import { createContext, useContext, useState, ReactNode, useRef, useCallback } from 'react';

interface HeaderMetric {
  label: string;
  value: string | number;
  accentColor: 'blue' | 'green' | 'amber' | 'purple';
}

interface HeaderMetricsContextType {
  metrics: HeaderMetric[];
  setMetrics: (metrics: HeaderMetric[]) => void;
  clearMetrics: () => void;
}

const HeaderMetricsContext = createContext<HeaderMetricsContextType | undefined>(undefined);

export const useHeaderMetrics = () => {
  const context = useContext(HeaderMetricsContext);
  if (!context) {
    throw new Error('useHeaderMetrics must be used within a HeaderMetricsProvider');
  }
  return context;
};

interface HeaderMetricsProviderProps {
  children: ReactNode;
}

export const HeaderMetricsProvider: React.FC<HeaderMetricsProviderProps> = ({ children }) => {
  const [metrics, setMetrics] = useState<HeaderMetric[]>([]);
  const creditMetricRef = useRef<HeaderMetric | null>(null);
  const pageMetricsRef = useRef<HeaderMetric[]>([]);

  // Update combined metrics (credit + page metrics)
  const updateCombinedMetrics = useCallback(() => {
    const combined: HeaderMetric[] = [];
    
    // Add credit balance first if it exists
    if (creditMetricRef.current) {
      combined.push(creditMetricRef.current);
    }
    
    // Add page metrics (filter out any credit metric to avoid duplicates)
    const pageMetricsFiltered = pageMetricsRef.current.filter(
      m => m.label.toLowerCase() !== 'credits'
    );
    combined.push(...pageMetricsFiltered);
    
    setMetrics(combined);
  }, []);

  // Track last setter to distinguish between AppLayout and TablePageTemplate
  const lastSetterRef = useRef<'credit' | 'page' | null>(null);

  // Handle setMetrics - determine if it's credit balance or page metrics
  const handleSetMetrics = useCallback((newMetrics: HeaderMetric[]) => {
    // Check if this is a credit metric (single metric with label "Credits")
    const creditMetric = newMetrics.find(m => m.label.toLowerCase() === 'credits');
    
    if (newMetrics.length === 0) {
      // Empty array - use last setter to determine what to clear
      if (lastSetterRef.current === 'credit') {
        // AppLayout is clearing credit balance
        creditMetricRef.current = null;
      } else {
        // TablePageTemplate is clearing page metrics
        pageMetricsRef.current = [];
      }
      updateCombinedMetrics();
    } else if (creditMetric && newMetrics.length === 1) {
      // This is just credit balance - update credit ref
      creditMetricRef.current = creditMetric;
      lastSetterRef.current = 'credit';
      updateCombinedMetrics();
    } else {
      // This is page metrics - update page metrics ref (filter out credits)
      pageMetricsRef.current = newMetrics.filter(m => m.label.toLowerCase() !== 'credits');
      lastSetterRef.current = 'page';
      updateCombinedMetrics();
    }
  }, [updateCombinedMetrics]);

  const clearMetrics = useCallback(() => {
    setMetrics([]);
    pageMetricsRef.current = [];
    creditMetricRef.current = null;
  }, []);

  return (
    <HeaderMetricsContext.Provider value={{ metrics, setMetrics: handleSetMetrics, clearMetrics }}>
      {children}
    </HeaderMetricsContext.Provider>
  );
};