/**
 * Agent registry service. Tracks live agents so plugins can find them without
 * depending on the concrete loop package. Agent creation belongs to the loop.
 *
 * @module @deepseek-ai/dsh-agent
 */

import { Context, getTraceable, Service, symbols } from 'cordis'
import { scopeTarget } from '@deepseek-ai/dsh-scope'
import type { Scoped } from '@deepseek-ai/dsh-scope'
import type { SessionEvent, SessionId } from '@deepseek-ai/dsh-session'
import type { Agent, AgentOptions } from './types.ts'

export * from './types.ts'
export { agentEvents, assembleContextFor } from './dispatch.ts'
export type { AgentEventDispatch, AgentSubjectEvent } from './dispatch.ts'

declare module 'cordis' {
  interface Context {
    agents: AgentRegistry
    /**
     * The agent association installed as an own property on `Agent.ctx`, or
     * `undefined` on a plain context. Contexts derived from `Agent.ctx` inherit
     * the association; a deliberately nested scope may carry a nearer
     * `dsh-scope` tag while retaining it, so this field is DX context rather
     * than the scope resolver. {@link AgentRegistry} registers a root accessor
     * defaulting to `undefined`, and core packages below the agent layer use
     * `scopeOf()` for layer selection instead of reading this field.
     */
    agent?: Agent
  }
}

/**
 * Options for programmatically creating an agent through the registry factory
 * ({@link AgentRegistry.create}). The caller supplies the single live
 * `sessionId` shared by the agent registry and session log (e.g. an
 * ACP-generated id), plus optional session metadata (the validated `cwd`, fork
 * lineage); the factory creates the session and agent under that identity.
 */
export interface CreateAgentOptions {
  /** The live agent/session identity. */
  readonly sessionId: SessionId
  /**
   * Session creation metadata: validated absolute `cwd`, `parentSession`
   * fork lineage, and the `seedLength` seed boundary. Mirrors the
   * `cwd`/`parentSession`/`seedLength` fields of
   * {@link CreateSessionOptions.meta} in dsh-session (the internal-only
   * `createdAt`, used when reconstructing a persisted session, is deliberately
   * excluded — a factory caller never sets it). This is durable session data,
   * so the session boundary validates and snapshots it before asynchronous
   * setup begins.
   */
  readonly meta?: { readonly cwd?: string; readonly parentSession?: SessionId; readonly seedLength?: number }
  /**
   * Seed events to reconstruct the child session's log from (the fork lineage
   * primitive). When present, the factory creates the session with this event
   * prefix so `deriveMessages()`/`lastTurnNumber` continue from it — used by the
   * in-process FORK subagent backend to seed a child with a balanced
   * completed-turn prefix of the parent's log. The prefix MUST be contiguous
   * from seq 0, carry only lossless-JSON data, and be balanced (no open
   * turn/step, no dangling tool-call), or the session constructor (and the
   * dev-mode invariants replay) reject it. The factory passes the raw seed to
   * the session's durable validator/snapshot boundary. Absent for a fresh
   * (spawn) child.
   */
  readonly seed?: readonly SessionEvent[]
  /** Per-agent options (model, …). */
  readonly agentOptions?: AgentOptions
  /** Optional creation-only cancellation signal; detached before the returned handle becomes visible. */
  readonly signal?: AbortSignal
  /**
   * Creation-time composition of the agent's scoped world. The factory awaits
   * setup after minting `agentCtx` but BEFORE inserting or announcing either
   * the session or agent, so observers can never see a partially configured
   * world. Everything registered through `agentCtx` (scoped tools, prompt
   * sections/variables, `restrict()`, listeners, awaited child plugins) exists
   * before `session/created`, `agent/created`, `agent/session-start`, and the
   * first prompt assembly. A throw/rejection or owner disposal rolls the scope
   * back without publishing either id.
   *
   * **Setup composes, it never drives**: the callback is trusted same-process
   * code and receives the full scoped context, so this is a contract rather
   * than a runtime restriction. Drive the agent only after creation resolves.
   */
  readonly setup?: (agentCtx: Context) => Promise<void> | void
}

/**
 * Options for resuming an agent on a persisted session
 * ({@link AgentRegistry.resume}).
 */
export interface ResumeAgentOptions {
  /** The persisted session id to load and use as the live agent/session identity. */
  readonly resumeSessionId: SessionId
  /** Per-agent options (model, …). */
  readonly agentOptions?: AgentOptions
  /** Optional creation-only cancellation signal for persistence load/setup; detached before return. */
  readonly signal?: AbortSignal
  /**
   * Resume-time composition of the agent's fresh scoped world. Persistence is
   * loaded first; the factory then mints `agentCtx` and awaits setup while the
   * reconstructed session and agent remain unpublished. The callback has the
   * same trusted composition-only contract as
   * {@link CreateAgentOptions.setup}: all registrations exist before either
   * creation announcement, and rejection or owner disposal rolls the
   * transaction back without publishing either id.
   */
  readonly setup?: (agentCtx: Context) => Promise<void> | void
}

/**
 * An owned agent plus its disposer, returned by {@link AgentRegistry.create} /
 * {@link AgentRegistry.resume}. The disposer is a CAPABILITY: among consumers,
 * only the holder can tear this agent down. The registered factory provider is
 * also a structural owner because the scoped agent depends on that provider's
 * service surface; provider unload stops and drains every live handle it made.
 * `dispose()` stops the loop, awaits its exit and every outstanding
 * idle-injection flush (quiescence — NOT just the `disposed`
 * status flip), unregisters the agent, removes its session from the store, and
 * finally unwinds its scoped world. This order captures every agent-started
 * `session/flush` before the session is detached and keeps scoped listeners
 * alive through those checkpoints.
 *
 * `ctx.agents.get(id)` still returns a bare {@link Agent} — the handle is
 * exposed only to the consumer owner that created it; the structural provider
 * reaches the same teardown internally. Config-created agents (the loop's own
 * startup) are owned by the loop fiber and never need a handle.
 */
export interface AgentHandle {
  agent: Agent
  dispose(): Promise<void>
}

/**
 * The agent-creation factory the loop implementation provides to the registry
 * via {@link AgentRegistry.setFactory}. Kept on the `dsh-agent` interface so
 * consumers (e.g. the ACP bridge) program against `ctx.agents` without
 * depending on the concrete `dsh-agent-loop` package.
 */
export interface AgentFactory {
  /**
   * Create a new agent on a caller-supplied session id. Async because creation
   * awaits unpublished setup, inserts both session and agent, emits their
   * creation notifications in order, emits `agent/session-start`, and only
   * then starts the loop. The sequence is
   * rollback-covered, but notifications delivered before a later listener
   * failure remain observable; every agent or session creation announcement
   * that began is paired by `agent/disposed` or `session/disposed` during
   * rollback. The owner disposes the resolved handle to stop/drain,
   * unregister, remove the session, and unwind the scope.
   * The registry passes a context carrying the `create()` caller's fiber and
   * scope as `ownerCtx`. The implementation attaches the unpublished
   * transaction and resulting lifecycle to that owner; it must not infer
   * ownership from the factory object's registration context.
   * @param ownerCtx - caller-bound context that owns the transaction and live handle.
   * @param options - agent/session identity, configuration, and optional setup.
   * @returns the owned handle after setup, both announcements, and loop start complete.
   */
  createAgent(ownerCtx: Context, options: CreateAgentOptions): Promise<AgentHandle>
  /**
   * Load a persisted session and resume an agent on it. Async because it awaits
   * both `ctx.sessionPersistence.load` and the optional unpublished setup
   * transaction; must be called after that service exists (consumers inject
   * `sessionPersistence`). Publication follows the same ordered boundary as
   * {@link createAgent}.
   * @param ownerCtx - caller-bound context that owns load, setup, and the live handle.
   * @param options - persisted identity, configuration, and optional setup.
   * @returns the owned handle after setup, both announcements, and loop start complete.
   */
  resume(ownerCtx: Context, options: ResumeAgentOptions): Promise<AgentHandle>
}

/** Thrown when create/resume is called before an agent factory is registered. */
const NO_FACTORY_MESSAGE = 'no agent factory registered (load an agent-loop plugin)'

/** All mutable lifecycle state for one exact registry entry. */
interface AgentEntry {
  readonly id: SessionId
  readonly agent: Agent
  /** Runtime creator-agent ownership; independent of durable session lineage. */
  readonly owner: Agent | undefined
  readonly carrier: Scoped<Agent>
  announced: boolean
  announcing: boolean
  detachRequested: boolean
}

/** Plain holder prevents Cordis from tracing the factory field before the caller context is known. */
interface FactorySlot {
  readonly target: AgentFactory
}

/**
 * Agent registry (`ctx.agents`): tracks live agents so UI, hook, and
 * orchestrator plugins can find them without depending on the concrete loop
 * package. Agent *creation* is provided by whichever plugin implements the
 * {@link AgentFactory} (`@deepseek-ai/dsh-agent-loop`), registered via
 * {@link setFactory}.
 */
export class AgentRegistry extends Service {
  private store = new Map<SessionId, AgentEntry>()
  private factory: FactorySlot | undefined

  constructor(ctx: Context) {
    super(ctx, 'agents')
    // The `ctx.agent` DX accessor: default `undefined` on every context, so a
    // plain plugin context reads cleanly instead of hitting the Cordis
    // unknown-property throw. Each Agent.ctx shadows it with an own property
    // (own properties resolve before the context proxy is consulted), so the
    // accessor body never needs to resolve a scope itself. Effect-scoped:
    // unwinds with this service's fiber.
    ctx.accessor('agent', { get: () => undefined })
  }

  /**
   * Register the agent-creation factory (the loop calls this on construction,
   * effect-scoped). A traced Cordis service is canonicalized to its concrete
   * target; each create/resume call is then traced through that caller's
   * context so ownership follows the caller without stacking proxy layers.
   * Throws if a factory is already registered. Returns the disposer; on
   * dispose the factory slot is cleared.
   * @param factory - the loop-owned factory {@link create}/{@link resume} delegate to.
   * @returns the disposer that clears the factory slot. The exact
   *   Cordis effect disposer (single-shot): composite (generator) effects may
   *   yield it directly — exact identity nests the teardown in order.
   */
  setFactory(factory: AgentFactory): () => void {
    const dispose = this.ctx.effect(() => {
      if (this.factory !== undefined) throw new Error('an agent factory is already registered')
      // Avoid stacking two Cordis shadow layers when a caller passes a Service
      // already read through a context. Calls are re-traced through their
      // actual owner context below.
      const target = (factory as AgentFactory & { [symbols.original]?: AgentFactory })[symbols.original] ?? factory
      this.factory = { target }
      return () => { this.factory = undefined }
    }, 'agents.setFactory()')
    // The exact cordis effect disposer (the agents.register() convention): a
    // caller's composite effect can yield it for in-order teardown; the
    // loop's constructor effect returns it directly, identity-nesting the
    // registration under that effect.
    // eslint-disable-next-line @typescript-eslint/no-misused-promises -- synchronous cleanup; direct return preserves disposer identity
    return dispose
  }

  /** Return the active creation factory. */
  private requireFactory(): FactorySlot {
    if (this.factory === undefined) throw new Error(NO_FACTORY_MESSAGE)
    return this.factory
  }

  /**
   * Create and publish a new agent through the registered factory.
   * Distinct from {@link register} (which records an already-constructed
   * agent): this constructs the agent and its session. Rejects if no factory is
   * registered or creation/setup fails. The resolved {@link AgentHandle} lets
   * the owner tear down exactly this agent.
   * @param options - shared identity, session seed/metadata, and agent options.
   * @returns the handle after setup, rollback-covered publication, and loop start complete.
   */
  async create(options: CreateAgentOptions): Promise<AgentHandle> {
    const ownerCtx = this.ctx
    // Re-trace a Service-backed factory through the accessing context
    // explicitly. This preserves AgentLoop's dependency origin while binding
    // its effects to ownerCtx; plain factories receive ownerCtx as an explicit
    // capability and need no Cordis tracker magic.
    const { target } = this.requireFactory()
    const receiver = getTraceable(ownerCtx, target)
    // eslint-disable-next-line @typescript-eslint/unbound-method -- Reflect.apply intentionally supplies the caller-traced receiver
    return Reflect.apply(target.createAgent, receiver, [ownerCtx, options])
  }

  /**
   * Load a persisted session and resume an agent on it through the registered
   * factory. Rejects if no factory is registered; the factory rejects if
   * session persistence is not configured or persistence/setup fails.
   * @param options - persisted identity, configuration, and optional setup.
   * @returns the handle after setup, rollback-covered publication, and loop start complete.
   */
  async resume(options: ResumeAgentOptions): Promise<AgentHandle> {
    const ownerCtx = this.ctx
    const { target } = this.requireFactory()
    const receiver = getTraceable(ownerCtx, target)
    // eslint-disable-next-line @typescript-eslint/unbound-method -- Reflect.apply intentionally supplies the caller-traced receiver
    return Reflect.apply(target.resume, receiver, [ownerCtx, options])
  }

  /**
   * Register a live agent. Throws if an agent with the same id is already
   * registered. Emits `agent/created` on registration and `agent/disposed`
   * when the calling fiber is disposed — both with the agent's scope carrier
   * (`scopeTarget(agent, agent)`): the subject is the agent in hand, so the
   * emits are scope-filtered regardless of which context invoked `register`
   * (calling through `agent.ctx` scopes EFFECTS; dispatch scoping always
   * requires passing the carrier). Returns the disposer.
   * @param agent - the already-constructed agent to record in the store.
   * @returns the EXACT Cordis effect disposer (single-shot; a repeat call
   *   returns undefined without awaiting an in-flight teardown). Exact
   *   identity is load-bearing: a composite (generator) effect that owns a
   *   teardown ORDER — the agent factory's lifecycle chain — must yield THIS
   *   function so Cordis nests the unregistration at that yield position;
   *   yielding a wrapper would leave it disposing as a concurrent sibling on
   *   owner unload, unregistering the agent (and emitting `agent/disposed`)
   *   while its final turn is still draining.
   */
  register(agent: Agent): () => void {
    const dispose = this.ctx.effect(function* (this: AgentRegistry) {
      yield this.enter(agent, this.ctx.agent)
      this.announce(agent)
    }.bind(this), 'agents.register()')
    // eslint-disable-next-line @typescript-eslint/no-misused-promises -- synchronous cleanup; direct return preserves disposer identity
    return dispose
  }

  /**
   * Insert an already-constructed agent without announcing it. This is the
   * advanced ordered-lifecycle primitive used by the async agent factory: it
   * first completes setup while the agent is unpublished, then assigns the
   * returned detach closure into its pre-installed composite teardown before
   * calling {@link announce}. Ordinary callers use {@link register}.
   * @param agent - the prepared, unpublished agent.
   * @param owner - live agent whose scoped context created this agent, or
   *   undefined for a top-level runtime root. This is runtime ownership, not
   *   the resumed session's durable parent lineage.
   * @returns an idempotent closure that removes this exact entry and emits
   *   `agent/disposed` with listener failures contained. When called from a
   *   synchronous `agent/created` listener, removal and disposal wait until
   *   that creation dispatch unwinds.
   */
  enter(agent: Agent, owner: Agent | undefined): () => void {
    const id = agent.id
    if (id !== agent.session.id) {
      throw new Error(`agent id "${id}" does not match session id "${agent.session.id}"`)
    }
    const carrier = scopeTarget(agent, agent)
    // This is the authoritative collision boundary. Concurrent create/resume
    // operations may both prepare, but only one exact entry can publish.
    if (this.store.has(id)) throw new Error(`agent "${id}" is already registered`)
    const entry: AgentEntry = {
      id,
      agent,
      owner,
      carrier,
      announced: false,
      announcing: false,
      detachRequested: false,
    }
    this.store.set(id, entry)
    let entered = true
    const detach = (): void => {
      if (!entered) return
      entered = false
      // Every callback reached by this creation dispatch must observe the same
      // live entry, and disposal must follow creation. A listener may own
      // the advanced detach capability, so make that ordering structural:
      // visibility and the paired disposal are deferred until announce()'s
      // synchronous dispatch has unwound.
      if (entry.announcing) {
        entry.detachRequested = true
        return
      }
      this.detachEntered(entry)
    }
    return detach
  }

  /** Remove one exact entered agent and emit its paired disposal when announced. */
  private detachEntered(entry: AgentEntry): void {
    entry.detachRequested = false
    // A stale capability can never delete a later same-id lifecycle. The
    // captured entry identity is the final boundary.
    /* v8 ignore next -- enter() rejects replacement while this single-shot detach capability is live. */
    if (this.store.get(entry.id) !== entry) return
    this.store.delete(entry.id)
    // An insertion rolled back before announce was never externally created,
    // so emitting disposed would invent an impossible lifecycle edge. Marking
    // happens before the created emit: if a later created listener throws,
    // earlier listeners may already have observed it and must see disposal.
    if (!entry.announced) return
    this.emitDisposed(entry)
  }

  /** Emit the paired disposal edge through the entry's stable carrier. */
  private emitDisposed(entry: AgentEntry): void {
    const args: unknown[] = [entry.carrier, 'agent/disposed', entry.agent]
    for (const callback of this.ctx.events.dispatch('emit', args)) {
      try {
        const returned: unknown = callback(...args)
        void Promise.resolve(returned).catch((error: unknown) => {
          this.ctx.logger.warn(`agent "${entry.id}": agent/disposed listener rejected: ${String(error)}`)
        })
      } catch (error: unknown) {
        this.ctx.logger.warn(`agent "${entry.id}": agent/disposed listener threw: ${String(error)}`)
      }
    }
  }

  /**
   * Announce an agent previously inserted with {@link enter}.
   * @param agent - the live inserted agent to announce.
   * @throws if `agent` is not the exact live registry entry for its id, or its
   *   creation announcement already began (including a reentrant call from a
   *   creation listener).
   */
  announce(agent: Agent): void {
    const entry = this.store.get(agent.id)
    if (entry === undefined || entry.agent !== agent) {
      throw new Error(`agent "${agent.id}" is not live in this registry`)
    }
    if (entry.announced || entry.announcing) {
      throw new Error(`agent "${entry.id}" was already announced`)
    }
    // Mark before dispatch so a listener cannot recursively create a second
    // lifecycle edge; detach still pairs a partially delivered first edge.
    entry.announcing = true
    entry.announced = true
    const args: unknown[] = [entry.carrier, 'agent/created', entry.agent]
    try {
      for (const callback of this.ctx.events.dispatch('emit', args)) {
        // A synchronous creation failure vetoes publication and rolls back.
        // Returned-promise rejection happens after this synchronous boundary, so
        // observe and report it instead of leaking an unhandled rejection.
        const returned: unknown = callback(...args)
        void Promise.resolve(returned).catch((error: unknown) => {
          this.ctx.logger.warn(`agent "${entry.id}": agent/created listener rejected: ${String(error)}`)
        })
      }
    } finally {
      entry.announcing = false
      if (entry.detachRequested) this.detachEntered(entry)
    }
  }

  /**
   * Look up a live agent.
   * @param id - the shared agent/session id to look up.
   * @returns the agent, or undefined when no live agent has that id.
   */
  get(id: SessionId): Agent | undefined {
    return this.store.get(id)?.agent
  }

  /**
   * Test whether a live agent was created through one exact parent agent's
   * scoped context. Runtime ownership is independent of durable session
   * lineage and remains unambiguous when unrelated providers reuse an id.
   * @param id - the candidate child agent's shared agent/session id.
   * @param owner - the expected runtime creator agent.
   * @returns true only while the exact child entry is live under that owner.
   */
  isOwnedBy(id: SessionId, owner: Agent): boolean {
    return this.store.get(id)?.owner === owner
  }

  /**
   * All live agents, in registration order.
   * @returns a fresh array; mutating it does not affect the registry.
   */
  list(): Agent[] {
    return [...this.store.values()].map(entry => entry.agent)
  }

  /**
   * All live top-level agents in registration order. A top-level agent was
   * created without an owning agent context; durable session lineage does not
   * affect this runtime relation, so a resumed fork may still be a root.
   * @returns a fresh array; mutating it does not affect the registry.
   */
  roots(): Agent[] {
    return [...this.store.values()]
      .filter(entry => entry.owner === undefined)
      .map(entry => entry.agent)
  }
}

export default AgentRegistry