Merge pull request #9 from ncsurobotics/skeleton

Add state machine skeleton

Author: Bennett-Petzold

app/src/main/java/org/aquapackrobotics/sw8s/App.java

@@ -3,12 +3,23 @@
  */
 package org.aquapackrobotics.sw8s;
 
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+
+import org.aquapackrobotics.sw8s.missions.Mission;
+import org.aquapackrobotics.sw8s.missions.AutoMission;
+
 public class App {
+
+    static final int POOLSIZE = 1;
+
     public String getGreeting() {
         return "Hello World!";
     }
 
     public static void main(String[] args) {
-        System.out.println(new App().getGreeting());
+        ScheduledThreadPoolExecutor pool = new ScheduledThreadPoolExecutor(POOLSIZE);
+        Mission mission = (Mission) new AutoMission(pool);
+
+        mission.run();
     }
 }

app/src/main/java/org/aquapackrobotics/sw8s/missions/AutoMission.java

@@ -0,0 +1,32 @@
+package org.aquapackrobotics.sw8s.missions;
+
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+
+import org.aquapackrobotics.sw8s.states.State;
+
+/**
+ * Competition mission, fully autonomous.
+ */
+public class AutoMission extends Mission {
+
+    public AutoMission(ScheduledThreadPoolExecutor pool) {
+        super(pool);
+    }
+
+    // TODO: implement
+    @Override
+    protected State initialState() {
+        return null;
+    }
+
+    // TODO: implement
+    @Override
+    protected void executeState(State state) {
+    }
+
+    // TODO: implement
+    @Override
+    protected State nextState(State state) {
+        return null;
+    }
+}

app/src/main/java/org/aquapackrobotics/sw8s/missions/Mission.java

@@ -0,0 +1,69 @@
+package org.aquapackrobotics.sw8s.missions;
+
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+
+import org.aquapackrobotics.sw8s.states.State;
+
+/**
+ * Robot behavior interface.
+ * <p>
+ * Missions are state machines, using State objects to progress.
+ */
+public abstract class Mission {
+    /**
+     * Processing thread pool.
+     * <p>
+     * Repeated tasks are Runnables, submitted with FixedRate.
+     * <p>
+     * Single tasks with a return value are Callables, submitted with schedule
+     */
+    protected ScheduledThreadPoolExecutor pool;
+
+    /**
+     * Generic Mission constructor.
+     * <p>
+     * Extension isn't expected.
+     * Guarantees all Mission objects use a thread pool.
+     *
+     * @param pool A non-filled thread pool
+     */
+    public Mission(ScheduledThreadPoolExecutor pool) {
+        this.pool = pool;
+    }
+
+    /**
+     * Execute the state machine.
+     * <p>
+     * Proceeds through all states in graph.
+     */
+    public void run() {
+        State currentState = initialState();
+        while (currentState != null) {
+            executeState(currentState);
+            currentState = nextState(currentState);
+        }
+    }
+
+    /**
+     * Returns the machine's starting state.
+     */
+    protected abstract State initialState();
+
+    /**
+     * Wraps running the code in a state.
+     * <p>
+     * Wrapper is useful for non-state actions, i.e. checking operator input
+     *
+     * @param state current machine state
+     */
+    protected abstract void executeState(State state);
+
+    /**
+     * Computes the next machine state.
+     * <p>
+     * Uses fields from the current state and Mission parameters.
+     *
+     * @param state current machine state
+     */
+    protected abstract State nextState(State state);
+}

app/src/main/java/org/aquapackrobotics/sw8s/states/InitState.java

@@ -0,0 +1,27 @@
+package org.aquapackrobotics.sw8s.states;
+
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+
+public class InitState extends State {
+    public InitState(ScheduledThreadPoolExecutor pool) {
+        super(pool);
+    }
+
+    // TODO: implement
+    public void onEnter() {
+    }
+
+    // TODO: implement
+    public boolean onPeriodic() {
+        return false;
+    }
+
+    // TODO: implement
+    public void onExit() {
+    }
+
+    // TODO: implement
+    public State nextState() {
+        return null;
+    }
+}

app/src/main/java/org/aquapackrobotics/sw8s/states/State.java

@@ -0,0 +1,58 @@
+package org.aquapackrobotics.sw8s.states;
+
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+
+/**
+ * One step of machine execution.
+ * <p>
+ * Every separate task that is completed should be a different state.
+ * Each task has start conditions, execution logic, and end conditions
+ */
+public abstract class State {
+    protected ScheduledThreadPoolExecutor pool;
+
+    /**
+     * Creates a state instance.
+     * <p>
+     * Do not preserve State instances, create new ones when a task repeats.
+     *
+     * @param pool the Missions' pool for task submission
+     */
+    public State(ScheduledThreadPoolExecutor pool) {
+        this.pool = pool;
+    }
+
+    /**
+     * Enforce starting conditions.
+     */
+    abstract public void onEnter();
+
+    /**
+     * Repeatedly called by state machine.
+     * <p>
+     * Should not loop.
+     * Looping here can trap the state machine.
+     * Condition checking should be if, not while.
+     *
+     * @return if exit conditions are met
+     */
+    abstract public boolean onPeriodic();
+
+    /**
+     * Cleans up state effects and threads.
+     * <p>
+     * After onExit, the robot and thread pool state should be identical to
+     * before onEnter.
+     */
+    abstract public void onExit();
+
+    /**
+     * Recommends the next state.
+     * <p>
+     * May be ignored by a state machine override.
+     * Otherwise should be the main decision on the next state.
+     *
+     * @return an instance for the next state
+     */
+    abstract public State nextState();
+}