Build the Preferences API

Task

Create an authenticated endpoint for reading and updating ReaderPreference.

Route

Create:

app/api/preferences/reader/route.ts

Load the current user’s preference record:

const preference = await prisma.readerPreference.findUnique({
  where: { userId: user.id },
});

Update with an ownership predicate represented by the unique userId relation:

await prisma.readerPreference.upsert({
  where: { userId: user.id },
  create: {
    userId: user.id,
    theme,
    fontFamily,
    fontSize,
    lineHeight,
    contentWidth,
  },
  update: {
    theme,
    fontFamily,
    fontSize,
    lineHeight,
    contentWidth,
  },
});

Validate every value before persisting it.

Test

GET the preferences, update one setting, reload, and GET again.

Checkpoint

Reader preferences have a user-scoped persistence boundary.