1 package cz.cuni.amis.pogamut.sposh.engine;
2
3 /**
4 * Result of ElementExecutors, it specified how should be drive stack modified.
5 * Only FOLLOW requires specification of nextElement.
6 *
7 * @author Honza
8 */
9 public final class FireResult {
10
11 /**
12 * Value returned by the executor of an element on the stack, it determines
13 * how should drive stack be modified.
14 */
15 public enum Type {
16
17 /**
18 * The element is finished and result is success.
19 */
20 FULFILLED,
21 /**
22 * The element is finished and it failed.
23 */
24 FAILED,
25 /**
26 * Element wasn't yet finished.
27 */
28 CONTINUE,
29 /**
30 * Some child element is supposed to be evaluated.
31 */
32 FOLLOW,
33 /**
34 * Well, not many will use this I suppose, but move up in the stack,
35 * something like return from function. This is the only type that
36 * causes the sposh logic controller to stop iterating. If {@link PoshEngine#evaluatePlan(cz.cuni.amis.pogamut.sposh.executor.IWorkExecutor)
37 * } returns any other value, the sposh logic controller will call
38 * another round of {@link PoshEngine#evaluatePlan(cz.cuni.amis.pogamut.sposh.executor.IWorkExecutor)}
39 */
40 SURFACE,
41 /**
42 * E.g. surface (pop element on the stack), but also indicates that
43 * execution should continue.
44 */
45 SURFACE_CONTINUE,
46 }
47 private Type type;
48 private StackElement nextElement;
49
50 /**
51 * Create result for modification of stack, the {@link #getNextElement() }
52 * is null.
53 *
54 * @param type How should be stack modified, not {@link Type#FOLLOW}.
55 */
56 protected FireResult(Type type) {
57 this(type, null);
58 }
59
60 /**
61 * Create structure saying how the should be the drive stack modified.
62 *
63 * Example: Follow + some element of stack will result in stack of drive
64 * adding the elemnet of stack on the top of the stack.
65 *
66 * @param type How should be stack of drive modified.
67 * @param nextElement What should {@link #getNextElement() } be.
68 */
69 protected FireResult(Type type, StackElement nextElement) {
70 this.type = type;
71 this.nextElement = nextElement;
72 }
73
74 /**
75 * @return How should stack be modified?
76 */
77 public Type getType() {
78 return type;
79 }
80
81 /**
82 * Get element that should be put at the top of the stack. This method can
83 * be called only if {@link #getType() } is {@link Type#FOLLOW}.
84 *
85 * @return the nextElement that be added to the top of the stack
86 */
87 public StackElement getNextElement() {
88 assert (nextElement != null) : "NextElement is null, type of FireResult should be such, that we never ask for it (is " + getType() + ")";
89 return nextElement;
90 }
91 }