segment prototype

vacuum_gambit.p8

@@ -665,6 +665,85 @@ function destination:target_from(fx, fy)
  return rx, ry
 end
 
+segment = mknew{
+ -- On loop, where to set index?
+ loop_idx = 1,
+ -- current index
+ current_idx = 1,
+ -- how long does this segment
+ -- last? 0 is erroneous,
+ -- positive values are a frame
+ -- count, negative values are
+ -- a number of loops.
+ limit = -1,
+
+ -- remain: remaining steps until end
+ -- prev_x, prev_y: stored previous
+ --  location to figure out
+ --  approach/depart
+ -- dest_x, dest_y: stored
+ --  current destination to
+ --  figure out approach/depart
+ -- [1..n]: destinations
+ init = function(x)
+  x.remain = x.limit
+ end
+}
+
+function segment:reset()
+ self.current_idx = 1
+ self.remain = self.limit
+ self.prev_x = nil
+ self.prev_y = nil
+ self.was_approaching = false
+end
+
+function segment:target_from(fx, fy)
+ local rx, ry = self[self.current_idx]:target_from(fx, fy)
+ self.dest_x, self.dest_y = rx, ry
+ return rx, ry
+end
+
+function segment:update(x, y)
+ local rem = self.remain
+ -- frame check
+ if (rem > 0) rem -= 1
+
+ if self:should_step(x, y) then
+  if self.current_idx == #self then
+   self.current_idx = self.loop_idx
+   if (rem < 0) rem += 1
+  else
+   self.current_idx += 1
+  end
+ end
+ self.remain = rem
+ return rem != 0
+end
+
+function segment:should_step(x, y)
+ local dest_x, dest_y, ret = self.dest_x, self.dest_y, false
+ local dx1, dy1 = x - dest_x, y-dest_y
+ if abs(dx1) <= 4 and abs(dy1) <= 4 then
+  self.was_approaching = false
+  ret = true
+ end
+ if self.prev_x then
+  local dx0, dy0 = dest_x = self.prev_x - dest_x, self.prev_y - dest_y
+  if dx1 * dx1 + dy1 * dy1 > dx0 * dx0 + dy0 * dy0 then
+   if self.was_approaching then
+    self.was_approaching = false
+    ret = true
+   end
+  else
+   self.was_approaching = true
+  end
+ end
+ self.prev_x, self.prev_y = x, y
+ return ret
+end
+
+
 -->8
 -- bullet and gun behaviors