defmodule ServerWeb.HostDetailLive do
  use ServerWeb, :live_view

  alias Server.{Metrics, Repo, Schema.Host}

  @impl true
  def mount(%{"name" => name}, _session, socket) do
    case Repo.get_by(Host, name: name) do
      nil ->
        {:ok,
         socket
         |> put_flash(:error, "Host not found")
         |> push_navigate(to: ~p"/")}

      %Host{} = host ->
        if connected?(socket),
          do: Phoenix.PubSub.subscribe(Server.PubSub, "metrics:#{host.id}")

        {:ok, socket |> assign(host: host, page_title: host.name) |> load_samples()}
    end
  end

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

  defp load_samples(socket) do
    host_id = socket.assigns.host.id

    assign(socket,
      fast: Metrics.latest_sample(host_id, "fast"),
      medium: Metrics.latest_sample(host_id, "medium"),
      slow: Metrics.latest_sample(host_id, "slow")
    )
  end

  @impl true
  def render(assigns) do
    ~H"""
    <ServerWeb.DashboardNav.nav active={:overview} />

    <div class="page">
      <div class="pagehead">
        <div>
          <h1>{@host.name}</h1>
          <div class="sub">
            {sys_line(@slow)} · uptime {uptime(@fast)} · last seen {last_seen(@host.last_seen_at)}
          </div>
        </div>
        <span class="badge" data-status={@host.status}>{@host.status}</span>
      </div>

      <div class="panel">
        <header><span>Host</span></header>
        <div class="body">
          <dl class="kv">
            <dt>load (1/5/15)</dt><dd>{host_load(@fast)}</dd>
            <dt>memory</dt><dd>{host_mem(@fast)}</dd>
            <dt>agent</dt><dd>{@host.agent_version || "—"}</dd>
          </dl>
        </div>
      </div>

      <div class="panel">
        <header><span>ZFS pools</span><span class="mono">{length(pools(@fast))}</span></header>
        <div class="body tight">
          <div :if={pools(@fast) == []} class="empty">No data.</div>
          <div :for={pool <- pools(@fast)} class="pool-block">
            <div class="head">
              <div>
                <span class="mono" style="color: var(--fg-bright); font-weight: 600;">{pool["name"]}</span>
                <span class="layout">{pool_layout(pool)}</span>
              </div>
              <span class="badge" style={pool_badge_style(pool["health"])}>{pool["health"]}</span>
            </div>

            <div class="capbar" data-level={capbar_level(pool["capacity_percent"])}>
              <span style={"width: #{capbar_width(pool["capacity_percent"])}%"}></span>
            </div>

            <div class="sizes">
              used {format_bytes(pool["allocated_bytes"] || 0)} ·
              free {format_bytes(pool["free_bytes"] || 0)} ·
              total {format_bytes(pool["size_bytes"] || 0)}
              <span class="muted">({pool["capacity_percent"] || 0}%)</span>
            </div>

            <div class="details">
              frag {pool["fragmentation_percent"] || 0}% ·
              err {pool["error_count"] || 0} ·
              vdevs {pool["vdev_count"] || 0} (deg {pool["degraded_vdev_count"] || 0}) ·
              {pool_scrub_line(pool)}
            </div>

            <div :for={v <- degraded_vdevs(pool)} class="callout err" style="margin-top: 0.4rem;">
              {v["name"]} {v["state"]} · r={v["read_errors"]} w={v["write_errors"]} cksum={v["checksum_errors"]}
            </div>
          </div>
        </div>
      </div>

      <div class="panel">
        <header><span>Snapshots</span><span class="mono">{length(datasets(@medium))}</span></header>
        <div class="body tight">
          <table class="tbl" :if={datasets(@medium) != []}>
            <thead>
              <tr><th>Dataset</th><th>Count</th><th>Oldest</th><th>Newest</th></tr>
            </thead>
            <tbody>
              <tr :for={ds <- datasets(@medium)}>
                <td class="mono">{ds["name"]}</td>
                <td class="num">{ds["snapshot_count"]}</td>
                <td class="mono">{unix_to_date(ds["oldest_snapshot_unix"])}</td>
                <td class="mono">{unix_to_date(ds["newest_snapshot_unix"])}</td>
              </tr>
            </tbody>
          </table>
          <div :if={datasets(@medium) == []} class="empty">No data.</div>
        </div>
      </div>

      <div class="panel">
        <header><span>Storage</span><span class="mono">{length(storages(@fast))}</span></header>
        <div class="body tight">
          <table class="tbl" :if={storages(@fast) != []}>
            <thead>
              <tr><th>Name</th><th>Type</th><th>Usage</th></tr>
            </thead>
            <tbody>
              <tr :for={s <- storages(@fast)}>
                <td class="mono">{s["name"]}</td>
                <td>{s["type"]}</td>
                <td class="mono">{storage_usage(s)}</td>
              </tr>
            </tbody>
          </table>
          <div :if={storages(@fast) == []} class="empty">No data.</div>
        </div>
      </div>

      <div class="panel">
        <header><span>VMs / LXCs</span><span class="mono">{length(vms(@fast))}</span></header>
        <div class="body tight">
          <table class="tbl" :if={vms(@fast) != []}>
            <thead>
              <tr><th>VMID</th><th>Name</th><th>Type</th><th>Status</th></tr>
            </thead>
            <tbody>
              <tr :for={vm <- vms(@fast)}>
                <td class="num">{vm["vmid"]}</td>
                <td class="mono">{vm["name"]}</td>
                <td>{vm["type"]}</td>
                <td><span class="badge" data-status={vm_status(vm)}>{vm["status"]}</span></td>
              </tr>
            </tbody>
          </table>
          <div :if={vms(@fast) == []} class="empty">No data.</div>
        </div>
      </div>
    </div>
    """
  end

  defp vm_status(%{"status" => "running"}), do: "ok"
  defp vm_status(%{"status" => "stopped"}), do: "offline"
  defp vm_status(_), do: "warning"

  defp pool_badge_style("ONLINE"), do: "color: var(--ok);"
  defp pool_badge_style(_), do: "color: var(--crit);"

  defp pool_layout(pool) do
    case pool["pool_type"] do
      nil -> "—"
      "" -> "—"
      t -> t
    end
  end

  defp capbar_level(cap) when is_number(cap) and cap >= 90, do: "crit"
  defp capbar_level(cap) when is_number(cap) and cap >= 80, do: "warn"
  defp capbar_level(_), do: "ok"

  defp capbar_width(cap) when is_number(cap), do: cap |> max(0) |> min(100)
  defp capbar_width(_), do: 0

  defp pool_scrub_line(%{"scan_state" => "SCANNING"} = pool) do
    "#{scan_verb(pool)} scanning"
  end

  defp pool_scrub_line(%{"last_scrub_end" => end_time} = pool)
       when is_binary(end_time) and end_time != "" do
    prefix =
      case pool["scan_state"] do
        "FINISHED" -> "#{scan_verb(pool)} finished "
        _ -> "#{scan_verb(pool)} "
      end

    prefix <> end_time
  end

  defp pool_scrub_line(_), do: "scrub never"

  defp scan_verb(%{"scan_function" => "resilver"}), do: "resilver"
  defp scan_verb(_), do: "scrub"

  defp degraded_vdevs(pool) do
    (pool["vdevs"] || [])
    |> Enum.filter(fn v -> Map.get(v, "state") not in [nil, "ONLINE"] end)
  end

  defp sys_line(nil), do: "—"
  defp sys_line(%{payload: p}) do
    get_in(p, ["system_info", "pve_version"]) || "—"
  end

  defp uptime(nil), do: "—"
  defp uptime(%{payload: p}) do
    case get_in(p, ["host", "uptime_seconds"]) do
      nil -> "—"
      s when is_integer(s) -> "#{div(s, 86_400)}d"
      _ -> "—"
    end
  end

  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 host_load(nil), do: "—"
  defp host_load(%{payload: p}) do
    l1 = get_in(p, ["host", "load1"]) || "—"
    l5 = get_in(p, ["host", "load5"]) || "—"
    l15 = get_in(p, ["host", "load15"]) || "—"
    "#{l1} / #{l5} / #{l15}"
  end

  defp host_mem(nil), do: "—"
  defp host_mem(%{payload: p}) do
    used = get_in(p, ["host", "mem_used_bytes"])
    total = get_in(p, ["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)}% (#{format_bytes(u)} / #{format_bytes(t)})"
      _ -> "—"
    end
  end

  defp pools(nil), do: []
  defp pools(%{payload: p}), do: get_in(p, ["zfs_pools", "pools"]) || []

  defp datasets(nil), do: []
  defp datasets(%{payload: p}), do: get_in(p, ["zfs_datasets", "datasets"]) || []

  defp storages(nil), do: []
  defp storages(%{payload: p}), do: get_in(p, ["storage", "storages"]) || []

  defp vms(nil), do: []
  defp vms(%{payload: p}), do: get_in(p, ["vms_runtime", "vms"]) || []

  defp storage_usage(%{"used_bytes" => u, "total_bytes" => t})
       when is_integer(u) and is_integer(t) and t > 0 do
    "#{Float.round(u / t * 100, 1)}% (#{format_bytes(u)} / #{format_bytes(t)})"
  end

  defp storage_usage(_), do: "—"

  defp unix_to_date(nil), do: "—"
  defp unix_to_date(unix) when is_integer(unix) do
    case DateTime.from_unix(unix) do
      {:ok, dt} -> Calendar.strftime(dt, "%Y-%m-%d")
      _ -> "—"
    end
  end

  defp format_bytes(n) when is_integer(n) do
    units = ["B", "KB", "MB", "GB", "TB"]

    {val, unit} =
      Enum.reduce_while(units, {n * 1.0, "B"}, fn u, {v, _} ->
        if v < 1024, do: {:halt, {v, u}}, else: {:cont, {v / 1024, u}}
      end)

    "#{Float.round(val, 1)} #{unit}"
  end
end