TESTS

defmodule Foundation.Contract.ConfigurableContractTest do
  use ExUnit.Case, async: false

  # This test runs against any module that implements the Configurable behaviour.
  # We will test the default implementation: Foundation.Services.ConfigServer
  @module Foundation.Services.ConfigServer

  # Setup: Ensure the service is running
  setup do
    Foundation.TestHelpers.ensure_config_available()
    :ok
  end

  describe "Configurable Behaviour Contract for #{@module}" do
    test "get/0 returns a valid Config struct or an error" do
      # Assert the shape and type of the return value
    end

    test "get/1 returns a value for a valid path and an error for an invalid one" do
      # Test with both valid and deeply nested invalid paths
    end

    test "update/2 succeeds for an updatable path and fails for a forbidden one" do
      # Use `updatable_paths/0` to dynamically pick paths for testing
    end
    
    test "validate/1 correctly validates or rejects a Config struct" do
      # Test with both a default config and a known-invalid one
    end

    test "updatable_paths/0 returns a list of lists of atoms" do
      # Assert the structure and type of the returned paths
    end

    test "reset/0 restores the configuration to a default state" do
      # Update a value, then reset, then verify it's back to default
    end

    test "available?/0 returns a boolean" do
      # Assert the return type is always a boolean
    end
  end
end

defmodule Foundation.Smoke.SystemSmokeTest do
  use ExUnit.Case, async: false
  @moduletag :smoke

  describe "Foundation System Smoke Test" do
    test "application starts and all services report healthy" do
      # This test relies on the default ExUnit setup starting the app.
      # 1. Check overall health
      assert {:ok, health} = Foundation.health()
      assert health.status == :healthy
      assert Foundation.available?()
    end

    test "core APIs are responsive and return correct shapes" do
      # 1. Config: Can we read a value?
      assert {:ok, _} = Foundation.Config.get([:dev, :debug_mode])

      # 2. Events: Can we store and retrieve an event?
      {:ok, event} = Foundation.Events.new_event(:smoke_test, %{time: System.os_time()})
      {:ok, id} = Foundation.Events.store(event)
      assert {:ok, ^event} = Foundation.Events.get(id)

      # 3. Telemetry: Can we emit and get metrics?
      :ok = Foundation.Telemetry.emit_counter([:smoke_test, :run], %{})
      assert {:ok, metrics} = Foundation.Telemetry.get_metrics()
      assert is_map(metrics)

      # 4. Service Registry: Can we look up a core service?
      assert {:ok, _pid} = Foundation.ServiceRegistry.lookup(:production, :config_server)
    end
  end
end

defmodule Foundation.Stress.SustainedLoadTest do
  use ExUnit.Case, async: false
  @moduletag :stress

  test "system remains stable and responsive under sustained concurrent load" do
    # 1. Start a high number of concurrent tasks (e.g., 100).
    # 2. Each task runs in a loop for 30 seconds, continuously and randomly:
    #    - Reading config values.
    #    - Writing new events.
    #    - Emitting telemetry counters and gauges.
    #    - Querying the EventStore.
    # 3. During the test, periodically check the memory usage of core service PIDs
    #    and their message queue lengths (`Process.info(pid, [:memory, :message_queue_len])`).
    # 4. Assert that memory usage and queue lengths do not grow unbounded and stay
    #    within a reasonable threshold.
    # 5. After the test, assert that the system is still healthy and responsive.
  end
end

defmodule Foundation.Stress.ChaosResilienceTest do
  use ExUnit.Case, async: false
  @moduletag :stress

  test "system recovers gracefully after random service failures under load" do
    # 1. Start a sustained load (similar to the test above).
    # 2. In a separate process (the "Chaos Monkey"), loop for 20 seconds:
    #    - Every 2-3 seconds, randomly select a core service PID 
    #      (ConfigServer, EventStore, TelemetryService).
    #    - Kill the selected process using `Process.exit(pid, :kill)`.
    # 3. During this time, the load-generating tasks will experience errors. This is expected.
    #    The test should assert that these errors are handled gracefully and do not crash the tasks.
    # 4. After the chaos period, stop the load generators.
    # 5. Wait for a "cool down" period (e.g., 5 seconds) for supervisors to stabilize the system.
    # 6. Assert that `Foundation.health()` returns `:healthy`.
    # 7. Assert that all core API functions are responsive again.
  end
end

defmodule Foundation.Benchmark.CoreOperations do
  use ExUnit.Case, async: false
  @moduletag :benchmark

  # Setup: Ensure all services are running and primed.
  
  # Benchee suite to measure critical path functions.
  Benchee.run(
    %{
      "Config.get/1" => fn -> Foundation.Config.get([:dev, :debug_mode]) end,
      "EventStore.store/1" => fn -> 
        {:ok, event} = Foundation.Events.new_event(:bench, %{})
        Foundation.Events.store(event) 
      end,
      "ServiceRegistry.lookup/2" => fn -> 
        Foundation.ServiceRegistry.lookup(:production, :config_server)
      end,
      "Telemetry.emit_counter/2" => fn ->
        Foundation.Telemetry.emit_counter([:bench, :count], %{})
      end,
      "Infrastructure.execute_protected (no-op)" => fn ->
        Foundation.Infrastructure.execute_protected(:noop, [], fn -> :ok end)
      end
    },
    time: 5, # seconds
    memory_time: 2 # seconds
  )
end

defmodule Foundation.Integration.GracefulDegradationIntegrationTest do
  use ExUnit.Case, async: false

  describe "when ConfigServer is down" do
    test "Events and Telemetry services continue to operate" do
      # 1. Stop ConfigServer.
      # 2. Assert that `Events.store/1` still returns :ok (or a non-crashing error) 
      #    because it should not have a hard dependency.
      # 3. Assert `Telemetry.emit_counter/2` still returns :ok.
      # 4. Restart ConfigServer and verify full functionality is restored.
    end
  end

  describe "when EventStore is down" do
    test "Config updates still succeed and Telemetry is emitted" do
      # 1. Stop EventStore.
      # 2. Assert `Config.update/2` on an updatable path still returns :ok,
      #    even though the corresponding audit event cannot be stored.
      # 3. Assert `Telemetry.get_metrics/0` is still responsive.
      # 4. Restart EventStore and verify it can now store events.
    end
  end
end