refactoring in preparation for adding more resolvers

__tests__/lossy.ts

@@ -1,8 +1,8 @@
 import Debug from 'debug';
 import {Delta, PointerTarget} from "../src/delta";
-import {lastValueFromDeltas} from "../src/last-write-wins";
+import {lastValueFromDeltas, valueFromCollapsedDelta} from "../src/last-write-wins";
 import {Lossless, LosslessViewOne} from "../src/lossless";
-import {Lossy, valueFromCollapsedDelta} from "../src/lossy";
+import {Lossy} from "../src/lossy";
 import {RhizomeNode} from "../src/node";
 const debug = Debug('test:lossy');
 
@@ -16,45 +16,45 @@ type Summary = {
   roles: Role[];
 };
 
-
-function initializer(): Summary {
-  return {
-    roles: []
-  };
-}
-
-// TODO: Add more rigor to this example approach to generating a summary.
-// it's really not CRDT, it likely depends on the order of the pointers.
-// TODO: Prove with failing test
-
-const reducer = (acc: Summary, cur: LosslessViewOne): Summary => {
-  if (cur.referencedAs.includes("role")) {
-    const {delta, value: actor} = lastValueFromDeltas("actor", cur.propertyDeltas["actor"]) ?? {};
-    if (!delta) throw new Error('expected to find delta');
-    if (!actor) throw new Error('expected to find actor');
-    const film = valueFromCollapsedDelta("film", delta);
-    if (!film) throw new Error('expected to find film');
-    acc.roles.push({
-      role: cur.id,
-      actor,
-      film
-    });
+class Summarizer extends Lossy<Summary, Summary> {
+  initializer(): Summary {
+    return {
+      roles: []
+    };
   }
 
-  return acc;
-}
+  // TODO: Add more rigor to this example approach to generating a summary.
+  // it's really not CRDT, it likely depends on the order of the pointers.
+  // TODO: Prove with failing test
 
-const resolver = (acc: Summary): Summary => {
-  return acc;
-}
+  reducer(acc: Summary, cur: LosslessViewOne): Summary {
+    if (cur.referencedAs.includes("role")) {
+      const {delta, value: actor} = lastValueFromDeltas("actor", cur.propertyDeltas["actor"]) ?? {};
+      if (!delta) throw new Error('expected to find delta');
+      if (!actor) throw new Error('expected to find actor');
+      const film = valueFromCollapsedDelta("film", delta);
+      if (!film) throw new Error('expected to find film');
+      acc.roles.push({
+        role: cur.id,
+        actor,
+        film
+      });
+    }
 
+    return acc;
+  }
+
+  resolver(acc: Summary): Summary {
+    return acc;
+  }
+}
 
 describe('Lossy', () => {
   describe('use a provided initializer, reducer, and resolver to resolve entity views', () => {
     const node = new RhizomeNode();
     const lossless = new Lossless(node);
 
-    const lossy = new Lossy(lossless, initializer, reducer, resolver);
+    const lossy = new Summarizer(lossless);
 
     beforeAll(() => {
       lossless.ingestDelta(new Delta({

__tests__/relational.ts

@@ -0,0 +1,13 @@
+describe('Relational', () => {
+  it.skip('Allows expressing a domain ontology as a relational schema', async () => {});
+
+  // Deltas can be filtered at time of view resolution, and 
+  // excluded if they violate schema constraints;
+  // Ideally the sender minimizes this by locally validating against the constraints.
+  // For cases where deltas conflict, there can be a resolution process, 
+  // with configurable parameters such as duration, quorum, and so on;
+  // or a deterministic algorithm can be applied.
+  
+  it.skip('Can validate a delta against a relational constraint', async () => {});
+  it.skip('Can validate a delta against a set of relational constraints', async () => {});
+});

src/last-write-wins.ts

@@ -1,7 +1,7 @@
 // import Debug from 'debug';
 import {EntityProperties} from "./entity";
-import {CollapsedDelta, Lossless, LosslessViewOne} from "./lossless";
-import {Lossy, valueFromCollapsedDelta} from './lossy';
+import {CollapsedDelta, LosslessViewOne} from "./lossless";
+import {Lossy} from './lossy';
 import {DomainEntityID, PropertyID, PropertyTypes, Timestamp, ViewMany} from "./types";
 // const debug = Debug('rz:lossy:last-write-wins');
 
@@ -27,7 +27,21 @@ export type ResolvedViewMany = ViewMany<ResolvedViewOne>;
 type Accumulator = LossyViewMany<TimestampedProperties>;
 type Result = LossyViewMany<EntityProperties>;
 
-// Function for resolving a value for an entity by last write wins
+// Extract a particular value from a delta's pointers
+export function valueFromCollapsedDelta(
+  key: string,
+  delta: CollapsedDelta
+): string | number | undefined {
+  for (const pointer of delta.pointers) {
+    for (const [k, value] of Object.entries(pointer)) {
+      if (k === key && (typeof value === "string" || typeof value === "number")) {
+        return value;
+      }
+    }
+  }
+}
+
+// Resolve a value for an entity by last write wins
 export function lastValueFromDeltas(
   key: string,
   deltas?: CollapsedDelta[]
@@ -55,46 +69,41 @@ export function lastValueFromDeltas(
   return res;
 }
 
-function initializer(): Accumulator {
-  return {};
-};
-
-function reducer(acc: Accumulator, cur: LosslessViewOne): Accumulator {
-  if (!acc[cur.id]) {
-    acc[cur.id] = {id: cur.id, properties: {}};
-  }
-
-  for (const [key, deltas] of Object.entries(cur.propertyDeltas)) {
-    const {value, timeUpdated} = lastValueFromDeltas(key, deltas) || {};
-    if (!value || !timeUpdated) continue;
-
-    if (timeUpdated > (acc[cur.id].properties[key]?.timeUpdated || 0)) {
-      acc[cur.id].properties[key] = {
-        value,
-        timeUpdated
-      };
-    }
-  }
-  return acc;
-};
-
-function resolver(cur: Accumulator): Result {
-  const res: Result = {};
-
-  for (const [id, ent] of Object.entries(cur)) {
-    res[id] = {id, properties: {}};
-    for (const [key, {value}] of Object.entries(ent.properties)) {
-      res[id].properties[key] = value;
-    }
-  }
-
-  return res;
-};
-
 export class LastWriteWins extends Lossy<Accumulator, Result> {
-  constructor(
-    readonly lossless: Lossless,
-  ) {
-    super(lossless, initializer, reducer, resolver);
+  initializer(): Accumulator {
+    return {};
   }
+
+  reducer(acc: Accumulator, cur: LosslessViewOne): Accumulator {
+    if (!acc[cur.id]) {
+      acc[cur.id] = {id: cur.id, properties: {}};
+    }
+
+    for (const [key, deltas] of Object.entries(cur.propertyDeltas)) {
+      const {value, timeUpdated} = lastValueFromDeltas(key, deltas) || {};
+      if (!value || !timeUpdated) continue;
+
+      if (timeUpdated > (acc[cur.id].properties[key]?.timeUpdated || 0)) {
+        acc[cur.id].properties[key] = {
+          value,
+          timeUpdated
+        };
+      }
+    }
+    return acc;
+  };
+
+  resolver(cur: Accumulator): Result {
+    const res: Result = {};
+
+    for (const [id, ent] of Object.entries(cur)) {
+      res[id] = {id, properties: {}};
+      for (const [key, {value}] of Object.entries(ent.properties)) {
+        res[id].properties[key] = value;
+      }
+    }
+
+    return res;
+  };
 }
+

src/lossy.ts

@@ -4,38 +4,21 @@
 
 import Debug from 'debug';
 import {DeltaFilter, DeltaID} from "./delta";
-import {CollapsedDelta, Lossless, LosslessViewOne} from "./lossless";
+import {Lossless, LosslessViewOne} from "./lossless";
 import {DomainEntityID} from "./types";
 const debug = Debug('rz:lossy');
 
-export type Initializer<Accumulator> = (v: LosslessViewOne) => Accumulator;
-export type Reducer<Accumulator> = (acc: Accumulator, cur: LosslessViewOne) => Accumulator;
-export type Resolver<Accumulator, Result> = (cur: Accumulator) => Result;
-
-// Extract a particular value from a delta's pointers
-export function valueFromCollapsedDelta(
-  key: string,
-  delta: CollapsedDelta
-): string | number | undefined {
-  for (const pointer of delta.pointers) {
-    for (const [k, value] of Object.entries(pointer)) {
-      if (k === key && (typeof value === "string" || typeof value === "number")) {
-        return value;
-      }
-    }
-  }
-}
-
 // We support incremental updates of lossy models.
-export class Lossy<Accumulator, Result> {
+export abstract class Lossy<Accumulator, Result> {
   deltaFilter?: DeltaFilter;
   accumulator?: Accumulator;
 
+  abstract initializer(v: LosslessViewOne): Accumulator;
+  abstract reducer(acc: Accumulator, cur: LosslessViewOne): Accumulator;
+  abstract resolver(cur: Accumulator): Result;
+
   constructor(
     readonly lossless: Lossless,
-    readonly initializer: Initializer<Accumulator>,
-    readonly reducer: Reducer<Accumulator>,
-    readonly resolver: Resolver<Accumulator, Result>,
   ) {
     this.lossless.eventStream.on("updated", (id, deltaIds) => {
       debug(`[${this.lossless.rhizomeNode.config.peerId}] entity ${id} updated, deltaIds:`,

src/relational.ts

@@ -0,0 +1,9 @@
+import {Collection} from "./collection";
+
+
+
+
+export class RelationalCollection extends Collection {
+  // lossy?: 
+
+}