export type MeasurementSystem = 'metric' | 'imperial';

export interface UnitPreferences {
  measurement_system: MeasurementSystem;
  temperature: 'celsius' | 'fahrenheit';
  auto_detect: boolean;
}

// Get unit labels (helper functions - use getDisplayUnit for conversion logic)
export function getSpeedUnit(system: MeasurementSystem): string {
  return system === 'imperial' ? 'mph' : 'km/h';
}

export function getDistanceUnit(system: MeasurementSystem): string {
  return system === 'imperial' ? 'ft' : 'm';
}

export function getHeightUnit(system: MeasurementSystem): string {
  return system === 'imperial' ? 'in' : 'cm';
}

export function getShortDistanceUnit(system: MeasurementSystem): string {
  return system === 'imperial' ? 'ft' : 'm';
}

// Countries that primarily use imperial system
export const IMPERIAL_COUNTRIES = ['US', 'LR', 'MM'];

// Detect measurement system from country code
export function getMeasurementSystemFromCountry(countryCode: string): MeasurementSystem {
  return IMPERIAL_COUNTRIES.includes(countryCode.toUpperCase()) ? 'imperial' : 'metric';
}

// Unit type detection
export type UnitType = 'speed' | 'distance' | 'height' | 'weight' | 'unknown';

export function detectUnitType(unit: string): UnitType {
  const normalized = unit.toLowerCase().trim();
  
  // Speed units
  if (['km/h', 'kmh', 'kph', 'mph', 'm/s', 'ms'].includes(normalized)) {
    return 'speed';
  }
  
  // Distance units (meters/feet)
  if (['m', 'meter', 'meters', 'metre', 'metres', 'ft', 'feet', 'foot'].includes(normalized)) {
    return 'distance';
  }
  
  // Height units (cm/inches)
  if (['cm', 'centimeter', 'centimeters', 'in', 'inch', 'inches'].includes(normalized)) {
    return 'height';
  }
  
  // Weight units
  if (['kg', 'kilogram', 'kilograms', 'lb', 'lbs', 'pound', 'pounds'].includes(normalized)) {
    return 'weight';
  }
  
  return 'unknown';
}

// Convert any value to metric based on its unit
export function convertValueToMetric(value: number, unit: string): number {
  const normalized = unit.toLowerCase().trim();
  
  // Speed conversions to km/h
  if (normalized === 'mph') {
    return Math.round(value / 0.621371);
  }
  if (['m/s', 'ms'].includes(normalized)) {
    return Math.round(value * 3.6);
  }
  if (['km/h', 'kmh', 'kph'].includes(normalized)) {
    return Math.round(value);
  }
  
  // Distance conversions to meters
  if (['ft', 'feet', 'foot'].includes(normalized)) {
    return Math.round(value / 3.28084);
  }
  if (['m', 'meter', 'meters', 'metre', 'metres'].includes(normalized)) {
    return Math.round(value);
  }
  
  // Height conversions to cm
  if (['in', 'inch', 'inches'].includes(normalized)) {
    return Math.round(value / 0.393701);
  }
  if (['cm', 'centimeter', 'centimeters'].includes(normalized)) {
    return Math.round(value);
  }
  
  // Weight conversions to kg
  if (['lb', 'lbs', 'pound', 'pounds'].includes(normalized)) {
    return Math.round(value / 2.20462);
  }
  if (['kg', 'kilogram', 'kilograms'].includes(normalized)) {
    return Math.round(value);
  }
  
  // Unknown unit, return as-is
  return value;
}

// Convert metric value to target unit
export function convertValueFromMetric(value: number, targetUnit: string, metricUnit: string): number {
  const normalized = targetUnit.toLowerCase().trim();
  const metricNormalized = metricUnit.toLowerCase().trim();
  
  // Speed conversions from km/h
  if (metricNormalized === 'km/h' || metricNormalized === 'kmh' || metricNormalized === 'kph') {
    if (normalized === 'mph') {
      return Math.round(value * 0.621371);
    }
    if (normalized === 'm/s' || normalized === 'ms') {
      return Math.round(value / 3.6);
    }
  }
  
  // Distance conversions from meters
  if (metricNormalized === 'm' || metricNormalized === 'meter' || metricNormalized === 'meters') {
    if (['ft', 'feet', 'foot'].includes(normalized)) {
      return Math.round(value * 3.28084);
    }
  }
  
  // Height conversions from cm
  if (metricNormalized === 'cm' || metricNormalized === 'centimeter' || metricNormalized === 'centimeters') {
    if (['in', 'inch', 'inches'].includes(normalized)) {
      return Math.round(value * 0.393701);
    }
  }
  
  // Weight conversions from kg
  if (metricNormalized === 'kg' || metricNormalized === 'kilogram' || metricNormalized === 'kilograms') {
    if (['lb', 'lbs', 'pound', 'pounds'].includes(normalized)) {
      return Math.round(value * 2.20462);
    }
  }
  
  return value;
}

// Get metric unit for a given unit type
export function getMetricUnit(unit: string): string {
  const unitType = detectUnitType(unit);
  
  switch (unitType) {
    case 'speed':
      return 'km/h';
    case 'distance':
      return 'm';
    case 'height':
      return 'cm';
    case 'weight':
      return 'kg';
    default:
      return unit;
  }
}

// Get display unit based on unit type and measurement system
export function getDisplayUnit(metricUnit: string, system: MeasurementSystem): string {
  const unitType = detectUnitType(metricUnit);
  
  switch (unitType) {
    case 'speed':
      return system === 'imperial' ? 'mph' : 'km/h';
    case 'distance':
      return system === 'imperial' ? 'ft' : 'm';
    case 'height':
      return system === 'imperial' ? 'in' : 'cm';
    case 'weight':
      return system === 'imperial' ? 'lbs' : 'kg';
    default:
      return metricUnit;
  }
}