Split the Projection interface into distinct reader / writer sides.

https://github.com/the-draupnir-project/planning/issues/150

packages/matrix-protection-suite/src/Projection/Projection.ts

@@ -17,6 +17,8 @@ import {
   ProjectionNode,
 } from "./ProjectionNode";
 
+export const ProjectionOrchestrationKey = Symbol("ProjectionOrchestration");
+
 export type ProjectionNodeListener<
   TProjectionNode extends ProjectionNode = ProjectionNode,
 > = (
@@ -25,10 +27,9 @@ export type ProjectionNodeListener<
   previousNode: TProjectionNode
 ) => void;
 
-export interface Projection<
+export interface ProjectionOrchestration<
   TProjectionNode extends AnyProjectionNode = AnyProjectionNode,
 > {
-  readonly currentNode: TProjectionNode;
   addOutput(projection: Projection): this;
   removeOutput(projection: Projection): this;
   applyInput(input: ExtractProjectionInputs<TProjectionNode>): void;
@@ -36,6 +37,13 @@ export interface Projection<
   removeNodeListener(listener: ProjectionNodeListener<TProjectionNode>): this;
 }
 
+export interface Projection<
+  TProjectionNode extends AnyProjectionNode = AnyProjectionNode,
+> {
+  readonly currentNode: TProjectionNode;
+  readonly [ProjectionOrchestrationKey]: ProjectionOrchestration<TProjectionNode>;
+}
+
 export type ExtractProjectionNode<TProjection> =
   TProjection extends Projection<infer TProjectionNode>
     ? TProjectionNode
@@ -57,7 +65,7 @@ export type ExtractProjectionNode<TProjection> =
 export class ProjectionOutputHelper<
   TProjectionNode extends ProjectionNode = ProjectionNode,
 > {
-  private readonly outputs = new Set<Projection<ProjectionNode>>();
+  private readonly outputs = new Set<ProjectionOrchestration<ProjectionNode>>();
   private readonly emitter = new EventEmitter();
   public constructor(public currentNode: TProjectionNode) {
     // nothing to do.
@@ -81,12 +89,12 @@ export class ProjectionOutputHelper<
   }
 
   addOutput(projection: Projection): this {
-    this.outputs.add(projection);
+    this.outputs.add(projection[ProjectionOrchestrationKey]);
     return this;
   }
 
   removeOutput(projection: Projection): this {
-    this.outputs.delete(projection);
+    this.outputs.delete(projection[ProjectionOrchestrationKey]);
     return this;
   }
 

packages/matrix-protection-suite/src/Protection/ProtectionHandles.ts

@@ -12,6 +12,7 @@ import { ProtectedRoomsSet } from "./ProtectedRoomsSet";
 import { Protection, ProtectionDescription } from "./Protection";
 import { AnyProjectionNode } from "../Projection/ProjectionNode";
 import { StandardHandleRegistryDescription } from "./HandleRegistry/StandardHandleRegistryDescription";
+import { ProjectionOrchestrationKey } from "../Projection/Projection";
 
 export const ProtectionIntentProjectionNodeHandle: HandleDescription<
   "handleIntentProjectionNode",
@@ -38,11 +39,15 @@ export const ProtectionIntentProjectionNodeHandle: HandleDescription<
       protection.handleIntentProjectionNode?.(node, delta);
     return lifetime.allocateResource(
       () => {
-        protection.intentProjection?.addNodeListener(listener);
+        protection.intentProjection?.[
+          ProjectionOrchestrationKey
+        ].addNodeListener(listener);
         return Ok(listener);
       },
       () => () => {
-        protection.intentProjection?.removeNodeListener(listener);
+        protection.intentProjection?.[
+          ProjectionOrchestrationKey
+        ].removeNodeListener(listener);
       }
     ) as Result<void>;
   },

packages/matrix-protection-suite/src/Protection/StandardProtections/MemberBanSynchronisation/MemberBanIntentProjection.ts

@@ -14,6 +14,7 @@ import {
 } from "../../../MembershipPolicies/SetMembershipPolicyRevisionIssuer";
 import {
   Projection,
+  ProjectionOrchestrationKey,
   ProjectionOutputHelper,
 } from "../../../Projection/Projection";
 import {
@@ -44,6 +45,10 @@ export class StandardMemberBanIntentProjection
     );
   }
 
+  public get [ProjectionOrchestrationKey]() {
+    return this;
+  }
+
   private handleUpstreamRevision = ((_revision, delta) => {
     this.applyInput(delta);
   }) satisfies SetMembershipPolicyRevisionListener;

packages/matrix-protection-suite/src/Protection/StandardProtections/ServerBanSynchronisation/ServerBanIntentProjection.ts

@@ -14,6 +14,7 @@ import {
 } from "../../../PolicyList/PolicyListRevisionIssuer";
 import {
   Projection,
+  ProjectionOrchestrationKey,
   ProjectionOutputHelper,
 } from "../../../Projection/Projection";
 import {
@@ -49,4 +50,8 @@ export class StandardServerBanIntentProjection
     this.policyListRevisionIssuer.off("revision", this.handleUpstreamRevision);
     super[Symbol.dispose]();
   }
+
+  public get [ProjectionOrchestrationKey]() {
+    return this;
+  }
 }