/**
 * Carbon Equivalencies - EPA/DEFRA/IMO 2024 Verified Conversion Factors
 * Ported from frontend src/utils/carbonEquivalencies.ts and impactSelector.ts
 */

// Carbon equivalency conversion factors (units per metric ton of CO2e)
export const CARBON_EQUIVALENCIES = {
  // TRANSPORTATION (EPA 2024)
  MILES_DRIVEN_AVG_CAR: 2560,
  GALLONS_GASOLINE: 113,

  // AVIATION (DEFRA 2024)
  FLIGHT_KM_ECONOMY_SHORT: 6667,
  FLIGHT_KM_ECONOMY_LONG: 7692,

  // NATURAL (EPA 2024)
  TREE_SEEDLINGS_10YR: 16.7,
  FOREST_ACRES_1YR: 1.0,
  FOREST_ACRES_10YR: 1.32,

  // ENERGY (EPA 2024)
  ELECTRICITY_KWH: 2540,
  HOME_ENERGY_YEARS: 0.134,
  BARRELS_OIL: 2.33,

  // YACHT-SPECIFIC (IMO 2024)
  MGO_LITERS_AVOIDED: 373,
  MGO_TONNES_AVOIDED: 0.312,
  CRUISING_HOURS_60M: 1.24,
  SUPERYACHT_NAUTICAL_MILES: 149,
  SHORE_POWER_DAYS: 25.4,

  // LIFESTYLE
  SMARTPHONE_CHARGES: 115000,
  POUNDS_COAL_BURNED: 1000,
};

// Comparison definitions with emoji icons (email-compatible)
const COMPARISON_DEFINITIONS = {
  MILES_DRIVEN: {
    icon: '🚗',
    unit: 'miles',
    label: 'Miles driven in an average car',
  },
  GALLONS_GASOLINE: {
    icon: '⛽',
    unit: 'gallons',
    label: 'Gallons of gasoline not burned',
  },
  FLIGHT_KM_SHORT: {
    icon: '✈️',
    unit: 'passenger-km',
    label: 'Short-haul flight distance (economy)',
  },
  FLIGHT_KM_LONG: {
    icon: '🛫',
    unit: 'passenger-km',
    label: 'Long-haul flight distance (economy)',
  },
  TREE_SEEDLINGS: {
    icon: '🌲',
    unit: 'trees',
    label: 'Tree seedlings grown for 10 years',
  },
  FOREST_ACRES_1YR: {
    icon: '🌳',
    unit: 'acres',
    label: 'Acres of forest preserved for 1 year',
  },
  FOREST_ACRES_10YR: {
    icon: '🌳',
    unit: 'acres',
    label: 'Acres of forest carbon sequestration over 10 years',
  },
  ELECTRICITY_KWH: {
    icon: '⚡',
    unit: 'kWh',
    label: 'Kilowatt-hours of electricity',
  },
  HOME_ENERGY_YEARS: {
    icon: '🏠',
    unit: 'home-years',
    label: 'Years of home electricity use',
  },
  BARRELS_OIL: {
    icon: '💧',
    unit: 'barrels',
    label: 'Barrels of oil not consumed',
  },
  MGO_LITERS: {
    icon: '🌊',
    unit: 'liters',
    label: 'Liters of Marine Gas Oil avoided',
  },
  MGO_TONNES: {
    icon: '💧',
    unit: 'tonnes',
    label: 'Tonnes of Marine Gas Oil avoided',
  },
  CRUISING_HOURS: {
    icon: '⚓',
    unit: 'hours',
    label: 'Hours of 60m yacht cruising avoided',
  },
  SUPERYACHT_NAUTICAL_MILES: {
    icon: '🚢',
    unit: 'nautical miles',
    label: 'Nautical miles of superyacht voyaging',
  },
  SHORE_POWER_DAYS: {
    icon: '🔋',
    unit: 'days',
    label: 'Days of shore power for large yacht',
  },
  SMARTPHONE_CHARGES: {
    icon: '📱',
    unit: 'charges',
    label: 'Smartphone charges',
  },
  POUNDS_COAL: {
    icon: '🔥',
    unit: 'pounds',
    label: 'Pounds of coal not burned',
  },
};

// Smart scaling ranges - different comparisons for different CO2 amounts
const SCALING_RANGES = [
  {
    minTons: 0,
    maxTons: 0.1,
    comparisonKeys: ['MILES_DRIVEN', 'SMARTPHONE_CHARGES', 'TREE_SEEDLINGS'],
  },
  {
    minTons: 0.1,
    maxTons: 1,
    comparisonKeys: ['MILES_DRIVEN', 'TREE_SEEDLINGS', 'GALLONS_GASOLINE'],
  },
  {
    minTons: 1,
    maxTons: 5,
    comparisonKeys: ['FLIGHT_KM_SHORT', 'TREE_SEEDLINGS', 'ELECTRICITY_KWH'],
  },
  {
    minTons: 5,
    maxTons: 20,
    comparisonKeys: ['FLIGHT_KM_LONG', 'FOREST_ACRES_1YR', 'MGO_LITERS'],
  },
  {
    minTons: 20,
    maxTons: 100,
    comparisonKeys: ['CRUISING_HOURS', 'FOREST_ACRES_1YR', 'HOME_ENERGY_YEARS'],
  },
  {
    minTons: 100,
    maxTons: Infinity,
    comparisonKeys: ['FOREST_ACRES_10YR', 'CRUISING_HOURS', 'SUPERYACHT_NAUTICAL_MILES'],
  },
];

// Factor mapping for conversion
const FACTOR_MAP = {
  MILES_DRIVEN: CARBON_EQUIVALENCIES.MILES_DRIVEN_AVG_CAR,
  GALLONS_GASOLINE: CARBON_EQUIVALENCIES.GALLONS_GASOLINE,
  FLIGHT_KM_SHORT: CARBON_EQUIVALENCIES.FLIGHT_KM_ECONOMY_SHORT,
  FLIGHT_KM_LONG: CARBON_EQUIVALENCIES.FLIGHT_KM_ECONOMY_LONG,
  TREE_SEEDLINGS: CARBON_EQUIVALENCIES.TREE_SEEDLINGS_10YR,
  FOREST_ACRES_1YR: CARBON_EQUIVALENCIES.FOREST_ACRES_1YR,
  FOREST_ACRES_10YR: CARBON_EQUIVALENCIES.FOREST_ACRES_10YR,
  ELECTRICITY_KWH: CARBON_EQUIVALENCIES.ELECTRICITY_KWH,
  HOME_ENERGY_YEARS: CARBON_EQUIVALENCIES.HOME_ENERGY_YEARS,
  BARRELS_OIL: CARBON_EQUIVALENCIES.BARRELS_OIL,
  MGO_LITERS: CARBON_EQUIVALENCIES.MGO_LITERS_AVOIDED,
  MGO_TONNES: CARBON_EQUIVALENCIES.MGO_TONNES_AVOIDED,
  CRUISING_HOURS: CARBON_EQUIVALENCIES.CRUISING_HOURS_60M,
  SUPERYACHT_NAUTICAL_MILES: CARBON_EQUIVALENCIES.SUPERYACHT_NAUTICAL_MILES,
  SHORE_POWER_DAYS: CARBON_EQUIVALENCIES.SHORE_POWER_DAYS,
  SMARTPHONE_CHARGES: CARBON_EQUIVALENCIES.SMARTPHONE_CHARGES,
  POUNDS_COAL: CARBON_EQUIVALENCIES.POUNDS_COAL_BURNED,
};

/**
 * Calculate equivalency value
 */
function calculateEquivalency(tons, factor) {
  return tons * factor;
}

/**
 * Format large numbers with appropriate precision
 */
function formatEquivalencyValue(value) {
  if (value < 0.01) {
    return value.toExponential(2);
  } else if (value < 1) {
    return value.toFixed(2);
  } else if (value < 100) {
    return value.toFixed(1);
  } else if (value < 1000) {
    return Math.round(value).toLocaleString();
  } else {
    return Math.round(value).toLocaleString();
  }
}

/**
 * Select the most appropriate comparisons for the given CO2 amount
 * @param {number} tons - Metric tons of CO2e to offset
 * @param {number} count - Number of comparisons to return (default: 3)
 * @returns {Array} Array of carbon comparisons with calculated values
 */
export function selectComparisons(tons, count = 3) {
  // Find the appropriate range for this amount
  const range = SCALING_RANGES.find(
    (r) => tons >= r.minTons && tons < r.maxTons
  );

  if (!range) {
    console.warn(`No comparison range found for ${tons} tons, using default`);
    return getDefaultComparisons(tons, count);
  }

  // Get the comparison definitions for this range
  const comparisons = range.comparisonKeys
    .slice(0, count)
    .map((key) => {
      const definition = COMPARISON_DEFINITIONS[key];
      const factor = FACTOR_MAP[key];
      const value = calculateEquivalency(tons, factor);

      return {
        ...definition,
        value: formatEquivalencyValue(value),
      };
    });

  return comparisons;
}

/**
 * Get default comparisons when no range matches
 */
function getDefaultComparisons(tons, count) {
  const defaultKeys = ['MILES_DRIVEN', 'TREE_SEEDLINGS', 'ELECTRICITY_KWH'];

  return defaultKeys.slice(0, count).map((key) => {
    const definition = COMPARISON_DEFINITIONS[key];
    const factor = FACTOR_MAP[key];
    const value = calculateEquivalency(tons, factor);

    return {
      ...definition,
      value: formatEquivalencyValue(value),
    };
  });
}