1 files changed, 76 insertions, 1 deletions
diff --git a/src/shared/shr_roll.erl b/src/shared/shr_roll.erl
index 8e688c7..7c9e1c5 100644
--- a/src/shared/shr_roll.erl
+++ b/src/shared/shr_roll.erl
@@ -11,7 +11,9 @@
 (
    [
       percentage/0,
-      between/2
+      between/2,
+      percentage_with_luck/2,
+      conflict_with_luck/3
    ]
 ).
 
@@ -30,3 +32,76 @@ between (Min, Max) ->
 -spec percentage () -> 0..100.
 percentage () ->
    between(0, 100).
+
+-spec percentage_with_luck
+   (
+      non_neg_integer(),
+      integer()
+   )
+   -> {0..100, boolean(), integer()}.
+percentage_with_luck (Target, Luck) ->
+   BaseRoll = percentage(),
+   ModedRoll = max(0, min((BaseRoll - Luck), 100)),
+   IsSuccess = (ModedRoll =< Target),
+
+   NewLuck =
+      case {IsSuccess, (Target > 50)} of
+         {true, true} ->
+            % Succeeded, was likely to succeed.
+            % Only pay what was used.
+            MissingPoints = max(0, (BaseRoll - Target)),
+            (Luck - MissingPoints);
+
+         {true, false} ->
+            % Succeeded, was unlikely to succeed.
+            % Pay a lot!
+            MissingPoints = (55 - Target),
+            (Luck - MissingPoints);
+
+         {false, true} ->
+            % Failure due to bad roll.
+            % Was likely to succeed, you get a lot!
+            OwedPoints = (Target - 45),
+            (Luck + OwedPoints);
+
+         _ -> Luck
+      end,
+
+   {ModedRoll, IsSuccess, NewLuck}.
+
+-spec conflict_with_luck
+   (
+      non_neg_integer(),
+      integer(),
+      integer()
+   )
+   -> {0..100, boolean(), integer(), integer()}.
+conflict_with_luck (Target, LuckA, LuckB) ->
+   BaseRoll = percentage(),
+   ModedRoll = max(0, min((BaseRoll - (LuckA - LuckB)), 100)),
+   IsSuccess = (ModedRoll =< Target),
+
+   {NewLuckA, NewLuckB} =
+      case {IsSuccess, (Target > 50)} of
+         {true, true} ->
+            % Succeeded, was likely to succeed.
+            % Only pay what was used.
+            MissingPoints = max(0, (BaseRoll - Target)),
+            {(LuckA - MissingPoints), LuckB};
+
+         {true, false} ->
+            % Succeeded, was unlikely to succeed.
+            % Pay a lot!
+            MissingPoints = (55 - Target),
+            {(LuckA - MissingPoints), (LuckB + MissingPoints)};
+
+         {false, true} ->
+            % Failure due to bad roll.
+            % Was likely to succeed, you get a lot!
+            OwedPoints = (Target - 45),
+            {(LuckA + OwedPoints), (LuckB - OwedPoints)};
+
+         _ -> {LuckA, LuckB}
+      end,
+
+   {ModedRoll, IsSuccess, NewLuckA, NewLuckB}.