[hal,wpilib] Move Alert to HAL (#8646)

SystemCore implementation is not yet connected to MRCComm.

wpilibj/src/main/java/org/wpilib/driverstation/Alert.java

@@ -0,0 +1,155 @@
+// 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.
+
+package org.wpilib.driverstation;
+
+import org.wpilib.hardware.hal.AlertJNI;
+
+/**
+ * Persistent alert to be sent via NetworkTables. Alerts are tagged with a type of {@code ERROR},
+ * {@code WARNING}, or {@code INFO} to denote urgency. See {@link
+ * org.wpilib.driverstation.Alert.Level Level} for suggested usage of each type. Alerts can be
+ * displayed on supported dashboards, and are shown in a priority order based on type and recency of
+ * activation, with newly activated alerts first.
+ *
+ * <p>Alerts should be created once and stored persistently, then updated to "active" or "inactive"
+ * as necessary. {@link #set(boolean)} can be safely called periodically.
+ *
+ * <pre>
+ * class Robot {
+ *   Alert alert = new Alert("Something went wrong", Alert.Level.WARNING);
+ *
+ *   periodic() {
+ *     alert.set(...);
+ *   }
+ * }
+ * </pre>
+ *
+ * <p>Alternatively, alerts which are only used once at startup can be created and activated inline.
+ *
+ * <pre>
+ * public Robot() {
+ *   new Alert("Failed to load auto paths", Alert.Level.ERROR).set(true);
+ * }
+ * </pre>
+ */
+public class Alert implements AutoCloseable {
+  /** Represents an alert's level of urgency. */
+  public enum Level {
+    /**
+     * High priority alert - displayed first with a red "X" symbol. Use this type for problems which
+     * will seriously affect the robot's functionality and thus require immediate attention.
+     */
+    HIGH(AlertJNI.LEVEL_HIGH),
+
+    /** Alternate name for a high priority alert. */
+    ERROR(HIGH.m_value),
+
+    /**
+     * Medium priority alert - displayed second with a yellow "!" symbol. Use this type for problems
+     * which could affect the robot's functionality but do not necessarily require immediate
+     * attention.
+     */
+    MEDIUM(AlertJNI.LEVEL_MEDIUM),
+
+    /** Alternate name for a medium priority alert. */
+    WARNING(MEDIUM.m_value),
+
+    /**
+     * Low priority alert - displayed last with a green "i" symbol. Use this type for problems which
+     * are unlikely to affect the robot's functionality, or any other alerts which do not fall under
+     * the other categories.
+     */
+    LOW(AlertJNI.LEVEL_LOW),
+
+    /** Alternate name for a low priority alert. */
+    INFO(LOW.m_value);
+
+    private final int m_value;
+
+    Level(int value) {
+      m_value = value;
+    }
+  }
+
+  private final Level m_type;
+  private int m_handle;
+
+  /**
+   * Creates a new alert in the default group - "Alerts". If this is the first to be instantiated,
+   * the appropriate entries will be added to NetworkTables.
+   *
+   * @param text Text to be displayed when the alert is active.
+   * @param type Alert urgency level.
+   */
+  public Alert(String text, Level type) {
+    this("Alerts", text, type);
+  }
+
+  /**
+   * Creates a new alert. If this is the first to be instantiated in its group, the appropriate
+   * entries will be added to NetworkTables.
+   *
+   * @param group Group identifier, used as the entry name in NetworkTables.
+   * @param text Text to be displayed when the alert is active.
+   * @param type Alert urgency level.
+   */
+  public Alert(String group, String text, Level type) {
+    m_type = type;
+    m_handle = AlertJNI.createAlert(group, text, type.m_value);
+  }
+
+  /**
+   * Sets whether the alert should currently be displayed. This method can be safely called
+   * periodically.
+   *
+   * @param active Whether to display the alert.
+   */
+  public void set(boolean active) {
+    AlertJNI.setAlertActive(m_handle, active);
+  }
+
+  /**
+   * Gets whether the alert is active.
+   *
+   * @return whether the alert is active.
+   */
+  public boolean get() {
+    return AlertJNI.isAlertActive(m_handle);
+  }
+
+  /**
+   * Updates current alert text. Use this method to dynamically change the displayed alert, such as
+   * including more details about the detected problem.
+   *
+   * @param text Text to be displayed when the alert is active.
+   */
+  public void setText(String text) {
+    AlertJNI.setAlertText(m_handle, text);
+  }
+
+  /**
+   * Gets the current alert text.
+   *
+   * @return the current text.
+   */
+  public String getText() {
+    return AlertJNI.getAlertText(m_handle);
+  }
+
+  /**
+   * Get the type of this alert.
+   *
+   * @return the type
+   */
+  public Level getType() {
+    return m_type;
+  }
+
+  @Override
+  public void close() {
+    AlertJNI.destroyAlert(m_handle);
+    m_handle = 0;
+  }
+}