Syncing capture models

[stephenwf]

Currently if you are running a project, capture models are copied when you start working on a canvas. That copy is not updated if the project is updated. This ensures that any work done on a canvas is preserved and editable, however it also makes it more difficult to add fields or make corrections. Here is an overview of what could and could not be synchronised in a capture model.

Safe to sync

• Existing field descriptive updates label, description at position
• Adding a new field to an entity
• Existing field functional updates (multiline, dropdown options etc.)
• New entity with new fields
• Adding selector to field

Possible risk

• Updating dropdown options: the chosen value may not be in the new dropdown values for models
• Initial values (no way to know if an empty value is correct)
• Changing selector type (if there is an existing value)

Things we cannot sync (for now)

• Capture model field changing type (we might be able to, if the values can be mapped, but not initially).
• Removing a field - this goes against the capture model format. Existing data will remain.
• Removing an entity
• Changing entity or field from allowMultiple=true to allowMultiple=false
• Moving fields and preserving values

There is also the question of how to perform these synchronisations. Currently the updating of capture models is a slow process and aims to be reliable at the cost of speed. However, for these broad synchronisations it may be impractically slow. For each of the safe to synchronise, and the possible risk list, we could generate a list of bulk operations across all existing models. This would involve loading all of the existing models and parsing them. The update operation could be a single request with a batch-style request of atomic changes. For example:

[
  {
    "type": "update-field-descriptive",
    "payload": {
      "field_id": "1234abc-1234abc-1234abc-1234abc",
      "label" "new label value"
    }
  },
  {
    "type": "new-field",
    "payload": {
      "entity_id": "1234abc-1234abc-1234abc-1234abc",
      "field": {
        "id": "4567abc-4567abc-4567abc-4567abc",
        "label": "new label value",
        "type": "text-field"
      }
    }
  },
  {
    "type": "attach-selector",
    "payload": {
      "field_id": "1234abc-1234abc-1234abc-1234abc",
      "selector": {
        "type": "box-selector"
      }
    }
  }
]

As an example. This could then be processed directly by the capture model service and all models updated at once.