Add scheduled investment plans (3d-10)

2 files changed, 82 insertions, 0 deletions

diff --git a/tests/FundLab.Domain.Tests/FundLab.Domain.Tests.fsproj b/tests/FundLab.Domain.Tests/FundLab.Domain.Tests.fsproj
index 2ba20b5..a9c6fc0 100644
--- a/tests/FundLab.Domain.Tests/FundLab.Domain.Tests.fsproj
+++ b/tests/FundLab.Domain.Tests/FundLab.Domain.Tests.fsproj
@@ -20,6 +20,7 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="DomainTests.fs" />
+    <Compile Include="InvestmentPlanTests.fs" />
     <Compile Include="Program.fs" />
   </ItemGroup>
 </Project>
diff --git a/tests/FundLab.Domain.Tests/InvestmentPlanTests.fs b/tests/FundLab.Domain.Tests/InvestmentPlanTests.fs
new file mode 100644
index 0000000..9a5e2b9
--- /dev/null
+++ b/tests/FundLab.Domain.Tests/InvestmentPlanTests.fs
@@ -0,0 +1,81 @@
+namespace FundLab.Domain.Tests
+
+module InvestmentPlanTests =
+
+    open System
+    open Xunit
+    open FundLab.Domain
+
+    let private anchor = DateOnly(2026, 9, 21)
+
+    [<Fact>]
+    let ``frequency parsing and text roundtrip`` () =
+        Assert.Equal(Some InvestmentFrequency.Daily, InvestmentPlanPolicy.parseFrequency "daily")
+        Assert.Equal(Some InvestmentFrequency.Weekly, InvestmentPlanPolicy.parseFrequency "weekly")
+        Assert.Equal(Some InvestmentFrequency.Monthly, InvestmentPlanPolicy.parseFrequency "monthly")
+        Assert.Equal(None, InvestmentPlanPolicy.parseFrequency "biweekly")
+        Assert.Equal(None, InvestmentPlanPolicy.parseFrequency null)
+        Assert.Equal("daily", InvestmentPlanPolicy.frequencyText InvestmentFrequency.Daily)
+        Assert.Equal("weekly", InvestmentPlanPolicy.frequencyText InvestmentFrequency.Weekly)
+        Assert.Equal("monthly", InvestmentPlanPolicy.frequencyText InvestmentFrequency.Monthly)
+
+    [<Fact>]
+    let ``amount validation requires positive two-decimal cash`` () =
+        Assert.Equal(Ok(), InvestmentPlanPolicy.validateAmount 200.00m)
+        Assert.Equal(Error "investment plan amount must be positive", InvestmentPlanPolicy.validateAmount 0m)
+        Assert.Equal(Error "investment plan amount must be positive", InvestmentPlanPolicy.validateAmount -1.00m)
+        Assert.Equal(Error "investment plan amount exceeds cash precision", InvestmentPlanPolicy.validateAmount 1.005m)
+
+    [<Fact>]
+    let ``daily schedule runs every weekday and skips weekends`` () =
+        Assert.Equal(DateOnly(2026, 9, 21), InvestmentPlanPolicy.nextRunDate InvestmentFrequency.Daily anchor anchor)
+        Assert.Equal(DateOnly(2026, 9, 22), InvestmentPlanPolicy.nextRunDate InvestmentFrequency.Daily anchor (DateOnly(2026, 9, 22)))
+        // Friday -> next scheduled run is Monday
+        Assert.Equal(DateOnly(2026, 9, 28), InvestmentPlanPolicy.nextRunDate InvestmentFrequency.Daily anchor (DateOnly(2026, 9, 26)))
+
+        let due =
+            InvestmentPlanPolicy.dueDates InvestmentFrequency.Daily (DateOnly(2026, 9, 25)) (DateOnly(2026, 9, 25)) (DateOnly(2026, 9, 28))
+
+        Assert.Equal<DateOnly list>([ DateOnly(2026, 9, 25); DateOnly(2026, 9, 28) ], due)
+
+    [<Fact>]
+    let ``weekly schedule keeps the seven day cadence`` () =
+        Assert.Equal(DateOnly(2026, 9, 21), InvestmentPlanPolicy.nextRunDate InvestmentFrequency.Weekly anchor anchor)
+        Assert.Equal(DateOnly(2026, 9, 28), InvestmentPlanPolicy.nextRunDate InvestmentFrequency.Weekly anchor (DateOnly(2026, 9, 22)))
+
+        let due =
+            InvestmentPlanPolicy.dueDates InvestmentFrequency.Weekly anchor anchor (DateOnly(2026, 10, 5))
+
+        Assert.Equal<DateOnly list>(
+            [ DateOnly(2026, 9, 21); DateOnly(2026, 9, 28); DateOnly(2026, 10, 5) ],
+            due
+        )
+
+    [<Fact>]
+    let ``monthly schedule clamps to month end and rolls off weekends`` () =
+        // 2026-02-15 is a Sunday, so the February run rolls to Monday 2026-02-16
+        Assert.Equal(DateOnly(2026, 2, 16), InvestmentPlanPolicy.nextRunDate InvestmentFrequency.Monthly (DateOnly(2026, 1, 15)) (DateOnly(2026, 2, 1)))
+
+        // 2026-02 has 28 days, so a 31st anchor clamps to the 28th then rolls to Monday 2026-03-02
+        Assert.Equal(DateOnly(2026, 3, 2), InvestmentPlanPolicy.nextRunDate InvestmentFrequency.Monthly (DateOnly(2026, 1, 31)) (DateOnly(2026, 2, 1)))
+
+        let due =
+            InvestmentPlanPolicy.dueDates InvestmentFrequency.Monthly anchor anchor (DateOnly(2026, 11, 30))
+
+        // 2026-11-21 is a Saturday, so the November run rolls to Monday 2026-11-23
+        Assert.Equal<DateOnly list>(
+            [ DateOnly(2026, 9, 21); DateOnly(2026, 10, 21); DateOnly(2026, 11, 23) ],
+            due
+        )
+
+    [<Fact>]
+    let ``due dates are truncated at the processing window`` () =
+        Assert.Equal<DateOnly list>([], InvestmentPlanPolicy.dueDates InvestmentFrequency.Daily anchor anchor (DateOnly(2026, 9, 20)))
+
+        let truncated =
+            InvestmentPlanPolicy.dueDates InvestmentFrequency.Daily anchor anchor (DateOnly(2026, 9, 22))
+
+        Assert.Equal<DateOnly list>([ DateOnly(2026, 9, 21); DateOnly(2026, 9, 22) ], truncated)
+
+        // a repeat drive over the same window yields the same dates (idempotent schedule)
+        Assert.Equal<DateOnly list>(truncated, InvestmentPlanPolicy.dueDates InvestmentFrequency.Daily anchor anchor (DateOnly(2026, 9, 22)))