Phase7: Void/Refund logic

src/app/api/admin/billing/invoices/[id]/refund/route.ts

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+import { NextResponse } from "next/server";
+import { z } from "zod";
+import { requirePlatformRole, getSessionUser } from "@/lib/session";
+import { refundInvoice, RefundNotAllowedError } from "@/lib/billing";
+import { safeError } from "@/lib/errors";
+
+/**
+ * POST /api/admin/billing/invoices/[id]/refund
+ *
+ * Phase 7. Refunds a paid invoice (full or partial) and issues a
+ * credit note. For Stripe-paid invoices, calls Stripe's Refund API
+ * before any local recording. For invoice-paid customers (bank
+ * transfer), records the refund locally and assumes the admin
+ * handled the actual money movement out-of-band.
+ *
+ * Body:
+ *   {
+ *     amountChf: number,   // positive, <= remaining refundable
+ *     reason: string       // required, free-text, max 500
+ *   }
+ *
+ * Authorization: platform admin.
+ *
+ * Status codes:
+ *   200 — refund issued, credit note returned
+ *   400 — bad request (zero/negative amount, etc.)
+ *   401 / 403 — not authenticated / not platform admin
+ *   409 — invoice not in a refundable state, or amount exceeds remaining
+ *   500 — Stripe call failed or another internal error
+ *
+ * Idempotency caveats: this endpoint is NOT idempotent against
+ * client retries. Issuing two refunds quickly will result in two
+ * Stripe refund calls (and two credit notes). The admin UI should
+ * disable the submit button while the request is in flight to
+ * prevent accidental double-clicks. The Stripe charge.refunded
+ * webhook is idempotent and will not double-count if it fires
+ * after this endpoint already recorded the refund.
+ */
+
+const bodySchema = z.object({
+  amountChf: z.number().positive().multipleOf(0.01),
+  reason: z.string().trim().min(1).max(500),
+});
+
+export async function POST(
+  request: Request,
+  { params }: { params: Promise<{ id: string }> }
+) {
+  let user;
+  try {
+    await requirePlatformRole();
+    user = await getSessionUser();
+  } catch {
+    return NextResponse.json({ error: "Forbidden" }, { status: 403 });
+  }
+  if (!user) {
+    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+  }
+  const { id } = await params;
+  const body = await request.json().catch(() => ({}));
+  const parsed = bodySchema.safeParse(body);
+  if (!parsed.success) {
+    return NextResponse.json(
+      { error: "Invalid request", details: parsed.error.flatten() },
+      { status: 400 }
+    );
+  }
+  try {
+    const creditNote = await refundInvoice({
+      invoiceId: id,
+      amountChf: parsed.data.amountChf,
+      reason: parsed.data.reason,
+      refundedBy: user.id,
+    });
+    return NextResponse.json({ creditNote });
+  } catch (e) {
+    if (e instanceof RefundNotAllowedError) {
+      return NextResponse.json(
+        { error: e.message, currentStatus: e.currentStatus },
+        { status: 409 }
+      );
+    }
+    return NextResponse.json(safeError(e), { status: 500 });
+  }
+}

src/app/api/admin/billing/invoices/[id]/void/route.ts

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+import { NextResponse } from "next/server";
+import { z } from "zod";
+import { requirePlatformRole, getSessionUser } from "@/lib/session";
+import { voidInvoice, VoidNotAllowedError } from "@/lib/billing";
+import { safeError } from "@/lib/errors";
+
+/**
+ * POST /api/admin/billing/invoices/[id]/void
+ *
+ * Phase 7. Voids an unpaid invoice and issues a credit note.
+ *
+ * Body:
+ *   {
+ *     reason: string  // required, free-text, max 500
+ *   }
+ *
+ * Authorization: platform admin (same as mark-paid, generate, etc.).
+ * The acting user's ID lands in invoices.voided_by and on the
+ * credit_notes.issued_by audit columns.
+ *
+ * Status codes:
+ *   200 — voided, credit note returned in body
+ *   400 — bad request (missing reason etc.)
+ *   401 / 403 — not authenticated / not platform admin
+ *   409 — invoice not in a voidable state
+ *   500 — anything else (Stripe shouldn't apply here, but if PDF
+ *         render fails the void still went through — see body
+ *         payload for the credit-note number to re-render later)
+ */
+
+const bodySchema = z.object({
+  reason: z.string().trim().min(1).max(500),
+});
+
+export async function POST(
+  request: Request,
+  { params }: { params: Promise<{ id: string }> }
+) {
+  let user;
+  try {
+    await requirePlatformRole();
+    user = await getSessionUser();
+  } catch {
+    return NextResponse.json({ error: "Forbidden" }, { status: 403 });
+  }
+  if (!user) {
+    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+  }
+  const { id } = await params;
+  const body = await request.json().catch(() => ({}));
+  const parsed = bodySchema.safeParse(body);
+  if (!parsed.success) {
+    return NextResponse.json(
+      { error: "Invalid request", details: parsed.error.flatten() },
+      { status: 400 }
+    );
+  }
+  try {
+    const creditNote = await voidInvoice({
+      invoiceId: id,
+      reason: parsed.data.reason,
+      voidedBy: user.id,
+    });
+    return NextResponse.json({ creditNote });
+  } catch (e) {
+    if (e instanceof VoidNotAllowedError) {
+      return NextResponse.json(
+        { error: e.message, currentStatus: e.currentStatus },
+        { status: 409 }
+      );
+    }
+    return NextResponse.json(safeError(e), { status: 500 });
+  }
+}