From 614fc8936d94eb835e8b409e8ea991916e872daa Mon Sep 17 00:00:00 2001
From: gnuxie <Gnuxie@protonmail.com>
Date: Mon, 20 Apr 2026 13:09:24 +0100
Subject: [PATCH] Make the node state delta authoritative in existing
 projections.

https://github.com/the-draupnir-project/planning/issues/123
---
 .../MemberBanIntentProjectionNode.ts          | 52 ++++++++++++-------
 .../ServerBanIntentProjectionNode.ts          | 42 +++++++++------
 2 files changed, 60 insertions(+), 34 deletions(-)

diff --git a/packages/matrix-protection-suite/src/Protection/StandardProtections/MemberBanSynchronisation/MemberBanIntentProjectionNode.ts b/packages/matrix-protection-suite/src/Protection/StandardProtections/MemberBanSynchronisation/MemberBanIntentProjectionNode.ts
index 0218daf5..e5bf2e62 100644
--- a/packages/matrix-protection-suite/src/Protection/StandardProtections/MemberBanSynchronisation/MemberBanIntentProjectionNode.ts
+++ b/packages/matrix-protection-suite/src/Protection/StandardProtections/MemberBanSynchronisation/MemberBanIntentProjectionNode.ts
@@ -39,14 +39,17 @@ export type MemberBanInputProjectionNode = ProjectionNode<
 > &
   MembershipPolicyRevision;
 
+export interface MemberBanIntentProjectionDelta {
+  ban: StringUserID[];
+  recall: StringUserID[];
+}
+
 // use add/remove for steady state intents
 // When the intent becomes effectual, matches will be removed
 // upstream and so this model will remain consistent
-export interface MemberBanIntentProjectionDelta {
+export interface MemberBanIntentProjectionStateDelta {
   add: MemberPolicyMatch[];
   remove: MemberPolicyMatch[];
-  ban: StringUserID[];
-  recall: StringUserID[];
 }
 
 function isPolicyRelevant(policy: LiteralPolicyRule | GlobPolicyRule): boolean {
@@ -59,7 +62,7 @@ function isPolicyRelevant(policy: LiteralPolicyRule | GlobPolicyRule): boolean {
 export type MemberBanIntentProjectionNode = ProjectionNode<
   [MemberBanInputProjectionNode],
   MemberBanIntentProjectionDelta,
-  undefined,
+  MemberBanIntentProjectionStateDelta,
   {
     allMembersWithRules(): MemberPolicyMatches[];
     allRulesMatchingMember(
@@ -71,8 +74,8 @@ export type MemberBanIntentProjectionNode = ProjectionNode<
 export const MemberBanIntentProjectionNodeHelper = Object.freeze({
   reduceMembershipPolicyDelta(
     input: MembershipPolicyRevisionDelta
-  ): Pick<MemberBanIntentProjectionDelta, "add" | "remove"> {
-    const output: Pick<MemberBanIntentProjectionDelta, "add" | "remove"> = {
+  ): MemberBanIntentProjectionStateDelta {
+    const output: MemberBanIntentProjectionStateDelta = {
       add: [],
       remove: [],
     };
@@ -89,7 +92,7 @@ export const MemberBanIntentProjectionNodeHelper = Object.freeze({
     return output;
   },
   reduceIntentDelta(
-    input: Pick<MemberBanIntentProjectionDelta, "add" | "remove">,
+    input: MemberBanIntentProjectionStateDelta,
     policies: PersistentMap<
       StringUserID,
       List<LiteralPolicyRule | GlobPolicyRule>
@@ -102,7 +105,6 @@ export const MemberBanIntentProjectionNodeHelper = Object.freeze({
       (rule) => rule.entity as StringUserID
     );
     return {
-      ...input,
       ban: intents.intend,
       recall: intents.recall,
     };
@@ -138,23 +140,28 @@ export class StandardMemberBanIntentProjectionNode implements MemberBanIntentPro
 
   reduceInput(
     input: ExtractInputDeltaShapes<[MemberBanInputProjectionNode]>
-  ): ProjectionNodeDelta<MemberBanIntentProjectionDelta, undefined> {
+  ): ProjectionNodeDelta<
+    MemberBanIntentProjectionDelta,
+    MemberBanIntentProjectionStateDelta
+  > {
+    const nodeStateDelta =
+      MemberBanIntentProjectionNodeHelper.reduceMembershipPolicyDelta(input);
     return {
       downstreamDelta: MemberBanIntentProjectionNodeHelper.reduceIntentDelta(
-        MemberBanIntentProjectionNodeHelper.reduceMembershipPolicyDelta(input),
+        nodeStateDelta,
         this.intents
       ),
-      nodeStateDelta: undefined,
+      nodeStateDelta,
     };
   }
 
   reduceDelta(
     projectionNodeDelta: ProjectionNodeDelta<
       MemberBanIntentProjectionDelta,
-      undefined
+      MemberBanIntentProjectionStateDelta
     >
   ): MemberBanIntentProjectionNode {
-    const input = projectionNodeDelta.downstreamDelta;
+    const input = projectionNodeDelta.nodeStateDelta;
     let nextIntents = this.intents;
     nextIntents = ListMultiMap.addValues(
       nextIntents,
@@ -174,7 +181,10 @@ export class StandardMemberBanIntentProjectionNode implements MemberBanIntentPro
 
   reduceInitialInputs([membershipPolicyRevision]: [
     MemberBanInputProjectionNode,
-  ]): ProjectionNodeDelta<MemberBanIntentProjectionDelta, undefined> {
+  ]): ProjectionNodeDelta<
+    MemberBanIntentProjectionDelta,
+    MemberBanIntentProjectionStateDelta
+  > {
     if (!this.isEmpty()) {
       throw new TypeError(
         "This can only be called on an empty projection node"
@@ -183,17 +193,21 @@ export class StandardMemberBanIntentProjectionNode implements MemberBanIntentPro
     const matches = membershipPolicyRevision
       .allMembersWithRules()
       .map((member) =>
-        member.policies.map((policy) => ({ userID: member.userID, policy }))
+        member.policies
+          .filter(isPolicyRelevant)
+          .map((policy) => ({ userID: member.userID, policy }))
       )
       .flat();
+    const nodeStateDelta = {
+      add: matches,
+      remove: [],
+    };
     return {
       downstreamDelta: {
-        add: matches,
-        ban: matches.map((match) => match.userID),
-        remove: [],
+        ban: [...new Set(matches.map((match) => match.userID))],
         recall: [],
       },
-      nodeStateDelta: undefined,
+      nodeStateDelta,
     };
   }
 
diff --git a/packages/matrix-protection-suite/src/Protection/StandardProtections/ServerBanSynchronisation/ServerBanIntentProjectionNode.ts b/packages/matrix-protection-suite/src/Protection/StandardProtections/ServerBanSynchronisation/ServerBanIntentProjectionNode.ts
index a0098a40..5c6ebb08 100644
--- a/packages/matrix-protection-suite/src/Protection/StandardProtections/ServerBanSynchronisation/ServerBanIntentProjectionNode.ts
+++ b/packages/matrix-protection-suite/src/Protection/StandardProtections/ServerBanSynchronisation/ServerBanIntentProjectionNode.ts
@@ -31,6 +31,9 @@ import { ListMultiMap } from "../../../Projection/ListMultiMap";
 export type ServerBanIntentProjectionDelta = {
   deny: StringServerName[];
   recall: StringServerName[];
+};
+
+export type ServerBanIntentProjectionStateDelta = {
   add: (LiteralPolicyRule | GlobPolicyRule)[];
   remove: (LiteralPolicyRule | GlobPolicyRule)[];
 };
@@ -41,7 +44,7 @@ export type ServerBanIntentProjectionDelta = {
 export type ServerBanIntentProjectionNode = ProjectionNode<
   [PolicyListBridgeProjectionNode],
   ServerBanIntentProjectionDelta,
-  undefined,
+  ServerBanIntentProjectionStateDelta,
   {
     deny: StringServerName[];
   }
@@ -50,11 +53,11 @@ export type ServerBanIntentProjectionNode = ProjectionNode<
 export const ServerBanIntentProjectionHelper = Object.freeze({
   reducePolicyDelta(
     input: PolicyRuleChange[]
-  ): Pick<ServerBanIntentProjectionDelta, "add" | "remove"> {
-    const output: Pick<ServerBanIntentProjectionDelta, "add" | "remove"> = {
+  ): ServerBanIntentProjectionStateDelta {
+    const output: ServerBanIntentProjectionStateDelta = {
       add: [],
       remove: [],
-    } satisfies Pick<ServerBanIntentProjectionDelta, "add" | "remove">;
+    };
     for (const change of input) {
       if (change.rule.kind !== PolicyRuleType.Server) {
         continue;
@@ -85,7 +88,7 @@ export const ServerBanIntentProjectionHelper = Object.freeze({
   },
 
   reduceIntentDelta(
-    input: Pick<ServerBanIntentProjectionDelta, "add" | "remove">,
+    input: ServerBanIntentProjectionStateDelta,
     policies: PersistentMap<
       StringServerName,
       List<GlobPolicyRule | LiteralPolicyRule>
@@ -98,7 +101,6 @@ export const ServerBanIntentProjectionHelper = Object.freeze({
       (rule) => rule.entity as StringServerName
     );
     return {
-      ...input,
       deny: intents.intend,
       recall: intents.recall,
     };
@@ -128,19 +130,27 @@ export class StandardServerBanIntentProjectionNode implements ServerBanIntentPro
 
   reduceInput(
     input: PolicyRuleChange[]
-  ): ProjectionNodeDelta<ServerBanIntentProjectionDelta, undefined> {
+  ): ProjectionNodeDelta<
+    ServerBanIntentProjectionDelta,
+    ServerBanIntentProjectionStateDelta
+  > {
+    const nodeStateDelta =
+      ServerBanIntentProjectionHelper.reducePolicyDelta(input);
     return {
       downstreamDelta: ServerBanIntentProjectionHelper.reduceIntentDelta(
-        ServerBanIntentProjectionHelper.reducePolicyDelta(input),
+        nodeStateDelta,
         this.policies
       ),
-      nodeStateDelta: undefined,
+      nodeStateDelta,
     };
   }
 
   reduceInitialInputs([policyListRevision]: [
     PolicyListBridgeProjectionNode,
-  ]): ProjectionNodeDelta<ServerBanIntentProjectionDelta, undefined> {
+  ]): ProjectionNodeDelta<
+    ServerBanIntentProjectionDelta,
+    ServerBanIntentProjectionStateDelta
+  > {
     if (!this.isEmpty()) {
       throw new TypeError("Cannot reduce initial inputs when inialised");
     }
@@ -156,14 +166,16 @@ export class StandardServerBanIntentProjectionNode implements ServerBanIntentPro
     ].filter((rule) => rule.matchType !== PolicyRuleMatchType.HashedLiteral);
     const names = new Set(serverPolicies.map((policy) => policy.entity));
     const downstreamDelta = {
-      add: serverPolicies,
       deny: [...names] as StringServerName[],
-      remove: [],
       recall: [],
     };
+    const nodeStateDelta = {
+      add: serverPolicies,
+      remove: [],
+    };
     return {
       downstreamDelta,
-      nodeStateDelta: undefined,
+      nodeStateDelta,
     };
   }
 
@@ -172,10 +184,10 @@ export class StandardServerBanIntentProjectionNode implements ServerBanIntentPro
   }
 
   reduceDelta({
-    downstreamDelta: input,
+    nodeStateDelta: input,
   }: ProjectionNodeDelta<
     ServerBanIntentProjectionDelta,
-    undefined
+    ServerBanIntentProjectionStateDelta
   >): ServerBanIntentProjectionNode {
     let nextPolicies = this.policies;
     nextPolicies = ListMultiMap.addValues(