[wpilib] Add persistent alerts API (#6735)

wpilibc/src/main/native/cpp/Alert.cpp

@@ -0,0 +1,68 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "frc/Alert.h"
+
+#include <frc/Timer.h>
+#include <frc/smartdashboard/SmartDashboard.h>
+
+#include <networktables/NTSendableBuilder.h>
+
+using namespace frc;
+
+Alert::Alert(std::string_view text, AlertType type)
+    : Alert("Alerts", text, type) {}
+
+wpi::StringMap<Alert::SendableAlerts> Alert::groups;
+
+Alert::Alert(std::string_view group, std::string_view text, AlertType type)
+    : m_type(type), m_text(text) {
+  if (!groups.contains(group)) {
+    groups[group] = SendableAlerts();
+    frc::SmartDashboard::PutData(group, &groups[group]);
+  }
+  groups[group].m_alerts.push_back(std::shared_ptr<Alert>(this));
+}
+
+void Alert::Set(bool active) {
+  if (active && !m_active) {
+    m_activeStartTime = frc::Timer::GetFPGATimestamp();
+  }
+  m_active = active;
+}
+
+void Alert::SetText(std::string_view text) {
+  m_text = text;
+}
+
+void Alert::SendableAlerts::InitSendable(nt::NTSendableBuilder& builder) {
+  builder.SetSmartDashboardType("Alerts");
+  builder.AddStringArrayProperty(
+      "errors", [this]() { return GetStrings(AlertType::kError); }, nullptr);
+  builder.AddStringArrayProperty(
+      "warnings", [this]() { return GetStrings(AlertType::kWarning); },
+      nullptr);
+  builder.AddStringArrayProperty(
+      "infos", [this]() { return GetStrings(AlertType::kInfo); }, nullptr);
+}
+
+std::vector<std::string> Alert::SendableAlerts::GetStrings(
+    AlertType type) const {
+  wpi::SmallVector<std::shared_ptr<Alert>> alerts;
+  alerts.reserve(m_alerts.size());
+  for (auto alert : m_alerts) {
+    if (alert->m_active && alert->m_type == type) {
+      alerts.push_back(alert);
+    }
+  }
+  std::sort(alerts.begin(), alerts.end(), [](const auto a, const auto b) {
+    return a->m_activeStartTime > b->m_activeStartTime;
+  });
+  std::vector<std::string> output{alerts.size()};
+  for (unsigned int i = 0; i < alerts.size(); ++i) {
+    std::string text{alerts[i]->m_text};
+    output[i] = text;
+  }
+  return output;
+}