🧑‍💻 Fixed an transfer transaction helper

prisma/migrations/20221019142757_modules/migration.sql

@@ -0,0 +1,16 @@
+-- RedefineTables
+PRAGMA foreign_keys=OFF;
+CREATE TABLE "new_GuildMember" (
+    "userId" TEXT NOT NULL,
+    "guildId" TEXT NOT NULL,
+    "creditsEarned" INTEGER NOT NULL DEFAULT 0,
+    "pointsEarned" INTEGER NOT NULL DEFAULT 0,
+    CONSTRAINT "GuildMember_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User" ("id") ON DELETE RESTRICT ON UPDATE CASCADE,
+    CONSTRAINT "GuildMember_guildId_fkey" FOREIGN KEY ("guildId") REFERENCES "Guild" ("id") ON DELETE RESTRICT ON UPDATE CASCADE
+);
+INSERT INTO "new_GuildMember" ("creditsEarned", "guildId", "pointsEarned", "userId") SELECT coalesce("creditsEarned", 0) AS "creditsEarned", "guildId", coalesce("pointsEarned", 0) AS "pointsEarned", "userId" FROM "GuildMember";
+DROP TABLE "GuildMember";
+ALTER TABLE "new_GuildMember" RENAME TO "GuildMember";
+CREATE UNIQUE INDEX "GuildMember_userId_guildId_key" ON "GuildMember"("userId", "guildId");
+PRAGMA foreign_key_check;
+PRAGMA foreign_keys=ON;

prisma/schema.prisma

@@ -2,7 +2,8 @@
 // learn more about it in the docs: https://pris.ly/d/prisma-schema
 
 generator client {
-  provider = "prisma-client-js"
+  provider        = "prisma-client-js"
+  previewFeatures = ["interactiveTransactions"]
 }
 
 datasource db {
@@ -86,8 +87,8 @@ model GuildMember {
   // Settings
 
   // Modules
-  creditsEarned Int?
-  pointsEarned  Int?
+  creditsEarned Int @default(0)
+  pointsEarned  Int @default(0)
 
   // Unique Identifier
   @@unique([userId, guildId])

src/helpers/transferCredits.ts

@@ -0,0 +1,93 @@
+import { Guild, User } from "discord.js";
+import prisma from "../prisma";
+
+export default async (guild: Guild, from: User, to: User, amount: number) => {
+  return await prisma.$transaction(async (tx) => {
+    // 1. Decrement amount from the sender.
+    const sender = await tx.guildMember.upsert({
+      update: {
+        creditsEarned: {
+          decrement: amount,
+        },
+      },
+      create: {
+        user: {
+          connectOrCreate: {
+            create: {
+              id: from.id,
+            },
+            where: {
+              id: from.id,
+            },
+          },
+        },
+        guild: {
+          connectOrCreate: {
+            create: {
+              id: guild.id,
+            },
+            where: {
+              id: guild.id,
+            },
+          },
+        },
+        creditsEarned: -amount,
+      },
+      where: {
+        userId_guildId: {
+          userId: from.id,
+          guildId: guild.id,
+        },
+      },
+    });
+
+    if (!sender) throw new Error("No sender available");
+
+    if (!sender.creditsEarned) throw new Error("No credits available");
+
+    // 2. Verify that the sender's balance didn't go below zero.
+    if (sender.creditsEarned < 0) {
+      throw new Error(`${from} doesn't have enough to send ${amount}`);
+    }
+
+    // 3. Increment the recipient's balance by amount
+    const recipient = await tx.guildMember.upsert({
+      update: {
+        creditsEarned: {
+          increment: amount,
+        },
+      },
+      create: {
+        user: {
+          connectOrCreate: {
+            create: {
+              id: to.id,
+            },
+            where: {
+              id: to.id,
+            },
+          },
+        },
+        guild: {
+          connectOrCreate: {
+            create: {
+              id: guild.id,
+            },
+            where: {
+              id: guild.id,
+            },
+          },
+        },
+        creditsEarned: +amount,
+      },
+      where: {
+        userId_guildId: {
+          userId: to.id,
+          guildId: guild.id,
+        },
+      },
+    });
+
+    return recipient;
+  });
+};