feat(transactions): Payment button to record existing transaction as debt payment

src/app/transactions/page.tsx

@@ -2,7 +2,7 @@
 
 import { useState, useCallback, useRef, useEffect, Suspense } from "react";
 import { useSearchParams } from "next/navigation";
-import { useTransactions, useBanks, useUpdateTransaction, useBulkAction, useTags, useStatement, useCreateRule } from "@/lib/hooks";
+import { useTransactions, useBanks, useUpdateTransaction, useBulkAction, useTags, useStatement, useCreateRule, useParticipants, useRecordPayment, useCurrentUser } from "@/lib/hooks";
 import { CATEGORIES, formatCategory } from "@/lib/categories";
 import { SplitModal } from "@/components/split-modal";
 import { TagPicker } from "@/components/tag-picker";
@@ -206,6 +206,142 @@ function InlineEdit({
   );
 }
 
+// ── Mark as Payment modal ─────────────────────────────────────────────────────
+function MarkAsPaymentModal({
+  transaction,
+  onClose,
+}: {
+  transaction: TransactionRow;
+  onClose: () => void;
+}) {
+  const { data: participants = [] } = useParticipants();
+  const { data: me } = useCurrentUser();
+  const record = useRecordPayment();
+
+  const others = participants.filter((p) => p.name !== "Me");
+
+  const [participantId, setParticipantId] = useState<number | "">(others[0]?.id ?? "");
+  // For credits/refunds the default direction is "they paid me"
+  const [direction, setDirection] = useState<"received" | "sent">(
+    SPEND_TYPES.has(transaction.transaction_type) ? "sent" : "received"
+  );
+  const [amount, setAmount] = useState(transaction.amount.toFixed(2));
+  const [date, setDate] = useState(transaction.transaction_date.slice(0, 10));
+  const [notes, setNotes] = useState("");
+  const [error, setError] = useState("");
+
+  const selectedParticipant = others.find((p) => p.id === participantId);
+
+  async function handleSave() {
+    setError("");
+    if (!participantId || !me) { setError("Select a participant"); return; }
+    const amt = parseFloat(amount);
+    if (!amt || amt <= 0) { setError("Enter a valid amount"); return; }
+    try {
+      await record.mutateAsync({
+        from_participant_id: direction === "received" ? participantId : me.id,
+        to_participant_id: direction === "received" ? me.id : participantId,
+        amount: amt,
+        payment_date: date,
+        notes: notes || undefined,
+        linked_transaction_id: transaction.id,
+      });
+      onClose();
+    } catch (e) {
+      setError(e instanceof Error ? e.message : "Failed to record");
+    }
+  }
+
+  return (
+    <div className="fixed inset-0 z-50 flex items-center justify-center bg-black/60" onClick={onClose}>
+      <div
+        className="bg-zinc-900 border border-zinc-700 rounded-xl w-full max-w-sm mx-4 shadow-2xl p-6 space-y-4"
+        onClick={(e) => e.stopPropagation()}
+      >
+        <div>
+          <h3 className="font-semibold text-sm text-zinc-300">Record as Debt Payment</h3>
+          <p className="text-xs text-zinc-500 mt-0.5 truncate">{transaction.description}</p>
+        </div>
+
+        {/* Participant */}
+        <div>
+          <label className="block text-xs text-zinc-500 mb-1">Participant</label>
+          <select
+            value={participantId}
+            onChange={(e) => setParticipantId(Number(e.target.value))}
+            className="w-full bg-zinc-800 border border-zinc-700 rounded px-2 py-1.5 text-sm"
+          >
+            {others.map((p) => (
+              <option key={p.id} value={p.id}>{p.name}</option>
+            ))}
+          </select>
+        </div>
+
+        {/* Direction */}
+        <div className="flex rounded-lg overflow-hidden border border-zinc-700 text-sm">
+          <button
+            type="button"
+            onClick={() => setDirection("received")}
+            className={`flex-1 py-1.5 transition-colors ${direction === "received" ? "bg-emerald-700 text-white" : "bg-zinc-800 text-zinc-400 hover:bg-zinc-700"}`}
+          >
+            {selectedParticipant?.name ?? "They"} paid me
+          </button>
+          <button
+            type="button"
+            onClick={() => setDirection("sent")}
+            className={`flex-1 py-1.5 transition-colors ${direction === "sent" ? "bg-blue-700 text-white" : "bg-zinc-800 text-zinc-400 hover:bg-zinc-700"}`}
+          >
+            I paid {selectedParticipant?.name ?? "them"}
+          </button>
+        </div>
+
+        <div className="grid grid-cols-2 gap-3">
+          <div>
+            <label className="block text-xs text-zinc-500 mb-1">Amount</label>
+            <div className="relative">
+              <span className="absolute left-2.5 top-1/2 -translate-y-1/2 text-zinc-500 text-sm">$</span>
+              <input
+                type="number" step="0.01" min="0.01" value={amount}
+                onChange={(e) => setAmount(e.target.value)}
+                className="w-full bg-zinc-800 border border-zinc-700 rounded px-2 py-1.5 text-sm pl-6"
+              />
+            </div>
+          </div>
+          <div>
+            <label className="block text-xs text-zinc-500 mb-1">Date</label>
+            <input
+              type="date" value={date} onChange={(e) => setDate(e.target.value)}
+              className="w-full bg-zinc-800 border border-zinc-700 rounded px-2 py-1.5 text-sm"
+            />
+          </div>
+        </div>
+
+        <div>
+          <label className="block text-xs text-zinc-500 mb-1">Notes (optional)</label>
+          <input
+            value={notes} onChange={(e) => setNotes(e.target.value)}
+            placeholder="e.g. bank transfer reference"
+            className="w-full bg-zinc-800 border border-zinc-700 rounded px-2 py-1.5 text-sm"
+          />
+        </div>
+
+        {error && <p className="text-red-400 text-xs">{error}</p>}
+
+        <div className="flex gap-2">
+          <button type="button" onClick={onClose}
+            className="flex-1 px-4 py-2 bg-zinc-800 hover:bg-zinc-700 text-zinc-300 rounded-lg text-sm">
+            Cancel
+          </button>
+          <button type="button" onClick={handleSave} disabled={record.isPending}
+            className="flex-1 px-4 py-2 bg-indigo-600 hover:bg-indigo-500 disabled:opacity-50 text-white rounded-lg text-sm font-medium">
+            {record.isPending ? "Saving…" : "Record Payment"}
+          </button>
+        </div>
+      </div>
+    </div>
+  );
+}
+
 // ── Query bar parser ──────────────────────────────────────────────────────────
 interface QueryToken { key: string; label: string }
 interface ParsedQuery { text: string; amountMin?: number; amountMax?: number; tokens: QueryToken[] }
@@ -365,6 +501,7 @@ function TransactionsContent() {
   const [splitModal, setSplitModal] = useState<{ transactionId?: number; transactionIds?: number[]; amount?: number; description: string; merchant?: string } | null>(null);
   const [addModal, setAddModal] = useState<{ prefill?: Parameters<typeof AddTransactionModal>[0]["prefill"]; title?: string } | null>(null);
   const [editModal, setEditModal] = useState<TransactionRow | null>(null);
+  const [paymentModal, setPaymentModal] = useState<TransactionRow | null>(null);
   const [rulePrompt, setRulePrompt] = useState<{
     tx: { id: number; effective_merchant: string; description: string; bank_name: string };
     field: "category" | "merchant";
@@ -738,6 +875,15 @@ function TransactionsContent() {
                     >
                       Edit
                     </button>
+                    {!SPEND_TYPES.has(t.transaction_type) && (
+                      <button
+                        onClick={() => setPaymentModal(t)}
+                        className="text-xs text-emerald-600 hover:text-emerald-400 px-2 py-0.5 rounded hover:bg-zinc-800 transition-colors"
+                        title="Record as debt payment"
+                      >
+                        Payment
+                      </button>
+                    )}
                     <button
                       onClick={() => setAddModal({
                         title: "Duplicate Transaction",
@@ -790,6 +936,13 @@ function TransactionsContent() {
         />
       )}
 
+      {paymentModal && (
+        <MarkAsPaymentModal
+          transaction={paymentModal}
+          onClose={() => setPaymentModal(null)}
+        />
+      )}
+
       {rulePrompt && (
         <SaveAsRulePrompt
           tx={rulePrompt.tx}