Idempotency keys for contract write endpoints

src/index.ts

@@ -0,0 +1 @@
+import { idempotency } from './middleware/idempotency';

src/middleware/idempotency.ts

@@ -0,0 +1,71 @@
+import { Request, Response, NextFunction } from 'express';
+import { PrismaClient } from '@prisma/client';
+
+const prisma = new PrismaClient();
+const KEY_TTL_HOURS = 24;
+
+export const idempotency = async (req: Request, res: Response, next: NextFunction) => {
+  if (req.method !== 'POST' && req.method !== 'PUT') {
+    return next();
+  }
+
+  const idempotencyKey = req.headers['idempotency-key'] as string;
+
+  if (!idempotencyKey) {
+    return next();
+  }
+
+  try {
+    const existingRecord = await prisma.idempotencyKey.findUnique({
+      where: { key: idempotencyKey },
+    });
+
+    if (existingRecord) {
+      const expirationDate = new Date();
+      expirationDate.setHours(expirationDate.getHours() - KEY_TTL_HOURS);
+
+      if (existingRecord.createdAt < expirationDate) {
+        await prisma.idempotencyKey.delete({ where: { key: idempotencyKey } });
+      } else if (existingRecord.status === 'STARTED') {
+        return res.status(409).json({
+          error: 'Conflict',
+          message: 'A request with this idempotency key is already in progress.',
+        });
+      } else if (existingRecord.status === 'COMPLETED') {
+        return res.status(existingRecord.responseCode || 200).json(existingRecord.responseBody);
+      }
+    }
+
+    await prisma.idempotencyKey.create({
+      data: { key: idempotencyKey, status: 'STARTED' },
+    });
+
+    const originalJson = res.json;
+    res.json = function (body) {
+      if (res.statusCode >= 200 && res.statusCode < 500) {
+        prisma.idempotencyKey.update({
+          where: { key: idempotencyKey },
+          data: {
+            status: 'COMPLETED',
+            responseCode: res.statusCode,
+            responseBody: body,
+          },
+        }).catch(err => console.error('Failed to save idempotency response:', err));
+      } else {
+        prisma.idempotencyKey.delete({ where: { key: idempotencyKey } }).catch(() => {});
+      }
+
+      return originalJson.call(this, body);
+    };
+
+    next();
+  } catch (error: any) {
+    if (error.code === 'P2002') {
+      return res.status(409).json({
+        error: 'Conflict',
+        message: 'A request with this idempotency key is already in progress.',
+      });
+    }
+    next(error);
+  }
+};