Ekklesia/packages/contracts/src/module-runtime.ts

import type { ModuleConfiguration } from "./module-configuration.js";
import type { CapabilityId, ModuleId } from "./identifiers.js";
import { moduleIdSchema } from "./identifiers.js";
import type { ModuleRuntimeServices } from "./module-database.js";
import type { ModuleHttpRouteRegistrar } from "./module-http.js";
import { semanticVersionSchema } from "./versions.js";

export type Awaitable<Value> = Value | PromiseLike<Value>;

export interface RegisteredCapability {
  readonly id: CapabilityId;
  readonly implementation: unknown;
  readonly moduleId: ModuleId;
  readonly version: string;
}

export interface CapabilityResolver {
  resolve(capabilityId: CapabilityId): RegisteredCapability | undefined;
}

export interface CapabilityRegistrar extends CapabilityResolver {
  provide(capabilityId: CapabilityId, implementation: unknown): void;
}

export interface ModuleRegistrationContext {
  readonly capabilities: CapabilityRegistrar;
  /** Available only during `register` — never on `ModuleRuntimeContext` — so a route can only ever
   * be declared while Core is still building the immutable startup snapshot, never added or removed
   * afterward from `start`, `stop`, or any other post-registration code path. */
  readonly http: ModuleHttpRouteRegistrar;
  readonly moduleId: ModuleId;
  /**
   * This module's own validated configuration, available here as well as at runtime (ADR 0029).
   *
   * Present during `register` deliberately, and without reopening the rule that registration stays
   * declarative and I/O-free: this is an already-resolved frozen snapshot held in memory, not a
   * database-backed getter, so reading it performs no query and cannot fail. That is exactly why
   * `services` — which *is* a live database facade — remains absent from this context.
   */
  readonly config: ModuleConfiguration;
}

/** The same context shape for both `start` and `stop`: whichever hook runs, it receives the exact
 * same frozen `services` object identity as the other, for a given API runtime — never a fresh
 * `ModuleRuntimeServices` built per hook invocation. Unlike `ModuleRegistrationContext`, this never
 * carries `http`: a route can only ever be declared during `register`. */
export interface ModuleRuntimeContext {
  readonly capabilities: CapabilityResolver;
  readonly moduleId: ModuleId;
  readonly services: ModuleRuntimeServices;
  /**
   * This module's own validated configuration, frozen for the lifetime of the process.
   *
   * Deliberately **not** a field on `ModuleRuntimeServices`: that object is one shared instance
   * every module receives, and configuration is per-module by definition. It sits beside `moduleId`
   * — the context's other per-module fact — so the scoping is visible in the shape rather than
   * asserted in a comment.
   *
   * Immutable for the process lifetime: a configuration change is applied by the next restart, so a
   * value read during `start` and the same value read in a request handler an hour later are the
   * same value (ADR 0029).
   */
  readonly config: ModuleConfiguration;
}

export interface ModuleRuntimeDefinition {
  readonly id: ModuleId;
  readonly register?: (context: ModuleRegistrationContext) => Awaitable<void>;
  readonly start?: (context: ModuleRuntimeContext) => Awaitable<void>;
  readonly stop?: (context: ModuleRuntimeContext) => Awaitable<void>;
  readonly version: string;
}

const runtimeDefinitionKeys = new Set(["id", "register", "start", "stop", "version"]);

function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === "object" && value !== null && !Array.isArray(value);
}

export function isModuleRuntimeDefinition(value: unknown): value is ModuleRuntimeDefinition {
  if (
    !isRecord(value) ||
    !moduleIdSchema.safeParse(value.id).success ||
    !semanticVersionSchema.safeParse(value.version).success
  ) {
    return false;
  }
  if (Object.keys(value).some((key) => !runtimeDefinitionKeys.has(key))) {
    return false;
  }
  return [value.register, value.start, value.stop].every(
    (hook) => hook === undefined || typeof hook === "function",
  );
}

export function parseModuleRuntimeDefinition(value: unknown): ModuleRuntimeDefinition {
  if (!isModuleRuntimeDefinition(value)) {
    throw new TypeError("Invalid Ekklesia module runtime definition.");
  }
  return Object.freeze({
    id: value.id,
    version: value.version,
    ...(value.register ? { register: value.register } : {}),
    ...(value.start ? { start: value.start } : {}),
    ...(value.stop ? { stop: value.stop } : {}),
  });
}