# All files / lib/reflection introspection.ts

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     // lib/reflection/introspection.ts

    import { subscribe, AwarenessEvent, AwarenessEventPayload } from '@/lib/awareness';
    import { SignalType, type Signal } from './types';
    import { _pushLatestSignals } from './memory';
    import { isReflectionEnabled, isVerbose } from './flags';

    // ========================================
    //   Configuration
    // ========================================

    let INTROSPECTION_INTERVAL = 5000; // 5 seconds (mutable for test overrides)

    // ========================================
    //   Module State
    // ========================================

    type SignalAggregator = {
      windowOpenCount: number;
      windowCloseCount: number;
      focusChangeCount: number;
    };

    let aggregator: SignalAggregator = createEmptyAggregator();
    let intervalId: NodeJS.Timeout | null = null;
    let isRunning = false;
    let unsubscribeFromAwareness: (() => void) | null = null;

    let onSignalComputed: ((signal: Signal) => void) | null = null;

    // ========================================
    //   Private Logic
    // ========================================

    function createEmptyAggregator(): SignalAggregator {
      return {
        windowOpenCount: 0,
        windowCloseCount: 0,
        focusChangeCount: 0,
      };
    }

    /**
     * Processes a raw awareness event and updates the aggregator.
     * @param event The awareness event.
     */
    function processEvent(event: AwarenessEventPayload): void {
      if (!isReflectionEnabled()) return;

      switch (event.type) {
        case AwarenessEvent.WINDOW_OPENED:
          aggregator.windowOpenCount++;
          break;
        case AwarenessEvent.WINDOW_CLOSED:
          aggregator.windowCloseCount++;
          break;
        case AwarenessEvent.WINDOW_FOCUSED:
          aggregator.focusChangeCount++;
          break;
        // Other events can be processed here for other signals
      }
    }

    /**
     * Computes signals from the aggregated data and emits them.
     */
    function computeAndEmitSignals(): void {
      const now = performance.now();
      const intervalInSeconds = INTROSPECTION_INTERVAL / 1000;

      // 1. Window Churn Signal
      const windowChurn =
        (aggregator.windowOpenCount + aggregator.windowCloseCount) / intervalInSeconds;
      const churnSignal: Signal = {
        type: 'WINDOW_CHURN',
        value: windowChurn,
        timestamp: now,
        metadata: {
          opens: aggregator.windowOpenCount,
          closes: aggregator.windowCloseCount,
          interval: INTROSPECTION_INTERVAL,
        },
      };

      // 2. Focus Stability Signal
      const focusStability = aggregator.focusChangeCount / intervalInSeconds;
      const focusSignal: Signal = {
        type: 'FOCUS_STABILITY',
        value: focusStability,
        timestamp: now,
        metadata: {
          count: aggregator.focusChangeCount,
          interval: INTROSPECTION_INTERVAL,
        },
      };

      // Notify subscribers if present
      if (onSignalComputed) {
        onSignalComputed(churnSignal);
        onSignalComputed(focusSignal);
      }

      if (isVerbose()) {
        console.log('[Reflection/Introspection] Computed Signals:', { churnSignal, focusSignal });
      }

      // push latest signals to memory buffer for tests and introspection consumers
      _pushLatestSignals([churnSignal, focusSignal]);

      // Reset aggregator for the next interval
      aggregator = createEmptyAggregator();
    }

    // ========================================
    //   Public API
    // ========================================

    /**
     * Starts the introspection engine.
     * Subscribes to the awareness bus and starts the signal computation interval.
     * @param onComputed Callback function to be invoked when a signal is computed.
     */
    export function startIntrospection(
      onComputed?: (signal: Signal) => void,
      intervalMs?: number
    ): void {
      if (isRunning || !isReflectionEnabled()) {
        return;
      }

      if (typeof intervalMs === 'number' && intervalMs > 0) {
        INTROSPECTION_INTERVAL = intervalMs;
      }

      if (isVerbose()) {
        console.log('[Reflection/Introspection] Starting engine...');
      }

      onSignalComputed = onComputed ?? null;
      unsubscribeFromAwareness = subscribe(processEvent);
      intervalId = setInterval(computeAndEmitSignals, INTROSPECTION_INTERVAL);
      isRunning = true;
    }

    /**
     * Stops the introspection engine.
     */
    export function stopIntrospection(): void {
      if (!isRunning || !intervalId) {
        return;
      }

      if (isVerbose()) {
        console.log('[Reflection/Introspection] Stopping engine...');
      }

      clearInterval(intervalId);
      if (unsubscribeFromAwareness) {
        unsubscribeFromAwareness();
        unsubscribeFromAwareness = null;
      }

      intervalId = null;
      isRunning = false;
      onSignalComputed = null;
    }

    /**
     * Resets the engine's state.
     * (For testing purposes)
     */
    export function _resetIntrospection(): void {
      stopIntrospection();
      aggregator = createEmptyAggregator();
    }

    // ------------------------------------------------------------------
    // Test & compatibility exports
    // ------------------------------------------------------------------

    /**
     * Backwards-compatible name expected by tests.
     * startIntrospectionEngine(intervalOrOnComputed?) supports either
     * - nothing: uses internal interval and no onComputed
     * - a number: interval override
     * - a function: onComputed callback
     */
    export function startIntrospectionEngine(arg?: any): void {
      // startIntrospectionEngine()
      if (arg === undefined) {
        startIntrospection();
        return;
      }

      // startIntrospectionEngine(interval: number)
      if (typeof arg === 'number') {
        startIntrospection(undefined, arg);
        return;
      }

      // startIntrospectionEngine(onComputed: function)
      if (typeof arg === 'function') {
        startIntrospection(arg as (s: Signal) => void);
        return;
      }

      // fallback
      startIntrospection();
    }

    export function stopIntrospectionEngine(): void {
      stopIntrospection();
    }

    /**
     * Manual computation helper for tests. Returns the computed signals array.
     */
    export function computeSignalsNow(): Signal[] {
      const signals: Signal[] = [];
      const now = performance.now();
      const intervalInSeconds = INTROSPECTION_INTERVAL / 1000;

      const windowChurn =
        (aggregator.windowOpenCount + aggregator.windowCloseCount) / intervalInSeconds;
      signals.push({
        type: 'WINDOW_CHURN',
        value: windowChurn,
        timestamp: now,
        metadata: {
          opens: aggregator.windowOpenCount,
          closes: aggregator.windowCloseCount,
          interval: INTROSPECTION_INTERVAL,
        },
      });

      const focusStability = aggregator.focusChangeCount / intervalInSeconds;
      signals.push({
        type: 'FOCUS_STABILITY',
        value: focusStability,
        timestamp: now,
        metadata: { count: aggregator.focusChangeCount, interval: INTROSPECTION_INTERVAL },
      });

      // reset aggregator since this mimics the interval tick
      aggregator = createEmptyAggregator();
      return signals;
    }

    export function _resetIntrospectionForTests(): void {
      _resetIntrospection();
    }