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.MetricBatch
  alias Towerops.Agents
  alias Towerops.Snmp

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

  Returns polling configuration for all equipment assigned to the authenticated agent.
  """
  def get_config(conn, _params) do
    agent_token = conn.assigns.current_agent_token
    equipment_list = Agents.list_agent_equipment(agent_token.id)

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

    json(conn, config)
  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.
  """
  def heartbeat(conn, params) do
    agent_token = conn.assigns.current_agent_token
    ip = to_string(:inet_parse.ntoa(conn.remote_ip))

    metadata = %{
      "version" => Map.get(params, "version"),
      "hostname" => Map.get(params, "hostname"),
      "uptime_seconds" => Map.get(params, "uptime_seconds")
    }

    # Update synchronously in the heartbeat endpoint
    Agents.update_agent_token_heartbeat(agent_token.id, ip, metadata)

    json(conn, %{status: "ok"})
  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, fn metric ->
      case metric do
        %{"type" => "sensor_reading"} = m ->
          Snmp.create_sensor_reading(%{
            sensor_id: m["sensor_id"],
            value: m["value"],
            status: m["status"] || "ok",
            checked_at: parse_timestamp(m["timestamp"])
          })

        %{"type" => "interface_stat"} = m ->
          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"])
          })

        _ ->
          :ok
      end
    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
          }

        _ ->
          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
end