Per organized-ideas.md §8. Backend tables/RLS (diagrams, diagram_collaborators,
diagram_snapshots) already existed from an earlier phase — this is the
frontend for them, plus two small backend additions.
Backend (supabase/migrations/20260913000000_diagram_sharing.sql):
- find_user_id_by_username(text): lets any authenticated user resolve a
username to an id for "share with @username" — unlike general profile
browsing (blocked by profiles_select_self_or_super_admin), a username is
meant to be a shareable handle, so this is deliberately not gated.
- diagram_collaborator_usernames / diagram_snapshot_saved_by_usernames:
same pattern as the admin-review-queue phase's submitter-username
lookup — batched per diagram, gated to "can you see this diagram at all"
(reusing diagrams_select's own helper functions).
- prune_diagram_snapshots trigger: keeps the 50 most recent snapshots per
diagram, enforced at write time rather than a scheduled job (diagram_
snapshots has no update/delete policy for regular users at all).
- 14 new pgTAP tests (52/52 total).
Frontend:
- DiagramCollaboratorRepository/store + DiagramSharingModal: add/remove
collaborators by username, per-person view/edit permission, owner-only
controls.
- DiagramSnapshotRepository/store + VersionHistoryModal (its own top-bar
button, not nested under Share — moved there after review): periodic
checkpoints (one per 5 min of active editing) written as a side effect
of normal saves, list + restore.
- Restore's duplicate-snapshot problem: repeatedly jumping between old
versions without editing in between was writing a near-duplicate safety
snapshot on every jump. Fixed by having projectStore track which
snapshot the diagram was last restored from and its updatedAt at that
moment (touch() always advances updatedAt on a genuine edit) — a restore
skips the safety snapshot when nothing has changed since the last one,
and the tracking clears on any real edit so in-progress work stays
protected.
- DiagramRepository gains getAccess() (owner id + your own permission for
the open diagram) — surfaced in projectStore as `access`.
- View-only enforcement: FlowCanvas disables drag/connect/drop
(nodesDraggable/nodesConnectable + guarded handlers), DeviceInspector/
ConnectionInspector wrap their controls in a disabled <fieldset>,
DevicePalette disables adding devices to the canvas, TopBar disables the
rename field, and a ViewOnlyBanner makes the restriction visible instead
of leaving a collaborator to discover it as controls that just don't
work. Autosave itself also refuses to write for a view-only user, as a
backstop behind the UI-level lockdown.
Verified: tsc -b and oxlint clean; supabase db reset + 52/52 pgTAP tests
pass; confirmed find_user_id_by_username works through the real REST API
via a live curl call (signup, confirm, resolve). Manually tested two-
account sharing (view vs. edit), restoring history, and the duplicate-
snapshot fix.
