1 files changed, 27 insertions, 0 deletions
diff --git a/src/FundLab.Domain/Capital.fs b/src/FundLab.Domain/Capital.fs
new file mode 100644
index 0000000..b2ae697
--- /dev/null
+++ b/src/FundLab.Domain/Capital.fs
@@ -0,0 +1,27 @@
+namespace FundLab.Domain
+
+open System
+
+module CapitalPolicy =
+    let cashMaximum = 999999999999999999.99m
+
+    let validateDeposit (amount: decimal) : Result<unit, string> =
+        if amount <= 0m then
+            Error "deposit amount must be positive"
+        elif Decimal.Round(amount, 2) <> amount then
+            Error "deposit amount exceeds cash precision"
+        elif amount > cashMaximum then
+            Error "deposit amount exceeds database precision"
+        else
+            Ok ()
+
+    let settle (availableCash: decimal) (amount: decimal) : Result<decimal, string> =
+        match validateDeposit amount with
+        | Error message -> Error message
+        | Ok() ->
+            let updated = availableCash + amount
+
+            if updated > cashMaximum then
+                Error "available cash exceeds database precision"
+            else
+                Ok updated