feature(editor) Snatching of control support.

- Modified `UpdateProjectServerState` to take a `Partial<ProjectServerState>`.
- Renamed `releaseControl` to `clearAllControlFromThisEditor`.
- Created `CollaborationStateUpdater` component to manage the visibility changes of the editor.
- Added `SnatchProjectControl` and `ReleaseProjectControl` to `CollaborationRequest`.
- Renamed `ClaimProjectControlResult` to `RequestProjectControlResult`.
- Renamed `ClearAllOfCollaboratorsControlResult` to `ReleaseControlResult`.
- Added `snatchControlOverProject` and releaseControlOverProject`.
- Renamed `releaseControl` to `clearAllControlFromThisEditor`.
- Modified `editorDispatchClosingOut` to use `result.projectServerState` instead of `storedState.projectServerState`.
- Modified `editorDispatchInner` to take account of `projectServerState` when determining if anything has changed.
- Changed `getProjectServerState` to return a more useful value for test environments and to check
  if the user owns a project before attempting to claim ownership.
- Added `owner_id` column to `project_collaboration`.
- Updated some database logic to take account of `owner_id` in `project_collaboration`.
- Added `forceClaimCollaborationControl` and `releaseCollaborationControl` to the database handling.
- Added `SnatchCollaborationControl` and `ReleaseCollaborationControl` to `ServiceTypes`.
- Modified `ClearCollaboratorOwnership` to take the user ID.

editor/src/components/editor/action-types.ts

@@ -1052,7 +1052,7 @@ export interface ClearPostActionSession {
 
 export interface UpdateProjectServerState {
   action: 'UPDATE_PROJECT_SERVER_STATE'
-  serverState: ProjectServerState
+  serverState: Partial<ProjectServerState>
 }
 
 export interface UpdateTopLevelElementsFromCollaborationUpdate {

editor/src/components/editor/actions/action-creators.ts

@@ -1659,7 +1659,7 @@ export function clearPostActionData(): ClearPostActionSession {
 }
 
 export function updateProjectServerState(
-  projectServerState: ProjectServerState,
+  projectServerState: Partial<ProjectServerState>,
 ): UpdateProjectServerState {
   return {
     action: 'UPDATE_PROJECT_SERVER_STATE',

editor/src/components/editor/editor-component.tsx

@@ -70,6 +70,7 @@ import { useDisplayOwnershipWarning } from './project-owner-hooks'
 import { EditorModes } from './editor-modes'
 import { allowedToEditProject } from './store/collaborative-editing'
 import { useDataThemeAttributeOnBody } from '../../core/commenting/comment-hooks'
+import { CollaborationStateUpdater } from './store/collaboration-state'
 
 const liveModeToastId = 'play-mode-toast'
 
@@ -556,7 +557,9 @@ export function EditorComponent(props: EditorProps) {
           forkedFromProjectId={forkedFromProjectId}
           dispatch={dispatch}
         >
-          <EditorComponentInner {...props} />
+          <CollaborationStateUpdater projectId={projectId} dispatch={dispatch}>
+            <EditorComponentInner {...props} />
+          </CollaborationStateUpdater>
         </ProjectServerStateUpdater>
       </DndProvider>
     </RoomProvider>

editor/src/components/editor/persistence/persistence.ts

@@ -27,7 +27,7 @@ import {
   userLogOutEvent,
 } from './generic/persistence-machine'
 import type { PersistenceBackendAPI, PersistenceContext } from './generic/persistence-types'
-import { releaseControl } from '../store/collaborative-editing'
+import { clearAllControlFromThisEditor } from '../store/collaborative-editing'
 
 export class PersistenceMachine {
   private interpreter: Interpreter<
@@ -136,7 +136,7 @@ export class PersistenceMachine {
 
     window.addEventListener('beforeunload', async (e) => {
       if (this.isSafeToClose()) {
-        void releaseControl()
+        void clearAllControlFromThisEditor()
       } else {
         this.sendThrottledSave()
         e.preventDefault()

editor/src/components/editor/store/collaboration-state.tsx

@@ -0,0 +1,49 @@
+import React from 'react'
+import type { EditorDispatch } from '../action-types'
+import { releaseControlOverProject, snatchControlOverProject } from './collaborative-editing'
+import { Substores, useEditorState } from './store-hook'
+import { updateProjectServerState } from '../actions/action-creators'
+
+interface CollaborationStateUpdaterProps {
+  projectId: string | null
+  dispatch: EditorDispatch
+}
+
+export const CollaborationStateUpdater = React.memo(
+  (props: React.PropsWithChildren<CollaborationStateUpdaterProps>) => {
+    const { projectId, dispatch, children } = props
+    const isMyProject = useEditorState(
+      Substores.projectServerState,
+      (store) => store.projectServerState.isMyProject,
+      'CollaborationStateUpdater isMyProject',
+    )
+    React.useEffect(() => {
+      function handleVisibilityChange(): void {
+        if (projectId != null) {
+          // If the document is hidden, that means the editor is in the background
+          // or minimised, so release control. Otherwise if it has become unhidden
+          // then snatch control of the project.
+          if (document.hidden) {
+            void releaseControlOverProject(projectId).then(() => {
+              dispatch([updateProjectServerState({ currentlyHolderOfTheBaton: false })])
+            })
+          } else {
+            // Only attempt to do any kind of snatching of control if the project is "mine".
+            if (isMyProject === 'yes') {
+              void snatchControlOverProject(projectId).then((controlResult) => {
+                dispatch([
+                  updateProjectServerState({ currentlyHolderOfTheBaton: controlResult ?? false }),
+                ])
+              })
+            }
+          }
+        }
+      }
+      document.addEventListener('visibilitychange', handleVisibilityChange)
+      return () => {
+        document.removeEventListener('visibilitychange', handleVisibilityChange)
+      }
+    }, [dispatch, projectId, isMyProject])
+    return <>{children}</>
+  },
+)

editor/src/components/editor/store/collaborative-editing.ts

@@ -630,6 +630,40 @@ export function claimProjectControl(
   }
 }
 
+export interface SnatchProjectControl {
+  type: 'SNATCH_PROJECT_CONTROL'
+  projectID: string
+  collaborationEditor: string
+}
+
+export function snatchProjectControl(
+  projectID: string,
+  collaborationEditor: string,
+): SnatchProjectControl {
+  return {
+    type: 'SNATCH_PROJECT_CONTROL',
+    projectID: projectID,
+    collaborationEditor: collaborationEditor,
+  }
+}
+
+export interface ReleaseProjectControl {
+  type: 'RELEASE_PROJECT_CONTROL'
+  projectID: string
+  collaborationEditor: string
+}
+
+export function releaseProjectControl(
+  projectID: string,
+  collaborationEditor: string,
+): ReleaseProjectControl {
+  return {
+    type: 'RELEASE_PROJECT_CONTROL',
+    projectID: projectID,
+    collaborationEditor: collaborationEditor,
+  }
+}
+
 export interface ClearAllOfCollaboratorsControl {
   type: 'CLEAR_ALL_OF_COLLABORATORS_CONTROL'
   collaborationEditor: string
@@ -644,18 +678,22 @@ export function clearAllOfCollaboratorsControl(
   }
 }
 
-export type CollaborationRequest = ClaimProjectControl | ClearAllOfCollaboratorsControl
+export type CollaborationRequest =
+  | ClaimProjectControl
+  | SnatchProjectControl
+  | ReleaseProjectControl
+  | ClearAllOfCollaboratorsControl
 
-export interface ClaimProjectControlResult {
-  type: 'CLAIM_PROJECT_CONTROL_RESULT'
+export interface RequestProjectControlResult {
+  type: 'REQUEST_PROJECT_CONTROL_RESULT'
   successfullyClaimed: boolean
 }
 
-export interface ClearAllOfCollaboratorsControlResult {
-  type: 'CLEAR_ALL_OF_COLLABORATORS_CONTROL_RESULT'
+export interface ReleaseControlResponse {
+  type: 'RELEASE_CONTROL_RESULT'
 }
 
-export type CollaborationResponse = ClaimProjectControlResult | ClearAllOfCollaboratorsControlResult
+export type CollaborationResponse = RequestProjectControlResult | ReleaseControlResponse
 
 const collaborationEditor = UUID()
 
@@ -681,22 +719,51 @@ export async function claimControlOverProject(projectID: string | null): Promise
   if (projectID == null || !isFeatureEnabled('Baton Passing For Control')) {
     return null
   }
+  if (document.hidden) {
+    return false
+  }
 
   const request = claimProjectControl(projectID, collaborationEditor)
   const response = await callCollaborationEndpoint(request)
-  if (response.type === 'CLAIM_PROJECT_CONTROL_RESULT') {
+  if (response.type === 'REQUEST_PROJECT_CONTROL_RESULT') {
+    return response.successfullyClaimed
+  } else {
+    throw new Error(`Unexpected response: ${JSON.stringify(response)}`)
+  }
+}
+
+export async function snatchControlOverProject(projectID: string | null): Promise<boolean | null> {
+  if (projectID == null || !isFeatureEnabled('Baton Passing For Control')) {
+    return null
+  }
+
+  const request = snatchProjectControl(projectID, collaborationEditor)
+  const response = await callCollaborationEndpoint(request)
+  if (response.type === 'REQUEST_PROJECT_CONTROL_RESULT') {
     return response.successfullyClaimed
   } else {
     throw new Error(`Unexpected response: ${JSON.stringify(response)}`)
   }
 }
 
-export async function releaseControl(): Promise<void> {
+export async function releaseControlOverProject(projectID: string | null): Promise<void> {
+  if (projectID == null || !isFeatureEnabled('Baton Passing For Control')) {
+    return
+  }
+
+  const request = releaseProjectControl(projectID, collaborationEditor)
+  const response = await callCollaborationEndpoint(request)
+  if (response.type !== 'RELEASE_CONTROL_RESULT') {
+    throw new Error(`Unexpected response: ${JSON.stringify(response)}`)
+  }
+}
+
+export async function clearAllControlFromThisEditor(): Promise<void> {
   if (isFeatureEnabled('Baton Passing For Control')) {
     const request = clearAllOfCollaboratorsControl(collaborationEditor)
 
     const response = await callCollaborationEndpoint(request)
-    if (response.type !== 'CLEAR_ALL_OF_COLLABORATORS_CONTROL_RESULT') {
+    if (response.type !== 'RELEASE_CONTROL_RESULT') {
       throw new Error(`Unexpected response: ${JSON.stringify(response)}`)
     }
   }

editor/src/components/editor/store/dispatch.tsx

@@ -628,7 +628,7 @@ export function editorDispatchClosingOut(
     ]),
     saveCountThisSession: saveCountThisSession + (shouldSave ? 1 : 0),
     builtInDependencies: storedState.builtInDependencies,
-    projectServerState: storedState.projectServerState,
+    projectServerState: result.projectServerState,
     collaborativeEditingSupport: storedState.collaborativeEditingSupport,
   }
 
@@ -830,6 +830,7 @@ function editorDispatchInner(
       storedState.nothingChanged &&
       storedState.unpatchedEditor === result.unpatchedEditor &&
       storedState.userState === result.userState &&
+      storedState.projectServerState === result.projectServerState &&
       storedState.postActionInteractionSession === result.postActionInteractionSession
 
     const domMetadataChanged =

editor/src/components/editor/store/editor-update.tsx

@@ -521,6 +521,9 @@ export function runUpdateProjectServerState(
 ): EditorStoreUnpatched {
   return {
     ...working,
-    projectServerState: action.serverState,
+    projectServerState: {
+      ...working.projectServerState,
+      ...action.serverState,
+    },
   }
 }

editor/src/components/editor/store/project-server-state.tsx

@@ -80,7 +80,11 @@ export async function getProjectServerState(
   forkedFromProjectId: string | null,
 ): Promise<ProjectServerState> {
   if (IS_TEST_ENVIRONMENT) {
-    return emptyProjectServerState()
+    return {
+      ...emptyProjectServerState(),
+      isMyProject: 'yes',
+      currentlyHolderOfTheBaton: true,
+    }
   } else {
     const projectListing = projectId == null ? null : await fetchProjectMetadata(projectId)
     const forkedFromProjectListing =
@@ -95,7 +99,9 @@ export async function getProjectServerState(
     }
     const ownership = await getOwnership()
 
-    const holderOfTheBaton = (await claimControlOverProject(projectId)) ?? ownership.isOwner
+    const holderOfTheBaton = ownership.isOwner
+      ? (await claimControlOverProject(projectId)) ?? ownership.isOwner
+      : false
 
     return {
       isMyProject: ownership.isOwner ? 'yes' : 'no',

server/migrations/005.sql

@@ -0,0 +1,2 @@
+ALTER TABLE ONLY "public"."project_collaboration"
+    ADD COLUMN "owner_id" character varying;