feat: communication spine — gateway, TUI, Discord (#61)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/gateway/src/chat/chat.controller.ts

@@ -0,0 +1,75 @@
+import { Controller, Post, Body, Logger, HttpException, HttpStatus } from '@nestjs/common';
+import type { AgentSessionEvent } from '@mariozechner/pi-coding-agent';
+import { AgentService } from '../agent/agent.service.js';
+import { v4 as uuid } from 'uuid';
+
+interface ChatRequest {
+  conversationId?: string;
+  content: string;
+}
+
+interface ChatResponse {
+  conversationId: string;
+  text: string;
+}
+
+@Controller('api/chat')
+export class ChatController {
+  private readonly logger = new Logger(ChatController.name);
+
+  constructor(private readonly agentService: AgentService) {}
+
+  @Post()
+  async chat(@Body() body: ChatRequest): Promise<ChatResponse> {
+    const conversationId = body.conversationId ?? uuid();
+
+    try {
+      let agentSession = this.agentService.getSession(conversationId);
+      if (!agentSession) {
+        agentSession = await this.agentService.createSession(conversationId);
+      }
+    } catch (err) {
+      this.logger.error(
+        `Session creation failed for conversation=${conversationId}`,
+        err instanceof Error ? err.stack : String(err),
+      );
+      throw new HttpException('Agent session unavailable', HttpStatus.SERVICE_UNAVAILABLE);
+    }
+
+    let responseText = '';
+
+    const done = new Promise<void>((resolve, reject) => {
+      const timer = setTimeout(() => {
+        cleanup();
+        this.logger.error(`Agent response timed out after 120s for conversation=${conversationId}`);
+        reject(new Error('Agent response timed out'));
+      }, 120_000);
+
+      const cleanup = this.agentService.onEvent(conversationId, (event: AgentSessionEvent) => {
+        if (event.type === 'message_update' && event.assistantMessageEvent.type === 'text_delta') {
+          responseText += event.assistantMessageEvent.delta;
+        }
+        if (event.type === 'agent_end') {
+          clearTimeout(timer);
+          cleanup();
+          resolve();
+        }
+      });
+    });
+
+    try {
+      await this.agentService.prompt(conversationId, body.content);
+      await done;
+    } catch (err) {
+      if (err instanceof HttpException) throw err;
+      const message = err instanceof Error ? err.message : String(err);
+      if (message.includes('timed out')) {
+        throw new HttpException('Agent response timed out', HttpStatus.GATEWAY_TIMEOUT);
+      }
+      this.logger.error(`Chat prompt failed for conversation=${conversationId}`, String(err));
+      throw new HttpException('Agent processing failed', HttpStatus.INTERNAL_SERVER_ERROR);
+    }
+
+    return { conversationId, text: responseText };
+  }
+}