defmodule Integrations.Ping do
  @moduledoc """
  ICMP ping monitor.

  Sends a configurable number of ICMP echo requests and reports packet loss
  and round-trip time. Uses the system `ping` binary (which carries the
  setuid bit allowing unprivileged use) rather than raw sockets, which would
  require `CAP_NET_RAW` inside a container.

  Collection only — see `Integrations.Ping.Display` (same package) for the
  dashboard panel. `Display.BundledDefault` auto-hooks it whenever this
  monitor starts, same as a single-module package would; a release without
  `raven_web` simply never compiles the display half and runs this monitor
  headless.

  ## Params

    * `:host`                    — Hostname or IP address to ping. Required.
    * `:count`                   — Number of packets to send. Defaults to `4`.
    * `:timeout_ms`              — Wait timeout per packet in milliseconds.
                                   Defaults to `1000`.
    * `:packet_loss_degraded_pct`— Packet loss percentage that triggers
                                   `:degraded`. Defaults to `25`.
    * `:packet_loss_down_pct`    — Packet loss percentage that triggers
                                   `:down`. Defaults to `100`.
    * `:latency_degraded_ms`     — Average RTT that triggers `:degraded`.
                                   Defaults to `200`.

  ## Health signal

    * `:up`       — All packets received; RTT within threshold.
    * `:degraded` — Partial loss or RTT above `:latency_degraded_ms`.
    * `:down`     — All packets lost or host unreachable.
  """

  use CodeNameRaven.Monitor

  @default_count               4
  @default_timeout_ms          1_000
  @default_degraded_loss_pct   25
  @default_down_loss_pct       100
  @default_latency_degraded_ms 200

  @impl true
  def params_template do
    %{host: "", count: "4", timeout_ms: "1000"}
  end

  @impl true
  def params_schema do
    [
      host:                     [type: :string,          required: true, doc: "Hostname or IP address to ping"],
      count:                    [type: :non_neg_integer, default: 4,     doc: "Number of ICMP packets to send"],
      timeout_ms:               [type: :non_neg_integer, default: 1_000, doc: "Per-packet timeout in milliseconds"],
      packet_loss_degraded_pct: [type: :non_neg_integer, default: 25,    doc: "Packet loss % threshold for degraded"],
      packet_loss_down_pct:     [type: :non_neg_integer, default: 100,   doc: "Packet loss % threshold for down"],
      latency_degraded_ms:      [type: :non_neg_integer, default: 200,   doc: "Average RTT threshold for degraded"]
    ]
  end

  @impl true
  def target_uri(params) do
    case get_param(params, :host) do
      nil  -> :none
      host -> {:ok, "icmp://#{host}"}
    end
  end

  @impl true
  def identity_params(params), do: %{host: get_param(params, :host)}

  # ---------------------------------------------------------------------------
  # Collect
  # ---------------------------------------------------------------------------

  @impl true
  def collect(params, state) do
    host = get_param(params, :host)

    if is_nil(host) do
      {:error, "missing required param :host", state}
    else
      count      = parse_int(get_param(params, :count), @default_count)
      timeout_ms = parse_int(get_param(params, :timeout_ms), @default_timeout_ms)
      timeout_s  = max(1, div(timeout_ms, 1_000))

      case :os.find_executable('ping') do
        false ->
          {:error, "ping binary not found; install iputils-ping on the host system", state}
        _ ->
          {os_type, _} = :os.type()
          args = build_args(os_type, host, count, timeout_s)
          run_ping(args, os_type, state)
      end
    end
  end

  defp run_ping(args, os_type, state) do
    case System.cmd("ping", args, stderr_to_stdout: true) do
      {output, 0} ->
        {:ok, parse_output(output, os_type), state}

      {output, _exit_code} ->
        result = parse_output(output, os_type)

        if result.packets_transmitted > 0 do
          {:ok, result, state}
        else
          {:error, String.trim(output), state}
        end
    end
  end

  # ---------------------------------------------------------------------------
  # Healthy?
  # ---------------------------------------------------------------------------

  @impl true
  def healthy?(result) do
    degraded_pct = result[:loss_degraded_pct] || @default_degraded_loss_pct
    down_pct     = result[:loss_down_pct]     || @default_down_loss_pct
    lat_deg_ms   = result[:latency_degraded_ms] || @default_latency_degraded_ms

    loss = result.packet_loss_pct

    cond do
      loss >= down_pct                                     -> :down
      loss >= degraded_pct                                 -> :degraded
      is_number(result.avg_rtt_ms) and
        result.avg_rtt_ms >= lat_deg_ms                   -> :degraded
      true                                                 -> :up
    end
  end

  # ---------------------------------------------------------------------------
  # Metrics
  # ---------------------------------------------------------------------------

  @impl true
  def metrics(result) do
    %{
      packet_loss_pct:      result.packet_loss_pct,
      packets_transmitted:  result.packets_transmitted,
      packets_received:     result.packets_received
    }
    |> maybe_put(:avg_rtt_ms, result.avg_rtt_ms)
    |> maybe_put(:min_rtt_ms, result.min_rtt_ms)
    |> maybe_put(:max_rtt_ms, result.max_rtt_ms)
  end

  # ---------------------------------------------------------------------------
  # Platform-specific arg builders
  # ---------------------------------------------------------------------------

  # Linux: -c count -W timeout_per_packet_seconds
  defp build_args(:unix, host, count, timeout_s),
    do: ["-c", to_string(count), "-W", to_string(timeout_s), host]

  # macOS: -c count -W timeout_ms (milliseconds on macOS)
  defp build_args(:win32, host, count, _timeout_s),
    do: ["-n", to_string(count), host]

  # Fallback (BSD / macOS share the :unix os_type; detect via uname if needed)
  defp build_args(_, host, count, timeout_s),
    do: ["-c", to_string(count), "-W", to_string(timeout_s), host]

  # ---------------------------------------------------------------------------
  # Output parsers
  # ---------------------------------------------------------------------------

  defp parse_output(output, _os_type) do
    {transmitted, received, loss_pct} = parse_packet_stats(output)
    {min_rtt, avg_rtt, max_rtt}       = parse_rtt_stats(output)

    %{
      packets_transmitted: transmitted,
      packets_received:    received,
      packet_loss_pct:     loss_pct,
      min_rtt_ms:          min_rtt,
      avg_rtt_ms:          avg_rtt,
      max_rtt_ms:          max_rtt
    }
  end

  # iputils:  "4 packets transmitted, 4 received, 0% packet loss"
  # BusyBox:  "4 packets transmitted, 4 packets received, 0% packet loss"
  #           (the extra "packets" before "received" — everything else
  #           identical — is why this used to fall through to the 0/0/100
  #           catch-all below on every BusyBox-based container image,
  #           reporting false 100% loss regardless of real connectivity)
  defp parse_packet_stats(output) do
    with [[_, tx, rx, loss]] <-
           Regex.scan(~r/(\d+) packets transmitted.*?(\d+)(?: packets)? received.*?(\d+)% packet loss/, output) do
      {String.to_integer(tx), String.to_integer(rx), String.to_integer(loss)}
    else
      _ ->
        # Windows: "Sent = 4, Received = 4, Lost = 0 (0% loss)"
        with [[_, tx, rx, loss]] <-
               Regex.scan(~r/Sent\s*=\s*(\d+),\s*Received\s*=\s*(\d+),\s*Lost\s*=\s*\d+\s*\((\d+)%/, output) do
          {String.to_integer(tx), String.to_integer(rx), String.to_integer(loss)}
        else
          _ -> {0, 0, 100}
        end
    end
  end

  # "rtt min/avg/max/mdev = 0.123/0.456/0.789/0.100 ms"
  defp parse_rtt_stats(output) do
    with [[_, min, avg, max, _]] <-
           Regex.scan(~r|rtt min/avg/max/\w+ = ([\d.]+)/([\d.]+)/([\d.]+)/([\d.]+) ms|, output) do
      {
        parse_float(min),
        parse_float(avg),
        parse_float(max)
      }
    else
      # macOS: "round-trip min/avg/max/stddev = 0.123/0.456/0.789/0.100 ms"
      _ ->
        with [[_, min, avg, max, _]] <-
               Regex.scan(~r|round-trip min/avg/max/\w+ = ([\d.]+)/([\d.]+)/([\d.]+)/([\d.]+) ms|, output) do
          {parse_float(min), parse_float(avg), parse_float(max)}
        else
          # BusyBox: "round-trip min/avg/max = 0.123/0.456/0.789 ms" — only
          # three values, no mdev/stddev column at all (not just a
          # differently-named one, like the macOS case above).
          _ ->
            with [[_, min, avg, max]] <-
                   Regex.scan(~r|round-trip min/avg/max = ([\d.]+)/([\d.]+)/([\d.]+) ms|, output) do
              {parse_float(min), parse_float(avg), parse_float(max)}
            else
              # Windows: "Minimum = 1ms, Maximum = 2ms, Average = 1ms"
              _ ->
                with [[_, min]] <- Regex.scan(~r/Minimum\s*=\s*(\d+)ms/, output),
                     [[_, avg]] <- Regex.scan(~r/Average\s*=\s*(\d+)ms/, output),
                     [[_, max]] <- Regex.scan(~r/Maximum\s*=\s*(\d+)ms/, output) do
                  {parse_float(min), parse_float(avg), parse_float(max)}
                else
                  _ -> {nil, nil, nil}
                end
            end
        end
    end
  end

  # ---------------------------------------------------------------------------
  # Helpers
  # ---------------------------------------------------------------------------

  defp get_param(params, key) when is_atom(key) do
    v = params[key] || params[to_string(key)]
    if is_binary(v) and String.trim(v) == "", do: nil, else: v
  end

  defp maybe_put(map, _key, nil), do: map
  defp maybe_put(map, key, val),  do: Map.put(map, key, val)

  defp parse_int(nil, default), do: default
  defp parse_int(v, _) when is_integer(v), do: v
  defp parse_int(v, default) when is_binary(v) do
    case Integer.parse(v) do
      {n, _} -> n
      :error -> default
    end
  end
  defp parse_int(_, default), do: default

  defp parse_float(s) when is_binary(s) do
    case Float.parse(s) do
      {f, _} -> Float.round(f, 3)
      :error -> nil
    end
  end
  defp parse_float(_), do: nil
end