# School JSON format, version 3

Export: `GET /api/dance-schools/{id}/export` downloads readable JSON.
Preview: `POST /api/dance-schools/import/preview` accepts the file itself as
`application/json`, validates without writing, and returns `name`, `dancers`,
`groups`, `shows`, `existingId` and `existingName`.
Commit: `POST /api/dance-schools/import` accepts the same file. For replacement,
provide `?replaceId=<existingId>` as explicit confirmation. A mismatch is rejected;
refresh the preview if another import added or removed the school meanwhile.
There is no merge endpoint.

```json
{
  "formatVersion": 3,
  "key": "1b8fe22c-5ac3-4ab9-a2c8-d1d28d2becee",
  "name": "Studio",
  "dancers": [{ "id": "d1", "name": "Sam", "birthDate": "2010-05-12" }],
  "coaches": [{ "id": "c1", "name": "Alex", "dancerId": "d1" }],
  "groups": [{
    "id": "g1", "category": "Hiphop", "type": "REGULAR",
    "startAge": 12, "endAge": 18, "styles": ["HIPHOP"],
    "dancerIds": ["d1"], "coachId": "c1"
  }],
  "shows": [{
    "id": "s1", "name": "Summer show", "preferredDayParts": 1, "finalized": false,
    "dayParts": [{ "date": "2027-06-12", "type": "MORNING", "groupIds": ["g1"] }]
  }]
}
```

`key` is a persistent UUID independent of the server's numeric school ID. IDs
inside each collection are nonblank strings, unique within that collection, and
local to this file. They can change on export. References must resolve within the
file. A dancer or coach can be referenced by multiple groups. A group can appear
in multiple day parts. A date/type combination can occur once per show, with at most six dayparts.

The optional `coachId` and coach `dancerId` references may be absent or null.
`preferredDayParts` defaults to two (one for a single daypart); `finalized`
defaults to false. Legacy version 2 files remain supported; version 1 is rejected.
Legacy `appearances` counts may be present but do not govern S18 scheduling.
Every imported schedule becomes a draft, even when exported as final.
`preferredDayParts` must be an integer from one to six; a retained value exceeding
the daypart count must be corrected before scheduling or finalization. Collections
may be empty. Names/category must be nonblank. Dates use ISO `yyyy-MM-dd`;
birth dates cannot be in the future. Ages are nonnegative integers with
`startAge <= endAge`. Enum values use the same uppercase names as the management
API. Day-part types are `MORNING`, `AFTERNOON`, `EVENING`.
Unknown fields, duplicate JSON properties, duplicate IDs or membership references, invalid
values and unsupported versions are rejected. Validation is repeated on commit.
The entire school is prepared before publishing it under the shared service lock.
Replacing retains the numeric school ID for existing browser links; imported
child IDs are reassigned to avoid collisions with other schools.

Group types: `SHOW_CASE`, `PRE_EDUCATION`, `SELECTION`, `REGULAR`, `PRE_SCHOOLER`.
Styles: `HIPHOP`, `JAZZ`, `MODERN`, `STREETDANCE`, `CLASSIC`, `BREAKDANCE`.