/**
 * parent-snapshot.ts — Capture parent session state as a plain data snapshot.
 */

import { buildParentContext } from "#src/session/context";
import type { SessionContext } from "#src/types";

/**
 * Plain data snapshot of the parent session state captured at spawn time.
 * Replaces live `ExtensionContext` references so queued agents don't read stale state.
 */
export interface ParentSnapshot {
  /** Parent working directory. */
  cwd: string;
  /** Parent's effective system prompt (for append-mode agents). */
  systemPrompt: string;
  /** Parent's current model instance (fallback when agent config has no model). */
  model: unknown;
  /** Parent's current effective thinking level, used when the child inherits it. */
  thinkingLevel?: SessionContext["thinkingLevel"];
  /** Model registry compatibility facade used for synchronous model lookup. */
  modelRegistry: {
    find(provider: string, modelId: string): unknown;
    getAvailable?(): Array<{ provider: string; id: string }>;
  };
  /** Canonical parent model/auth runtime, when exposed by the host Pi version. */
  modelRuntime?: unknown;
  /** Pre-built parent conversation text (when inheritContext was requested). */
  parentContext?: string;
}

/**
 * Build an immutable snapshot of the parent session state.
 *
 * Called once at spawn time so queued agents capture state as it existed
 * when the user requested the agent, not when a queue slot opens.
 */
export function buildParentSnapshot(
  ctx: SessionContext,
  inheritContext?: boolean,
): ParentSnapshot {
  const parentContext = inheritContext ? buildParentContext(ctx) : undefined;
  const modelRegistry = ctx.modelRegistry!;
  // Pi exposes ModelRegistry as a compatibility facade. Modern createAgentSession
  // consumes its underlying ModelRuntime; carrying that same runtime preserves
  // extension-registered providers and in-memory auth state in child sessions.
  const modelRuntime = (modelRegistry as unknown as { runtime?: unknown }).runtime;

  return {
    cwd: ctx.cwd,
    systemPrompt: ctx.getSystemPrompt(),
    model: ctx.model,
    thinkingLevel: ctx.thinkingLevel,
    modelRegistry,
    modelRuntime,
    // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing -- || intentional: converts empty string to undefined as well as null/undefined
    parentContext: parentContext || undefined,
  };
}