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+/*
+ * libjingle
+ * Copyright 2004--2005, Google Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without 
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *  1. Redistributions of source code must retain the above copyright notice, 
+ *     this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright notice,
+ *     this list of conditions and the following disclaimer in the documentation
+ *     and/or other materials provided with the distribution.
+ *  3. The name of the author may not be used to endorse or promote products 
+ *     derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+ * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _TASK_H_
+#define _TASK_H_
+
+#include <vector>
+#include <string>
+
+#include "talk/base/sigslot.h"
+
+/////////////////////////////////////////////////////////////////////
+//
+// TASK
+//
+/////////////////////////////////////////////////////////////////////
+//
+// Task is a state machine infrastructure.  States are pushed forward by
+// pushing forwards a TaskRunner that holds on to all Tasks.  The purpose
+// of Task is threefold:
+// 
+// (1) It manages ongoing work on the UI thread.  Multitasking without
+// threads, keeping it easy, keeping it real. :-)  It does this by
+// organizing a set of states for each task.  When you return from your
+// Process*() function, you return an integer for the next state.  You do
+// not go onto the next state yourself.  Every time you enter a state,
+// you check to see if you can do anything yet.  If not, you return
+// STATE_BLOCKED.  If you _could_ do anything, do not return
+// STATE_BLOCKED - even if you end up in the same state, return
+// STATE_mysamestate.  When you are done, return STATE_DONE and then the
+// task will self-delete sometimea afterwards.
+// 
+// (2) It helps you avoid all those reentrancy problems when you chain
+// too many triggers on one thread.  Basically if you want to tell a task
+// to process something for you, you feed your task some information and
+// then you Wake() it.  Don't tell it to process it right away.  If it
+// might be working on something as you send it infomration, you may want
+// to have a queue in the task.
+// 
+// (3) Finally it helps manage parent tasks and children.  If a parent
+// task gets aborted, all the children tasks are too.  The nice thing
+// about this, for example, is if you have one parent task that
+// represents, say, and Xmpp connection, then you can spawn a whole bunch
+// of infinite lifetime child tasks and now worry about cleaning them up.
+//  When the parent task goes to STATE_DONE, the task engine will make
+// sure all those children are aborted and get deleted.
+// 
+// Notice that Task has a few built-in states, e.g.,
+// 
+// STATE_INIT - the task isn't running yet
+// STATE_START - the task is in its first state
+// STATE_RESPONSE - the task is in its second state
+// STATE_DONE - the task is done
+// 
+// STATE_ERROR - indicates an error - we should audit the error code in
+// light of any usage of it to see if it should be improved.  When I
+// first put down the task stuff I didn't have a good sense of what was
+// needed for Abort and Error, and now the subclasses of Task will ground
+// the design in a stronger way.
+// 
+// STATE_NEXT - the first undefined state number.  (like WM_USER) - you
+// can start defining more task states there.
+// 
+// When you define more task states, just override Process(int state) and
+// add your own switch statement.  If you want to delegate to
+// Task::Process, you can effectively delegate to its switch statement.
+// No fancy method pointers or such - this is all just pretty low tech,
+// easy to debug, and fast.
+// 
+
+namespace buzz {
+
+class TaskRunner;
+
+// A task executes a sequence of steps
+
+class Task;
+class RootTask;
+
+class Task {
+public:
+  Task(Task * parent);
+  virtual ~Task() {}
+  
+  void Start();
+  void Step();
+  int GetState() const { return state_; }
+  bool HasError() const { return (GetState() == STATE_ERROR); }
+  bool Blocked() const { return blocked_; }
+  bool IsDone() const { return done_; }
+  unsigned long long ElapsedTime();
+  virtual void Poll() {}
+
+  Task * GetParent() { return parent_; }
+  TaskRunner * GetRunner() { return runner_; }
+  virtual Task * GetParent(int code) { return parent_->GetParent(code); }
+
+  // Called from outside to stop task without any more callbacks
+  void Abort(bool nowake = false);
+  
+  // For managing children
+  bool AllChildrenDone();
+  bool AnyChildError();
+
+
+protected:
+
+  enum {
+    STATE_BLOCKED = -1,
+    STATE_INIT = 0,
+    STATE_START = 1,
+    STATE_DONE = 2,
+    STATE_ERROR = 3,
+    STATE_RESPONSE = 4,
+    STATE_NEXT = 5, // Subclasses which need more states start here and higher
+  };
+
+  // Called inside the task to signal that the task may be unblocked
+  void Wake();
+
+  // Called inside to advise that the task should wake and signal an error
+  void Error();
+
+  unsigned long long CurrentTime();
+  
+  virtual std::string GetStateName(int state) const;
+  virtual int Process(int state);
+  virtual void Stop();
+  virtual int ProcessStart() = 0;
+  virtual int ProcessResponse() { return STATE_DONE; }
+
+  // for managing children (if any)
+  void AddChild(Task * child);
+  void AbortAllChildren();
+
+private:
+  void Done();
+  void OnChildStopped(Task * child);
+  
+  int state_;
+  Task * parent_;
+  TaskRunner * runner_;
+  bool blocked_;
+  bool done_;
+  bool aborted_;
+  bool busy_;
+  bool error_;
+  bool child_error_;
+  unsigned long long start_time_;
+
+  // for managing children
+  typedef std::set<Task *> ChildSet;
+  ChildSet children_;
+  
+};
+
+
+
+
+}
+
+#endif