// Process-scoped bridge owner.
//
// One process must hold exactly one bridge runtime even when the extension
// module is evaluated more than once: a nested (subagent) ModelRuntime
// re-imports this module, but its provider calls must route through the same
// stream closure and the same reentrant QueryContexts as the creating activation.
//
// A private Symbol.for() registry holds that single owner. The first activation
// builds it and owns its lifecycle; later activations borrow it. This module never receives
// ExtensionAPI — index.ts passes an ordinary build factory and does all Pi
// registration and event wiring itself.

import type { Provider } from "@earendil-works/pi-ai";

const OWNER_KEY = Symbol.for("doppelclaude:owner");

export interface BridgeOwner<TRuntime extends object, TProvider extends Provider> {
  provider: TProvider;
  runtime: TRuntime;
}

export interface OwnerAcquisition<TRuntime extends object, TProvider extends Provider> {
  /** The shared Provider/runtime pair: built once per process, reused by borrowers. */
  owner: BridgeOwner<TRuntime, TProvider>;
  /** True only for the activation that created and manages the owner. */
  ownsLifecycle: boolean;
  /**
   * Owner-only teardown: drop the owner so the next activation starts a fresh
   * generation. A borrower's release is a no-op — it cannot clear the shared
   * owner out from under the root.
   */
  release(): void;
}

export function acquireBridgeOwner<TRuntime extends object, TProvider extends Provider>(
  build: () => BridgeOwner<TRuntime, TProvider>,
): OwnerAcquisition<TRuntime, TProvider> {
  const registry = globalThis as Record<symbol, unknown>;
  const existing = registry[OWNER_KEY];
  if (existing !== undefined) {
    return {
      owner: existing as BridgeOwner<TRuntime, TProvider>,
      ownsLifecycle: false,
      release() {},
    };
  }
  const owner = build();
  registry[OWNER_KEY] = owner;
  return {
    owner,
    ownsLifecycle: true,
    release() {
      if (registry[OWNER_KEY] === owner) registry[OWNER_KEY] = undefined;
    },
  };
}