bsip35: adjust mechanism handling settle order

bsip-0035.md

@@ -182,15 +182,23 @@ The detailed rules proposes in this BSIP (new rules highlighted):
     * **if the smaller order would get nothing after the round-down, cancel it**
   * when matching a limit order with a call order, in favor of call order,
     round down receiving collateral amount
-    * **if the call order is receiving the whole debt (so the short position
+    * **if the call order is receiving the whole debt amount (so the short
-   will be closed) but paying nothing, let it pay 1 Satoshi (round up);**
+   position will be closed) but paying nothing, let it pay 1 Satoshi
+   (round up);**
     * **otherwise, if the limit order would get nothing after the round-down,
    cancel it (it's smaller, so safe to cancel)**
   * when matching a settle order with a call order, in favor of call order,
     round down receiving collateral amount
-    * **if the settle order would get nothing after the round-down, give it 1
+    * **if the call order is receiving the whole debt amount (so the short
-   Satoshi (round up); after paid both side, check if a black swan event would
+   position will be closed) but paying nothing, let it pay 1 Satoshi
-   be triggered by the round-up, if yes, trigger it**
+   (round up);**
+    * **otherwise, if the settle order would be completely filled but would
+   receive nothing, cancel it;**
+    * **otherwise, it means both orders won't be completely filled, which may
+   due to hitting `maximum_force_settlement_volume`, in this case, don't fill
+   any one of the two orders, and stop matching for this asset at this block;**
+    * **that said, only round up when the call order is completely filled, so
+   won't trigger a black swan event, nor need to check for it.**
   * when globally settling, in favor of call order, round down receiving
     collateral amount
     * **when the asset is not a prediction market, if a call order would pay
@@ -243,15 +251,23 @@ so the order will be cancelled later.
 In `check_call_orders(...)` function of `database` class,
 after calculated `order_receives`, check if it is zero.
 If the answer is `true`,
-* if `call_receives` is equal to `call_itr->debt`, set `order_receives` to 1;
+* if `call_receives` is equal to `call_itr->debt`, set `order_receives` to `1`;
 * otherwise, skip filling and cancel the limit order.
 
 ## When Matching A Settle Order With A Call Order
 
 In `match( const call_order_object&, ... )` function of `database` class,
-after calculated `call_pays`, round up it to `1` if it is zero.
+after calculated `call_pays`, check if it is zero.
+If the answer is `true`,
+* if `call_receives` is equal to `call_debt`, set `call_pays` to `1`;
+* otherwise, if `call_receives` is equal to `settle.balance`,
+  call `cancel_order(...)` with parameter set to `settle`,
+  then return a zero-amount collateral asset object;
+* otherwise, return a zero-amount collateral asset object directly.
 
-If rounded up, after filled both orders, check and allow a black swan event.
+After returned, need to check the amount of returned asset at where calling the
+`match(...)` function, specifically, `clear_expired_orders()` function of
+`database` class. If the returned amount is `0`, break out of the `while` loop.
 
 ## When Globally Settling