid} =
        L1Integrity.start_link(l1_root: root, expected_hash: L1Reader.expected_hash(), interval: :never)

      on_exit(fn ->
        # The witness is linked to the test process and may already be
        # gone when on_exit runs (seed 221974, 2026-10-15): stopping a
        # process that has exited is not a failure of the scroll.
        try do
          if Process.alive?(pid), do: GenServer.stop(pid)
        catch
          :exit, _ -> :ok
        end

        {:ok, _} = Supervisor.restart_child(VavPipeline.Supervisor, L1Integrity)
        MannaLedger.reset()
        File.rm(VavPipeline.Manna.provision_file())
      end)

      :ok
    end

    test "verify_integrity fails, though integrity.sha256 still holds the pinned hash" do
      recorded = L1Reader.l1_root() |> Path.join("integrity.sha256") |> File.read!() |> String.trim()
      assert recorded == L1Reader.expected_hash()

      assert {:error, reason} = L1Reader.verify_integrity()
      assert reason =~ "L1_INTEGRITY_FAILED"
      assert reason =~ "the scroll on disk hashes to"
    end

    test "health says l1_hash: fail and the vessel is not ready" do
      conn = conn(:get, "/kodesh/health") |> Router.call(@opts)
      body = Jason.decode!(conn.resp_body)

      assert conn.status == 503
      assert body["checks"]["l1_hash"] == "fail"
    end

    test "no cycle runs on it — /peah/ask does not answer from an altered scroll" do
      conn =
        conn(:post, "/peah/ask", Jason.encode!(%{question: "בראשית ברא אלהים"}))
        |> put_req_header("content-type", "application/json")
        |> Router.call(@opts)

      refute conn.status == 200
      refute Map.has_key?(Jason.decode!(conn.resp_body), "answer")
    end
  end

  # ------------------------------------------------------------
  # Helpers
  # ------------------------------------------------------------

  defp small_scroll do
    root = Path.join(System.tmp_dir!(), "tablet38_#{System.unique_integer([:positive])}")
    on_exit(fn -> File.rm_rf!(root) end)

    files = %{
      "index.json" => "INDEX",
      "alef/1/1.json" => "one",
      "alef/1/2.json" => "two",
      "alef/1/10.json" => "ten",
      "alef/2/1.json" => "second chapter"
    }

    for {rel, bytes} <- files do
      path = Path.join([root, "torah", rel])
      File.mkdir_p!(Path.dirname(path))
      File.write!(path, bytes)
    end

    root
  end

  defp eventually(fun, tries \\ 100) do
    cond do
      fun.() -> true
      tries == 0 -> false
      true -> Process.sleep(20) && eventually(fun, tries - 1)
    end
  end

  defp write_provision(compute_units) do
    today = Date.utc_today() |> Date.to_iso8601()
    expires = DateTime.utc_now() |> DateTime.add(6 * 3600) |> DateTime.to_iso8601()

    provision = %{
      "date" => today,
      "provision" => %{
        "compute_units" => compute_units,
        "memory_mb" => 512,
        "api_calls_external" => 5,
        "storage_delta_mb" => 2,
        "sanhedrin_panels_max" => 2
      },
      "type" => "regular",
      "expires_at" => expires,
      "written_by" => "tablet38_test",
      "written_at" => DateTime.utc_now() |> DateTime.to_iso8601()
    }

    path = VavPipeline.Manna.provision_file()
    File.mkdir_p!(Path.dirname(path))
    File.write!(path, Jason.encode!(provision))
  end
end