/**
 * Cost Calculator Service
 * Estimates filament/resin costs based on file size
 */

// Default material costs (per kg)
const DEFAULT_COSTS = {
  // FDM Filaments
  'pla': 15,           // PLA ~$15/kg
  'abs': 18,           // ABS ~$18/kg
  'petg': 20,          // PETG ~$20/kg
  'nylon': 35,         // Nylon ~$35/kg
  'tpu': 40,           // TPU ~$40/kg
  'carbon': 50,        // Carbon Fiber ~$50/kg
  'bamboo': 25,        // Bamboo ~$25/kg
  
  // Resin
  'standard': 12,      // Standard Resin ~$12/ml
  'tough': 18,         // Tough Resin ~$18/ml
  'flexible': 20,      // Flexible Resin ~$20/ml
  'castable': 25,      // Castable Resin ~$25/ml
};

// Density of materials (g/cm³)
const MATERIAL_DENSITY = {
  // FDM Filaments
  'pla': 1.24,
  'abs': 1.04,
  'petg': 1.27,
  'nylon': 1.14,
  'tpu': 1.21,
  'carbon': 1.30,
  'bamboo': 1.25,
  
  // Resin
  'standard': 1.15,
  'tough': 1.18,
  'flexible': 1.20,
  'castable': 1.22,
};

/**
 * Estimate material weight from file size
 * Using heuristic: file size in bytes → approximate volume → weight
 * 
 * Formula: Weight (g) = (File Size in MB) * 50 * density / material_type_factor
 * This is a rough estimation since we don't have actual 3D geometry
 */
export function estimateWeight(fileSizeBytes, materialType = 'pla') {
  // Convert bytes to MB
  const fileSizeMB = fileSizeBytes / (1024 * 1024);
  
  // Heuristic factor: roughly 50-70g per MB of STL/OBJ, less for compressed 3MF
  // Average density is ~1.2, so we use that as baseline
  const baseFactor = 55;
  const density = MATERIAL_DENSITY[materialType] || 1.2;
  
  // Estimate weight in grams
  const weightGrams = fileSizeMB * baseFactor * (density / 1.2);
  
  return Math.max(weightGrams, 1); // Minimum 1 gram
}

/**
 * Calculate cost based on estimated weight and material type
 */
export function calculateCost(fileSizeBytes, materialType = 'pla', customCostPerUnit = null) {
  const costPerUnit = customCostPerUnit || DEFAULT_COSTS[materialType] || DEFAULT_COSTS['pla'];
  const weight = estimateWeight(fileSizeBytes, materialType);
  
  // Convert to kg for FDM or ml for resin
  const units = weight / 1000;
  
  return {
    material: materialType,
    weight: Math.round(weight * 100) / 100, // grams
    units: Math.round(units * 100) / 100,
    costPerUnit: costPerUnit,
    estimatedCost: Math.round(units * costPerUnit * 100) / 100,
    confidence: 'low' // Note: This is a rough estimate
  };
}

/**
 * Get all available materials with their costs
 */
export function getMaterials() {
  return Object.keys(DEFAULT_COSTS).map(material => ({
    type: material,
    costPerUnit: DEFAULT_COSTS[material],
    density: MATERIAL_DENSITY[material]
  }));
}

/**
 * Update cost for a material
 */
export function updateMaterialCost(materialType, costPerUnit) {
  if (DEFAULT_COSTS.hasOwnProperty(materialType)) {
    DEFAULT_COSTS[materialType] = costPerUnit;
    return true;
  }
  return false;
}

/**
 * Batch calculate costs for multiple models
 */
export function batchCalculateCosts(models, materialType = 'pla') {
  return models.map(model => ({
    modelId: model.id,
    name: model.name,
    ...calculateCost(model.file_size, materialType)
  }));
}

export default {
  estimateWeight,
  calculateCost,
  getMaterials,
  updateMaterialCost,
  batchCalculateCosts
};