defmodule ToweropsWeb.Api.AgentController do
  @moduledoc """
  API controller for remote agent communication.

  Provides endpoints for agents to:
  - Fetch polling configuration
  - Submit metrics
  - Send heartbeats
  """

  use ToweropsWeb, :controller

  alias Towerops.Agent.AgentConfig
  alias Towerops.Agent.HeartbeatMetadata
  alias Towerops.Agent.HeartbeatResponse
  alias Towerops.Agent.MetricBatch
  alias Towerops.Agents
  alias Towerops.Snmp

  @doc """
  GET /api/v1/agent/config

  Returns polling configuration for all equipment that should be polled by this agent.
  This includes directly assigned equipment plus equipment that inherits the agent
  from site or organization defaults.

  Supports both JSON and Protocol Buffers response formats based on Accept header.
  """
  def get_config(conn, _params) do
    agent_token = conn.assigns.current_agent_token
    equipment_list = Agents.list_agent_polling_targets(agent_token.id)

    config = %{
      version: "1.0",
      poll_interval_seconds: 60,
      equipment: Enum.map(equipment_list, &build_equipment_config/1)
    }

    # Check Accept header for protobuf support
    case get_req_header(conn, "accept") do
      ["application/x-protobuf" | _] ->
        # Convert to protobuf and send
        proto_config = convert_config_to_proto(config)
        binary = AgentConfig.encode(proto_config)

        conn
        |> put_resp_content_type("application/x-protobuf")
        |> send_resp(200, binary)

      _ ->
        # Default to JSON
        json(conn, config)
    end
  end

  @doc """
  POST /api/v1/agent/metrics

  Accepts a batch of metrics from the agent and processes them asynchronously.
  Supports both JSON (legacy) and Protocol Buffers (efficient).
  """
  def submit_metrics(conn, params) do
    agent_token = conn.assigns.current_agent_token

    metrics =
      case get_req_header(conn, "content-type") do
        ["application/x-protobuf" | _] ->
          # Decode protobuf
          {:ok, body, _conn} = Plug.Conn.read_body(conn)
          batch = MetricBatch.decode(body)
          convert_protobuf_metrics(batch.metrics)

        _ ->
          # JSON format (fallback)
          Map.get(params, "metrics", [])
      end

    _ =
      Task.start(fn ->
        process_metrics(agent_token, metrics)
      end)

    json(conn, %{status: "accepted", received: length(metrics)})
  end

  @doc """
  POST /api/v1/agent/heartbeat

  Updates the agent's last_seen_at timestamp and metadata.
  Supports both JSON and Protocol Buffers formats.
  """
  def heartbeat(conn, params) do
    require Logger

    agent_token = conn.assigns.current_agent_token
    ip = get_client_ip(conn)

    # Log heartbeat request for debugging intermittent 502 errors
    Logger.debug(
      "Heartbeat received from agent",
      agent_token_id: agent_token.id,
      client_ip: ip,
      content_type: List.first(get_req_header(conn, "content-type")),
      request_id: conn.assigns[:request_id]
    )

    # Parse metadata based on content type
    metadata =
      case get_req_header(conn, "content-type") do
        ["application/x-protobuf" | _] ->
          # Decode protobuf
          case Plug.Conn.read_body(conn) do
            {:ok, body, _conn} ->
              try do
                proto_metadata = HeartbeatMetadata.decode(body)

                %{
                  "version" => proto_metadata.version,
                  "hostname" => proto_metadata.hostname,
                  "uptime_seconds" => proto_metadata.uptime_seconds
                }
              rescue
                e ->
                  require Logger

                  Logger.error("Failed to decode protobuf heartbeat: #{inspect(e)}")
                  # Return empty metadata on decode error
                  %{}
              end

            {:error, reason} ->
              require Logger

              Logger.error("Failed to read heartbeat body: #{inspect(reason)}")
              %{}
          end

        _ ->
          # JSON format (fallback)
          %{
            "version" => Map.get(params, "version"),
            "hostname" => Map.get(params, "hostname"),
            "uptime_seconds" => Map.get(params, "uptime_seconds")
          }
      end

    # In test environment, update synchronously to avoid DB ownership issues
    # In production, update asynchronously for better performance
    if Application.get_env(:towerops, :env) == :test do
      Agents.update_agent_token_heartbeat(agent_token.id, ip, metadata)
    else
      Task.start(fn ->
        try do
          Agents.update_agent_token_heartbeat(agent_token.id, ip, metadata)
        rescue
          e ->
            Logger.error(
              "Failed to update agent heartbeat",
              agent_token_id: agent_token.id,
              error: inspect(e),
              stacktrace: Exception.format_stacktrace(__STACKTRACE__)
            )
        end
      end)
    end

    # Return response in appropriate format
    case get_req_header(conn, "content-type") do
      ["application/x-protobuf" | _] ->
        proto_response = %HeartbeatResponse{status: "ok"}
        binary = HeartbeatResponse.encode(proto_response)

        conn
        |> put_resp_content_type("application/x-protobuf")
        |> send_resp(200, binary)

      _ ->
        json(conn, %{status: "ok"})
    end
  end

  # Private helpers

  defp build_equipment_config(equipment) do
    device = equipment.snmp_device

    %{
      id: equipment.id,
      name: equipment.name,
      ip_address: equipment.ip_address,
      snmp: %{
        enabled: equipment.snmp_enabled,
        version: equipment.snmp_version,
        community: equipment.snmp_community,
        port: equipment.snmp_port || 161
      },
      poll_interval_seconds: equipment.check_interval_seconds || 60,
      sensors: build_sensor_config(device),
      interfaces: build_interface_config(device)
    }
  end

  defp build_sensor_config(nil), do: []

  defp build_sensor_config(device) do
    Enum.map(device.sensors, fn sensor ->
      %{
        id: sensor.id,
        type: sensor.sensor_type,
        oid: sensor.sensor_oid,
        divisor: sensor.sensor_divisor,
        unit: sensor.sensor_unit,
        metadata: sensor.metadata
      }
    end)
  end

  defp build_interface_config(nil), do: []

  defp build_interface_config(device) do
    Enum.map(device.interfaces, fn interface ->
      %{
        id: interface.id,
        if_index: interface.if_index,
        if_name: interface.if_name
      }
    end)
  end

  defp process_metrics(_agent_token, metrics) do
    Enum.each(metrics, &process_single_metric/1)
  end

  defp process_single_metric(%{"type" => "sensor_reading"} = m) do
    Snmp.create_sensor_reading(%{
      sensor_id: m["sensor_id"],
      value: m["value"],
      status: m["status"] || "ok",
      checked_at: parse_timestamp(m["timestamp"])
    })
  end

  defp process_single_metric(%{"type" => "interface_stat"} = m) do
    Snmp.create_interface_stat(%{
      interface_id: m["interface_id"],
      if_in_octets: m["if_in_octets"],
      if_out_octets: m["if_out_octets"],
      if_in_errors: m["if_in_errors"],
      if_out_errors: m["if_out_errors"],
      if_in_discards: m["if_in_discards"],
      if_out_discards: m["if_out_discards"],
      checked_at: parse_timestamp(m["timestamp"])
    })
  end

  defp process_single_metric(%{"type" => "neighbor_discovery"} = m) do
    process_neighbor_discovery(m)
  end

  defp process_single_metric(_), do: :ok

  defp process_neighbor_discovery(m) do
    case Snmp.get_interface(m["interface_id"]) do
      nil ->
        :ok

      interface ->
        Snmp.upsert_neighbor(%{
          interface_id: m["interface_id"],
          equipment_id: interface.equipment_id,
          protocol: m["protocol"],
          remote_chassis_id: m["remote_chassis_id"],
          remote_system_name: m["remote_system_name"],
          remote_system_description: m["remote_system_description"],
          remote_platform: m["remote_platform"],
          remote_port_id: m["remote_port_id"],
          remote_port_description: m["remote_port_description"],
          remote_address: m["remote_address"],
          remote_capabilities: m["remote_capabilities"] || [],
          last_discovered_at: parse_timestamp(m["timestamp"])
        })
    end
  end

  defp convert_protobuf_metrics(metrics) do
    metrics
    |> Enum.map(fn metric ->
      case metric.metric_type do
        {:sensor_reading, sr} ->
          %{
            "type" => "sensor_reading",
            "sensor_id" => sr.sensor_id,
            "value" => sr.value,
            "status" => sr.status,
            "timestamp" => sr.timestamp
          }

        {:interface_stat, is} ->
          %{
            "type" => "interface_stat",
            "interface_id" => is.interface_id,
            "if_in_octets" => is.if_in_octets,
            "if_out_octets" => is.if_out_octets,
            "if_in_errors" => is.if_in_errors,
            "if_out_errors" => is.if_out_errors,
            "if_in_discards" => is.if_in_discards,
            "if_out_discards" => is.if_out_discards,
            "timestamp" => is.timestamp
          }

        {:neighbor_discovery, nd} ->
          %{
            "type" => "neighbor_discovery",
            "interface_id" => nd.interface_id,
            "protocol" => nd.protocol,
            "remote_chassis_id" => nd.remote_chassis_id,
            "remote_system_name" => nd.remote_system_name,
            "remote_system_description" => nd.remote_system_description,
            "remote_platform" => nd.remote_platform,
            "remote_port_id" => nd.remote_port_id,
            "remote_port_description" => nd.remote_port_description,
            "remote_address" => nd.remote_address,
            "remote_capabilities" => nd.remote_capabilities,
            "timestamp" => nd.timestamp
          }

        _ ->
          nil
      end
    end)
    |> Enum.reject(&is_nil/1)
  end

  defp parse_timestamp(nil), do: DateTime.truncate(DateTime.utc_now(), :second)

  defp parse_timestamp(ts) when is_integer(ts) do
    ts
    |> DateTime.from_unix!(:second)
    |> DateTime.truncate(:second)
  end

  defp parse_timestamp(ts) when is_binary(ts) do
    case DateTime.from_iso8601(ts) do
      {:ok, dt, _} -> DateTime.truncate(dt, :second)
      _ -> DateTime.truncate(DateTime.utc_now(), :second)
    end
  end

  # Convert internal config format to protobuf
  defp convert_config_to_proto(config) do
    %AgentConfig{
      version: config.version,
      poll_interval_seconds: config.poll_interval_seconds,
      equipment: Enum.map(config.equipment, &convert_equipment_to_proto/1)
    }
  end

  defp convert_equipment_to_proto(eq) do
    %Towerops.Agent.Equipment{
      id: eq.id,
      name: eq.name,
      ip_address: eq.ip_address,
      snmp: convert_snmp_to_proto(eq.snmp),
      poll_interval_seconds: eq.poll_interval_seconds,
      sensors: Enum.map(eq.sensors, &convert_sensor_to_proto/1),
      interfaces: Enum.map(eq.interfaces, &convert_interface_to_proto/1)
    }
  end

  defp convert_snmp_to_proto(snmp) do
    %Towerops.Agent.SnmpConfig{
      enabled: snmp.enabled,
      version: snmp.version,
      community: snmp.community,
      port: snmp.port
    }
  end

  defp convert_sensor_to_proto(sensor) do
    %Towerops.Agent.Sensor{
      id: sensor.id,
      type: sensor.type,
      oid: sensor.oid,
      divisor: sensor.divisor || 0.0,
      unit: sensor.unit || "",
      metadata: convert_metadata_to_proto(sensor.metadata)
    }
  end

  defp convert_interface_to_proto(interface) do
    %Towerops.Agent.Interface{
      id: interface.id,
      if_index: interface.if_index,
      if_name: interface.if_name
    }
  end

  defp convert_metadata_to_proto(nil), do: %{}

  defp convert_metadata_to_proto(metadata) when is_map(metadata) do
    Map.new(metadata, fn {k, v} -> {to_string(k), to_string(v)} end)
  end

  # Get the real client IP, checking forwarded headers first
  defp get_client_ip(conn) do
    # Check X-Forwarded-For header first (set by load balancers/proxies)
    case get_req_header(conn, "x-forwarded-for") do
      [forwarded | _] ->
        # X-Forwarded-For can have multiple IPs (client, proxy1, proxy2...)
        # Take the first one (original client)
        forwarded
        |> String.split(",")
        |> List.first()
        |> String.trim()

      [] ->
        # Fall back to X-Real-IP
        case get_req_header(conn, "x-real-ip") do
          [real_ip | _] ->
            String.trim(real_ip)

          [] ->
            # Fall back to conn.remote_ip
            to_string(:inet_parse.ntoa(conn.remote_ip))
        end
    end
  end
end