[Freeciv-Dev] Unit Move Turns 4 (PR#1349)

[Raahul Kumar <raahul_da_man@xxxxxxxxx>]

Original Author:        Raimar
Changes:                Raahul 
Patch Name:             unit_move_turns4.diff
Dependencies:           This patch has no dependencies on other patches.
Supercedes:             All earlier versions.
CVS version:            diffed against March 22
Compile intruction:     The usual ./configure, make, make install
Savegames:              Not tested
Compiles successfully:  Yes

The changes made are:

Removal of 

struct player *pplayer = unit_owner(punit);

Use of a case statement to replace the barely readable if statements,
and insertion of debugging messages.

More progress being made towards the goal of using the same variable names
throughtout the code. This is in contrast to the current situation where we
have the same thing (punit->move_rate) named move_rate and val.

Thanks to the usual suspects, Per and Greg.

Unless the comments are from the maintainers or I have violated the coding
sytle
doc, no more comments on formatting please. I've wasted enough time on this 
issue.

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diff -ruN -Xdiff_ignore /home/rkumar/tmp/cvs-freeciv/ai/aiunit.c 
/home/rkumar/tmp/freeciv/ai/aiunit.c
--- /home/rkumar/tmp/cvs-freeciv/ai/aiunit.c    Sun Mar 24 18:15:01 2002
+++ /home/rkumar/tmp/freeciv/ai/aiunit.c        Tue Mar 26 12:49:46 2002
@@ -147,29 +147,88 @@
   return FALSE;
 }
 
-/********************************************************************** 
-  ...
-***********************************************************************/
+
+/**********************************************************************
+ Precondition: A warmap must already be generated for the punit.
+
+ Returns the minimal amount of turns required to reach the given
+ destination position. The actual turn at which the unit will
+ reach the given point depends on the movement points it has remaining.
+
+ For example: Unit has a move rate of 3, path cost is 5, unit has 2
+ move points left.
+
+ path1 costs: first tile = 3, second tile = 2
+
+
+ turn 0: points=2, unit has to wait
+ turn 1: points=3, unit can move, points=0, has to wait
+ turn 2: points=3, unit can move, points=1
+
+ path2 costs: first tile=2, second tile=3
+
+ turn 0: points=2, unit can move, points=0, has to wait
+ turn 1: points=3, unit can move, points=0
+
+
+ In spite of the path costs being the same, these two units will arrive
+ at different times. This function also does not take into account ZOC.
+ 
+ Note: even if a unit has only fractional move points left, there is
+ still a possibility it could cross the tile.
+
+**************************************************************************/
+
 static int unit_move_turns(struct unit *punit, int x, int y)
 {
-  int m, d;
-  m = unit_type(punit)->move_rate;
-  if (unit_flag(punit, F_IGTER)) m *= SINGLE_MOVE;
-  if(is_sailing_unit(punit)) {
-    struct player *pplayer = unit_owner(punit);
-    if (player_owns_active_wonder(pplayer, B_LIGHTHOUSE)) 
-      m += SINGLE_MOVE;
-    if (player_owns_active_wonder(pplayer, B_MAGELLAN))
-      m += (improvement_variant(B_MAGELLAN)==1) ? SINGLE_MOVE : 2 * 
SINGLE_MOVE;
-    m += num_known_tech_with_flag(pplayer, TF_BOAT_FAST) * SINGLE_MOVE;
-  }
-
-  if (unit_type(punit)->move_type == LAND_MOVING)
-    d = warmap.cost[x][y] / m;
-  else if (unit_type(punit)->move_type == SEA_MOVING)
-    d = warmap.seacost[x][y] / m;
-  else d = real_map_distance(punit->x, punit->y, x, y) * SINGLE_MOVE / m;
-  return(d);
+
+ int move_time, move_rate = unit_type(punit)->move_rate;
+
+ switch (unit_type(punit)->move_type) {
+ case LAND_MOVING:
+ 
+  /* FIXME: IGTER units should have their move rates multiplied by 
igter_speedup.
+  * Note: actually, igter units should never have their move rates multiplied.
+  * The correct behaviour is to have every tile they cross cost 1/3 of a 
movement
+  * point. ---RK */
+
+   if (unit_flag(punit, F_IGTER)) {
+     move_rate *= 3;
+   }
+   move_time = warmap.cost[x][y] / move_rate;
+   break;
+
+ case SEA_MOVING:
+  
+   if (player_owns_active_wonder(unit_owner(punit), B_LIGHTHOUSE)) {
+       move_rate += SINGLE_MOVE;
+   }
+   
+   if (player_owns_active_wonder(unit_owner(punit), B_MAGELLAN)) {
+       move_rate += (improvement_variant(B_MAGELLAN) == 1) ?
+       SINGLE_MOVE : 2 * SINGLE_MOVE;
+   }
+     
+   if (player_knows_techs_with_flag(unit_owner(punit), TF_BOAT_FAST)) {
+       move_rate += SINGLE_MOVE;
+   }
+     
+   move_time = warmap.seacost[x][y] / move_rate;
+   break;
+
+ case HELI_MOVING:
+ case AIR_MOVING:
+    move_time = real_map_distance(punit->x, punit->y, x,y) * SINGLE_MOVE / 
move_rate;
+    break;
+
+ default:
+   assert(0);
+   freelog(LOG_FATAL, "In ai/aiunit.c: function unit_move_turns");
+   freelog(LOG_FATAL, "Illegal move type %s",unit_type(punit)->move_type);
+   exit(EXIT_FAILURE);
+   move_time = -1;
+ }
+ return move_time;
 }
 
 /**************************************************************************