From 2a3097217e872d379bf7c034c745e786c9bd8bd9 Mon Sep 17 00:00:00 2001
From: iris <vinzenz.f.s@gmail.com>
Date: Wed, 29 Jul 2026 20:26:52 +0200
Subject: [PATCH] snapshot the Pfand rate used for returns, like every other
 money value already is
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Line items correctly snapshot both unit_price_cents and
pfand_cents_per_unit, so a later price change doesn't rewrite history.
Returns didn't get the same treatment: transactions.pfand_returns
stored a bare count, and the euro value came from the bar's
pfand_cents at that moment but was never recorded — change a bar's
deposit mid-event and no historical refund amount could be
recomputed from the database.

Writing returns as transaction_items rows (the schema's is_return
column) doesn't fit cleanly: a Pfand return isn't tied to a specific
drink, but transaction_items.drink_id is NOT NULL. Add
transactions.pfand_cents_at_sale instead — same snapshot idea, at
the transaction level where pfand_returns already lives. Also added
to the transactions CSV export so the recovered value is actually
visible somewhere in the app, not just reachable via raw SQL.
---
 server/migrations/004_pfand_return_snapshot.sql |  7 +++++++
 server/src/routes/admin.ts                      |  4 ++--
 server/src/routes/public.ts                     | 16 +++++++++++++---
 3 files changed, 22 insertions(+), 5 deletions(-)
 create mode 100644 server/migrations/004_pfand_return_snapshot.sql

diff --git a/server/migrations/004_pfand_return_snapshot.sql b/server/migrations/004_pfand_return_snapshot.sql
new file mode 100644
index 0000000..5b35f72
--- /dev/null
+++ b/server/migrations/004_pfand_return_snapshot.sql
@@ -0,0 +1,7 @@
+-- Snapshot the Pfand rate used to price this transaction's returns, same
+-- as unit_price_cents/pfand_cents_per_unit already do per line item.
+-- Without this, transactions.pfand_returns is a bare count and the euro
+-- value depends on whatever bars.pfand_cents happens to be *now* — change
+-- a bar's deposit mid-event and no historical refund amount is
+-- recoverable from the database.
+ALTER TABLE transactions ADD COLUMN pfand_cents_at_sale INTEGER NOT NULL DEFAULT 0;
diff --git a/server/src/routes/admin.ts b/server/src/routes/admin.ts
index c092acd..64ca739 100644
--- a/server/src/routes/admin.ts
+++ b/server/src/routes/admin.ts
@@ -267,11 +267,11 @@ export function registerAdminRoutes(app: FastifyInstance, db: DB) {
     let rows: any[];
     let header: string[];
     if (what === 'transactions') {
-      header = ['id', 'bar_id', 'bar_name', 'created_at', 'total_cents', 'crew', 'pfand_returns', 'client_ip', 'client_uuid'];
+      header = ['id', 'bar_id', 'bar_name', 'created_at', 'total_cents', 'crew', 'pfand_returns', 'pfand_cents_at_sale', 'client_ip', 'client_uuid'];
       rows = db
         .prepare(
           `SELECT t.id, t.bar_id, b.name AS bar_name, t.created_at, t.total_cents,
-                  t.crew, t.pfand_returns, t.client_ip, t.client_uuid
+                  t.crew, t.pfand_returns, t.pfand_cents_at_sale, t.client_ip, t.client_uuid
              FROM transactions t JOIN bars b ON b.id = t.bar_id
             ORDER BY t.id`
         )
diff --git a/server/src/routes/public.ts b/server/src/routes/public.ts
index b574116..2e82a51 100644
--- a/server/src/routes/public.ts
+++ b/server/src/routes/public.ts
@@ -135,8 +135,9 @@ export function registerPublicRoutes(app: FastifyInstance, db: DB) {
     const clientIp = req.ip ?? null;
 
     const insertTx = db.prepare(
-      `INSERT INTO transactions (bar_id, created_at, total_cents, crew, pfand_returns, client_ip, client_uuid)
-       VALUES (?, ?, ?, ?, ?, ?, ?)`
+      `INSERT INTO transactions
+         (bar_id, created_at, total_cents, crew, pfand_returns, pfand_cents_at_sale, client_ip, client_uuid)
+       VALUES (?, ?, ?, ?, ?, ?, ?, ?)`
     );
     const insertItem = db.prepare(
       `INSERT INTO transaction_items
@@ -148,7 +149,16 @@ export function registerPublicRoutes(app: FastifyInstance, db: DB) {
     let txId: number;
     try {
       txId = db.transaction(() => {
-        const info = insertTx.run(bar_id, createdAt, paidTotal, crew ? 1 : 0, pfand_returns, clientIp, client_uuid);
+        const info = insertTx.run(
+          bar_id,
+          createdAt,
+          paidTotal,
+          crew ? 1 : 0,
+          pfand_returns,
+          bar.pfand_cents,
+          clientIp,
+          client_uuid
+        );
         const id = Number(info.lastInsertRowid);
         for (const p of priced) {
           insertItem.run(id, p.drink_id, p.qty, p.unit_price_cents, p.pfand_cents_per_unit);