Exercise 2: Handling P2002 and P2025 — Possible Solution
==========================================================

// users.ts
import { prisma } from "./lib/prisma";
import { Prisma } from "./generated/prisma/client";

export async function registerUser(email: string, name: string) {
  try {
    const user = await prisma.user.create({ data: { email, name } });
    return `Welcome, ${user.name}!`;
  } catch (e) {
    if (e instanceof Prisma.PrismaClientKnownRequestError && e.code === "P2002") {
      return "That email is already registered.";
    }
    throw e;   // anything else is a real problem
  }
}

export async function recordView(slug: string) {
  try {
    return await prisma.post.update({
      where: { slug },
      data:  { viewCount: { increment: 1 } },
    });
  } catch (e) {
    if (e instanceof Prisma.PrismaClientKnownRequestError && e.code === "P2025") {
      return null;    // no post with that slug
    }
    throw e;
  }
}

Why this approach:

  - Catching the database's own error, rather than checking "does this
    email exist?" first, avoids a race: two sign-ups could both pass a
    check and then one would still fail. The unique constraint is the
    real guarantee.
  - Only the expected codes are handled; everything else is re-thrown,
    so real bugs aren't hidden.
  - increment is atomic, so simultaneous views are all counted.

WHY THIS WORKS AS AN ANSWER
------------------------------
It handles the two most common error codes precisely, re-throws
anything unexpected, and explains why relying on the database's
constraint is safer than checking first.