feat: implement credentials login

implements the credentials login functionality

src/lib/auth/register.ts

@@ -0,0 +1,75 @@
+'use server';
+
+import type { z } from 'zod';
+import bcrypt from 'bcryptjs';
+import { registerSchema } from '@/lib/validation/user';
+import { prisma } from '@/prisma';
+
+export async function registerAction(data: z.infer<typeof registerSchema>) {
+  try {
+    const result = await registerSchema.safeParseAsync(data);
+
+    if (!result.success) {
+      return {
+        error: result.error.errors[0].message,
+      };
+    }
+
+    const { email, password, firstName, lastName, username } = result.data;
+
+    const user = await prisma.user.findUnique({
+      where: {
+        email,
+      },
+    });
+
+    if (user) {
+      return {
+        error: 'User already exist with this email',
+      };
+    }
+
+    const existingUsername = await prisma.user.findUnique({
+      where: {
+        name: username,
+      },
+    });
+
+    if (existingUsername) {
+      return {
+        error: 'Username already exists',
+      };
+    }
+
+    const passwordHash = await bcrypt.hash(password, 10);
+
+    await prisma.$transaction(async (tx) => {
+      const { id } = await tx.user.create({
+        data: {
+          email,
+          name: username,
+          password_hash: passwordHash,
+          first_name: firstName,
+          last_name: lastName,
+          emailVerified: new Date(), // TODO: handle email verification
+        },
+      });
+
+      await tx.account.create({
+        data: {
+          userId: id,
+          type: 'credentials',
+          provider: 'credentials',
+          providerAccountId: id,
+        },
+      });
+    });
+
+    return {};
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  } catch (_error) {
+    return {
+      error: 'System error. Please contact support',
+    };
+  }
+}