defmodule CodeNameRaven.MonitorComponents do
  @moduledoc """
  The standard component library for monitor panels.

  Monitor authors may use these components to build custom renders that fit
  naturally into the Raven dashboard, or ignore them entirely and write
  whatever HEEx they want.

  The `default_render/1` function is the render implementation used by any
  monitor that does not override `render/1`.

  ## Platform features available in renders

  The following are supported platform features that integrations can opt
  into displaying. All data is available in the assigns passed to `render/1`.

  ### Silence (`@config.silenced_until`)

  When a monitor is silenced, `@config.silenced_until` holds a `DateTime`
  in the future. The platform automatically suppresses warning logs and shows
  a "SILENCED" badge on the card, but your render can also surface this state.
  Use `silence_badge/1` to show a compact inline indicator:

      <.silence_badge silenced_until={@config.silenced_until} />

  Silence is managed from the card flip side — no integration code required.
  """

  use Phoenix.Component

  @doc """
  The default panel render used when a monitor does not provide its own.

  Shows status, last check time, last error, and the collect result as a
  key-value table when one is available.
  """
  def default_render(assigns) do
    ~H"""
    <div class="space-y-2">
      <div class="flex items-center gap-2">
        <.status_chip status={@status} />
        <.check_time checked_at={@last_checked_at} />
      </div>
      <.error_message message={@last_error} />
      <.result_table :if={is_map(@result) and map_size(@result) > 0} result={@result} />
    </div>
    """
  end

  attr :status, :atom, values: [:up, :degraded, :down, :unknown], required: true

  @doc """
  A status badge showing the monitor's current health.

  Renders a coloured badge with an indicator dot and label for
  `:up` (green), `:degraded` (yellow), `:down` (red), or `:unknown` (grey).
  """
  def status_badge(%{status: :up} = assigns) do
    ~H"""
    <span class="badge badge-success gap-1">
      <span class="w-2 h-2 rounded-full bg-success-content"></span> Up
    </span>
    """
  end

  def status_badge(%{status: :degraded} = assigns) do
    ~H"""
    <span class="badge badge-warning gap-1">
      <span class="w-2 h-2 rounded-full bg-warning-content"></span> Degraded
    </span>
    """
  end

  def status_badge(%{status: :down} = assigns) do
    ~H"""
    <span class="badge badge-error gap-1">
      <span class="w-2 h-2 rounded-full bg-error-content"></span> Down
    </span>
    """
  end

  def status_badge(%{status: :unknown} = assigns) do
    ~H"""
    <span class="badge badge-neutral gap-1">
      <span class="w-2 h-2 rounded-full bg-neutral-content"></span> Unknown
    </span>
    """
  end

  # Matches status_chip/1's own fallback — any status outside the declared
  # four renders as "Unknown" instead of a FunctionClauseError.
  def status_badge(assigns) do
    ~H"""
    <span class="badge badge-neutral gap-1">
      <span class="w-2 h-2 rounded-full bg-neutral-content"></span> Unknown
    </span>
    """
  end

  attr :silenced_until, :any, default: nil

  @doc """
  A compact badge shown when the monitor's failure warnings are silenced.

  Renders nothing when `silenced_until` is `nil` or in the past, so it is
  safe to include unconditionally in any render:

      <.silence_badge silenced_until={@config.silenced_until} />

  The platform already shows a card-level "SILENCED" overlay automatically.
  Use this component when you want the silence state visible inside your
  integration's own content area — for example, next to the status badge.
  """
  def silence_badge(%{silenced_until: nil} = assigns) do
    ~H""
  end

  def silence_badge(assigns) do
    if DateTime.compare(assigns.silenced_until, DateTime.utc_now()) == :gt do
      ~H"""
      <span class="badge badge-warning badge-sm gap-1 font-semibold"
            title={"Silenced until #{Calendar.strftime(@silenced_until, "%b %-d %H:%M UTC")}"}>
        Silenced
      </span>
      """
    else
      ~H""
    end
  end

  attr :checked_at, :any, default: nil

  @doc """
  Displays the monitor's last check time in a human-readable `YYYY-MM-DD HH:MM:%S UTC` format.

  Shows "Not yet checked" when passed `nil`.
  """
  def check_time(%{checked_at: nil} = assigns) do
    ~H"""
    <p class="text-xs text-base-content/50">Not yet checked</p>
    """
  end

  def check_time(assigns) do
    ~H"""
    <p class="text-xs text-base-content/50">
      Last checked: {Calendar.strftime(@checked_at, "%Y-%m-%d %H:%M:%S UTC")}
    </p>
    """
  end

  attr :message, :string, default: nil

  @doc """
  Displays the monitor's last error message in a red monospace font, if present.

  Shows nothing when `nil`. Hover for full message text on truncation.
  """
  def error_message(%{message: nil} = assigns), do: ~H""

  def error_message(assigns) do
    ~H"""
    <p class="text-xs text-error font-mono truncate" title={@message}>
      {@message}
    </p>
    """
  end

  attr :status, :atom, values: [:up, :degraded, :down, :unknown], required: true

  @doc """
  A compact status chip with a coloured dot and label.

  Suitable for panel headers and inline status indicators. Uses badge styling
  matched to the status severity.
  """
  def status_chip(assigns) do
    {label, cls} =
      case assigns.status do
        :up       -> {"Up",      "badge-success"}
        :degraded -> {"Degraded", "badge-warning"}
        :down     -> {"Down",    "badge-error"}
        _         -> {"Unknown", "badge-neutral"}
      end

    assigns = assign(assigns, label: label, cls: cls)

    ~H"""
    <span class={"badge #{@cls} gap-1 px-3 py-3 text-xs font-semibold shrink-0"}>
      <span class="w-1.5 h-1.5 rounded-full bg-current"></span>{@label}
    </span>
    """
  end

  attr :label, :string, required: true
  attr :value, :string, required: true

  @doc """
  A single metric stat block — label above, value below in monospace.

  Use within a flex row to display a small set of key measurements side
  by side (e.g. status code and latency).
  """
  def stat(assigns) do
    ~H"""
    <div class="bg-base-300 rounded-lg px-3 py-2 flex-1 text-center">
      <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

  attr :result, :map, required: true

  @doc """
  Renders a collect result map as a compact key-value table.

  Used by `default_render/1` to show raw result data for integrations that
  have not defined a custom panel. Keys are displayed in insertion order.
  """
  def result_table(assigns) do
    ~H"""
    <table class="w-full text-xs font-mono">
      <tbody>
        <tr :for={{k, v} <- @result} class="border-t border-base-300 first:border-0">
          <td class="py-0.5 pr-3 text-base-content/40 whitespace-nowrap">{k}</td>
          <td class="py-0.5 text-base-content/80 break-all">{inspect(v)}</td>
        </tr>
      </tbody>
    </table>
    """
  end

  attr :id, :string, required: true
  attr :samples, :list, required: true
  attr :local_id, :any, required: true

  @doc """
  Server-rendered SVG latency chart for monitor panels.

  Thin wrapper around `metric_chart/1` that plots the `latency_ms` metric.
  Reads from `sample.metrics["latency_ms"]` when present, falling back to
  `sample.latency_ms` for older samples that pre-date the JSONB column.
  """
  def line_chart(assigns) do
    assigns = assign(assigns, metric_name: "latency_ms", y_max: nil, y_min: 0.0)
    metric_chart(assigns)
  end

  attr :id, :string, required: true
  attr :samples, :list, required: true
  attr :local_id, :any, required: true
  attr :metric_name, :string, required: true
  attr :y_max, :float, default: nil
  attr :y_min, :float, default: 0.0

  @doc """
  Server-rendered SVG chart for any metric stored in `sample.metrics`.

  Reads `sample.metrics[metric_name]` (string key, as stored by JSONB) from
  each sample. For `metric_name: "latency_ms"` falls back to
  `sample.latency_ms` when the JSONB field is absent, so HTTP's latency
  chart keeps working against pre-JSONB samples.

  Pass `y_max` to pin the y-axis ceiling (e.g. `1.0` for a 0–1 ratio chart).
  Pass `y_min` to pin the floor instead of the default `0.0` — useful for
  zooming into a metric whose meaningful range sits well above zero (e.g.
  a healthy buffer-hit-ratio that only ever dips between 0.9 and 1.0).
  Renders a placeholder when fewer than 2 samples have non-nil values.
  """
  def metric_chart(assigns) do
    vw = 600
    vh = 200
    pl = 44
    pr = 8
    pt = 10
    pb = 24
    pw     = vw - pl - pr
    ph     = vh - pt - pb
    bottom = pt + ph

    metric_name = assigns.metric_name

    by_instance = Enum.group_by(assigns.samples, & &1.instance_id)

    all_values =
      assigns.samples
      |> Enum.map(&mc_value(&1, metric_name))
      |> Enum.filter(&is_number/1)

    if length(all_values) < 2 do
      ~H"""
      <p class="text-xs text-base-content/20 italic">Chart appears after the second check…</p>
      """
    else
      computed_max =
        all_values
        |> Enum.max()
        |> max(0)
        |> mc_nice_ceil()

      # `assigns.y_max || computed_max` would treat an explicitly-pinned
      # `0.0` ceiling as "unset" (0 is truthy in Elixir) and fall through to
      # computed_max instead — an is_nil check is the only way to actually
      # distinguish "not provided" from "provided as zero".
      y_max = if is_nil(assigns.y_max), do: computed_max, else: assigns.y_max
      y_min = assigns.y_min

      t_unix = Enum.map(assigns.samples, &DateTime.to_unix(&1.collected_at))
      t_min  = Enum.min(t_unix)
      t_max  = Enum.max(t_unix)
      t_span = max(t_max - t_min, 1)

      geo = %{t_min: t_min, t_span: t_span, pw: pw, pl: pl, ph: ph, bottom: bottom, y_max: y_max, y_min: y_min}
      svg_traces = build_svg_traces(by_instance, assigns.local_id, metric_name, geo)

      y_ticks =
        [y_min, y_min + (y_max - y_min) * 0.25, y_min + (y_max - y_min) * 0.5, y_min + (y_max - y_min) * 0.75, y_max]
        |> Enum.map(fn val ->
          y = bottom - round(safe_ratio(val - y_min, y_max - y_min) * ph)
          {y, mc_fmt_y(val)}
        end)
        |> Enum.uniq_by(&elem(&1, 0))

      t_mid = t_min + div(t_span, 2)
      x_ticks =
        [{pl, t_min}, {pl + div(pw, 2), t_mid}, {pl + pw, t_max}]
        |> Enum.map(fn {x, t} ->
          {x, Calendar.strftime(DateTime.from_unix!(t), "%I:%M %p")}
        end)

      assigns =
        assign(assigns,
          svg_traces: svg_traces,
          y_ticks:    y_ticks,
          x_ticks:    x_ticks,
          bottom:     bottom,
          multi:      map_size(by_instance) > 1,
          pl:         pl,
          pw:         pw,
          pt:         pt
        )

      ~H"""
      <svg id={@id} class="chart-svg" viewBox="0 0 600 200" width="100%" height="200" xmlns="http://www.w3.org/2000/svg">
        <g :for={{y, label} <- @y_ticks}>
          <line x1={@pl} y1={y} x2={@pl + @pw} y2={y} stroke="currentColor" stroke-opacity="0.1" stroke-width="1" />
          <text x={@pl - 4} y={y + 3} text-anchor="end" font-size="9" fill="currentColor" fill-opacity="0.45">{label}</text>
        </g>

        <g :for={t <- @svg_traces}>
          <path
            d={t.area_d}
            fill={if t.is_local, do: "var(--color-primary)", else: "var(--color-warning)"}
            fill-opacity={if t.is_local, do: "0.08", else: "0.05"}
          />
          <polyline
            points={t.line_pts}
            fill="none"
            stroke={if t.is_local, do: "var(--color-primary)", else: "var(--color-warning)"}
            stroke-width="1.5"
            stroke-linejoin="round"
            stroke-linecap="round"
          />
          <circle :for={{x, y, fill} <- t.dots} cx={x} cy={y} r="3" fill={fill} />
        </g>

        <text
          :for={{x, label} <- @x_ticks}
          x={x}
          y={@bottom + 14}
          text-anchor="middle"
          font-size="9"
          fill="currentColor"
          fill-opacity="0.4"
        >{label}</text>

        <g :if={@multi}>
          <g :for={{t, i} <- Enum.with_index(@svg_traces)}>
            <rect
              x={@pl + i * 72}
              y={@pt}
              width="10"
              height="4"
              rx="2"
              fill={if t.is_local, do: "var(--color-primary)", else: "var(--color-warning)"}
            />
            <text
              x={@pl + i * 72 + 14}
              y={@pt + 5}
              font-size="9"
              fill="currentColor"
              fill-opacity="0.55"
            >{t.label}</text>
          </g>
        </g>
      </svg>
      """
    end
  end

  defp build_svg_traces(by_instance, local_id, metric_name, geo) do
    by_instance
    |> Enum.map(fn {instance_id, inst_samples} ->
      {instance_id == local_id, build_dots(inst_samples, metric_name, geo)}
    end)
    # An instance whose samples all lack this particular metric (e.g. a
    # ratio metric that's only emitted once traffic starts flowing) now
    # produces no dots at all — nothing to draw a trace from, and hd/1 and
    # List.last/1 below would raise on an empty list.
    |> Enum.reject(fn {_is_local, dots} -> dots == [] end)
    |> Enum.map(fn {is_local, dots} ->
      {x0, _, _} = hd(dots)
      {xn, _, _} = List.last(dots)
      inner    = Enum.map_join(dots, " L ", &dot_xy/1)
      %{
        is_local: is_local,
        line_pts: Enum.map_join(dots, " ", &dot_xy/1),
        dots:     dots,
        area_d:   "M #{x0},#{geo.bottom} L #{inner} L #{xn},#{geo.bottom} Z",
        label:    if(is_local, do: "Local", else: "Sibling")
      }
    end)
  end

  defp build_dots(inst_samples, metric_name, geo) do
    inst_samples
    |> Enum.sort_by(&DateTime.to_unix(&1.collected_at))
    |> Enum.map(&build_dot(&1, metric_name, geo))
    |> Enum.reject(&is_nil/1)
  end

  # A sample with no value for this metric (never checked yet, or a ratio
  # metric that's only meaningful once some activity has occurred) is a gap
  # in the data, not a real zero — plotting it as 0 would draw a false dip
  # to the bottom of the chart that reads as an incident.
  defp build_dot(s, metric_name, geo) do
    case mc_value(s, metric_name) do
      nil ->
        nil

      raw_val ->
        t   = DateTime.to_unix(s.collected_at)
        x   = geo.pl + round((t - geo.t_min) / geo.t_span * geo.pw)
        val = raw_val |> max(geo.y_min) |> min(geo.y_max)
        y   = geo.bottom - round(safe_ratio(val - geo.y_min, geo.y_max - geo.y_min) * geo.ph)
        {x, y, mc_dot_fill(s.status)}
    end
  end

  # An explicitly-pinned range of zero width (y_max == y_min, e.g. both left
  # at their 0.0 defaults) is now honored rather than silently swapped for a
  # computed ceiling (see metric_chart/1) — which means it's real and
  # reachable, not just a theoretical gap in the public contract. A
  # zero-width range has no proportional space to plot against, so every
  # value collapses to the baseline instead of dividing by zero.
  defp safe_ratio(_numerator, denominator) when denominator == 0, do: 0.0
  defp safe_ratio(numerator, denominator), do: numerator / denominator

  defp dot_xy({x, y, _}), do: "#{x},#{y}"

  # Reads a metric value from a sample. For "latency_ms" falls back to the
  # dedicated column so HTTP samples (which don't populate metrics JSONB)
  # continue to chart correctly via line_chart.
  defp mc_value(%{metrics: m} = s, "latency_ms") when is_map(m) do
    Map.get(m, "latency_ms") || s.latency_ms
  end
  defp mc_value(s, "latency_ms"), do: s.latency_ms
  defp mc_value(%{metrics: m}, name) when is_map(m), do: Map.get(m, name)
  defp mc_value(_s, _name), do: nil

  defp mc_nice_ceil(n) when n <= 0,          do: 1.0
  defp mc_nice_ceil(n) when n <= 1.0,        do: 1.0
  defp mc_nice_ceil(n) when n <= 10,         do: 10
  defp mc_nice_ceil(n) when n <= 50,         do: 50
  defp mc_nice_ceil(n) when n <= 100,        do: 100
  defp mc_nice_ceil(n) when n <= 250,        do: 250
  defp mc_nice_ceil(n) when n <= 500,        do: 500
  defp mc_nice_ceil(n) when n <= 1_000,      do: 1_000
  defp mc_nice_ceil(n) when n <= 2_500,      do: 2_500
  defp mc_nice_ceil(n) when n <= 5_000,      do: 5_000
  defp mc_nice_ceil(n) when n <= 10_000,     do: 10_000
  defp mc_nice_ceil(n) when n <= 100_000,    do: 100_000
  defp mc_nice_ceil(n) when n <= 1_000_000,  do: 1_000_000
  defp mc_nice_ceil(n),                      do: ceil(n / 1_000_000) * 1_000_000

  # Its only call site (the y-axis tick labels in metric_chart/1) always
  # passes a number, so a catch-all clause here is unreachable dead code —
  # confirmed by the compiler's own "this clause is never used" warning.
  defp mc_fmt_y(val) when val == 0, do: "0"
  defp mc_fmt_y(val) when is_number(val) do
    v = val * 1.0
    cond do
      v >= 1.0e9  -> "#{Float.round(v / 1.0e9, 1)}G"
      v >= 1.0e6  -> "#{Float.round(v / 1.0e6, 1)}M"
      v >= 1.0e3  -> "#{Float.round(v / 1.0e3, 1)}k"
      v < 10.0    -> :erlang.float_to_binary(Float.round(v, 2), decimals: 2)
      true        -> "#{round(v)}"
    end
  end

  defp mc_dot_fill("up"),       do: "var(--color-success)"
  defp mc_dot_fill("degraded"), do: "var(--color-warning)"
  defp mc_dot_fill("down"),     do: "var(--color-error)"
  defp mc_dot_fill(_),          do: "#94a3b8"
end