boocode/apps/coder/src/services/frame-emitter.ts

/**
 * AgentEvent → WS-frame emitter + turn accumulators.
 *
 * Extracted (v2.7 audit reshape) from `AcpStreamContext.handleSessionUpdate` in
 * `acp-dispatch.ts` — the `AgentEvent → broker.publishFrame` switch that maps a
 * backend's normalized events onto the wire frames the UI consumes, while
 * accumulating the turn's text / reasoning / tool snapshots for persistence.
 *
 * The same shape backs the dispatcher's 4 inline `onEvent` copies (DEFERRED while
 * dispatcher.ts has uncommitted edits), hence the optional `dcp` stripper + the
 * `finalize()` flush: the opencode dispatch path strips dcp tags from text deltas,
 * the ACP path does not (passes no `dcp`, so text is emitted verbatim — identical
 * to the prior AcpStreamContext behavior).
 *
 * Publishing is gated on `canStream()` (all of broker/sessionId/chatId/assistantId
 * present) exactly as the original — a one-shot dispatch with no broker accumulates
 * but never publishes.
 */
import type { Broker } from '@boocode/server/broker';
import type { WsFrame } from '@boocode/contracts/ws-frames';
import type { AgentEvent } from './agent-backend.js';
import { type AcpToolSnapshot, snapshotToWireToolCall } from './acp-tool-snapshot.js';
import { mergeTaskCommands, getTaskCommands } from './agent-commands-cache.js';
import type { DcpStreamStripper } from './dcp-strip.js';

export interface FrameEmitterOpts {
  broker?: Broker;
  sessionId?: string;
  chatId?: string;
  /** The assistant message id — the frames' `message_id`. */
  assistantId?: string;
  /** Per-turn task id, for the agent_commands frame + command cache. */
  taskId?: string;
  /** Optional cross-chunk dcp stripper for text deltas (opencode path). When
   *  provided, text is stripped before push/publish and `finalize()` flushes the
   *  held-back tail. The ACP path passes none → text emitted verbatim. */
  dcp?: DcpStreamStripper;
}

export interface FrameEmitter {
  /** Map one AgentEvent to its WS frame(s) + accumulate it. */
  onEvent: (e: AgentEvent) => void;
  /** Flush a dcp stripper's held-back tail at turn end (no-op without `dcp`). */
  finalize: () => void;
  /** The merge accumulator for tool snapshots (toolCallId → snapshot). */
  readonly toolSnapshots: Map<string, AcpToolSnapshot>;
  /** Accumulated assistant text (post-dcp-strip when a stripper is set). */
  readonly output: string;
  /** Accumulated reasoning text. */
  readonly reasoningText: string;
  /** Tool snapshots in insertion order. */
  readonly snapshots: AcpToolSnapshot[];
}

export function makeFrameEmitter(opts: FrameEmitterOpts): FrameEmitter {
  const { broker, sessionId, chatId, assistantId, taskId, dcp } = opts;
  const textChunks: string[] = [];
  const reasoningChunks: string[] = [];
  const toolSnapshots = new Map<string, AcpToolSnapshot>();

  const canStream = (): boolean => !!(broker && sessionId && chatId && assistantId);

  const publishText = (content: string): void => {
    textChunks.push(content);
    if (canStream()) {
      broker!.publishFrame(sessionId!, {
        type: 'delta',
        message_id: assistantId!,
        chat_id: chatId!,
        content,
      } as WsFrame);
    }
  };

  const onEvent = (e: AgentEvent): void => {
    switch (e.type) {
      case 'text': {
        const safe = dcp ? dcp.push(e.text) : e.text;
        if (safe) publishText(safe);
        break;
      }
      case 'reasoning':
        reasoningChunks.push(e.text);
        if (canStream()) {
          broker!.publishFrame(sessionId!, {
            type: 'reasoning_delta',
            message_id: assistantId!,
            chat_id: chatId!,
            content: e.text,
          } as WsFrame);
        }
        break;
      case 'tool_call':
      case 'tool_update':
        toolSnapshots.set(e.toolCall.toolCallId, e.toolCall);
        if (canStream()) {
          broker!.publishFrame(sessionId!, {
            type: 'tool_call',
            message_id: assistantId!,
            chat_id: chatId!,
            tool_call: snapshotToWireToolCall(e.toolCall),
          } as WsFrame);
        }
        break;
      case 'commands':
        if (taskId && e.commands.length > 0) {
          mergeTaskCommands(taskId, e.commands);
          if (canStream() && sessionId) {
            const all = getTaskCommands(taskId) ?? e.commands;
            broker!.publishFrame(sessionId, {
              type: 'agent_commands',
              task_id: taskId,
              session_id: sessionId,
              commands: all,
            } as WsFrame);
          }
        }
        break;
    }
  };

  const finalize = (): void => {
    if (!dcp) return;
    const tail = dcp.flush();
    if (tail) publishText(tail);
  };

  return {
    onEvent,
    finalize,
    toolSnapshots,
    get output() {
      return textChunks.join('');
    },
    get reasoningText() {
      return reasoningChunks.join('');
    },
    get snapshots() {
      return [...toolSnapshots.values()];
    },
  };
}