1 /*
2  * Copyright (C) 2011 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package vogar.tasks;
18 
19 import java.util.ArrayList;
20 import java.util.Collection;
21 import java.util.List;
22 import vogar.Console;
23 import vogar.Result;
24 
25 /**
26  * A task necessary to accomplish the user's requested actions. Tasks have
27  * prerequisites; a task must not be run until it reports that it is runnable.
28  * Tasks may be run at most once; running a task produces a result.
29  */
30 public abstract class Task {
31     private final String name;
32     final List<Task> tasksThatMustFinishFirst = new ArrayList<Task>();
33     final List<Task> tasksThatMustFinishSuccessfullyFirst = new ArrayList<Task>();
34     volatile Result result;
35     Exception thrown;
36 
Task(String name)37     protected Task(String name) {
38         this.name = name;
39     }
40 
41     /**
42      * Returns true if this task is an action task. The queue imposes limits
43      * on how many actions may be run concurrently.
44      */
isAction()45     public boolean isAction() {
46         return false;
47     }
48 
after(Task prerequisite)49     public Task after(Task prerequisite) {
50         tasksThatMustFinishFirst.add(prerequisite);
51         return this;
52     }
53 
after(Collection<Task> prerequisites)54     public Task after(Collection<Task> prerequisites) {
55         tasksThatMustFinishFirst.addAll(prerequisites);
56         return this;
57     }
58 
afterSuccess(Task prerequisite)59     public Task afterSuccess(Task prerequisite) {
60         tasksThatMustFinishSuccessfullyFirst.add(prerequisite);
61         return this;
62     }
63 
afterSuccess(Collection<Task> prerequisitess)64     public Task afterSuccess(Collection<Task> prerequisitess) {
65         tasksThatMustFinishSuccessfullyFirst.addAll(prerequisitess);
66         return this;
67     }
68 
isRunnable()69     public final boolean isRunnable() {
70         for (Task task : tasksThatMustFinishFirst) {
71             if (task.result == null) {
72                 return false;
73             }
74         }
75         for (Task task : tasksThatMustFinishSuccessfullyFirst) {
76             if (task.result != Result.SUCCESS) {
77                 return false;
78             }
79         }
80         return true;
81     }
82 
execute()83     protected abstract Result execute() throws Exception;
84 
run(Console console)85     final void run(Console console) {
86         if (result != null) {
87             throw new IllegalStateException();
88         }
89         try {
90             console.verbose("running " + this);
91             result = execute();
92         } catch (Exception e) {
93             thrown = e;
94             result = Result.ERROR;
95         }
96 
97         if (result != Result.SUCCESS) {
98             console.verbose("warning " + this + " " + result);
99         }
100     }
101 
toString()102     @Override public final String toString() {
103         return name;
104     }
105 }
106