defmodule ServerWeb.OverviewLive do
  use ServerWeb, :live_view

  alias Server.{Hosts, Metrics, Status}

  @impl true
  def mount(_params, _session, socket) do
    if connected?(socket), do: Phoenix.PubSub.subscribe(Server.PubSub, "metrics")
    {:ok, assign(socket, :hosts, load_hosts())}
  end

  @impl true
  def handle_info({:metric_inserted, _host_id, _interval}, socket) do
    {:noreply, assign(socket, :hosts, load_hosts())}
  end

  defp load_hosts do
    for host <- Hosts.list_all() do
      sample = Metrics.latest_sample(host.id, "fast")
      payload = sample && sample.payload
      %{host: host, sample: sample, status: Status.compute(host.status, payload)}
    end
  end

  @impl true
  def render(assigns) do
    ~H"""
    <div class="p-6 max-w-6xl mx-auto space-y-6">
      <header class="flex justify-between items-center">
        <div class="space-x-4">
          <h1 class="text-2xl font-bold inline">Proxmox Monitor</h1>
          <.link navigate={~p"/vms"} class="text-sm text-zinc-600 hover:text-zinc-900">VMs</.link>
          <.link navigate={~p"/admin/hosts"} class="text-sm text-zinc-600 hover:text-zinc-900">
            Admin
          </.link>
        </div>
        <.link href={~p"/logout"} method="delete" class="text-sm text-zinc-500">Sign out</.link>
      </header>

      <div class="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-4">
        <div
          :for={entry <- @hosts}
          data-role="host-card"
          data-status={Atom.to_string(entry.status)}
          class={"p-4 rounded-lg border-l-4 bg-white shadow-sm " <> border_class(entry.status)}
        >
          <.link navigate={~p"/hosts/#{entry.host.name}"} class="block space-y-2">
            <div class="flex justify-between items-baseline">
              <span class="font-semibold text-zinc-900">{entry.host.name}</span>
              <span class={"text-xs uppercase tracking-wide " <> text_class(entry.status)}>
                {entry.status}
              </span>
            </div>
            <div class="text-xs text-zinc-500">
              Last seen: {last_seen(entry.host.last_seen_at)}
            </div>
            <div :if={entry.sample} class="text-sm text-zinc-700 space-y-1">
              <div>Load: {format_load(entry.sample.payload)}</div>
              <div>RAM used: {format_mem(entry.sample.payload)}</div>
              <div>Pools: {pool_summary(entry.sample.payload)}</div>
              <div>VMs: {vm_count(entry.sample.payload)}</div>
            </div>
            <div :if={is_nil(entry.sample)} class="text-sm text-zinc-400 italic">
              No samples yet
            </div>
          </.link>
        </div>
      </div>

      <p :if={@hosts == []} class="text-zinc-500">
        No hosts registered yet. Add one via <code>/admin/hosts</code>.
      </p>
    </div>
    """
  end

  defp border_class(:ok), do: "border-green-500"
  defp border_class(:warning), do: "border-yellow-500"
  defp border_class(:critical), do: "border-red-500"
  defp border_class(:offline), do: "border-zinc-400"

  defp text_class(:ok), do: "text-green-600"
  defp text_class(:warning), do: "text-yellow-600"
  defp text_class(:critical), do: "text-red-600"
  defp text_class(:offline), do: "text-zinc-500"

  defp last_seen(nil), do: "never"

  defp last_seen(%DateTime{} = dt) do
    secs = DateTime.diff(DateTime.utc_now(), dt, :second)

    cond do
      secs < 60 -> "#{secs}s ago"
      secs < 3600 -> "#{div(secs, 60)}m ago"
      true -> "#{div(secs, 3600)}h ago"
    end
  end

  defp format_load(payload) do
    case get_in(payload, ["host", "load1"]) do
      nil -> "—"
      l -> :io_lib.format("~.2f", [l]) |> to_string()
    end
  end

  defp format_mem(payload) do
    used = get_in(payload, ["host", "mem_used_bytes"])
    total = get_in(payload, ["host", "mem_total_bytes"])

    case {used, total} do
      {u, t} when is_integer(u) and is_integer(t) and t > 0 ->
        "#{Float.round(u / t * 100, 1)}%"

      _ ->
        "—"
    end
  end

  defp pool_summary(payload) do
    pools = get_in(payload, ["zfs_pools", "pools"]) || []
    total = length(pools)
    bad = Enum.count(pools, &(&1["health"] != "ONLINE"))
    if total == 0, do: "—", else: "#{total - bad}/#{total} ok"
  end

  defp vm_count(payload) do
    vms = get_in(payload, ["vms_runtime", "vms"]) || []
    length(vms)
  end
end