diff --git a/lib/dotcom/system_status.ex b/lib/dotcom/system_status.ex
new file mode 100644
index 0000000000..492e0548d4
--- /dev/null
+++ b/lib/dotcom/system_status.ex
@@ -0,0 +1,32 @@
+defmodule Dotcom.SystemStatus do
+ @moduledoc """
+ Parent module for the system status feature
+ """
+
+ alias Dotcom.SystemStatus
+
+ @doc """
+ Returns a list of alerts that satisfy the following criteria:
+ - They are for one of the subway or trolley lines (including Mattapan), and
+ - They are either currently active, or will be later today
+ """
+ def subway_alerts_for_today() do
+ subway_alerts_for_day(Timex.now())
+ end
+
+ defp subway_alerts_for_day(datetime) do
+ [
+ "Red",
+ "Orange",
+ "Blue",
+ "Green-B",
+ "Green-C",
+ "Green-D",
+ "Green-E",
+ "Mattapan"
+ ]
+ |> Alerts.Repo.by_route_ids(datetime)
+ |> SystemStatus.Alerts.for_day(datetime)
+ |> SystemStatus.Alerts.filter_relevant()
+ end
+end
diff --git a/lib/dotcom/system_status/alerts.ex b/lib/dotcom/system_status/alerts.ex
new file mode 100644
index 0000000000..d92b87e483
--- /dev/null
+++ b/lib/dotcom/system_status/alerts.ex
@@ -0,0 +1,106 @@
+defmodule Dotcom.SystemStatus.Alerts do
+ @moduledoc """
+ A utility module intended to filter alerts for the system status feature,
+ relying on some specific criteria that are specific enough that they don't
+ belong in the main `Alerts` module.
+ """
+ @relevant_effects [:delay, :shuttle, :suspension, :station_closure]
+
+ @doc """
+ Checks to see whether an alert is active at some point later today, possibly including
+ `now`.
+
+ Returns `true` if
+ - The alert is currently active
+ - The alert will become active later in the day
+
+ ## Example (Currently Active)
+ iex> now = Timex.to_datetime(~N[2025-01-05 14:00:00], "America/New_York")
+ iex> one_hour_ago = Timex.to_datetime(~N[2025-01-05 13:00:00], "America/New_York")
+ iex> one_hour_from_now = Timex.to_datetime(~N[2025-01-05 15:00:00], "America/New_York")
+ iex> Dotcom.SystemStatus.Alerts.active_on_day?(
+ ...> %Alerts.Alert{active_period: [{one_hour_ago, one_hour_from_now}]},
+ ...> now
+ ...> )
+ true
+
+ ## Example (Active Later Today)
+ iex> now = Timex.to_datetime(~N[2025-01-05 14:00:00], "America/New_York")
+ iex> one_hour_from_now = Timex.to_datetime(~N[2025-01-05 15:00:00], "America/New_York")
+ iex> one_day_from_now = Timex.to_datetime(~N[2025-01-06 14:00:00], "America/New_York")
+ iex> Dotcom.SystemStatus.Alerts.active_on_day?(
+ ...> %Alerts.Alert{active_period: [{one_hour_from_now, one_day_from_now}]},
+ ...> now
+ ...> )
+ true
+
+ Returns `false` if the alert is not currently active, and either
+ - Was only active in the past (even if earlier today)
+ - Will next become active after the end of the day today
+
+ ## Example (Expired)
+ iex> now = Timex.to_datetime(~N[2025-01-05 14:00:00], "America/New_York")
+ iex> two_hours_ago = Timex.to_datetime(~N[2025-01-05 12:00:00], "America/New_York")
+ iex> one_hour_ago = Timex.to_datetime(~N[2025-01-05 13:00:00], "America/New_York")
+ iex> Dotcom.SystemStatus.Alerts.active_on_day?(
+ ...> %Alerts.Alert{active_period: [{two_hours_ago, one_hour_ago}]},
+ ...> now
+ ...> )
+ false
+
+ ## Example (Not Active Until Tomorrow)
+ iex> now = Timex.to_datetime(~N[2025-01-05 14:00:00], "America/New_York")
+ iex> one_day_from_now = Timex.to_datetime(~N[2025-01-06 14:00:00], "America/New_York")
+ iex> two_days_from_now = Timex.to_datetime(~N[2025-01-07 14:00:00], "America/New_York")
+ iex> Dotcom.SystemStatus.Alerts.active_on_day?(
+ ...> %Alerts.Alert{active_period: [{one_day_from_now, two_days_from_now}]},
+ ...> now
+ ...> )
+ false
+ """
+ def active_on_day?(alert, datetime) do
+ Enum.any?(alert.active_period, fn {active_period_start, active_period_end} ->
+ starts_before_end_of_day?(active_period_start, datetime) &&
+ has_not_ended?(active_period_end, datetime)
+ end)
+ end
+
+ @doc """
+ Given a list of alerts, filters only the ones that are active today, as defined in `&active_on_day?/2`.
+ See that function for details
+ """
+ def for_day(alerts, datetime) do
+ Enum.filter(alerts, &active_on_day?(&1, datetime))
+ end
+
+ @doc """
+ Given a list of alerts, returns only the alerts whose effects are one of
+ `[:delay, :shuttle, :suspension, :station_closure]`.
+
+ ## Examples
+ iex> alerts = [
+ ...> %Alerts.Alert{id: "include_this", effect: :delay},
+ ...> %Alerts.Alert{id: "exclude_this", effect: :escalator_closure}
+ ...> ]
+ iex> Dotcom.SystemStatus.Alerts.filter_relevant(alerts) |> Enum.map(& &1.id)
+ ["include_this"]
+ }
+ """
+ def filter_relevant(alerts) do
+ alerts |> Enum.filter(fn %{effect: effect} -> effect in @relevant_effects end)
+ end
+
+ # Returns true if the alert (as signified by the active_period_start provided)
+ # starts before the end of datetime's day.
+ defp starts_before_end_of_day?(active_period_start, datetime) do
+ datetime |> Timex.end_of_day() |> Timex.after?(active_period_start)
+ end
+
+ # Returns true if the alert (as signified by the active_period_end provided)
+ # ends before the given datetime. If active_period_end is nil, then the alert
+ # is indefinite, which means that it definitionally has not ended.
+ defp has_not_ended?(nil, _datetime), do: true
+
+ defp has_not_ended?(active_period_end, datetime),
+ do: datetime |> Timex.before?(active_period_end)
+end
diff --git a/lib/dotcom_web/live/admin.ex b/lib/dotcom_web/live/admin.ex
index 572b4a0c8a..b14b290b56 100644
--- a/lib/dotcom_web/live/admin.ex
+++ b/lib/dotcom_web/live/admin.ex
@@ -16,6 +16,11 @@ defmodule DotcomWeb.Live.Admin do
url: Helpers.live_path(socket, DotcomWeb.Live.TripPlanner),
title: "Trip Planner Preview",
description: "WIP on the trip planner rewrite."
+ },
+ %{
+ url: Helpers.live_path(socket, DotcomWeb.Live.SystemStatus),
+ title: "System Status Widget Preview",
+ description: "WIP on the system status widget."
}
]
)}
diff --git a/lib/dotcom_web/live/system_status.ex b/lib/dotcom_web/live/system_status.ex
new file mode 100644
index 0000000000..8e7457ca9e
--- /dev/null
+++ b/lib/dotcom_web/live/system_status.ex
@@ -0,0 +1,35 @@
+defmodule DotcomWeb.Live.SystemStatus do
+ @moduledoc """
+ A temporary LiveView for showing off the system status widget until we
+ put it into the homepage (and elsewhere).
+ """
+
+ alias Dotcom.SystemStatus
+ use DotcomWeb, :live_view
+
+ def render(assigns) do
+ assigns =
+ assigns
+ |> assign(:alerts, SystemStatus.subway_alerts_for_today())
+
+ ~H"""
+
+ <.alert :for={alert <- @alerts} alert={alert} />
+
+ """
+ end
+
+ defp alert(assigns) do
+ ~H"""
+
+
+ {@alert.severity} {@alert.effect}: {@alert.header}
+
+
+ Raw alert
+ {inspect(@alert, pretty: true)}
+
+
+ """
+ end
+end
diff --git a/lib/dotcom_web/router.ex b/lib/dotcom_web/router.ex
index f693dccf6e..1fadd9a87b 100644
--- a/lib/dotcom_web/router.ex
+++ b/lib/dotcom_web/router.ex
@@ -274,6 +274,15 @@ defmodule DotcomWeb.Router do
end
end
+ scope "/preview", DotcomWeb do
+ import Phoenix.LiveView.Router
+ pipe_through([:browser, :browser_live, :basic_auth_readonly])
+
+ live_session :system_status, layout: {DotcomWeb.LayoutView, :preview} do
+ live "/system-status", Live.SystemStatus
+ end
+ end
+
scope "/api", DotcomWeb do
pipe_through([:secure, :browser])
diff --git a/test/dotcom/system_status/alerts_test.exs b/test/dotcom/system_status/alerts_test.exs
new file mode 100644
index 0000000000..4b8570eae4
--- /dev/null
+++ b/test/dotcom/system_status/alerts_test.exs
@@ -0,0 +1,178 @@
+defmodule Dotcom.SystemStatus.AlertsTest do
+ use ExUnit.Case, async: true
+ doctest Dotcom.SystemStatus.Alerts
+
+ import Test.Support.Factories.Alerts.Alert
+
+ alias Dotcom.SystemStatus.Alerts
+
+ defp local_datetime(naive) do
+ DateTime.from_naive!(naive, "America/New_York")
+ end
+
+ describe "active_on_day?/2" do
+ test "returns true if the alert is currently active" do
+ assert Alerts.active_on_day?(
+ build(:alert,
+ active_period: [
+ {
+ local_datetime(~N[2025-01-09 12:00:00]),
+ local_datetime(~N[2025-01-09 20:00:00])
+ }
+ ]
+ ),
+ local_datetime(~N[2025-01-09 13:00:00])
+ )
+ end
+
+ test "returns false if the alert starts after end-of-service" do
+ refute Alerts.active_on_day?(
+ build(:alert,
+ active_period: [
+ {
+ local_datetime(~N[2025-01-10 12:00:00]),
+ local_datetime(~N[2025-01-10 20:00:00])
+ }
+ ]
+ ),
+ local_datetime(~N[2025-01-09 13:00:00])
+ )
+ end
+
+ test "returns true if the alert starts later, but before end-of-service" do
+ assert Alerts.active_on_day?(
+ build(:alert,
+ active_period: [
+ {
+ local_datetime(~N[2025-01-09 20:00:00]),
+ local_datetime(~N[2025-01-10 20:00:00])
+ }
+ ]
+ ),
+ local_datetime(~N[2025-01-09 13:00:00])
+ )
+ end
+
+ test "returns false if the alert has already ended" do
+ refute Alerts.active_on_day?(
+ build(:alert,
+ active_period: [
+ {
+ local_datetime(~N[2025-01-09 10:00:00]),
+ local_datetime(~N[2025-01-09 12:00:00])
+ }
+ ]
+ ),
+ local_datetime(~N[2025-01-09 13:00:00])
+ )
+ end
+
+ test "returns true if the alert has no end time" do
+ alert =
+ build(:alert,
+ active_period: [
+ {
+ local_datetime(~N[2025-01-09 10:00:00]),
+ nil
+ }
+ ]
+ )
+
+ assert Alerts.active_on_day?(
+ alert,
+ local_datetime(~N[2025-01-09 13:00:00])
+ )
+ end
+
+ test "returns false if the alert has no end time but hasn't started yet" do
+ refute Alerts.active_on_day?(
+ build(:alert,
+ active_period: [
+ {
+ local_datetime(~N[2025-01-10 10:00:00]),
+ nil
+ }
+ ]
+ ),
+ local_datetime(~N[2025-01-09 13:00:00])
+ )
+ end
+
+ test "returns true if a later part of the alert's active period is active" do
+ assert Alerts.active_on_day?(
+ build(:alert,
+ active_period: [
+ {
+ local_datetime(~N[2025-01-08 10:00:00]),
+ local_datetime(~N[2025-01-08 12:00:00])
+ },
+ {
+ local_datetime(~N[2025-01-09 10:00:00]),
+ local_datetime(~N[2025-01-09 12:00:00])
+ }
+ ]
+ ),
+ local_datetime(~N[2025-01-09 11:00:00])
+ )
+ end
+ end
+
+ describe "for_day/2" do
+ test "includes alerts that are active today" do
+ alert1 =
+ build(:alert,
+ active_period: [
+ {
+ local_datetime(~N[2025-01-09 12:00:00]),
+ local_datetime(~N[2025-01-09 20:00:00])
+ }
+ ]
+ )
+
+ alert2 =
+ build(:alert,
+ active_period: [
+ {
+ local_datetime(~N[2025-01-10 12:00:00]),
+ local_datetime(~N[2025-01-10 20:00:00])
+ }
+ ]
+ )
+
+ assert Alerts.for_day(
+ [alert1, alert2],
+ local_datetime(~N[2025-01-09 13:00:00])
+ ) == [alert1]
+ end
+ end
+
+ describe "filter_relevant/1" do
+ test "includes an alert if its effect is :delay" do
+ alert = build(:alert, effect: :delay)
+ assert Alerts.filter_relevant([alert]) == [alert]
+ end
+
+ test "includes an alert if its effect is :shuttle" do
+ alert = build(:alert, effect: :shuttle)
+ assert Alerts.filter_relevant([alert]) == [alert]
+ end
+
+ test "includes an alert if its effect is :suspension" do
+ alert = build(:alert, effect: :suspension)
+ assert Alerts.filter_relevant([alert]) == [alert]
+ end
+
+ test "includes an alert if its effect is :station_closure" do
+ alert = build(:alert, effect: :station_closure)
+ assert Alerts.filter_relevant([alert]) == [alert]
+ end
+
+ test "does not include alerts with other effects" do
+ assert Alerts.filter_relevant([
+ build(:alert, effect: :policy_change),
+ build(:alert, effect: :extra_service),
+ build(:alert, effect: :stop_closure)
+ ]) == []
+ end
+ end
+end