/**
 * Durable sandbox **instance** map — which provider sandbox (and snapshot) to
 * resume for a compound key. Owned by `@tanstack/ai-sandbox` (not chat
 * persistence): domain is runtime placement for `ensure`, not conversation state.
 *
 * Pass to `withSandbox(sandbox, { instances })`, which uses it in `ensure`
 * (in-memory fallback when absent). {@link SandboxInstanceStoreCapability} is
 * the ambient alternative for platform-level wiring.
 */
import { createCapability } from '@tanstack/ai'

/** One persisted sandbox instance, keyed by the compound sandbox instance key. */
export interface SandboxInstanceRecord {
  /** Compound key (see `computeSandboxKey`). */
  key: string
  /** Provider name that owns `providerSandboxId`. */
  provider: string
  /** Provider-assigned sandbox id used to resume. */
  providerSandboxId: string
  /** Most recent snapshot id, when the provider supports snapshots. */
  latestSnapshotId?: string
  threadId: string
  latestRunId?: string
  /**
   * Epoch ms of last write (for keepAlive / GC by the host app).
   */
  updatedAt: number
}

/**
 * Maps a compound key to the provider sandbox that should be resumed.
 *
 * Implement against your own database (BYO). Prove the contract with
 * `runSandboxInstanceStoreConformance` from `@tanstack/ai-sandbox/testkit`.
 */
export interface SandboxInstanceStore {
  /**
   * Return the record for `key`, or `null` if none exists.
   *
   * INVARIANT: missing keys return `null` (never throw).
   */
  get: (key: string) => Promise<SandboxInstanceRecord | null>
  /**
   * Insert or fully replace the record for `record.key`.
   *
   * INVARIANT (full replace): omitted optional fields (`latestSnapshotId`,
   * `latestRunId`) MUST clear any previously stored values. Do not merge with
   * the prior row — a create-without-snapshot path must not leave a stale
   * snapshot id.
   */
  upsert: (record: SandboxInstanceRecord) => Promise<void>
  /**
   * Remove the record for `key`.
   *
   * INVARIANT: deleting a missing key is a **no-op** (must not throw).
   */
  delete: (key: string) => Promise<void>
}

/**
 * Type a {@link SandboxInstanceStore} implementation inline: pass the object and
 * get autocomplete + contract checking, with no separate
 * `: SandboxInstanceStore` annotation. Hand the result to
 * `withSandbox(sandbox, { instances })`. Matches `defineLock` /
 * `defineMessageStore` style helpers elsewhere in the monorepo.
 */
export function defineSandboxInstanceStore(
  store: SandboxInstanceStore,
): SandboxInstanceStore {
  return store
}

/**
 * Capability for the instance map — the ambient alternative to
 * `withSandbox(sandbox, { instances })`. Provide it from any middleware with
 * {@link provideSandboxInstanceStore}; `withSandbox` reads it when no explicit
 * option was passed.
 */
export const SandboxInstanceStoreCapability =
  createCapability<SandboxInstanceStore>()('sandbox-instance-store')

/** Destructured accessors: `getSandboxInstanceStore` / `provideSandboxInstanceStore`. */
export const [getSandboxInstanceStore, provideSandboxInstanceStore] =
  SandboxInstanceStoreCapability

/** In-memory {@link SandboxInstanceStore}. Resume works only within one process. */
export class InMemorySandboxInstanceStore implements SandboxInstanceStore {
  private readonly map = new Map<string, SandboxInstanceRecord>()

  get(key: string): Promise<SandboxInstanceRecord | null> {
    return Promise.resolve(this.map.get(key) ?? null)
  }

  upsert(record: SandboxInstanceRecord): Promise<void> {
    this.map.set(record.key, record)
    return Promise.resolve()
  }

  delete(key: string): Promise<void> {
    this.map.delete(key)
    return Promise.resolve()
  }
}

/**
 * Wiring note: hand the store straight to the consumer —
 * `withSandbox(sandbox, { instances: store })`. That cannot be mis-ordered,
 * unlike a separate provider middleware composed after `withSandbox` (which
 * silently degrades to the in-memory fallback).
 *
 * ```ts
 * middleware: [
 *   withLocks(locks), // from @tanstack/ai/locks — multi-replica
 *   withSandbox(sandbox, { instances: instanceStore }),
 * ]
 * ```
 *
 * For ambient/platform wiring (a hosting layer injecting infra without touching
 * the call site), any middleware may still
 * `provideSandboxInstanceStore(ctx, store)` on the capability bus; an explicit
 * option takes precedence over it.
 */