feat: log entitlement purchases (#3)

### Explanation

_No response_

### Issue

_No response_

### Attestations

- [x] I have read and agree to the [Code of Conduct](https://docs.nhcarrigan.com/community/coc/)
- [x] I have read and agree to the [Community Guidelines](https://docs.nhcarrigan.com/community/guide/).
- [x] My contribution complies with the [Contributor Covenant](https://docs.nhcarrigan.com/dev/covenant/).

### Dependencies

- [x] I have pinned the dependencies to a specific patch version.

### Style

- [x] I have run the linter and resolved any errors.
- [x] My pull request uses an appropriate title, matching the conventional commit standards.
- [x] My scope of feat/fix/chore/etc. correctly matches the nature of changes in my pull request.

### Tests

- [ ] My contribution adds new code, and I have added tests to cover it.
- [ ] My contribution modifies existing code, and I have updated the tests to reflect these changes.
- [ ] All new and existing tests pass locally with my changes.
- [ ] Code coverage remains at or above the configured threshold.

### Documentation

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### Versioning

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Reviewed-on: #3
Co-authored-by: Naomi Carrigan <commits@nhcarrigan.com>
Co-committed-by: Naomi Carrigan <commits@nhcarrigan.com>

src/config/applicationData.ts

@@ -0,0 +1,96 @@
+/**
+ * @copyright nhcarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+/* eslint-disable @typescript-eslint/naming-convention -- We are using the numerical ids as the keys.*/
+export const applicationData: Record<string, { name: string; key: string }> = {
+  "1235128719836712970": {
+    key:  "e255cd3a348ce604e18e2f2c0f5a59a9273a420ca732630d569ef5f839f2143e",
+    name: "Celestine",
+  },
+  "1338596130207957035": {
+    key:  "ef9d2a3c8e9a4d165a12ca798be93d719dd51cc7ff901ade8136cb992cd7fe3e",
+    name: "Aria Iuvo",
+  },
+  "1338664192714211459": {
+    key:  "a28c9c2683acb209341e04d5b43bd2a24bc81f5b263095a1bf487e94ca6a3ff9",
+    name: "Cordelia Taryne",
+  },
+  "1338753576583041074": {
+    key:  "62468252371a68791c650b5aaa599ef2b7b148a7169bb5fa9f56075705ac405e",
+    name: "Melody Iuvo",
+  },
+  "1343341112437248041": {
+    key:  "3ccf23b9c10dda9a7af434e0c5fc116d05aba66caf2ebd8c738c60ba9875436f",
+    name: "Becca Lyria",
+  },
+  "1343370633916059668": {
+    key:  "a9146e39ab5f69129e3c50db5d5848c56bc4a2cb90bba10e492e08355acd3d12",
+    name: "Maylin Taryne",
+  },
+  "1343413943447584819": {
+    key:  "6d95c7132ee9f28a4ea5fffbc8dd33ecaffe0f50add0c631d5ef51cc071bd2df",
+    name: "Gwen Abalise",
+  },
+  "1347642447643017289": {
+    key:  "091be058344e543e87baafeb9fe20b004bd170ca5ee57b17afff595271080a27",
+    name: "Mommy",
+  },
+  "1386862413936328796": {
+    key:  "831e3981135a4c9d30e8c02e6f8cba73436d30c36b1a14f1fb7bc7147cd4cb75",
+    name: "Maribelle",
+  },
+  "1391117878182281316": {
+    key:  "b182039c954ba57216bf53bdc4d5ba3d89efc2b41c850cbf7f3430fbb6cc0c56",
+    name: "Hikari",
+  },
+  "1391488058913718374": {
+    key:  "fc1a838c3102351602221f2db63d997f9e4495510044d5ec436844038b9a5bd5",
+    name: "Rosalia Nightsong",
+  },
+  "1391489982887362761": {
+    key:  "ef173a181d6fcf506b72795812fca8ecc3a81c2ff382bfd39564bab63fd90eee",
+    name: "Sorielle",
+  },
+  "1391491102657482863": {
+    key:  "a412583e5d5510aebb6d54eb49f36797e62f9567efd79108863adbb93cf00236",
+    name: "Verena",
+  },
+  "1391492296222179459": {
+    key:  "aab61af4411fc1dc710d5b5aba5d16fba9effaad9415b878a3f1595428dbebcd",
+    name: "Liora",
+  },
+  "1391493722176356434": {
+    key:  "3dc2abd018271a5a1f65c09597738a711b2fc619d34da59189279d6c2a1922f4",
+    name: "Thessalia",
+  },
+  "1391494389477412906": {
+    key:  "8d11517cf954779e4645b8c10432697a0572dcfcecc0bb14d0fe2397f5a03453",
+    name: "Callista",
+  },
+  "1391495288421879849": {
+    key:  "fb0894e2dcd3e736addd70a675b40d5681d39c133289cdfe4f7378006163e817",
+    name: "Eirene",
+  },
+  "1391497269177483405": {
+    key:  "0887f7e12053d559f8944a06ed323ec237d34f8e15860b672fb7abe6dc32d192",
+    name: "Sybil",
+  },
+  "1391503229287928000": {
+    key:  "8a4d4f18dae4e2d0ec610e3da47254a812c39cfac6ee986cfaa20eb848a2db92",
+    name: "Clarion",
+  },
+  "1391503834073006181": {
+    key:  "60ffe0a3503d5166c1e4b7370753793dff60d75a28ebf4ace8b6623ad5207821",
+    name: "Evangeline",
+  },
+  "1391504577811185744": {
+    key:  "33bb085873b46199facfbfae00b7d71ed04d55377deeaa2a0c8afa303c68a75d",
+    name: "Theodora",
+  },
+  "1391505285465509978": {
+    key:  "edce882890078d52c00c653b9e305565a909a0807abf86b36f1d7679434b80fa",
+    name: "Veluna",
+  },
+};

src/interfaces/entitlement.ts

@@ -0,0 +1,31 @@
+/**
+ * @copyright nhcarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+
+/* eslint-disable @typescript-eslint/naming-convention -- Needs to match Discord's structure. */
+export interface Entitlement {
+  application_id: string;
+  event: {
+    data: {
+      application_id:  string;
+      consumed:        boolean;
+      deleted:         boolean;
+      ends_at:         string;
+      gift_code_flags: number;
+      guild_id:        string;
+      id:              string;
+      promotion_id:    string | null;
+      sku_id:          string;
+      starts_at:       string;
+      subscription_id: string;
+      type:            number;
+      user_id:         string;
+    };
+    timestamp: string;
+    type:      string;
+  };
+  type:    number;
+  version: number;
+}

src/modules/discord.ts

@@ -17,6 +17,7 @@ export const sendDiscord = async(
     body: JSON.stringify({
       components: [
         {
+          // eslint-disable-next-line @typescript-eslint/naming-convention -- Needs to match Discord's structure.
           accent_color: 15_418_782,
           components:   [
             {
@@ -40,6 +41,7 @@ export const sendDiscord = async(
       flags: 32_768,
     }),
     headers: {
+      // eslint-disable-next-line @typescript-eslint/naming-convention -- Needs to match Discord's structure.
       "Content-Type": "application/json",
     },
     method: "POST",

src/modules/validateWebhook.ts

@@ -0,0 +1,50 @@
+/**
+ * @copyright nhcarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+import { webcrypto } from "node:crypto";
+import { verify } from "discord-verify/node";
+import { applicationData } from "../config/applicationData.js";
+import { sendDiscord } from "./discord.js";
+import type { Entitlement } from "../interfaces/entitlement.js";
+import type { FastifyRequest } from "fastify";
+
+/**
+ * Validates that the webhook request is from Discord by checking the signature.
+ * @param request - The Fastify request object containing the webhook data.
+ * @returns A boolean indicating whether the webhook signature is valid.
+ */
+export const validateWebhook = async(
+  // eslint-disable-next-line @typescript-eslint/naming-convention -- Body must be capitalised for Fastify.
+  request: FastifyRequest<{ Body: Entitlement; Headers: {
+    // eslint-disable-next-line @typescript-eslint/naming-convention -- Header must be formatted for Fastify.
+    "x-signature-ed25519":   string;
+    // eslint-disable-next-line @typescript-eslint/naming-convention -- Header must be formatted for Fastify.
+    "x-signature-timestamp": string;
+  }; }>,
+): Promise<boolean> => {
+  const { application_id: applicationId } = request.body;
+  const appData = applicationData[applicationId];
+  if (appData === undefined) {
+    void sendDiscord(`[NOTIFICATION]: Invalid Application ID`, `Received an entitlement event for an invalid application ID: ${applicationId}`);
+    return false;
+  }
+  const signature = request.headers["x-signature-ed25519"];
+  const timestamp = request.headers["x-signature-timestamp"];
+  const rawBody = JSON.stringify(request.body);
+  const isValid = await verify(
+    rawBody,
+    signature,
+    timestamp,
+    appData.key,
+    webcrypto.subtle,
+  );
+  if (!isValid) {
+    void sendDiscord(
+      `[NOTIFICATION]: Invalid Webhook Signature`,
+      `Received an entitlement event with an invalid signature.\nApplication ID: ${applicationId}\nSignature: ${signature}\nTimestamp: ${timestamp}\nRaw Body: ${rawBody}`,
+    );
+  }
+  return isValid;
+};

src/server/serve.ts

@@ -5,12 +5,15 @@
  */
 
 import fastify from "fastify";
+import { applicationData } from "../config/applicationData.js";
 import { auth } from "../modules/auth.js";
 import { sendDiscord } from "../modules/discord.js";
 import { sendMail } from "../modules/sendMail.js";
+import { validateWebhook } from "../modules/validateWebhook.js";
 import { errorSchema } from "../schemas/errorSchema.js";
 import { logSchema } from "../schemas/logSchema.js";
 import { uptimeSchema } from "../schemas/uptimeSchema.js";
+import type { Entitlement } from "../interfaces/entitlement.js";
 import type { Error } from "../interfaces/error.js";
 import type { Log } from "../interfaces/log.js";
 import type { Uptime } from "../interfaces/uptime.js";
@@ -90,7 +93,10 @@ export const instantiateServer = (): void => {
           return;
         }
         const { application, context, stack, message } = request.body;
-        await sendMail(`[ERROR]: ${context} - ${application}`, `${message}\n\n${stack}`);
+        await sendMail(
+          `[ERROR]: ${context} - ${application}`,
+          `${message}\n\n${stack}`,
+        );
         await sendDiscord(
           `[ERROR]: ${context} - ${application}`,
           `${message}\n\n\`\`\`\n${stack}\n\`\`\``,
@@ -115,13 +121,72 @@ export const instantiateServer = (): void => {
       },
     );
 
+    // eslint-disable-next-line @typescript-eslint/naming-convention -- Body must be capitalised for Fastify.
+    server.post<{ Body: Entitlement; Headers: {
+    // eslint-disable-next-line @typescript-eslint/naming-convention -- Header must be formatted for Fastify.
+      "x-signature-ed25519":   string;
+      // eslint-disable-next-line @typescript-eslint/naming-convention -- Header must be formatted for Fastify.
+      "x-signature-timestamp": string;
+    }; }>(
+      "/entitlement",
+      // eslint-disable-next-line complexity -- Fuck off.
+      async(request, response) => {
+        const { type, application_id: applicationId, event } = request.body;
+        const appInfo = applicationData[applicationId];
+        const isValid = await validateWebhook(request);
+        if (!isValid) {
+          await response.status(401).send({ success: false });
+          void sendDiscord(
+            `[ENTITLEMENT]: ${appInfo?.name ?? applicationId}`,
+            "An invalid webhook signature was received.",
+          );
+          void sendMail(
+            `[ENTITLEMENT]: ${appInfo?.name ?? applicationId}`,
+            "An invalid webhook signature was received.",
+          );
+          return;
+        }
+        await response.status(204).send();
+        if (type === 0) {
+          void sendDiscord(
+            `[ENTITLEMENT]: ${appInfo?.name ?? applicationId}`,
+            "Received a ping from Discord.",
+          );
+          void sendMail(
+            `[ENTITLEMENT]: ${appInfo?.name ?? applicationId}`,
+            "Received a ping from Discord.",
+          );
+          return;
+        }
+        const {
+          user_id: userId,
+          guild_id: guildId,
+          ends_at: endsAt,
+        } = event.data;
+        await sendDiscord(
+          `[ENTITLEMENT]: ${appInfo?.name ?? applicationId}`,
+          `Entitlement purchased!\n- **User ID**: ${userId}\n- **Guild ID**: ${guildId}\n- **Ends At**: ${endsAt}`,
+        );
+        await sendMail(
+          `[ENTITLEMENT]: ${appInfo?.name ?? applicationId}`,
+          `Entitlement purchased!\n- **User ID**: ${userId}\n- **Guild ID**: ${guildId}\n- **Ends At**: ${endsAt}`,
+        );
+      },
+    );
+
     server.listen({ port: 5003 }, (error) => {
       const application = "Alert Server";
       if (error) {
         const { message, stack } = error;
         const context = "Server Startup";
-        void sendMail(`[ERROR]: ${context} - ${application}`, `${message}\n\n${String(stack)}`);
-        void sendDiscord(`[ERROR]: ${context} - ${application}`, `${message}\n\n\`\`\`\n${String(stack)}\n\`\`\``);
+        void sendMail(
+          `[ERROR]: ${context} - ${application}`,
+          `${message}\n\n${String(stack)}`,
+        );
+        void sendDiscord(
+          `[ERROR]: ${context} - ${application}`,
+          `${message}\n\n\`\`\`\n${String(stack)}\n\`\`\``,
+        );
         return;
       }
       const level = "debug";
@@ -134,7 +199,13 @@ export const instantiateServer = (): void => {
     const context = "Server Startup";
     // eslint-disable-next-line @typescript-eslint/consistent-type-assertions -- Totally being lazy.
     const { message, stack } = error as Error;
-    void sendMail(`[ERROR]: ${context} - ${application}`, `${message}\n\n${stack}`);
-    void sendDiscord(`[ERROR]: ${context} - ${application}`, `${message}\n\n\`\`\`\n${stack}\n\`\`\``);
+    void sendMail(
+      `[ERROR]: ${context} - ${application}`,
+      `${message}\n\n${stack}`,
+    );
+    void sendDiscord(
+      `[ERROR]: ${context} - ${application}`,
+      `${message}\n\n\`\`\`\n${stack}\n\`\`\``,
+    );
   }
 };