import { config, dashboardEndpoints } from '../config';
import { getMockData } from '../mock';
import type { DashboardData, Station } from '../types';

type ChangeListener = (data: DashboardData | null) => void;
type ModeListener = (mode: 'sse' | 'polling') => void;
type ErrorListener = (message: string) => void;

/** MES 各接口返回片段 */
interface EndpointOverview {
  production?: DashboardData['production'];
  warehouse?: DashboardData['warehouse'];
}
interface EndpointEquipment {
  stations?: Station[];
}
interface EndpointAlarms {
  items?: DashboardData['alarms'];
}

/**
 * 数据源：优先尝试 SSE（经 fetch 实现，可携带 X-API-TOKEN 请求头）；
 * SSE 建立或读取失败时降级为 10s HTTP 轮询。
 */
export class DashboardDataService {
  private baseUrl = config.mesBaseUrl;
  private token = config.internalToken;
  private useMock = config.useMock;

  private controller: AbortController | null = null;
  private timer: ReturnType<typeof setInterval> | null = null;

  private changeListeners = new Set<ChangeListener>();
  private modeListeners = new Set<ModeListener>();
  private errorListeners = new Set<ErrorListener>();

  mode: 'sse' | 'polling' | 'init' = 'init';
  private running = false;

  onChange(cb: ChangeListener): () => void {
    this.changeListeners.add(cb);
    return () => this.changeListeners.delete(cb);
  }
  onModeChange(cb: ModeListener): () => void {
    this.modeListeners.add(cb);
    return () => this.modeListeners.delete(cb);
  }
  onError(cb: ErrorListener): () => void {
    this.errorListeners.add(cb);
    return () => this.errorListeners.delete(cb);
  }

  private emit(data: DashboardData | null) {
    this.changeListeners.forEach((l) => l(data));
  }
  private setMode(m: 'sse' | 'polling') {
    this.mode = m;
    this.modeListeners.forEach((l) => l(m));
  }
  private emitError(msg: string) {
    this.errorListeners.forEach((l) => l(msg));
  }

  /** 启动数据流（幂等，可安全重复调用） */
  start() {
    if (this.running) return;
    this.running = true;
    if (this.useMock) {
      // 演示模式：直接给出数据
      this.setMode('polling');
      this.emit(getMockData());
      return;
    }
    void this.openSse();
  }

  /** 停止数据流并清理资源 */
  stop() {
    this.running = false;
    this.closeStream();
    this.clearTimer();
    this.changeListeners.clear();
    this.modeListeners.clear();
    this.errorListeners.clear();
  }

  /** 手动重试：恢复默认时先重新建立 SSE，失败则轮询 */
  retry() {
    if (!this.running) this.running = true;
    if (this.useMock) {
      this.emit(getMockData());
      return;
    }
    this.clearTimer();
    void this.openSse();
  }

  // ---------- SSE ----------
  private async openSse() {
    this.closeStream();
    const url = `${this.baseUrl}/api/internal/dashboard/stream`;
    const controller = new AbortController();
    this.controller = controller;
    try {
      const res = await fetch(url, {
        headers: { 'X-API-TOKEN': this.token },
        signal: controller.signal,
      });
      if (!res.ok || !res.body) throw new Error(`SSE 连接失败：HTTP ${res.status}`);
      this.setMode('sse');
      const reader = res.body.getReader();
      const decoder = new TextDecoder();
      let buffer = '';
      for (;;) {
        const { done, value } = await reader.read();
        if (done) break;
        buffer += decoder.decode(value, { stream: true });
        // 按空行切分 SSE 事件块
        const blocks = buffer.split('\n\n');
        buffer = blocks.pop() ?? '';
        for (const block of blocks) {
          const dataLine = block
            .split('\n')
            .find((l) => l.startsWith('data:'));
          if (!dataLine) continue;
          const payload = dataLine.replace(/^data:\s*/, '').trim();
          try {
            const parsed = JSON.parse(payload) as DashboardData;
            if (parsed) this.emit(parsed);
          } catch {
            // 忽略无法解析的单条事件，继续读取
          }
        }
      }
    } catch (err) {
      if (!this.running) return;
      if (err instanceof Error && err.name === 'AbortError') return;
      this.emitError('SSE 连接失败，已降级为 HTTP 轮询（每 10s 刷新）');
      this.fallbackToPolling();
    }
  }

  private closeStream() {
    this.controller?.abort();
    this.controller = null;
  }

  // ---------- HTTP 轮询（降级） ----------
  private fallbackToPolling() {
    this.clearTimer();
    void this.pollOnce();
    this.timer = setInterval(() => void this.pollOnce(), config.pollIntervalMs);
  }

  private async pollOnce() {
    try {
      const headers = { 'X-API-TOKEN': this.token };
      const fetchJson = async <T>(path: string): Promise<T> => {
        const res = await fetch(`${this.baseUrl}${path}`, { headers });
        if (!res.ok) throw new Error(`HTTP ${res.status}`);
        return (await res.json()) as T;
      };

      const [overview, equipment, progress, alarms, trends] = await Promise.all([
        fetchJson<EndpointOverview>(dashboardEndpoints.overview),
        fetchJson<EndpointEquipment>(dashboardEndpoints.equipment),
        fetchJson<DashboardData['progress']>(dashboardEndpoints.progress),
        fetchJson<EndpointAlarms>(dashboardEndpoints.alarms),
        fetchJson<DashboardData['trends']>(dashboardEndpoints.trends),
      ]);

      const assembled: DashboardData = {
        production: overview.production ?? this.emptyProduction(),
        warehouse: overview.warehouse ?? this.emptyWarehouse(),
        equipment: equipment.stations ?? [],
        progress: progress ?? this.emptyProgress(),
        alarms: alarms.items ?? [],
        trends: trends ?? { production: [] },
      };
      this.setMode('polling');
      this.emit(assembled);
    } catch (err) {
      this.emit(null);
      this.emitError(
        `数据加载失败：${err instanceof Error ? err.message : '网络异常或无 MES 服务'}`,
      );
    }
  }

  private clearTimer() {
    if (this.timer) {
      clearInterval(this.timer);
      this.timer = null;
    }
  }

  // ---------- 空值兜底 ----------
  private emptyProduction(): DashboardData['production'] {
    return {
      outputToday: 0,
      targetToday: 0,
      qualifiedRate: 0,
      qualityOk: 0,
      qualityNg: 0,
      stationSummary: { running: 0, idle: 0, offline: 0, alarm: 0 },
    };
  }
  private emptyWarehouse(): DashboardData['warehouse'] {
    return {
      totalStock: 0,
      materialTypes: 0,
      inboundToday: 0,
      outboundToday: 0,
      movements: [],
    };
  }
  private emptyProgress(): DashboardData['progress'] {
    return {
      orderNo: '-',
      productName: '-',
      totalQty: 0,
      doneQty: 0,
      completedQty: 0,
      currentProcess: '-',
      status: '-',
    };
  }
}