refactor(schema): extract public event definitions (#33579)

packages/schema/src/event.ts

@@ -0,0 +1,125 @@
+export * as Event from "./event"
+
+import { Schema } from "effect"
+import { ascending } from "./identifier"
+import { Location } from "./location"
+import { withStatics } from "./schema"
+
+export const ID = Schema.String.check(Schema.isStartsWith("evt_")).pipe(
+  Schema.brand("Event.ID"),
+  withStatics((schema) => ({ create: () => schema.make("evt_" + ascending()) })),
+)
+export type ID = typeof ID.Type
+
+export type Definition<
+  Type extends string = string,
+  DataSchema extends Schema.Codec<unknown, unknown> = Schema.Codec<unknown, unknown>,
+> = Schema.Top & {
+  readonly type: Type
+  readonly durable?: {
+    readonly version: number
+    readonly aggregate: string
+  }
+  readonly data: DataSchema
+}
+
+export type Data<D extends Definition> = Schema.Schema.Type<D["data"]>
+
+export type Payload<D extends Definition = Definition> = {
+  readonly id: ID
+  readonly type: D["type"]
+  readonly data: Data<D>
+  readonly durable?: {
+    readonly aggregateID: string
+    readonly seq: number
+    readonly version: number
+  }
+  readonly location?: Location.Ref
+  readonly metadata?: Record<string, unknown>
+}
+
+export function define<
+  const Type extends string,
+  Fields extends Readonly<Record<PropertyKey, Schema.Codec<unknown, unknown>>>,
+>(input: {
+  readonly type: Type
+  readonly durable?: {
+    readonly version: number
+    readonly aggregate: string
+  }
+  readonly schema: Fields
+}): Schema.Schema<Payload<Definition<Type, Schema.Struct<Fields>>>> & Definition<Type, Schema.Struct<Fields>> {
+  const data = Schema.Struct(input.schema)
+  return Object.assign(
+    Schema.Struct({
+      id: ID,
+      metadata: Schema.optional(Schema.Record(Schema.String, Schema.Unknown)),
+      type: Schema.Literal(input.type),
+      durable: Schema.optional(
+        Schema.Struct({ aggregateID: Schema.String, seq: Schema.Number, version: Schema.Number }),
+      ),
+      location: Schema.optional(Location.Ref),
+      data,
+    }).annotate({ identifier: input.type }),
+    {
+      type: input.type,
+      ...(input.durable === undefined ? {} : { durable: input.durable }),
+      data,
+    },
+  ) as Schema.Schema<Payload<Definition<Type, Schema.Struct<Fields>>>> & Definition<Type, Schema.Struct<Fields>>
+}
+
+export function inventory<const Definitions extends ReadonlyArray<Definition>>(...definitions: Definitions) {
+  return Object.freeze(definitions)
+}
+
+export function latest(definitions: ReadonlyArray<Definition>) {
+  return readonlyMap(
+    definitions.reduce((result, definition) => {
+      const existing = result.get(definition.type)
+      if (!existing) {
+        result.set(definition.type, definition)
+        return result
+      }
+      if (definition.durable && existing.durable && definition.durable.version !== existing.durable.version) {
+        if (definition.durable.version > existing.durable.version) result.set(definition.type, definition)
+        return result
+      }
+      if (definition !== existing) throw new Error(`Duplicate latest event definition for ${definition.type}`)
+      return result
+    }, new Map<string, Definition>()),
+  )
+}
+
+export function versionedType(type: string, version: number) {
+  return `${type}.${version}`
+}
+
+export function durable(definitions: ReadonlyArray<Definition>) {
+  return readonlyMap(
+    definitions.reduce((result, definition) => {
+      if (!definition.durable) return result
+      const key = versionedType(definition.type, definition.durable.version)
+      if (result.has(key)) throw new Error(`Duplicate durable event definition for ${key}`)
+      result.set(key, definition)
+      return result
+    }, new Map<string, Definition>()),
+  )
+}
+
+function readonlyMap<Key, Value>(map: Map<Key, Value>): ReadonlyMap<Key, Value> {
+  const result: ReadonlyMap<Key, Value> = Object.freeze({
+    get size() {
+      return map.size
+    },
+    entries: () => map.entries(),
+    forEach: (callback: (value: Value, key: Key, map: ReadonlyMap<Key, Value>) => void, thisArg?: unknown) =>
+      map.forEach((value, key) => callback.call(thisArg, value, key, result)),
+    get: (key: Key) => map.get(key),
+    has: (key: Key) => map.has(key),
+    keys: () => map.keys(),
+    values: () => map.values(),
+    [Symbol.iterator]: () => map[Symbol.iterator](),
+  })
+  return result
+}