/**
 * Parameter Importance Chart
 * Shows which design parameters have the most impact on objectives
 * Uses correlation analysis between parameters and objective values
 */

import { useMemo } from 'react';
import { BarChart, Bar, XAxis, YAxis, Tooltip, ResponsiveContainer, Cell } from 'recharts';

interface Trial {
  trial_number: number;
  values: number[];
  params: Record<string, number>;
}

interface DesignVariable {
  name: string;
  parameter?: string;
  unit?: string;
}

interface ParameterImportanceChartProps {
  trials: Trial[];
  designVariables: DesignVariable[];
  objectiveIndex?: number;
  objectiveName?: string;
}

// Calculate Pearson correlation coefficient
function pearsonCorrelation(x: number[], y: number[]): number {
  if (x.length !== y.length || x.length < 2) return 0;

  const n = x.length;
  const sumX = x.reduce((a, b) => a + b, 0);
  const sumY = y.reduce((a, b) => a + b, 0);
  const sumXY = x.reduce((acc, xi, i) => acc + xi * y[i], 0);
  const sumX2 = x.reduce((acc, xi) => acc + xi * xi, 0);
  const sumY2 = y.reduce((acc, yi) => acc + yi * yi, 0);

  const numerator = n * sumXY - sumX * sumY;
  const denominator = Math.sqrt((n * sumX2 - sumX * sumX) * (n * sumY2 - sumY * sumY));

  if (denominator === 0) return 0;
  return numerator / denominator;
}

export function ParameterImportanceChart({
  trials,
  designVariables,
  objectiveIndex = 0,
  objectiveName = 'Objective'
}: ParameterImportanceChartProps) {
  const importanceData = useMemo(() => {
    if (!trials || trials.length < 3 || !designVariables || designVariables.length === 0) {
      return [];
    }

    // Extract objective values
    const objectiveValues = trials
      .filter(t => t.values && t.values.length > objectiveIndex)
      .map(t => t.values[objectiveIndex]);

    if (objectiveValues.length < 3) return [];

    // Calculate correlation for each parameter
    const importances = designVariables.map(dv => {
      const paramName = dv.parameter || dv.name;
      const paramValues = trials
        .filter(t => t.params && paramName in t.params && t.values && t.values.length > objectiveIndex)
        .map(t => t.params[paramName]);

      const corrObjectiveValues = trials
        .filter(t => t.params && paramName in t.params && t.values && t.values.length > objectiveIndex)
        .map(t => t.values[objectiveIndex]);

      if (paramValues.length < 3) return { name: dv.name, importance: 0, correlation: 0 };

      const correlation = pearsonCorrelation(paramValues, corrObjectiveValues);
      // Use absolute correlation as importance (sign indicates direction)
      const importance = Math.abs(correlation);

      return {
        name: dv.name,
        importance: importance * 100, // Convert to percentage
        correlation,
        direction: correlation > 0 ? 'positive' : 'negative'
      };
    });

    // Sort by importance (descending)
    return importances.sort((a, b) => b.importance - a.importance);
  }, [trials, designVariables, objectiveIndex]);

  if (importanceData.length === 0) {
    return (
      <div className="bg-dark-700 rounded-lg p-6 border border-dark-500 shadow-sm">
        <h3 className="text-lg font-semibold mb-4 text-dark-100">Parameter Importance</h3>
        <div className="h-64 flex items-center justify-center text-dark-400">
          Need at least 3 trials for correlation analysis
        </div>
      </div>
    );
  }

  // Color based on correlation direction
  const getBarColor = (entry: typeof importanceData[0]) => {
    if (entry.correlation > 0) {
      // Positive correlation (increasing param increases objective) - red for minimization
      return '#f87171';
    } else {
      // Negative correlation (increasing param decreases objective) - green for minimization
      return '#34d399';
    }
  };

  return (
    <div className="bg-dark-700 rounded-lg p-6 border border-dark-500 shadow-sm">
      <div className="mb-4">
        <h3 className="text-lg font-semibold text-dark-100">Parameter Importance</h3>
        <p className="text-sm text-dark-400 mt-1">
          Correlation with {objectiveName} ({trials.length} trials)
        </p>
      </div>

      <div className="h-72">
        <ResponsiveContainer width="100%" height="100%">
          <BarChart
            data={importanceData}
            layout="vertical"
            margin={{ top: 5, right: 30, left: 120, bottom: 5 }}
          >
            <XAxis
              type="number"
              domain={[0, 100]}
              tickFormatter={(v) => `${v.toFixed(0)}%`}
              tick={{ fill: '#94a3b8', fontSize: 11 }}
              stroke="#334155"
            />
            <YAxis
              type="category"
              dataKey="name"
              width={110}
              tick={{ fill: '#94a3b8', fontSize: 11 }}
              stroke="#334155"
            />
            <Tooltip
              formatter={(value: number, _name: string, props: any) => {
                const corr = props.payload.correlation;
                return [
                  `${value.toFixed(1)}% (r=${corr.toFixed(3)})`,
                  'Importance'
                ];
              }}
              contentStyle={{
                backgroundColor: '#1e293b',
                border: '1px solid #334155',
                borderRadius: '8px',
                boxShadow: '0 4px 6px rgba(0,0,0,0.3)'
              }}
              labelStyle={{ color: '#e2e8f0' }}
            />
            <Bar dataKey="importance" radius={[0, 4, 4, 0]}>
              {importanceData.map((entry, index) => (
                <Cell key={index} fill={getBarColor(entry)} />
              ))}
            </Bar>
          </BarChart>
        </ResponsiveContainer>
      </div>

      {/* Legend */}
      <div className="flex gap-6 justify-center mt-4 text-sm border-t border-dark-500 pt-4">
        <div className="flex items-center gap-2">
          <div className="w-4 h-4 rounded" style={{ backgroundColor: '#34d399' }} />
          <span className="text-dark-300">Negative correlation (helps minimize)</span>
        </div>
        <div className="flex items-center gap-2">
          <div className="w-4 h-4 rounded" style={{ backgroundColor: '#f87171' }} />
          <span className="text-dark-300">Positive correlation (hurts minimize)</span>
        </div>
      </div>
    </div>
  );
}