import { Controller, Get, Res, UseGuards } from "@nestjs/common";
import { AgentStatus } from "@prisma/client";
import type { Response } from "express";
import { AuthGuard } from "../auth/guards/auth.guard";
import { PrismaService } from "../prisma/prisma.service";

const AGENT_POLL_INTERVAL_MS = 5_000;
const SSE_HEARTBEAT_MS = 15_000;

interface OrchestratorAgentDto {
  id: string;
  name: string | null;
  status: AgentStatus;
  type: string;
  createdAt: Date;
}

@Controller("orchestrator")
@UseGuards(AuthGuard)
export class OrchestratorController {
  constructor(private readonly prisma: PrismaService) {}

  @Get("agents")
  async getAgents(): Promise<OrchestratorAgentDto[]> {
    return this.fetchActiveAgents();
  }

  @Get("events")
  async streamEvents(@Res() res: Response): Promise<void> {
    res.setHeader("Content-Type", "text/event-stream");
    res.setHeader("Cache-Control", "no-cache");
    res.setHeader("Connection", "keep-alive");
    res.setHeader("X-Accel-Buffering", "no");

    if (typeof res.flushHeaders === "function") {
      res.flushHeaders();
    }

    let isClosed = false;
    let previousSnapshot = "";

    const emitSnapshotIfChanged = async (): Promise<void> => {
      if (isClosed) {
        return;
      }

      try {
        const agents = await this.fetchActiveAgents();
        const snapshot = JSON.stringify(agents);

        if (snapshot !== previousSnapshot) {
          previousSnapshot = snapshot;
          res.write(
            `data: ${JSON.stringify({
              type: "agents:updated",
              agents,
              timestamp: new Date().toISOString(),
            })}\n\n`
          );
        }
      } catch (error: unknown) {
        const message = error instanceof Error ? error.message : String(error);
        res.write(`event: error\n`);
        res.write(`data: ${JSON.stringify({ error: message })}\n\n`);
      }
    };

    await emitSnapshotIfChanged();

    const pollInterval = setInterval(() => {
      void emitSnapshotIfChanged();
    }, AGENT_POLL_INTERVAL_MS);

    const heartbeatInterval = setInterval(() => {
      if (!isClosed) {
        res.write(": keepalive\n\n");
      }
    }, SSE_HEARTBEAT_MS);

    res.on("close", () => {
      isClosed = true;
      clearInterval(pollInterval);
      clearInterval(heartbeatInterval);
      res.end();
    });
  }

  private async fetchActiveAgents(): Promise<OrchestratorAgentDto[]> {
    const agents = await this.prisma.agent.findMany({
      where: {
        status: {
          not: AgentStatus.TERMINATED,
        },
      },
      orderBy: {
        createdAt: "desc",
      },
      select: {
        id: true,
        name: true,
        status: true,
        role: true,
        createdAt: true,
      },
    });

    return agents.map((agent) => ({
      id: agent.id,
      name: agent.name,
      status: agent.status,
      type: agent.role ?? "agent",
      createdAt: agent.createdAt,
    }));
  }
}