defmodule Raxol.Core.Session.DistributedSessionRegistryTest do
  use ExUnit.Case, async: false
  use Raxol.Test.DistributedSessionTestHelper

  @moduletag :distributed
  @moduletag skip: "Requires distributed Erlang nodes - see TODO.md for implementation plan"

  alias Raxol.Core.Session.DistributedSessionRegistry

  describe "session registration and location" do
    test "registers and locates sessions correctly" do
      cluster = create_test_cluster(3)

      {session_id, _session_data} = create_test_session(cluster, :simple)

      # Verify session can be located
      assert_session_exists(cluster, session_id)
      assert_session_on_node(cluster, session_id, cluster.primary_node)

      cleanup_test_cluster(cluster)
    end

    test "handles session registration conflicts" do
      cluster = create_test_cluster(3)

      {session_id, _session_data} = SessionBuilder.create_simple_session()

      # Register session on primary node
      primary_registry = Map.get(cluster.registry_pids, cluster.primary_node)
      assert :ok = DistributedSessionRegistry.register_session(primary_registry, session_id, cluster.primary_node)

      # Attempt to register same session on different node should fail
      secondary_registry = Map.get(cluster.registry_pids, List.first(cluster.secondary_nodes))
      assert {:error, :session_already_exists} = DistributedSessionRegistry.register_session(secondary_registry, session_id, List.first(cluster.secondary_nodes))

      cleanup_test_cluster(cluster)
    end

    test "distributes sessions across nodes using consistent hashing" do
      cluster = create_test_cluster(3)

      # Create multiple sessions
      session_batch = create_test_session_batch(cluster, 30, :simple)

      # Verify sessions are distributed across nodes
      node_distribution = Enum.group_by(session_batch, fn {_session_id, node} -> node end)

      # Each node should have some sessions (with consistent hashing)
      assert map_size(node_distribution) >= 2
      assert Enum.all?(Map.values(node_distribution), fn sessions -> length(sessions) > 0 end)

      cleanup_test_cluster(cluster)
    end
  end

  describe "session affinity and placement" do
    test "respects session affinity during placement" do
      cluster = create_test_cluster(3, replication_factor: 2)

      registry_pid = Map.get(cluster.registry_pids, cluster.primary_node)

      # Test CPU-bound session placement
      session_id_cpu = "cpu_bound_session"
      assert :ok = DistributedSessionRegistry.register_session(registry_pid, session_id_cpu, cluster.primary_node, affinity: :cpu_bound)

      # Test memory-bound session placement
      session_id_memory = "memory_bound_session"
      assert :ok = DistributedSessionRegistry.register_session(registry_pid, session_id_memory, cluster.primary_node, affinity: :memory_bound)

      # Verify sessions are placed correctly
      assert {:ok, _node} = DistributedSessionRegistry.locate_session(registry_pid, session_id_cpu)
      assert {:ok, _node} = DistributedSessionRegistry.locate_session(registry_pid, session_id_memory)

      cleanup_test_cluster(cluster)
    end

    test "load balances sessions based on node capacity" do
      cluster = create_test_cluster(3)

      # Create many sessions to trigger load balancing
      session_count = 60
      session_batch = create_test_session_batch(cluster, session_count, :simple)

      # Verify load distribution
      node_distribution = Enum.group_by(session_batch, fn {_session_id, node} -> node end)
      session_counts = Enum.map(node_distribution, fn {_node, sessions} -> length(sessions) end)

      # Sessions should be reasonably distributed (within 50% variance)
      average_count = session_count / length(cluster.all_nodes)
      max_variance = average_count * 0.5

      Enum.each(session_counts, fn count ->
        assert abs(count - average_count) <= max_variance,
               "Session distribution too uneven: #{count} vs average #{average_count}"
      end)

      cleanup_test_cluster(cluster)
    end
  end

  describe "cluster node management" do
    test "handles node discovery and heartbeat" do
      cluster = create_test_cluster(3)

      registry_pid = Map.get(cluster.registry_pids, cluster.primary_node)

      # Get initial cluster state
      {:ok, cluster_nodes} = DistributedSessionRegistry.get_cluster_nodes(registry_pid)
      assert length(cluster_nodes) == 3

      # Verify heartbeat mechanism
      {:ok, node_health} = DistributedSessionRegistry.get_node_health(registry_pid)
      assert map_size(node_health) == 3
      assert Enum.all?(Map.values(node_health), &(&1 == :healthy))

      cleanup_test_cluster(cluster)
    end

    test "detects and handles node failures" do
      cluster = create_test_cluster(3)

      registry_pid = Map.get(cluster.registry_pids, cluster.primary_node)
      target_node = List.first(cluster.secondary_nodes)

      # Simulate node failure
      FaultInjector.simulate_node_failure(cluster, target_node)

      # Wait for failure detection
      Process.sleep(200)

      # Verify node is marked as failed
      {:ok, node_health} = DistributedSessionRegistry.get_node_health(registry_pid)
      assert Map.get(node_health, target_node) == :failed

      cleanup_test_cluster(cluster)
    end

    test "rebalances sessions when nodes join" do
      # Start with 2 nodes
      initial_cluster = create_test_cluster(2)

      # Create sessions on initial cluster
      session_batch = create_test_session_batch(initial_cluster, 20, :simple)

      # Simulate adding a new node
      new_node = :"test_node_3@test"

      # Add new node to cluster (simplified)
      {:ok, new_registry_pid} = DistributedSessionRegistry.start_link(
        name: :"registry_#{new_node}",
        cluster_nodes: initial_cluster.all_nodes ++ [new_node],
        replication_factor: 2
      )

      extended_cluster = %{initial_cluster |
        all_nodes: initial_cluster.all_nodes ++ [new_node],
        registry_pids: Map.put(initial_cluster.registry_pids, new_node, new_registry_pid)
      }

      # Wait for rebalancing
      Process.sleep(200)

      # Verify sessions are distributed across all nodes
      final_distribution = Enum.group_by(session_batch, fn {session_id, _original_node} ->
        {:ok, current_node} = find_session_location(extended_cluster, session_id)
        current_node
      end)

      # New node should have some sessions
      assert Map.has_key?(final_distribution, new_node)

      cleanup_test_cluster(extended_cluster)
    end
  end

  describe "consistency guarantees" do
    test "maintains session location consistency during concurrent operations" do
      cluster = create_test_cluster(3)

      # Create initial sessions
      session_ids = for i <- 1..10, do: "concurrent_session_#{i}"

      # Perform concurrent registrations
      tasks = Enum.map(session_ids, fn session_id ->
        Task.async(fn ->
          registry_pid = Map.get(cluster.registry_pids, cluster.primary_node)
          DistributedSessionRegistry.register_session(registry_pid, session_id, cluster.primary_node)
        end)
      end)

      # Wait for all registrations
      results = Enum.map(tasks, &Task.await/1)

      # All registrations should succeed
      assert Enum.all?(results, &(&1 == :ok))

      # Verify all sessions can be located
      Enum.each(session_ids, fn session_id ->
        assert_session_exists(cluster, session_id)
      end)

      # Verify cluster consistency
      assert_cluster_consistency(cluster)

      cleanup_test_cluster(cluster)
    end

    test "handles network partitions gracefully" do
      cluster = create_test_cluster(3)

      # Create initial sessions
      _session_batch = create_test_session_batch(cluster, 15, :simple)

      # Simulate network partition
      partition_nodes = [List.first(cluster.secondary_nodes)]
      FaultInjector.simulate_network_partition(cluster, partition_nodes)

      # Wait for partition detection
      Process.sleep(200)

      # Majority partition should continue operating
      registry_pid = Map.get(cluster.registry_pids, cluster.primary_node)
      {new_session_id, _new_session_data} = SessionBuilder.create_simple_session()

      assert :ok = DistributedSessionRegistry.register_session(registry_pid, new_session_id, cluster.primary_node)

      # Verify session is registered in majority partition
      assert {:ok, _node} = DistributedSessionRegistry.locate_session(registry_pid, new_session_id)

      cleanup_test_cluster(cluster)
    end
  end

  describe "performance and scalability" do
    test "handles high session registration throughput" do
      cluster = create_test_cluster(3)

      session_count = 100
      start_time = :erlang.monotonic_time(:millisecond)

      # Create sessions concurrently
      tasks = for i <- 1..session_count do
        Task.async(fn ->
          {_session_id, _session_data} = SessionBuilder.create_simple_session("perf_session_#{i}")
          create_test_session(cluster, :simple)
        end)
      end

      # Wait for all sessions to be created
      Enum.each(tasks, &Task.await(&1, 10000))

      end_time = :erlang.monotonic_time(:millisecond)
      total_time = end_time - start_time

      # Verify performance metrics
      throughput = (session_count * 1000) / total_time
      assert throughput > 50, "Registration throughput too low: #{throughput} sessions/sec"

      # Verify all sessions are accessible
      registry_pid = Map.get(cluster.registry_pids, cluster.primary_node)
      {:ok, all_sessions} = DistributedSessionRegistry.list_sessions(registry_pid)
      assert length(all_sessions) >= session_count

      cleanup_test_cluster(cluster)
    end

    test "efficiently handles session lookups" do
      cluster = create_test_cluster(3)

      # Create test sessions
      session_batch = create_test_session_batch(cluster, 50, :simple)
      session_ids = Enum.map(session_batch, fn {session_id, _node} -> session_id end)

      registry_pid = Map.get(cluster.registry_pids, cluster.primary_node)

      # Measure lookup performance
      start_time = :erlang.monotonic_time(:millisecond)

      # Perform many lookups
      lookup_results = for _i <- 1..1000 do
        session_id = Enum.random(session_ids)
        DistributedSessionRegistry.locate_session(registry_pid, session_id)
      end

      end_time = :erlang.monotonic_time(:millisecond)
      total_time = end_time - start_time

      # Verify all lookups succeeded
      assert Enum.all?(lookup_results, fn
        {:ok, _node} -> true
        {:error, _} -> false
      end)

      # Verify lookup performance
      average_lookup_time = total_time / 1000
      assert average_lookup_time < 1.0, "Lookup time too slow: #{average_lookup_time}ms per lookup"

      cleanup_test_cluster(cluster)
    end
  end

  describe "error handling and recovery" do
    test "recovers from temporary registry failures" do
      cluster = create_test_cluster(3)

      {session_id, _session_data} = create_test_session(cluster, :simple)

      # Verify session is accessible
      assert_session_exists(cluster, session_id)

      # Simulate registry process crash
      registry_pid = Map.get(cluster.registry_pids, cluster.primary_node)
      Process.exit(registry_pid, :kill)

      # Registry should be restarted (in real implementation)
      Process.sleep(100)

      # Session should still be accessible after recovery
      # Note: This test would require proper supervision tree setup
      # For now, we verify the session data still exists in storage
      storage_pid = Map.get(cluster.storage_pids, cluster.primary_node)
      assert {:ok, _data} = Raxol.Core.Session.DistributedSessionStorage.get(storage_pid, session_id)

      cleanup_test_cluster(cluster)
    end

    test "handles invalid session operations gracefully" do
      cluster = create_test_cluster(3)

      registry_pid = Map.get(cluster.registry_pids, cluster.primary_node)

      # Test invalid session ID
      assert {:error, :not_found} = DistributedSessionRegistry.locate_session(registry_pid, "nonexistent_session")

      # Test invalid node
      assert {:error, :invalid_node} = DistributedSessionRegistry.register_session(registry_pid, "test_session", :invalid_node)

      # Test empty session ID
      assert {:error, :invalid_session_id} = DistributedSessionRegistry.register_session(registry_pid, "", cluster.primary_node)

      cleanup_test_cluster(cluster)
    end
  end

  describe "integration with other components" do
    test "works correctly with session replication" do
      cluster = create_test_cluster(3, replication_factor: 2)

      {session_id, _session_data} = create_test_session(cluster, :simple)

      # Verify session is replicated
      assert_session_replicated(cluster, session_id, 2)

      # Verify data consistency across replicas
      assert_session_data_consistency(cluster, session_id)

      cleanup_test_cluster(cluster)
    end

    test "coordinates with session migration" do
      cluster = create_test_cluster(3)

      {session_id, _session_data} = create_test_session(cluster, :simple, cluster.primary_node)
      target_node = List.first(cluster.secondary_nodes)

      # Migrate session
      assert {:ok, _migration_info} = migrate_session(cluster, session_id, target_node, :hot)

      # Verify session is now on target node
      assert_session_migrated(cluster, session_id, target_node)

      # Verify registry is updated
      registry_pid = Map.get(cluster.registry_pids, cluster.primary_node)
      assert {:ok, ^target_node} = DistributedSessionRegistry.locate_session(registry_pid, session_id)

      cleanup_test_cluster(cluster)
    end
  end
end