deepseek-harness/packages/sdk/sdk-client/src/api.ts

/**
 * High-level turns API over {@link HarnessClient}: `DeepSeekHarness` owns one
 * runtime subprocess across many sessions; `HarnessSession.run` sends a
 * prompt and settles with the final response once `session.finished` arrives.
 * Mirrors the Python SDK's `DeepSeekHarness`/`Session` pair.
 *
 * @module @deepseek-ai/dsh-sdk-client/api
 */

import { randomUUID } from 'node:crypto'
import { resolve } from 'node:path'
import type { SessionEvent, TurnEndReason } from '@deepseek-ai/dsh-session'
import { HarnessClient, isRecord, SdkProtocolError } from './client.ts'
import type { ContentBlock, DeepSeekHarnessOptions, HarnessClientOptions, HarnessNotification, TurnResult } from './types.ts'

/**
 * Reusable SDK for running DeepSeek Harness agent turns in a runtime
 * subprocess. The subprocess starts lazily on first use and stays owned by
 * this instance until {@link close}; always close (or `await using`) so the
 * child is reaped.
 */
export class DeepSeekHarness implements AsyncDisposable {
  private clientInstance: HarnessClient
  private readonly launch: HarnessClientOptions
  private readonly cwd: string
  private readonly provider: string
  private readonly model: string
  private readonly maxTokens: number | undefined
  private initialized: Promise<void> | undefined
  private closed = false

  /** @param options - runtime launch spec plus the session route (cwd/provider/model). */
  constructor(options: DeepSeekHarnessOptions) {
    this.launch = options.launch
    this.clientInstance = new HarnessClient(options.launch)
    // Absolute before the handshake: the child spawns relative to THIS
    // process's cwd, but the wire cwd is resolved again inside the child — a
    // relative value would double-resolve (e.g. `worker` → `worker/worker`).
    this.cwd = resolve(options.cwd ?? options.launch.cwd ?? process.cwd())
    this.provider = options.provider ?? 'deepseek-official'
    this.model = options.model ?? 'deepseek-v4-flash'
    this.maxTokens = options.maxTokens
  }

  /**
   * The underlying JSON-RPC client (exposed for low-level access). A failed
   * handshake reaps its runtime and swaps in a fresh instance, so do not
   * cache this across a failed {@link start}.
   * @returns the client currently owning the runtime subprocess.
   */
  get client(): HarnessClient {
    return this.clientInstance
  }

  /**
   * Start the subprocess and perform the `initialize` handshake once. On
   * failure the runtime is reaped and a fresh client replaces it
   * (`HarnessClient.close` is permanent), so a later call retries with a new
   * subprocess — unless {@link close} already ended this harness.
   * @returns settlement of the (memoized) handshake.
   */
  start(): Promise<void> {
    this.initialized ??= (async () => {
      try {
        this.clientInstance.start()
        await this.clientInstance.initialize({
          cwd: this.cwd,
          provider: this.provider,
          model: this.model,
          ...this.maxTokens === undefined ? {} : { maxTokens: this.maxTokens },
        })
      } catch (error) {
        this.initialized = undefined
        await this.clientInstance.close()
        if (!this.closed) this.clientInstance = new HarnessClient(this.launch)
        throw error
      }
    })()
    return this.initialized
  }

  /**
   * Open a session handle (no wire traffic; the runtime creates the session
   * on its first prompt).
   * @param sessionId - explicit id to reuse; omitted mints a fresh one.
   * @returns the session handle.
   */
  session(sessionId?: string): HarnessSession {
    return new HarnessSession(this, sessionId ?? `session-${randomUUID().replaceAll('-', '')}`)
  }

  /**
   * Run one prompt on a fresh (or named) session.
   * @param input - prompt text, or content blocks sent verbatim.
   * @param options - optional session id and per-notification observer.
   * @returns the settled turn result.
   */
  run(input: string | ContentBlock[], options?: RunOptions): Promise<TurnResult> {
    return this.session(options?.sessionId).run(input, options)
  }

  /**
   * Shut down and reap the runtime subprocess. Idempotent and terminal —
   * a closed harness no longer retries a failed handshake.
   * @returns settlement of the complete teardown.
   */
  close(): Promise<void> {
    this.closed = true
    return this.clientInstance.close()
  }

  /**
   * `await using` support: {@link close}.
   * @returns settlement of the teardown.
   */
  [Symbol.asyncDispose](): Promise<void> {
    return this.close()
  }
}

/** Per-run options: target session and streaming observer. */
export interface RunOptions {
  /** Session id to run on; omitted mints a fresh session per call. */
  sessionId?: string
  /** Observer invoked with every notification for this session tree, in wire order. */
  onNotification?: (notification: HarnessNotification) => void
}

/**
 * One SDK session: a stable id plus the turn loop that pairs a
 * `session/prompt` with its `session.finished`.
 */
export class HarnessSession {
  /**
   * @param harness - the owning harness (supplies the client and handshake).
   * @param id - the wire session id this handle runs on.
   */
  constructor(readonly harness: DeepSeekHarness, readonly id: string) {}

  /**
   * Run one prompt turn to settlement.
   * @param input - prompt text, or content blocks sent verbatim.
   * @param options - optional per-notification observer.
   * @returns the settled turn result; rejects on transport loss, timeout, or
   * a protocol error — never on a model-level failure (that is
   * `status: 'error'` in the result).
   */
  async run(input: string | ContentBlock[], options?: Pick<RunOptions, 'onNotification'>): Promise<TurnResult> {
    await this.harness.start()
    const client = this.harness.client
    const contentBlocks = normalizeInput(input)
    const events: SessionEvent[] = []
    const notifications: HarnessNotification[] = []
    let status: TurnResult['status'] = 'error'
    let reason: TurnEndReason | undefined
    let finished = false

    const subscription = client.subscribeSessionTree(this.id)
    const collect = (notification: HarnessNotification): void => {
      if (notification.method === 'session.event' && notification.params.sessionId === this.id) {
        // Wire boundary: the envelope feeds the typed TurnResult, so a
        // malformed runtime surfaces as a protocol error, not as type-invalid
        // data (or a TypeError out of finalResponse).
        const event = validatedSessionEvent(notification.params.event)
        notifications.push(notification)
        options?.onNotification?.(notification)
        events.push(event)
        return
      }
      if (notification.method === 'session.finished' && notification.params.sessionId === this.id) {
        reason = validatedTurnEndReason(notification.params.reason)
        notifications.push(notification)
        options?.onNotification?.(notification)
        status = notification.params.status === 'ok' ? 'ok' : 'error'
        finished = true
        return
      }
      notifications.push(notification)
      options?.onNotification?.(notification)
    }
    const accepted = client.prompt(this.id, contentBlocks)
    // Drain concurrently so observers see progress while the prompt request
    // is still pending (its response arrives only after settlement).
    const drain = (async () => {
      while (!finished) collect(await subscription.next())
    })()
    try {
      await Promise.all([accepted, drain])
    } finally {
      // On a prompt rejection the drain is still parked on next(); closing the
      // subscription settles it, and the swallow keeps that secondary
      // TransportClosedError from surfacing as an unhandled rejection.
      subscription.close()
      await drain.catch(() => {})
    }

    return {
      sessionId: this.id,
      status,
      reason,
      finalResponse: finalResponse(events),
      events,
      notifications,
    }
  }
}

/**
 * Normalize run input: a string becomes one text block; blocks pass verbatim.
 * @param input - prompt text or content blocks.
 * @returns the content blocks to send.
 */
export function normalizeInput(input: string | ContentBlock[]): ContentBlock[] {
  return typeof input === 'string' ? [{ type: 'text', text: input }] : input
}

/** Validate a wire `session.event` envelope to the shape the typed result exposes. */
function validatedSessionEvent(value: unknown): SessionEvent {
  if (!isRecord(value) || typeof value.type !== 'string') {
    throw new SdkProtocolError(`session.event carried no event envelope: ${JSON.stringify(value)}`)
  }
  // The one variant this module reads into (finalResponse) must carry
  // kind-tagged content blocks; other variants pass through under their
  // envelope shape.
  if (value.type === 'assistant/message') {
    const message = isRecord(value.data) ? value.data.message : undefined
    const content = isRecord(message) ? message.content : undefined
    if (!Array.isArray(content) || !content.every(block => isRecord(block) && typeof block.type === 'string')) {
      throw new SdkProtocolError(`assistant/message event carried malformed content: ${JSON.stringify(value)}`)
    }
  }
  return value as unknown as SessionEvent
}

/** Validate a wire `session.finished` reason (absent, or a kind-tagged record). */
function validatedTurnEndReason(value: unknown): TurnEndReason | undefined {
  if (value === undefined) return undefined
  if (!isRecord(value) || typeof value.kind !== 'string') {
    throw new SdkProtocolError(`session.finished carried a malformed reason: ${JSON.stringify(value)}`)
  }
  return value as unknown as TurnEndReason
}

/**
 * Extract the concatenated text of the last assistant message.
 * @param events - the turn's `session.event` payloads in wire order.
 * @returns the final response text, or `''` when no assistant message exists.
 */
export function finalResponse(events: SessionEvent[]): string {
  for (let index = events.length - 1; index >= 0; index--) {
    const event = events[index]
    if (event?.type !== 'assistant/message') continue
    return event.data.message.content
      .filter((block): block is ContentBlock & { type: 'text' } => block.type === 'text')
      .map(block => block.text)
      .join('')
  }
  return ''
}