Use ceiling division

This keeps the rounding logic the same as the heavily audited Sundae v1 logic

lib/calculation/deposit.ak

@@ -72,10 +72,12 @@ pub fn do_deposit(
     // If we have more b than a, then we can only take up to an quivalent amount of b, and return the rest
     // otherwise if we have more a than b, we can return some amount of `a` to the user instead
     if b_in_units_of_a > user_gives_a {
-      let give_b =
-        pool_state.quantity_b.3rd
-          * user_gives_a
-          / pool_state.quantity_a.3rd
+      let num = pool_state.quantity_b.3rd * user_gives_a
+      let denom = pool_state.quantity_a.3rd
+      // Make sure to do ceiling division here, to round in favor fo the protocol
+      // That is, when in doubt, take up to one more token from the user than the
+      // LP tokens we issue would entail
+      let give_b = ((num - 1) / denom) + 1
       (user_gives_a, give_b)
     } else {
       (b_in_units_of_a, user_gives_b)

validators/tests/pool.ak

@@ -507,15 +507,15 @@ fn scoop_swap_deposit(options: ScoopTestOptions) {
     address: order2_out_addr,
     value: value.from_lovelace(2_000_000)
       |> value.add(constants.pool_script_hash, pool_lp_name(constants.pool_ident), 9_900_990)
-      |> value.add(constants.rberry_policy, constants.rberry_asset_name, 196_991),
+      |> value.add(constants.rberry_policy, constants.rberry_asset_name, 196_990),
     datum: order2_out_datum,
     reference_script: None,
   }
   let pool_output = Output {
     address: pool_address,
     value: option.or_else(options.edit_pool_output_value,
       value.from_lovelace(1_000_000_000 + 20_000_000 + 5_000_000 + 2_000_000)
-        |> value.add(constants.rberry_policy, constants.rberry_asset_name, 1_000_000_000 - 9_896_088 + 10_000_000 - 196_991)
+        |> value.add(constants.rberry_policy, constants.rberry_asset_name, 1_000_000_000 - 9_896_088 + 10_000_000 - 196_990)
         |> value.add(constants.pool_script_hash, pool_nft_name, 1)),
     datum: InlineDatum(pool_out_datum),
     reference_script: None,