/**
 * ROLLCALC V14 - QUALITY OF LIFE UPDATE
 * Standard Deviation Ranges (±2σ = 95% confidence)
 * ====================================================
 * 
 * Features:
 * 1. Direct Calc: Show MIN/NOM/MAX for diameter & weight (±2σ)
 * 2. Forklift Checker: Use worst-case weight (MAX)
 * 3. Load Optimizer: Use nominal values (current behavior)
 */

// ===================================================================
// ENHANCED WEIGHT CALCULATION WITH STDDEV
// ===================================================================
function calculateWeightRanges(areaWeight, areaWeightStddev, length, width) {
  if (!areaWeight || !length || !width) return null;
  
  const sigma = areaWeightStddev || 0;
  const aw_min = Math.max(0, areaWeight - 2 * sigma);  // Worst case
  const aw_nom = areaWeight;                            // Nominal
  const aw_max = areaWeight + 2 * sigma;                // Best case
  
  return {
    min: (aw_min * length * width / 1000),
    nom: (aw_nom * length * width / 1000),
    max: (aw_max * length * width / 1000),
    aw_min: aw_min,
    aw_nom: aw_nom,
    aw_max: aw_max
  };
}

// ===================================================================
// ENHANCED DIAMETER CALCULATION WITH STDDEV
// ===================================================================
function calculateDiameterRanges(coreDiameter, thickness, thicknessStddev, productLength) {
  if (!coreDiameter || !thickness || !productLength) return null;
  
  const d = coreDiameter;
  const L = productLength * 1000;  // Convert to mm
  const sigma = thicknessStddev || 0;
  
  // ±2σ = 95% confidence interval
  const t_min = Math.max(0, thickness - 2 * sigma);  // Thinnest (largest diameter)
  const t_nom = thickness;                            // Nominal
  const t_max = thickness + 2 * sigma;                // Thickest (smallest diameter)
  
  // D = √(d² + 4Lt/π)
  const d_nom = Math.sqrt(d*d + (4*L*t_nom)/Math.PI);
  const d_min = Math.sqrt(d*d + (4*L*t_min)/Math.PI);  // Thinnest product → largest roll
  const d_max = Math.sqrt(d*d + (4*L*t_max)/Math.PI);  // Thickest product → smallest roll
  
  return {
    min: d_min,   // Actually MAX diameter (thinnest product)
    nom: d_nom,   // Nominal diameter
    max: d_max,   // Actually MIN diameter (thickest product)
    t_min: t_min,
    t_nom: t_nom,
    t_max: t_max,
    note: "Note: Min/Max are swapped (thinner product → larger roll)"
  };
}

// ===================================================================
// DISPLAY RESULT WITH STDDEV RANGES
// ===================================================================
function displayDiameterResult(diameterRanges, weightRanges, tolerance = 0) {
  if (!diameterRanges || !weightRanges) return false;
  
  const resBox = document.getElementById('d-result');
  const resLabel = document.getElementById('d-res-label');
  const resVal = document.getElementById('d-res-val');
  const resRange = document.getElementById('d-res-range');
  
  if (!resBox || !resLabel || !resVal || !resRange) {
    console.warn('[StdDev] Result elements not found');
    return false;
  }
  
  resLabel.textContent = 'Roll Diameter (D)';
  resVal.textContent = diameterRanges.nom.toFixed(1) + ' mm';
  
  // Build range text with ±2σ
  const d_low = Math.min(diameterRanges.min, diameterRanges.max);
  const d_high = Math.max(diameterRanges.min, diameterRanges.max);
  
  let rangeText = `Range (±2σ): ${d_low.toFixed(1)} – ${d_high.toFixed(1)} mm`;
  
  if (tolerance && tolerance > 0) {
    const d_tol_min = diameterRanges.nom - tolerance;
    const d_tol_max = diameterRanges.nom + tolerance;
    rangeText += ` | Tol: ${d_tol_min.toFixed(1)} – ${d_tol_max.toFixed(1)} mm`;
  }
  
  resRange.textContent = rangeText;
  resBox.style.display = 'block';
  
  console.log('[StdDev] Diameter results displayed:', {
    nom: diameterRanges.nom.toFixed(1),
    min: d_low.toFixed(1),
    max: d_high.toFixed(1)
  });
  
  return true;
}

// ===================================================================
// DISPLAY WEIGHT WITH STDDEV RANGES
// ===================================================================
function displayWeightRanges(weightRanges) {
  if (!weightRanges) return false;
  
  const woField = document.getElementById('d-wo');
  if (!woField) {
    console.warn('[StdDev] Weight field not found');
    return false;
  }
  
  // Display nominal weight with data attributes for stddev
  woField.value = weightRanges.nom.toFixed(1);
  
  // Store ranges in data attributes for Forklift Checker to use
  woField.dataset.weight_nom = weightRanges.nom.toFixed(1);
  woField.dataset.weight_min = weightRanges.min.toFixed(1);
  woField.dataset.weight_max = weightRanges.max.toFixed(1);
  
  console.log('[StdDev] Weight ranges stored:', {
    nom: weightRanges.nom.toFixed(1),
    min: weightRanges.min.toFixed(1),
    max: weightRanges.max.toFixed(1)
  });
  
  return true;
}

// ===================================================================
// ENHANCED FORKLIFT CHECKER - Use worst-case weight
// ===================================================================
function evaluateForkliftWithStddev(coreMm, category) {
  const woField = document.getElementById('d-wo');
  if (!woField) return;
  
  // Get worst-case weight (maximum)
  const weight_nom = parseFloat(woField.value) || 0;
  const weight_max = parseFloat(woField.dataset.weight_max) || weight_nom;
  
  // Use worst-case for safety
  const weightToCheck = Math.max(weight_nom, weight_max);
  
  console.log('[StdDev-Forklift] Evaluating with worst-case weight:', {
    nominal: weight_nom.toFixed(1),
    worst_case: weight_max.toFixed(1),
    using: weightToCheck.toFixed(1)
  });
  
  if (window.ForkliftChecker) {
    return window.ForkliftChecker.evaluate(weightToCheck, coreMm, category);
  }
  
  return true;
}

// ===================================================================
// EXPORT FOR USE IN MAIN CALCULATOR
// ===================================================================
window.StdDevCalculator = {
  calculateWeightRanges: calculateWeightRanges,
  calculateDiameterRanges: calculateDiameterRanges,
  displayDiameterResult: displayDiameterResult,
  displayWeightRanges: displayWeightRanges,
  evaluateForkliftWithStddev: evaluateForkliftWithStddev
};

console.log('[StdDevCalculator] Module loaded');

// ===================================================================
// INTEGRATION PATCH FOR DIRECT CALCULATION
// ===================================================================
// This should be added to the main d-calc button handler

/*
USAGE IN DIRECT CALC:

// After article selection, when user clicks "Calculate":

const mode = document.querySelector('.mode-btn.active')?.dataset.mode || 'diameter';
const d_mm = parseFloat(document.getElementById('d-co').value) || 0;
const t_mm = parseFloat(document.getElementById('d-th').value) || 0;
const t_stddev = parseFloat(document.getElementById('d-th-stddev')?.value) || 0;  // NEW
const L_m = parseFloat(document.getElementById('d-le').value) || 0;
const wi = parseFloat(document.getElementById('de-wi').value) || 0;
const aw = parseFloat(document.getElementById('d-aw').value) || 0;
const aw_stddev = parseFloat(document.getElementById('d-aw-stddev')?.value) || 0; // NEW
const category = (document.getElementById('d-cat')?.value || '').toLowerCase();

// Calculate ranges
const diameterRanges = window.StdDevCalculator.calculateDiameterRanges(
  d_mm, t_mm, t_stddev, L_m
);
const weightRanges = window.StdDevCalculator.calculateWeightRanges(
  aw, aw_stddev, L_m, wi
);

// Display results with ranges
window.StdDevCalculator.displayDiameterResult(diameterRanges, weightRanges);
window.StdDevCalculator.displayWeightRanges(weightRanges);

// Forklift check with worst-case weight
window.StdDevCalculator.evaluateForkliftWithStddev(d_mm, category);
*/