From 9e3e6c70db955b84260c76b1d8865e84dca0cdd0 Mon Sep 17 00:00:00 2001
From: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>
Date: Thu, 16 Jul 2026 17:05:18 -0700
Subject: [PATCH] fix(xlsx): honor PMT/FV/PV/NPER type argument for annuity-due

PMT, FV, PV, and NPER accept an optional 5th type argument (0 = payment
at period end, the default; 1 = payment at beginning / annuity-due). The
four evaluators only read args[0..3] and never read args[4], so type=1
silently returned the ordinary-annuity result.

Read the optional type from args[4] (default 0) and apply the standard
annuity-due adjustment (the (1 + rate*type) factor from Excel's TVM
identity). type=0 and the omitted-5th-arg case are unchanged; the rate==0
short-circuits are left intact. PPMT's internal PMT delegation is kept on
the ordinary-annuity path so its observable output does not change.
---
 .../Core/Formula/FormulaEvaluator.Functions.cs    | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/officecli/Core/Formula/FormulaEvaluator.Functions.cs b/src/officecli/Core/Formula/FormulaEvaluator.Functions.cs
index 6b7e80a3c..1047f0e5c 100644
--- a/src/officecli/Core/Formula/FormulaEvaluator.Functions.cs
+++ b/src/officecli/Core/Formula/FormulaEvaluator.Functions.cs
@@ -1367,8 +1367,9 @@ private static bool MatchesAllCriteria(List<(FormulaResult?[] Range, string Crit
         if (args.Count < 3) return null;
         double rate = args[0] is FormulaResult r ? r.AsNumber() : 0, nper = args[1] is FormulaResult r2 ? r2.AsNumber() : 0, pv = args[2] is FormulaResult r3 ? r3.AsNumber() : 0;
         var fv = args.Count > 3 && args[3] is FormulaResult r4 ? r4.AsNumber() : 0;
+        var type = args.Count > 4 && args[4] is FormulaResult r5 && r5.AsNumber() != 0 ? 1 : 0;
         if (rate == 0) return FR(-(pv + fv) / nper);
-        return FR(-(rate * (pv * Math.Pow(1 + rate, nper) + fv) / (Math.Pow(1 + rate, nper) - 1)));
+        return FR(-(rate * (pv * Math.Pow(1 + rate, nper) + fv) / (Math.Pow(1 + rate, nper) - 1)) / (1 + rate * type));
     }
 
     private static FormulaResult? EvalFv(List<object> args)
@@ -1376,8 +1377,9 @@ private static bool MatchesAllCriteria(List<(FormulaResult?[] Range, string Crit
         if (args.Count < 3) return null;
         double rate = args[0] is FormulaResult r ? r.AsNumber() : 0, nper = args[1] is FormulaResult r2 ? r2.AsNumber() : 0, pmt = args[2] is FormulaResult r3 ? r3.AsNumber() : 0;
         var pv = args.Count > 3 && args[3] is FormulaResult r4 ? r4.AsNumber() : 0;
+        var type = args.Count > 4 && args[4] is FormulaResult r5 && r5.AsNumber() != 0 ? 1 : 0;
         if (rate == 0) return FR(-(pv + pmt * nper));
-        return FR(-(pv * Math.Pow(1 + rate, nper) + pmt * (Math.Pow(1 + rate, nper) - 1) / rate));
+        return FR(-(pv * Math.Pow(1 + rate, nper) + pmt * (1 + rate * type) * (Math.Pow(1 + rate, nper) - 1) / rate));
     }
 
     private static FormulaResult? EvalPv(List<object> args)
@@ -1385,8 +1387,9 @@ private static bool MatchesAllCriteria(List<(FormulaResult?[] Range, string Crit
         if (args.Count < 3) return null;
         double rate = args[0] is FormulaResult r ? r.AsNumber() : 0, nper = args[1] is FormulaResult r2 ? r2.AsNumber() : 0, pmt = args[2] is FormulaResult r3 ? r3.AsNumber() : 0;
         var fv = args.Count > 3 && args[3] is FormulaResult r4 ? r4.AsNumber() : 0;
+        var type = args.Count > 4 && args[4] is FormulaResult r5 && r5.AsNumber() != 0 ? 1 : 0;
         if (rate == 0) return FR(-(fv + pmt * nper));
-        return FR(-(fv / Math.Pow(1 + rate, nper) + pmt * (1 - Math.Pow(1 + rate, -nper)) / rate));
+        return FR(-(fv / Math.Pow(1 + rate, nper) + pmt * (1 + rate * type) * (1 - Math.Pow(1 + rate, -nper)) / rate));
     }
 
     private static FormulaResult? EvalNper(List<object> args)
@@ -1394,8 +1397,10 @@ private static bool MatchesAllCriteria(List<(FormulaResult?[] Range, string Crit
         if (args.Count < 3) return null;
         double rate = args[0] is FormulaResult r ? r.AsNumber() : 0, pmt = args[1] is FormulaResult r2 ? r2.AsNumber() : 0, pv = args[2] is FormulaResult r3 ? r3.AsNumber() : 0;
         var fv = args.Count > 3 && args[3] is FormulaResult r4 ? r4.AsNumber() : 0;
+        var type = args.Count > 4 && args[4] is FormulaResult r5 && r5.AsNumber() != 0 ? 1 : 0;
         if (rate == 0) return pmt != 0 ? FR(-(pv + fv) / pmt) : null;
-        return FR(Math.Log((-fv * rate + pmt) / (pv * rate + pmt)) / Math.Log(1 + rate));
+        var pmtEff = pmt * (1 + rate * type);
+        return FR(Math.Log((-fv * rate + pmtEff) / (pv * rate + pmtEff)) / Math.Log(1 + rate));
     }
 
     private static FormulaResult? EvalNpv(List<object> args)
@@ -1431,7 +1436,7 @@ private static bool MatchesAllCriteria(List<(FormulaResult?[] Range, string Crit
         // as nper).
         var pmtArgs = new List<object> { args[0], args[2], args[3] };
         if (args.Count > 4) pmtArgs.Add(args[4]);
-        if (args.Count > 5) pmtArgs.Add(args[5]);
+        // Annuity-due support for PPMT/IPMT is out of scope; do not half-apply it through PMT.
         var pmt = EvalPmt(pmtArgs)?.AsNumber() ?? 0;
         var ipmt = EvalIpmt(args)?.AsNumber() ?? 0;
         return FR(pmt - ipmt);