/**
 * sessions domain contract. Method signatures are the source of truth:
 * unary methods take the RpcRequest<P> narrow form and the impl echoes rpcId; everything
 * else references RequestPayload<'session.*'> / ResponseValue<'session.*'>.
 */

import type { ContentBlock } from '@deepseek-ai/dsh-llm/types'
import type { SessionEvent, SessionId, TodoItem } from '@deepseek-ai/dsh-session/types'
import type { RpcId, RpcRequest, RpcResponse } from './rpc.ts'
import type { ToolEventView } from './events.ts'
import type { WorkspaceId } from './workspace.ts'

declare module '@deepseek-ai/dsh-llm' {
  interface MessageSourceMap {
    /**
     * The prompt's rpcId is passed through MessageSource into the `user/message` event
     * (the client uses it to reconcile the optimistically
     * echoed provisional message with the event stream). kind stays `'user'` — the model face
     * carries no transport vocabulary; rpcId is an extra durable-JSON field passed back to the client with the event.
     */
    'user-rpc': { kind: 'user'; rpcId: RpcId }
  }
}

/**
 * One history page entry: the raw event plus the optional host-computed render
 * intent (same semantics as the mux frame's `view` slot — a pagination-time
 * derivation, never persisted).
 */
export interface HistoryEntry {
  event: SessionEvent
  view?: ToolEventView
}

/** Session list entry (v1 builds no index: list does readdir+stat). */
export interface SessionSummary {
  sessionId: SessionId
  /** Persisted file mtime. */
  updatedAt: number
  /** Status of the attached agent; always false for cold (unattached) sessions. */
  running: boolean
  /**
   * Derived emptiness bit: true while the session log holds zero events (no
   * user message yet). Clients hide blank sessions from lists and reuse them
   * for New Session on the same workspace. Always false for cold sessions —
   * lazy persistence keeps a never-appended session out of the store, so a
   * listed cold session necessarily has events.
   */
  blank: boolean
  /** fork/spawn lineage (session.header.parentSession passthrough); absent for root sessions. */
  parentSessionId?: SessionId
  /** Session working directory (header.cwd passthrough); absent when unrecorded. */
  cwd?: string
}

/** Session-domain unary methods (the map keys session.* of RpcMethodMap). */
export interface SessionsApi {
  /** Lists persisted sessions (updatedAt descending). v1 returns everything; cursor is a reserved seat, unimplemented. */
  list(request: RpcRequest<{ cursor?: string }>): Promise<RpcResponse<{ items: SessionSummary[] }>>

  /**
   * Creates a real session and its idle agent. At most one of `workspaceId` /
   * `cwd` is accepted; an omitted project uses the Host cwd. A caller may
   * preallocate `sessionId`: retries with the same id and cwd return the same
   * session, while a different cwd fails with `session-conflict`. Workspace
   * creation attaches the session after publication; an attach failure
   * returns `workspace-attach-failed` with the published session id.
   */
  create(request: RpcRequest<{ workspaceId?: WorkspaceId; cwd?: string; sessionId?: SessionId }>):
  Promise<RpcResponse<{ sessionId: SessionId }>>

  /**
   * Reads a window of history events; page boundaries align to message boundaries: one page =
   * all raw events owned by a whole number of messages (including their chunk / tool events),
   * never cut mid-message. The tail page (beforeSeq absent) additionally carries the in-flight
   * partial — chunk events already emitted for the last unfinalized message.
   * Each entry pairs the raw SessionEvent with the host-computed view (tool events whose
   * presenter produced one, evaluated against the registry at pagination time); the client
   * rebuilds the surface from the events with the shared fold.
   * The tail page (beforeSeq absent) also carries `todos` — the session's current todo
   * projection (latest `todo/write` over the FULL log, independent of the page window) —
   * so a paged client restores the plan without walking history; absent when the session
   * never wrote one. Older pages omit it (the projection is session-level, not per-page).
   */
  history(request: RpcRequest<{ sessionId: SessionId; beforeSeq?: number; maxMessages?: number }>):
  Promise<RpcResponse<{ events: HistoryEntry[]; hasMore: boolean; todos?: TodoItem[] }>>

  /** Sends a message. content is core's ContentBlock[] verbatim; mode maps 1:1 — queue→send, steer→steer. */
  prompt(request: RpcRequest<{ sessionId: SessionId; mode: 'queue' | 'steer'; content: ContentBlock[] }>):
  Promise<RpcResponse<{ accepted: true }>>

  /** Stops: clears both FIFOs + aborts the current step (1:1 with agent.cancel). */
  cancel(request: RpcRequest<{ sessionId: SessionId }>): Promise<RpcResponse<{ accepted: true }>>
}