Validation

Summary

How 2Wee validates field values — three layers, field locking, and the distinction between blur and save validation.

How it works

Validation layers

When a user leaves a field, validations run in order:

Layer 1: Type-Specific Parsing (synchronous, client-side)
  │  Date shorthand → full date
  │  Time shorthand → full time
  │  Fails? → Stay in edit mode, show parse error
  │
  ▼
Layer 2: Local Validation Rules (synchronous, client-side)
  │  Pattern (regex), Required, Min/Max length, Numeric bounds
  │  Fails? → Stay in edit mode, show validation error, select all
  │
  ▼
Layer 3: Server-Side Validation (asynchronous, network call)
  │  Lookup blur validation: GET /validate/{field_id}/{value}
  │  Succeeds? → Apply autofill values to related fields
  │  Fails? → Navigate back to field, enter edit mode, select all
  │  Network error? → Warning only, don't block user
  │
  ▼
(User can leave the field)

Layers 1 and 2 are synchronous (immediate). Layer 3 is asynchronous — the cursor moves to the next field, then the server responds. If the server rejects the value, the cursor bounces back.

Field locking

When any validation fails, the user cannot leave the field. They must either:

1. Fix the value — type a valid value, validation succeeds, they can leave
2. Press Esc — reverts to the last known good value

While locked:

Key	Behavior
Type a character	Replace selected text, continue editing
Enter / Tab / arrows	Attempt to leave → validation runs again → locked if still invalid
Esc	Revert to last good value, exit edit mode, clear error
Ctrl+S	Validation runs first — if it fails, stays locked

The revert value

The revert value is always the last known good value — not the rejected value. Esc always returns to a safe state.

Blur vs save validation

	Blur validation	Save validation
When	Cursor leaves field	User presses Ctrl+S
Scope	Single field	All changed fields
Endpoint	/validate/{field_id}/{value}	/screen/.../save
Autofill	Yes	No
Field lock	Yes	No (error shown, user decides)

Both are necessary. Blur validation gives instant feedback. Save validation is the final gate for cross-field rules and business logic.

Network error handling

If the validate endpoint is unreachable, the client shows a warning but does not block the user. A flaky network should not prevent editing. The save endpoint validates everything again.