defmodule Phoenix.Communication.Patterns do
  @moduledoc """
  Fundamental communication patterns in Phoenix:
  
  1. Point-to-Point: Direct agent communication
  2. Publish-Subscribe: Event distribution
  3. Request-Response: Synchronous interaction
  4. Pipeline: Ordered processing chains
  5. Gossip: Eventually consistent broadcast
  6. Consensus: Strongly consistent coordination
  """
  
  @type pattern :: 
    :point_to_point | 
    :publish_subscribe | 
    :request_response | 
    :pipeline | 
    :gossip | 
    :consensus
    
  @type message_characteristics :: %{
    size: :small | :medium | :large,
    priority: :low | :normal | :high | :critical,
    consistency: :eventual | :causal | :strong,
    ordering: :none | :causal | :total,
    delivery: :at_most_once | :at_least_once | :exactly_once
  }
end

defmodule Phoenix.Message do
  @moduledoc """
  Universal message format for Phoenix distributed agents.
  
  Based on CloudEvents v1.0.2 with Phoenix extensions for:
  - Distributed tracing and correlation
  - Causal consistency tracking
  - Delivery guarantee specifications
  - Routing and placement hints
  """
  
  use TypedStruct
  
  typedstruct do
    # CloudEvents v1.0.2 Core Fields
    field :specversion, String.t(), default: "1.0.2"
    field :id, String.t()
    field :source, String.t()
    field :type, String.t()
    field :subject, String.t()
    field :time, DateTime.t()
    field :datacontenttype, String.t(), default: "application/x-erlang-term"
    field :dataschema, String.t()
    field :data, term()
    
    # Phoenix Distributed Extensions
    field :phoenix_trace, Phoenix.Trace.Context.t()
    field :phoenix_causality, Phoenix.VectorClock.t()
    field :phoenix_delivery, Phoenix.Delivery.Guarantee.t()
    field :phoenix_routing, Phoenix.Routing.Metadata.t()
    field :phoenix_security, Phoenix.Security.Context.t()
    field :phoenix_qos, Phoenix.QoS.Requirements.t()
  end
  
  def new(data, opts \\ []) do
    %__MODULE__{
      id: generate_message_id(),
      source: Keyword.get(opts, :source, Phoenix.Node.local_id()),
      type: Keyword.get(opts, :type, "phoenix.agent.message"),
      time: DateTime.utc_now(),
      data: data,
      phoenix_trace: Phoenix.Trace.current_context(),
      phoenix_causality: Phoenix.VectorClock.tick(Phoenix.VectorClock.local()),
      phoenix_delivery: Keyword.get(opts, :delivery, default_delivery_guarantee()),
      phoenix_routing: build_routing_metadata(opts),
      phoenix_security: Phoenix.Security.current_context(),
      phoenix_qos: Keyword.get(opts, :qos, default_qos_requirements())
    }
  end
end

defmodule Phoenix.Message.Types do
  @moduledoc """
  Standardized message type taxonomy for Phoenix agents.
  
  Type format: phoenix.{domain}.{entity}.{action}[.{qualifier}]
  """
  
  # Control Plane Messages
  @control_plane [
    "phoenix.cluster.node.join",
    "phoenix.cluster.node.leave", 
    "phoenix.cluster.topology.update",
    "phoenix.agent.placement.request",
    "phoenix.agent.placement.response",
    "phoenix.agent.migration.start",
    "phoenix.agent.migration.complete"
  ]
  
  # Data Plane Messages  
  @data_plane [
    "phoenix.agent.message.send",
    "phoenix.agent.state.update",
    "phoenix.agent.action.execute",
    "phoenix.agent.action.result",
    "phoenix.agent.event.publish",
    "phoenix.agent.heartbeat.ping"
  ]
  
  # Observability Messages
  @observability [
    "phoenix.telemetry.metric.update",
    "phoenix.telemetry.trace.span",
    "phoenix.telemetry.log.entry",
    "phoenix.health.status.report",
    "phoenix.performance.measurement"
  ]
  
  def message_characteristics(message_type) do
    cond do
      message_type in @control_plane -> %{
        priority: :high,
        consistency: :strong,
        ordering: :total,
        delivery: :exactly_once
      }
      
      message_type in @data_plane -> %{
        priority: :normal,
        consistency: :causal,
        ordering: :causal,
        delivery: :at_least_once
      }
      
      message_type in @observability -> %{
        priority: :low,
        consistency: :eventual,
        ordering: :none,
        delivery: :at_most_once
      }
      
      true -> default_characteristics()
    end
  end
end

defmodule Phoenix.Message.Serialization do
  @moduledoc """
  Multi-format serialization with automatic format selection.
  
  Formats:
  - Erlang Term: Zero-copy within BEAM, type preservation
  - MessagePack: Compact binary, cross-language
  - Protocol Buffers: Schema evolution, efficient
  - JSON: Human readable, debugging
  """
  
  @type format :: :erlang_term | :msgpack | :protobuf | :json
  
  def serialize(message, format \\ :auto) do
    selected_format = select_format(message, format)
    
    case selected_format do
      :erlang_term -> 
        compressed_term = :erlang.term_to_binary(message, [:compressed])
        {:ok, compressed_term, :erlang_term}
        
      :msgpack -> 
        case Msgpax.pack(message) do
          {:ok, binary} -> {:ok, binary, :msgpack}
          {:error, reason} -> {:error, reason}
        end
        
      :protobuf -> 
        case PhoenixProto.Message.encode(message) do
          {:ok, binary} -> {:ok, binary, :protobuf}
          {:error, reason} -> {:error, reason}
        end
        
      :json -> 
        case Jason.encode(message) do
          {:ok, json} -> {:ok, json, :json}
          {:error, reason} -> {:error, reason}
        end
    end
  end
  
  defp select_format(message, :auto) do
    cond do
      # Local BEAM communication - use Erlang terms
      same_beam_cluster?(message.phoenix_routing.target) -> 
        :erlang_term
        
      # Cross-language communication - use MessagePack
      cross_language?(message.phoenix_routing.target) -> 
        :msgpack
        
      # Schema evolution important - use Protocol Buffers
      schema_evolution_required?(message.type) -> 
        :protobuf
        
      # Debugging or development - use JSON
      debug_mode?() -> 
        :json
        
      # Default to MessagePack for efficiency
      true -> 
        :msgpack
    end
  end
  
  defp select_format(_message, format) when format in [:erlang_term, :msgpack, :protobuf, :json] do
    format
  end
end

defmodule Phoenix.Transport.DistributedErlang do
  @moduledoc """
  Distributed Erlang transport for local cluster communication.
  
  Advantages:
  - Zero-copy message passing
  - Automatic process monitoring
  - Built-in clustering
  - Type preservation
  
  Use Cases:
  - Single datacenter clusters
  - Development environments
  - Small to medium scale (< 50 nodes)
  """
  
  @behaviour Phoenix.Transport
  
  def send_message(target, message, opts \\ []) do
    case resolve_target(target) do
      {:ok, {:local, pid}} -> 
        send(pid, message)
        {:ok, :sent}
        
      {:ok, {:remote, node, pid}} -> 
        case Node.ping(node) do
          :pong -> 
            send({pid, node}, message)
            {:ok, :sent}
          :pang -> 
            {:error, :node_unreachable}
        end
        
      {:error, reason} -> 
        {:error, reason}
    end
  end
  
  def broadcast_message(targets, message, opts \\ []) do
    delivery_mode = Keyword.get(opts, :delivery_mode, :async)
    
    case delivery_mode do
      :async -> 
        # Fire and forget to all targets
        Enum.each(targets, fn target ->
          send_message(target, message, opts)
        end)
        {:ok, :broadcast}
        
      :sync -> 
        # Wait for acknowledgment from all
        sync_broadcast(targets, message, opts)
    end
  end
  
  defp sync_broadcast(targets, message, opts) do
    timeout = Keyword.get(opts, :timeout, 5000)
    
    # Send to all targets with correlation ID
    correlation_id = generate_correlation_id()
    ack_message = add_ack_request(message, correlation_id)
    
    Enum.each(targets, fn target ->
      send_message(target, ack_message, opts)
    end)
    
    # Wait for acknowledgments
    wait_for_acks(targets, correlation_id, timeout)
  end
end

defmodule Phoenix.Transport.Partisan do
  @moduledoc """
  Partisan transport for large-scale cluster communication.
  
  Advantages:
  - Scales beyond Distributed Erlang limits
  - Pluggable overlay networks
  - Advanced failure detection
  - Message batching and compression
  
  Use Cases:
  - Large clusters (100+ nodes)
  - Cross-datacenter communication
  - High-throughput scenarios
  """
  
  @behaviour Phoenix.Transport
  
  def send_message(target, message, opts \\ []) do
    # Use Partisan's overlay network
    partisan_message = wrap_for_partisan(message, opts)
    
    case Partisan.send_message(target, partisan_message) do
      :ok -> {:ok, :sent}
      {:error, reason} -> {:error, reason}
    end
  end
  
  def configure_overlay(overlay_type, opts \\ []) do
    case overlay_type do
      :hyparview -> 
        # HyParView: Probabilistic broadcast
        Partisan.configure_overlay(:hyparview, [
          fanout: Keyword.get(opts, :fanout, 6),
          active_view_size: Keyword.get(opts, :active_view_size, 6),
          passive_view_size: Keyword.get(opts, :passive_view_size, 30)
        ])
        
      :client_server -> 
        # Client-Server: Traditional hub-and-spoke
        Partisan.configure_overlay(:client_server, [
          servers: Keyword.get(opts, :servers, []),
          connection_pool_size: Keyword.get(opts, :pool_size, 10)
        ])
        
      :tree -> 
        # Tree: Hierarchical topology
        Partisan.configure_overlay(:tree, [
          fanout: Keyword.get(opts, :tree_fanout, 4),
          depth: Keyword.get(opts, :max_depth, 6)
        ])
    end
  end
  
  defp wrap_for_partisan(message, opts) do
    %Partisan.Message{
      payload: message,
      metadata: %{
        priority: get_priority(opts),
        compression: should_compress?(message, opts),
        encryption: should_encrypt?(message, opts)
      }
    }
  end
end

defmodule Phoenix.Transport.HTTP2 do
  @moduledoc """
  HTTP/2 transport for cross-datacenter and hybrid cloud communication.
  
  Advantages:
  - Works across firewalls and NAT
  - Built-in TLS encryption
  - Stream multiplexing
  - Standardized protocol
  
  Use Cases:
  - Cross-datacenter communication
  - Hybrid cloud deployments
  - Internet-facing endpoints
  """
  
  @behaviour Phoenix.Transport
  
  def send_message(target, message, opts \\ []) do
    url = build_target_url(target)
    headers = build_headers(message, opts)
    body = Phoenix.Message.Serialization.serialize(message, :json)
    
    case Finch.request(
      Finch.build(:post, url, headers, body),
      PhoenixHTTP2Pool,
      receive_timeout: Keyword.get(opts, :timeout, 30_000)
    ) do
      {:ok, %Finch.Response{status: 200}} -> 
        {:ok, :sent}
      {:ok, %Finch.Response{status: status}} -> 
        {:error, {:http_error, status}}
      {:error, reason} -> 
        {:error, reason}
    end
  end
  
  def start_http2_server(port, opts \\ []) do
    # Phoenix HTTP/2 server for receiving messages
    Phoenix.HTTP2Server.start_link([
      port: port,
      transport_options: [
        max_connections: Keyword.get(opts, :max_connections, 1000),
        num_acceptors: Keyword.get(opts, :num_acceptors, 100)
      ],
      protocol_options: [
        max_frame_size: Keyword.get(opts, :max_frame_size, 16_384),
        max_concurrent_streams: Keyword.get(opts, :max_streams, 100)
      ]
    ])
  end
  
  defp build_headers(message, opts) do
    base_headers = [
      {"content-type", "application/json"},
      {"user-agent", "Phoenix-Agent/1.0"},
      {"x-phoenix-message-id", message.id},
      {"x-phoenix-message-type", message.type}
    ]
    
    # Add tracing headers
    trace_headers = Phoenix.Trace.to_headers(message.phoenix_trace)
    
    # Add authentication headers
    auth_headers = Phoenix.Auth.to_headers(message.phoenix_security)
    
    base_headers ++ trace_headers ++ auth_headers
  end
end

defmodule Phoenix.Transport.QUIC do
  @moduledoc """
  QUIC transport for low-latency and mobile communication.
  
  Advantages:
  - Reduced connection establishment time
  - Built-in multiplexing
  - Connection migration support
  - Optimized for mobile networks
  
  Use Cases:
  - Mobile agent clients
  - Edge computing scenarios
  - Low-latency requirements
  - Unreliable networks
  """
  
  @behaviour Phoenix.Transport
  
  def send_message(target, message, opts \\ []) do
    connection = get_or_create_connection(target, opts)
    
    # Serialize message for QUIC
    serialized = Phoenix.Message.Serialization.serialize(message, :msgpack)
    
    case QUICEx.send_datagram(connection, serialized) do
      :ok -> {:ok, :sent}
      {:error, reason} -> {:error, reason}
    end
  end
  
  def configure_quic_connection(target, opts \\ []) do
    connection_opts = [
      # Connection settings
      idle_timeout: Keyword.get(opts, :idle_timeout, 30_000),
      keep_alive: Keyword.get(opts, :keep_alive, 15_000),
      
      # Performance settings
      initial_rtt: Keyword.get(opts, :initial_rtt, 100),
      congestion_control: Keyword.get(opts, :congestion_control, :cubic),
      
      # Security settings
      verify_peer: Keyword.get(opts, :verify_peer, true),
      alpn_protocols: ["phoenix-agent/1.0"]
    ]
    
    QUICEx.connect(target, connection_opts)
  end
  
  defp get_or_create_connection(target, opts) do
    case Phoenix.ConnectionPool.get(target) do
      {:ok, connection} -> connection
      {:error, :not_found} -> 
        {:ok, connection} = configure_quic_connection(target, opts)
        Phoenix.ConnectionPool.put(target, connection)
        connection
    end
  end
end

defmodule Phoenix.Patterns.PointToPoint do
  @moduledoc """
  Direct agent-to-agent communication pattern.
  
  Characteristics:
  - Low latency
  - Direct routing
  - Strong delivery guarantees
  - Optional encryption
  """
  
  def send_direct(source_agent, target_agent, message, opts \\ []) do
    # Build direct message with routing metadata
    direct_message = Phoenix.Message.new(message, [
      type: "phoenix.agent.direct.send",
      source: source_agent,
      subject: target_agent,
      delivery: Keyword.get(opts, :delivery, :at_least_once),
      routing: %Phoenix.Routing.Metadata{
        pattern: :point_to_point,
        target: target_agent,
        priority: Keyword.get(opts, :priority, :normal)
      }
    ])
    
    # Route directly to target
    Phoenix.MessageRouter.route_message(direct_message, opts)
  end
  
  def request_response(source_agent, target_agent, request, opts \\ []) do
    timeout = Keyword.get(opts, :timeout, 5000)
    correlation_id = generate_correlation_id()
    
    # Send request with correlation ID
    request_message = Phoenix.Message.new(request, [
      type: "phoenix.agent.request.send",
      source: source_agent,
      subject: target_agent,
      correlation_id: correlation_id
    ])
    
    # Set up response handler
    response_handler = start_response_handler(correlation_id, timeout)
    
    # Send request
    case Phoenix.MessageRouter.route_message(request_message, opts) do
      {:ok, :sent} -> 
        wait_for_response(response_handler, timeout)
      {:error, reason} -> 
        cleanup_response_handler(response_handler)
        {:error, reason}
    end
  end
end

defmodule Phoenix.Patterns.PubSub do
  @moduledoc """
  Event-driven publish-subscribe communication pattern.
  
  Features:
  - Topic-based routing
  - Pattern matching subscriptions
  - Message fanout
  - Backpressure handling
  """
  
  def publish(topic, event, opts \\ []) do
    # Create publication message
    pub_message = Phoenix.Message.new(event, [
      type: "phoenix.pubsub.publish",
      subject: topic,
      routing: %Phoenix.Routing.Metadata{
        pattern: :publish_subscribe,
        topic: topic,
        fanout_strategy: Keyword.get(opts, :fanout, :immediate)
      }
    ])
    
    # Route to all subscribers
    Phoenix.PubSub.publish(topic, pub_message, opts)
  end
  
  def subscribe(agent_id, topic_pattern, opts \\ []) do
    subscription = %Phoenix.PubSub.Subscription{
      subscriber: agent_id,
      topic_pattern: topic_pattern,
      message_filter: Keyword.get(opts, :filter),
      delivery_guarantee: Keyword.get(opts, :delivery, :at_most_once),
      backpressure_strategy: Keyword.get(opts, :backpressure, :drop_oldest)
    }
    
    Phoenix.PubSub.subscribe(subscription)
  end
  
  def unsubscribe(agent_id, topic_pattern) do
    Phoenix.PubSub.unsubscribe(agent_id, topic_pattern)
  end
end

defmodule Phoenix.Patterns.Pipeline do
  @moduledoc """
  Ordered processing pipeline pattern.
  
  Features:
  - Sequential processing stages
  - Ordered message delivery
  - Stage-specific error handling
  - Dynamic pipeline reconfiguration
  """
  
  defstruct [
    :id,
    :stages,
    :error_strategy,
    :backpressure_strategy,
    :monitoring
  ]
  
  def create_pipeline(stages, opts \\ []) do
    pipeline = %__MODULE__{
      id: generate_pipeline_id(),
      stages: stages,
      error_strategy: Keyword.get(opts, :error_strategy, :retry),
      backpressure_strategy: Keyword.get(opts, :backpressure, :buffer),
      monitoring: Keyword.get(opts, :monitoring, true)
    }
    
    # Start pipeline coordinator
    {:ok, coordinator} = Phoenix.Pipeline.Coordinator.start_link(pipeline)
    
    # Register pipeline stages
    Enum.each(stages, fn stage ->
      Phoenix.Pipeline.register_stage(coordinator, stage)
    end)
    
    {:ok, pipeline}
  end
  
  def send_to_pipeline(pipeline_id, message, opts \\ []) do
    pipeline_message = Phoenix.Message.new(message, [
      type: "phoenix.pipeline.process",
      routing: %Phoenix.Routing.Metadata{
        pattern: :pipeline,
        pipeline_id: pipeline_id,
        ordering: :sequential
      }
    ])
    
    Phoenix.Pipeline.send_message(pipeline_id, pipeline_message, opts)
  end
end

defmodule Phoenix.Patterns.Gossip do
  @moduledoc """
  Eventually consistent gossip communication pattern.
  
  Features:
  - Epidemic-style message propagation
  - Redundant transmission for reliability
  - Convergence guarantees
  - Network partition tolerance
  """
  
  defstruct [
    :protocol_version,
    :fanout,
    :round_duration,
    :message_ttl,
    :compression_enabled
  ]
  
  def start_gossip_protocol(opts \\ []) do
    config = %__MODULE__{
      protocol_version: Keyword.get(opts, :version, "1.0"),
      fanout: Keyword.get(opts, :fanout, 3),
      round_duration: Keyword.get(opts, :round_duration, 1000),
      message_ttl: Keyword.get(opts, :message_ttl, 30_000),
      compression_enabled: Keyword.get(opts, :compression, true)
    }
    
    Phoenix.Gossip.Protocol.start_link(config)
  end
  
  def gossip_message(message, opts \\ []) do
    gossip_envelope = %Phoenix.Gossip.Envelope{
      id: generate_gossip_id(),
      payload: message,
      ttl: calculate_ttl(opts),
      hop_count: 0,
      origin_node: Phoenix.Node.local_id(),
      timestamp: Phoenix.VectorClock.now()
    }
    
    Phoenix.Gossip.initiate_gossip(gossip_envelope, opts)
  end
  
  def handle_gossip_reception(envelope) do
    # Check if message already seen
    case Phoenix.Gossip.MessageCache.seen?(envelope.id) do
      true -> 
        # Already processed, ignore
        :ignored
        
      false -> 
        # New message, process and forward
        Phoenix.Gossip.MessageCache.mark_seen(envelope.id)
        process_gossip_message(envelope)
        forward_gossip_message(envelope)
        :processed
    end
  end
end

defmodule Phoenix.Patterns.Consensus do
  @moduledoc """
  Strongly consistent consensus communication pattern.
  
  Features:
  - Raft consensus algorithm
  - Leader election
  - Log replication
  - Strong consistency guarantees
  """
  
  def propose_value(value, opts \\ []) do
    # Create consensus proposal
    proposal = %Phoenix.Consensus.Proposal{
      id: generate_proposal_id(),
      value: value,
      proposer: Phoenix.Node.local_id(),
      timestamp: DateTime.utc_now()
    }
    
    # Submit to Raft cluster
    case Phoenix.Raft.propose(proposal, opts) do
      {:ok, :committed} -> {:ok, proposal.id}
      {:ok, :queued} -> {:ok, :queued, proposal.id}
      {:error, :not_leader} -> {:error, :not_leader}
      {:error, reason} -> {:error, reason}
    end
  end
  
  def read_consensus_value(key, opts \\ []) do
    consistency = Keyword.get(opts, :consistency, :strong)
    
    case consistency do
      :strong -> 
        # Read from current leader
        Phoenix.Raft.read_from_leader(key, opts)
        
      :eventual -> 
        # Read from any replica
        Phoenix.Raft.read_from_replica(key, opts)
        
      :session -> 
        # Read your own writes
        Phoenix.Raft.read_with_session_consistency(key, opts)
    end
  end
end

defmodule Phoenix.Delivery.Guarantee do
  @moduledoc """
  Configurable delivery guarantee system for Phoenix messages.
  
  Guarantees:
  - at_most_once: Fire-and-forget (best performance)
  - at_least_once: Retry until success (reliability)
  - exactly_once: Idempotent delivery (correctness)
  - causal_order: Respects causal dependencies
  - total_order: Global ordering (expensive)
  """
  
  use TypedStruct
  
  typedstruct do
    field :delivery_mode, atom(), default: :at_least_once
    field :timeout, pos_integer(), default: 5000
    field :retry_strategy, atom(), default: :exponential_backoff
    field :max_retries, pos_integer(), default: 3
    field :ordering_requirement, atom(), default: :none
    field :acknowledgment_required, boolean(), default: true
    field :duplicate_detection, boolean(), default: false
  end
  
  def build(delivery_mode, opts \\ []) do
    %__MODULE__{
      delivery_mode: delivery_mode,
      timeout: Keyword.get(opts, :timeout, 5000),
      retry_strategy: Keyword.get(opts, :retry_strategy, :exponential_backoff),
      max_retries: Keyword.get(opts, :max_retries, 3),
      ordering_requirement: Keyword.get(opts, :ordering, :none),
      acknowledgment_required: Keyword.get(opts, :ack_required, true),
      duplicate_detection: Keyword.get(opts, :duplicate_detection, false)
    }
  end
end

defmodule Phoenix.Delivery.AtMostOnce do
  @moduledoc """
  Fire-and-forget delivery for high-performance scenarios.
  
  Characteristics:
  - Lowest latency
  - Highest throughput
  - No delivery guarantees
  - No message ordering
  """
  
  def deliver(target, message, opts \\ []) do
    # Send message without waiting for acknowledgment
    Phoenix.Transport.send_message(target, message, [
      delivery_mode: :fire_and_forget,
      timeout: Keyword.get(opts, :timeout, 1000)
    ])
    
    # Return immediately
    {:ok, :sent}
  end
end

defmodule Phoenix.Delivery.AtLeastOnce do
  @moduledoc """
  Reliable delivery with retry logic.
  
  Characteristics:
  - Guaranteed delivery (if target eventually available)
  - Possible duplicates
  - Configurable retry strategies
  - Exponential backoff with jitter
  """
  
  def deliver(target, message, guarantee) do
    message_id = message.id
    
    # Add delivery tracking
    tracked_message = add_delivery_tracking(message, guarantee)
    
    # Start retry loop
    retry_delivery(target, tracked_message, guarantee, 0)
  end
  
  defp retry_delivery(target, message, guarantee, attempt) do
    case Phoenix.Transport.send_message(target, message) do
      {:ok, :sent} -> 
        # Wait for acknowledgment
        case wait_for_ack(message.id, guarantee.timeout) do
          {:ok, :ack_received} -> 
            {:ok, :delivered}
          {:error, :timeout} -> 
            handle_retry(target, message, guarantee, attempt)
        end
        
      {:error, reason} -> 
        handle_retry(target, message, guarantee, attempt)
    end
  end
  
  defp handle_retry(target, message, guarantee, attempt) do
    if attempt >= guarantee.max_retries do
      {:error, :max_retries_exceeded}
    else
      backoff_time = calculate_backoff(guarantee.retry_strategy, attempt)
      :timer.sleep(backoff_time)
      retry_delivery(target, message, guarantee, attempt + 1)
    end
  end
end

defmodule Phoenix.Delivery.ExactlyOnce do
  @moduledoc """
  Idempotent delivery using distributed coordination.
  
  Characteristics:
  - No duplicates
  - Requires coordination overhead
  - Uses distributed locks or consensus
  - Higher latency
  """
  
  def deliver(target, message, guarantee) do
    delivery_id = generate_delivery_id(message)
    
    # Acquire distributed lock for delivery
    case Phoenix.DistributedLock.acquire(delivery_id, guarantee.timeout) do
      {:ok, lock} -> 
        try do
          perform_exactly_once_delivery(target, message, delivery_id, guarantee)
        after
          Phoenix.DistributedLock.release(lock)
        end
        
      {:error, :lock_timeout} -> 
        {:error, :coordination_timeout}
        
      {:error, :already_delivered} -> 
        {:ok, :already_delivered}
    end
  end
  
  defp perform_exactly_once_delivery(target, message, delivery_id, guarantee) do
    # Check if already delivered
    case Phoenix.DeliveryLog.check_delivery(delivery_id) do
      {:ok, :already_delivered} -> 
        {:ok, :already_delivered}
        
      {:ok, :not_delivered} -> 
        # Perform delivery
        case Phoenix.Transport.send_message(target, message) do
          {:ok, :sent} -> 
            # Record successful delivery
            Phoenix.DeliveryLog.record_delivery(delivery_id)
            {:ok, :delivered}
            
          {:error, reason} -> 
            {:error, reason}
        end
    end
  end
end

defmodule Phoenix.FlowControl do
  @moduledoc """
  Adaptive flow control system preventing message queue overflow.
  
  Strategies:
  - Token bucket: Rate limiting
  - Sliding window: Adaptive throttling
  - Circuit breaker: Failure isolation
  - Backpressure propagation: System-wide coordination
  """
  
  defstruct [
    :strategy,
    :max_queue_size,
    :high_watermark,
    :low_watermark,
    :backpressure_strategy
  ]
  
  def apply_flow_control(target, message, flow_control) do
    current_queue_size = get_queue_size(target)
    
    cond do
      current_queue_size >= flow_control.max_queue_size -> 
        handle_queue_overflow(target, message, flow_control)
        
      current_queue_size >= flow_control.high_watermark -> 
        apply_backpressure(target, message, flow_control)
        
      current_queue_size <= flow_control.low_watermark -> 
        release_backpressure(target)
        send_message(target, message)
        
      true -> 
        send_message(target, message)
    end
  end
  
  defp handle_queue_overflow(target, message, flow_control) do
    case flow_control.backpressure_strategy do
      :drop_oldest -> 
        drop_oldest_message(target)
        send_message(target, message)
        
      :drop_newest -> 
        {:error, :queue_full}
        
      :reject -> 
        {:error, :backpressure_active}
        
      :spill_to_disk -> 
        spill_message_to_disk(target, message)
        
      :redirect -> 
        redirect_to_alternative_target(message, flow_control)
    end
  end
end

defmodule Phoenix.RateLimit.TokenBucket do
  @moduledoc """
  Token bucket rate limiting for message sending.
  
  Features:
  - Configurable bucket size
  - Configurable refill rate
  - Burst allowance
  - Distributed token sharing
  """
  
  defstruct [
    :bucket_id,
    :capacity,
    :current_tokens,
    :refill_rate,
    :last_refill,
    :distributed
  ]
  
  def create_bucket(bucket_id, capacity, refill_rate, opts \\ []) do
    bucket = %__MODULE__{
      bucket_id: bucket_id,
      capacity: capacity,
      current_tokens: capacity,
      refill_rate: refill_rate,
      last_refill: System.monotonic_time(:millisecond),
      distributed: Keyword.get(opts, :distributed, false)
    }
    
    # Register bucket
    Phoenix.RateLimit.Registry.register_bucket(bucket)
    
    {:ok, bucket}
  end
  
  def acquire_tokens(bucket_id, tokens_needed) do
    case Phoenix.RateLimit.Registry.get_bucket(bucket_id) do
      {:ok, bucket} -> 
        # Refill tokens based on elapsed time
        updated_bucket = refill_tokens(bucket)
        
        if updated_bucket.current_tokens >= tokens_needed do
          # Grant tokens
          new_bucket = %{updated_bucket | 
            current_tokens: updated_bucket.current_tokens - tokens_needed
          }
          Phoenix.RateLimit.Registry.update_bucket(bucket_id, new_bucket)
          {:ok, :tokens_acquired}
        else
          # Insufficient tokens
          {:error, :insufficient_tokens, updated_bucket.current_tokens}
        end
        
      {:error, :not_found} -> 
        {:error, :bucket_not_found}
    end
  end
  
  defp refill_tokens(bucket) do
    now = System.monotonic_time(:millisecond)
    elapsed = now - bucket.last_refill
    
    # Calculate tokens to add
    tokens_to_add = (elapsed * bucket.refill_rate) / 1000
    new_token_count = min(
      bucket.capacity, 
      bucket.current_tokens + tokens_to_add
    )
    
    %{bucket | 
      current_tokens: new_token_count,
      last_refill: now
    }
  end
end

defmodule Phoenix.Security do
  @moduledoc """
  Message-level security for Phoenix communication.
  
  Features:
  - Message authentication
  - Payload encryption
  - Digital signatures
  - Key rotation
  """
  
  def secure_message(message, security_context) do
    # Add authentication
    authenticated_message = add_authentication(message, security_context)
    
    # Encrypt payload if required
    encrypted_message = maybe_encrypt_payload(authenticated_message, security_context)
    
    # Add digital signature
    signed_message = add_digital_signature(encrypted_message, security_context)
    
    {:ok, signed_message}
  end
  
  def verify_message(message, security_context) do
    with {:ok, _} <- verify_digital_signature(message, security_context),
         {:ok, decrypted_message} <- maybe_decrypt_payload(message, security_context),
         {:ok, _} <- verify_authentication(decrypted_message, security_context) do
      {:ok, decrypted_message}
    else
      {:error, reason} -> {:error, reason}
    end
  end
  
  defp add_authentication(message, context) do
    auth_header = %{
      agent_id: context.agent_id,
      timestamp: DateTime.utc_now(),
      nonce: generate_nonce(),
      signature: calculate_hmac(message, context.auth_key)
    }
    
    put_in(message.phoenix_security.authentication, auth_header)
  end
  
  defp add_digital_signature(message, context) do
    message_hash = calculate_message_hash(message)
    signature = :crypto.sign(:ecdsa, :sha256, message_hash, context.private_key)
    
    put_in(message.phoenix_security.signature, signature)
  end
end

defmodule Phoenix.Security.Transport do
  @moduledoc """
  Transport-level security configuration.
  
  Features:
  - TLS configuration
  - Certificate management
  - Mutual authentication
  - Perfect forward secrecy
  """
  
  def configure_tls(transport, opts \\ []) do
    tls_config = [
      # Certificate configuration
      certfile: Keyword.get(opts, :certfile, default_cert_path()),
      keyfile: Keyword.get(opts, :keyfile, default_key_path()),
      cacertfile: Keyword.get(opts, :cacertfile, default_ca_path()),
      
      # Security settings
      verify: Keyword.get(opts, :verify, :verify_peer),
      versions: Keyword.get(opts, :versions, [:"tlsv1.3", :"tlsv1.2"]),
      ciphers: Keyword.get(opts, :ciphers, secure_ciphers()),
      
      # Perfect forward secrecy
      honor_cipher_order: true,
      secure_renegotiate: true,
      
      # ALPN for protocol negotiation
      alpn_preferred_protocols: ["phoenix-agent/1.0"]
    ]
    
    Phoenix.Transport.configure_security(transport, tls_config)
  end
  
  defp secure_ciphers do
    [
      # TLS 1.3 cipher suites
      "TLS_AES_256_GCM_SHA384",
      "TLS_CHACHA20_POLY1305_SHA256",
      "TLS_AES_128_GCM_SHA256",
      
      # TLS 1.2 cipher suites (fallback)
      "ECDHE-ECDSA-AES256-GCM-SHA384",
      "ECDHE-RSA-AES256-GCM-SHA384",
      "ECDHE-ECDSA-CHACHA20-POLY1305",
      "ECDHE-RSA-CHACHA20-POLY1305"
    ]
  end
end

defmodule Phoenix.Optimization.Batching do
  @moduledoc """
  Message batching for improved throughput.
  
  Strategies:
  - Time-based batching
  - Size-based batching
  - Priority-aware batching
  - Adaptive batching
  """
  
  defstruct [
    :batch_id,
    :messages,
    :max_batch_size,
    :max_wait_time,
    :created_at,
    :priority_distribution
  ]
  
  def start_batching(target, opts \\ []) do
    batch_config = %__MODULE__{
      batch_id: generate_batch_id(),
      messages: [],
      max_batch_size: Keyword.get(opts, :max_size, 100),
      max_wait_time: Keyword.get(opts, :max_wait, 10),
      created_at: System.monotonic_time(:millisecond),
      priority_distribution: %{}
    }
    
    Phoenix.Batcher.start_batch(target, batch_config)
  end
  
  def add_to_batch(target, message, opts \\ []) do
    case Phoenix.Batcher.add_message(target, message) do
      {:ok, :added} -> 
        {:ok, :batched}
        
      {:ok, :batch_full} -> 
        Phoenix.Batcher.flush_batch(target)
        Phoenix.Batcher.add_message(target, message)
        
      {:error, reason} -> 
        {:error, reason}
    end
  end
  
  def flush_batch(target, reason \\ :manual) do
    case Phoenix.Batcher.get_batch(target) do
      {:ok, batch} when length(batch.messages) > 0 -> 
        # Create batch message
        batch_message = create_batch_message(batch, reason)
        
        # Send batch
        Phoenix.Transport.send_message(target, batch_message)
        
        # Clear batch
        Phoenix.Batcher.clear_batch(target)
        
      {:ok, _empty_batch} -> 
        :ok
        
      {:error, reason} -> 
        {:error, reason}
    end
  end
end

defmodule Phoenix.ConnectionPool do
  @moduledoc """
  Connection pooling for transport efficiency.
  
  Features:
  - Per-target connection pools
  - Connection health monitoring
  - Automatic connection recycling
  - Load balancing across connections
  """
  
  def get_connection(target, opts \\ []) do
    pool_name = build_pool_name(target)
    
    case :poolboy.checkout(pool_name, true, 5000) do
      :full -> 
        {:error, :pool_exhausted}
      connection -> 
        case verify_connection_health(connection) do
          :ok -> {:ok, connection}
          {:error, reason} -> 
            :poolboy.checkin(pool_name, connection)
            create_new_connection(target, opts)
        end
    end
  end
  
  def return_connection(target, connection) do
    pool_name = build_pool_name(target)
    :poolboy.checkin(pool_name, connection)
  end
  
  def start_pool(target, opts \\ []) do
    pool_config = [
      name: {:local, build_pool_name(target)},
      worker_module: Phoenix.Connection.Worker,
      size: Keyword.get(opts, :pool_size, 10),
      max_overflow: Keyword.get(opts, :max_overflow, 5)
    ]
    
    worker_args = [
      target: target,
      connect_opts: Keyword.get(opts, :connect_opts, [])
    ]
    
    :poolboy.start_link(pool_config, worker_args)
  end
end