Exercise 2: displayName and findByEmail — Possible Solution
=============================================================

export const userHelpers = Prisma.defineExtension((client) =>
  client.$extends({
    name: "userHelpers",
    result: {
      user: {
        displayName: {
          needs: { name: true, email: true },
          compute(user) {
            const name = user.name?.trim();
            return name ? name : user.email.split("@")[0];
          },
        },
      },
    },
    model: {
      user: {
        async findByEmail(email: string) {
          return client.user.findFirst({
            where: { email: { equals: email.trim(), mode: "insensitive" } },
          });
        },
      },
    },
  }),
);

const prisma = base.$extends(userHelpers);

const u = await prisma.user.findByEmail("  ADA@Example.com ");
console.log(u?.displayName);   // "Ada", or "ada" if she has no name

Notes:
- mode: "insensitive" works on PostgreSQL and MongoDB. On MySQL, case
  sensitivity depends on the column's collation; SQLite needs a
  different approach (for example storing emails in lower case).
- findFirst is used rather than findUnique, because findUnique only
  accepts exact matches on unique fields.
- A better long-term fix is to store emails lower-cased when users
  sign up, so a plain findUnique works everywhere.

WHY THIS WORKS AS AN ANSWER
------------------------------
displayName lists both fields it depends on in needs, so it works even
when the caller only selects displayName. The defineExtension(client
=> client.$extends(...)) form gives the model method access to the
client it's attached to, so it doesn't depend on a separate global.
The notes are honest about where case-insensitive matching is and
isn't supported.