[freeciv-ai] patch/rfc: goto and move/attack test wrapping

["Per I. Mathisen" <per@xxxxxxxxxxx>]

Taken from massive ai. Unless I get disagreeing comments, I will commit
these wrappers and the associated changes in the rest of the code.

This is an important API decision so please consider it carefully.

gothere is used for goto over several turns and goto with ferries, and is
the one which should eventually be expanded into a replacement for
military and settler gothere with associated ferrying capability. Before
calling it, always set goto destination explicitly.

goto is for one-turn gotos, for example run off and attack a target of
opportunity. It will _retain_ existing goto destination and role, ie it is
non-destructive for existing missions.

can_move is a wrapper which enables you to test for movement _without
going ACTIVITY_IDLE first_. This way, if you decide not to move after all,
your fortify status remains unchanged.

can_attack is the same for attack tests.

(The two latter are necessary but not sufficient to avoid the AI's
always-break fortification syndrome.)

  - Per

Index: ai/aitools.c
===================================================================
RCS file: /home/freeciv/CVS/freeciv/ai/aitools.c,v
retrieving revision 1.62
diff -u -r1.62 aitools.c
--- ai/aitools.c        2002/11/14 09:14:50     1.62
+++ ai/aitools.c        2002/11/18 13:43:50
@@ -112,18 +112,113 @@
 }


/**************************************************************************
+  This will eventually become the ferry-enabled goto. For now, it just
+  wraps ai_unit_goto()
+**************************************************************************/
+bool ai_unit_gothere(struct unit *punit)
+{
+  assert(valid_goto(punit));
+  if (ai_unit_goto(punit, punit->goto_dest_x, punit->goto_dest_y)) {
+    return TRUE; /* ... and survived */
+  } else {
+    return FALSE; /* we died */
+  }
+}
+
+/**************************************************************************
+  Go to specified destination but do not disturb existing role or activity
+  and do not clear the role's destination. Return FALSE iff we died.
+
+  FIXME: add some logging functionality to replace GOTO_LOG()
+**************************************************************************/
+bool ai_unit_goto(struct unit *punit, int x, int y)
+{
+  enum goto_result result;
+  int oldx = punit->goto_dest_x, oldy = punit->goto_dest_y;
+  enum unit_activity activity = punit->activity;
+
+  /* log error on same_pos with punit->x|y */
+  punit->goto_dest_x = x;
+  punit->goto_dest_y = y;
+  ai_unit_new_activity(punit, ACTIVITY_GOTO);
+  result = do_unit_goto(punit, GOTO_MOVE_ANY, FALSE);
+  ai_unit_new_activity(punit, activity);
+  punit->goto_dest_x = oldx;
+  punit->goto_dest_y = oldy;
+
+  return (result != GR_DIED);
+}
+
+/**************************************************************************
+  Check if unit can move to (x, y) without lifting current activity.
+**************************************************************************/
+bool ai_unit_can_move(struct unit *punit, int x, int y)
+{
+  enum unit_activity activity = punit->activity;
+  bool can_move;
+  bool igzoc = unit_flag(punit, F_IGZOC);
+
+  punit->activity = ACTIVITY_IDLE;
+  can_move = can_unit_move_to_tile(punit, x, y, igzoc);
+  punit->activity = activity;
+
+  return can_move;
+}
+
+/**************************************************************************
+  Check if unit can attack to (x, y) without lifting current activity.
+  This also involves checking if we can move there!
+**************************************************************************/
+bool ai_unit_can_attack(struct unit *patt, int x, int y)
+{
+  enum unit_activity activity = patt->activity;
+  bool can_attack;
+
+  patt->activity = ACTIVITY_IDLE;
+  can_attack = can_unit_attack_tile(patt, x, y);
+  patt->activity = activity;
+
+  return can_attack;
+}