defmodule Integrations.Postgres.Display do
  @moduledoc """
  Dashboard panel for `Integrations.Postgres` (same package).

  Nested under the monitor's own namespace deliberately — the package's
  top-level module name never changes, and this module's name is
  guaranteed distinct from any separately-published standalone display
  package. `Display.BundledDefault` auto-hooks this whenever
  `Integrations.Postgres` starts, the same as if they were still one module.
  """

  use CodeNameRaven.Display, category: :database, size_hint: :full

  @default_port     5432
  @default_database "postgres"

  @impl true
  def display_name, do: "Postgres"

  @impl true
  def compatible_monitors, do: [Integrations.Postgres]

  @impl true
  def render(assigns) do
    window_seconds = assigns.config.display_window_seconds
    cutoff         = DateTime.add(DateTime.utc_now(), -window_seconds, :second)
    samples        = CodeNameRaven.Runtime.recent_samples(assigns.config.id, limit: 120)
    samples        = Enum.filter(samples, &(DateTime.compare(&1.collected_at, cutoff) != :lt))
    local_id       = CodeNameRaven.Runtime.instance_id()
    result         = assigns[:result]
    role           = result && result.role_metrics
    db             = result && result.db_metrics
    bgw            = result && result.bgwriter_metrics

    assigns =
      Map.merge(assigns, %{
        samples:  samples,
        local_id: local_id,
        result:   result,
        role:     role,
        db:       db,
        bgw:      bgw
      })

    ~H"""
    <div class="space-y-4">
      <%!-- Header --%>
      <div class="flex items-start justify-between gap-2">
        <div class="min-w-0">
          <h2 class="text-sm font-semibold text-base-content truncate">
            <%= @config.name || @config.params[:host] || "Postgres" %>
          </h2>
          <p class="text-xs text-base-content/40 font-mono truncate">
            <%= subtitle(@config.params) %>
          </p>
        </div>
        <div class="flex flex-col items-end gap-1 shrink-0">
          <.status_chip status={@status} />
          <.role_badge :if={@result} result={@result} />
        </div>
      </div>

      <%!-- Row 1: Vital signs --%>
      <div class="flex gap-2 flex-wrap">
        <.stat label="Latency"       value={"#{@result && @result.latency_ms || "–"} ms"} />
        <.stat label="Connections"   value={conn_label(@role)} />
        <.stat label="Idle in Tx"    value={"#{(@role && @role.idle_in_transaction) || "–"}"} />
        <.stat label="Lock Waiters"  value={"#{(@role && @role.waiting_on_lock) || "–"}"} />
      </div>

      <%!-- Error --%>
      <p :if={@last_error} class="text-xs text-error font-mono truncate">
        <%= @last_error %>
      </p>

      <%!-- Row 2: Performance charts --%>
      <div class="grid grid-cols-1 sm:grid-cols-2 gap-3">
        <div>
          <p class="text-xs text-base-content/40 mb-1">Transactions / sec</p>
          <CodeNameRaven.MonitorComponents.metric_chart
            id={"chart-#{@config.id}-txrate"}
            samples={@samples}
            local_id={@local_id}
            metric_name="xact_commit_rate"
          />
        </div>
        <div>
          <p class="text-xs text-base-content/40 mb-1">Buffer Cache Hit Ratio</p>
          <CodeNameRaven.MonitorComponents.metric_chart
            id={"chart-#{@config.id}-bhr"}
            samples={@samples}
            local_id={@local_id}
            metric_name="buffer_hit_ratio"
            y_max={1.0}
          />
        </div>
        <div>
          <p class="text-xs text-base-content/40 mb-1">Tuple Throughput (fetched / sec)</p>
          <CodeNameRaven.MonitorComponents.metric_chart
            id={"chart-#{@config.id}-tuples"}
            samples={@samples}
            local_id={@local_id}
            metric_name="tup_fetched_rate"
          />
        </div>
        <div>
          <p class="text-xs text-base-content/40 mb-1">Deadlocks / sec</p>
          <CodeNameRaven.MonitorComponents.metric_chart
            id={"chart-#{@config.id}-deadlocks"}
            samples={@samples}
            local_id={@local_id}
            metric_name="deadlocks_rate"
          />
        </div>
      </div>

      <%!-- Row 3: Operational stats --%>
      <div class="flex gap-2 flex-wrap">
        <.stat label="DB Size"          value={format_bytes(@db && @db.db_size_bytes)} />
        <.stat label="XID Age"          value={format_xid_age(@db && @db.xid_wraparound_age)} />
        <.stat label="Checkpoint Req/s" value={format_rate(@bgw && @bgw.checkpoints_req_rate)} />
        <.stat label="Buffers Backend/s" value={format_rate(@bgw && @bgw.buffers_backend_rate)} />
      </div>

      <%!-- Row 4: Legacy latency chart --%>
      <div>
        <p class="text-xs text-base-content/40 mb-1">Latency</p>
        <CodeNameRaven.MonitorComponents.line_chart
          id={"chart-#{@config.id}-latency"}
          samples={@samples}
          local_id={@local_id}
        />
      </div>

      <%!-- Footer --%>
      <p class="text-xs text-base-content/30">
        Checked <%= CodeNameRaven.Timezone.format_datetime(@last_checked_at, __MODULE__) %>
      </p>
    </div>
    """
  end

  # ---------------------------------------------------------------------------
  # Private components
  # ---------------------------------------------------------------------------

  defp status_chip(%{status: :up} = assigns) do
    ~H"""
    <span class="badge badge-success gap-1 px-3 py-3 text-xs font-semibold">
      <span class="w-1.5 h-1.5 rounded-full bg-current"></span> Up
    </span>
    """
  end

  defp status_chip(%{status: :degraded} = assigns) do
    ~H"""
    <span class="badge badge-warning gap-1 px-3 py-3 text-xs font-semibold">
      <span class="w-1.5 h-1.5 rounded-full bg-current"></span> Degraded
    </span>
    """
  end

  defp status_chip(%{status: :down} = assigns) do
    ~H"""
    <span class="badge badge-error gap-1 px-3 py-3 text-xs font-semibold">
      <span class="w-1.5 h-1.5 rounded-full bg-current"></span> Down
    </span>
    """
  end

  defp status_chip(assigns) do
    ~H"""
    <span class="badge badge-neutral gap-1 px-3 py-3 text-xs font-semibold">
      <span class="w-1.5 h-1.5 rounded-full bg-current"></span> Unknown
    </span>
    """
  end

  defp role_badge(%{result: %{is_replica: false}} = assigns) do
    ~H"""
    <span class="badge badge-success badge-outline text-[10px] px-2 py-2 font-mono font-semibold">
      PRIMARY
    </span>
    """
  end

  defp role_badge(%{result: %{is_replica: true}} = assigns) do
    ~H"""
    <span class="badge badge-warning badge-outline text-[10px] px-2 py-2 font-mono font-semibold">
      REPLICA
    </span>
    """
  end

  defp role_badge(assigns), do: ~H""

  defp stat(assigns) do
    ~H"""
    <div class="bg-base-200 rounded-lg px-3 py-2 flex-1 text-center min-w-[80px]">
      <p class="text-xs text-base-content/40"><%= @label %></p>
      <p class="text-sm font-mono font-semibold text-base-content"><%= @value %></p>
    </div>
    """
  end

  # ---------------------------------------------------------------------------
  # Private helpers
  # ---------------------------------------------------------------------------

  defp subtitle(params) do
    host = params[:host] || params["host"] || "unknown"
    port = params[:port] || params["port"] || @default_port
    db   = params[:database] || params["database"] || @default_database
    "#{host}:#{port}/#{db}"
  end

  defp conn_label(nil), do: "–"
  defp conn_label(%{active_connections: a, max_connections: m}), do: "#{a}/#{m}"
  defp conn_label(_), do: "–"

  defp format_bytes(nil), do: "–"
  defp format_bytes(b) when b >= 1_073_741_824, do: "#{Float.round(b / 1_073_741_824, 1)} GB"
  defp format_bytes(b) when b >= 1_048_576,     do: "#{Float.round(b / 1_048_576, 1)} MB"
  defp format_bytes(b) when b >= 1_024,         do: "#{Float.round(b / 1_024, 1)} KB"
  defp format_bytes(b),                         do: "#{b} B"

  defp format_xid_age(nil), do: "–"
  defp format_xid_age(age) when age >= 1_000_000_000, do: "#{Float.round(age / 1.0e9, 2)}B"
  defp format_xid_age(age) when age >= 1_000_000,     do: "#{Float.round(age / 1.0e6, 1)}M"
  defp format_xid_age(age),                           do: "#{age}"

  defp format_rate(nil), do: "–"
  defp format_rate(r) when is_float(r), do: "#{Float.round(r, 2)}/s"
  defp format_rate(r),                  do: "#{r}/s"
end