import 'dart:math';
import '../enumerations.dart';
import '../models/language.dart';
import '../models/user_profile.dart';

/// Approximate determination of age
int calcAge(int? birthYear) {
  if (birthYear != null) {
    return (DateTime.now().year - birthYear);
  }
  return 0;
}

/// Returns the approximate age in parentheses,
/// or an empty string if [birthYear] is the current year or null.
String ageInfo(int? birthYear) {
  int age = calcAge(birthYear);
  String ageInfo = age > 0 ? '($age)' : '';
  return ageInfo;
}

/// Convert decimal coordinate to degrees minutes seconds (DMS).
String convertDecimalToDMS(double decimalValue, {required bool isLatitude}) {
  bool isNegative = decimalValue < 0;
  double absoluteValue = decimalValue.abs();

  int degrees = absoluteValue.toInt();
  double minutesDecimal = (absoluteValue - degrees) * 60;
  int minutes = minutesDecimal.toInt();
  double secondsDecimal = (minutesDecimal - minutes) * 60;
  double seconds = double.parse(secondsDecimal.toStringAsFixed(2));

  String direction;
  if (isLatitude) {
    direction = isNegative ? 'S' : 'N';
  } else {
    direction = isNegative ? 'W' : 'E';
  }

  // return formatted string
  return '${degrees.abs()}° ${minutes.abs()}\' ${seconds.abs().toStringAsFixed(2)}" $direction';
}

/// Distance in kilometers between two location coordinates
double calculateDistance(double lat1, double lon1, double lat2, double lon2) {
  const R = 6371; // earth radius in kilometers

  // Haversine formula to get distance between latitudes and longitudes
  // https://en.wikipedia.org/wiki/Haversine_formula
  final dLat = _degreesToRadians(lat2 - lat1);
  final dLon = _degreesToRadians(lon2 - lon1);

  final a = sin(dLat / 2) * sin(dLat / 2) +
      cos(_degreesToRadians(lat1)) *
          cos(_degreesToRadians(lat2)) *
          sin(dLon / 2) *
          sin(dLon / 2);
  final c = 2 * atan2(sqrt(a), sqrt(1 - a));

  return R * c;
}

double _degreesToRadians(double degrees) {
  return degrees * pi / 180;
}

/// Shortest distance between two users locations
double shortestDistanceBetweenUsers(
    UserProfile currentUser, UserProfile otherUser) {
  try {
    if (currentUser.locations.isEmpty || otherUser.locations.isEmpty) {
      return double.nan;
    }

    double shortestDistance = double.nan;
    // locations currentUser
    for (var loc1 in currentUser.locations.values) {
      if (loc1 != null && loc1.latitude != null && loc1.longitude != null) {
        for (var loc2 in otherUser.locations.values) {
          if (loc2 != null && loc2.latitude != null && loc2.longitude != null) {
            double distance = calculateDistance(loc1.latitude!, loc1.longitude!,
                loc2.latitude!, loc2.longitude!);
            if (shortestDistance.isNaN || distance < shortestDistance) {
              shortestDistance = distance;
            }
          }
        }
      }
    }

    return shortestDistance;
  } catch (e) {
    return double.nan;
  }
}

/// Calculates the matching score of [otherUser] for [currentUser].
double calculateMatchScore(UserProfile currentUser, UserProfile otherUser) {
  // Score on locations distance
  double distance = shortestDistanceBetweenUsers(currentUser, otherUser);
  double distanceScore = _distanceToPoints(distance);

  // Score on common languages
  List<Language> currentLang = currentUser.languages;
  List<Language> otherLang = otherUser.languages;
  int matchingLanguages =
      currentLang.toSet().intersection(otherLang.toSet()).length;
  int langScore = 0;
  if (matchingLanguages >= 3) {
    langScore = 10;
  } else if (matchingLanguages == 2) {
    langScore = 9;
  } else if (matchingLanguages == 1) {
    langScore = 8;
  }

  // Score on common Sectors
  List<SectorOption> currentSectors = currentUser.sectors;
  List<SectorOption> otherSectors = otherUser.sectors;
  int matchingSectors =
      currentSectors.toSet().intersection(otherSectors.toSet()).length;
  int sectorScore = 0;
  if (matchingSectors >= 4) {
    sectorScore = 10;
  } else if (matchingSectors == 3) {
    sectorScore = 9;
  } else if (matchingSectors == 2) {
    sectorScore = 7;
  } else if (matchingSectors == 1) {
    sectorScore = 5;
  }

  // Score on skills
  int matchingSkillsSought = currentUser.skillsSought
      .toSet()
      .intersection(otherUser.skills.toSet())
      .length;
  int matchingSkillsOffered = currentUser.skills
      .toSet()
      .intersection(otherUser.skillsSought.toSet())
      .length;

  int skillsOffered = otherUser.skills.length;

  int scoreSought = 0;
  if (matchingSkillsSought >= 3) {
    scoreSought = 15;
  } else if (matchingSkillsSought == 2) {
    scoreSought = 12;
  } else if (matchingSkillsSought == 1) {
    scoreSought = 9;
  }

  double valueOffered = matchingSkillsOffered / skillsOffered;
  int scoreOffered;
  if (valueOffered == 1) {
    scoreOffered = 15;
  } else if (valueOffered == 4 / 5) {
    scoreOffered = 14;
  } else if (valueOffered == 3 / 4) {
    scoreOffered = 13;
  } else if (valueOffered == 2 / 3) {
    scoreOffered = 12;
  } else if (valueOffered == 3 / 5) {
    scoreOffered = 11;
  } else if (valueOffered == 1 / 2) {
    scoreOffered = 10;
  } else if (valueOffered == 2 / 5) {
    scoreOffered = 9;
  } else if (valueOffered == 1 / 3) {
    scoreOffered = 8;
  } else if (valueOffered == 1 / 4) {
    scoreOffered = 7;
  } else if (valueOffered == 1 / 5) {
    scoreOffered = 6;
  } else {
    scoreOffered = 0;
  }

  double skillsScore = (scoreSought + scoreOffered) / 1.5;

  // Score on availability
  int availabilityScore;
  AvailabilityOption currentAvail = currentUser.availability;
  AvailabilityOption otherAvail = otherUser.availability;

  if (currentAvail != otherAvail &&
      (currentAvail == AvailabilityOption.flexible ||
          otherAvail == AvailabilityOption.flexible)) {
    availabilityScore = 4;
  } else {
    int availabilityDifference = (currentAvail.index - otherAvail.index).abs();
    // map possible values [0 1 2 3] to points {0 1 3 5]
    availabilityScore = (3 - availabilityDifference) * 2 - 1;
  }

  // Score on Vision
  List<VisionOption> currentVisions = currentUser.visions;
  List<VisionOption> otherVisions = otherUser.visions;
  int matchingVisions =
      currentVisions.toSet().intersection(otherVisions.toSet()).length;

  int visionScore;
  if (matchingVisions == 4 ||
      ((currentVisions.length == otherVisions.length) &&
          (matchingVisions == currentVisions.length))) {
    visionScore = 4; // full match, max score
  } else if (matchingVisions > 1) {
    visionScore = 3; // some match
  } else if (matchingVisions == 1) {
    visionScore = 2; // one match
  } else {
    visionScore = 0; // no match
  }

  // Score on WorkValues
  List<WorkValueOption> currentWorks = currentUser.workValues;
  List<WorkValueOption> otherWorks = otherUser.workValues;
  int matchingWorks =
      currentWorks.toSet().intersection(otherWorks.toSet()).length;

  int workScore;
  if (matchingWorks == 2 ||
      ((currentWorks.length == otherWorks.length) && (matchingWorks == 1))) {
    workScore = 4; // full match, max score
  } else if (matchingWorks == 1) {
    workScore = 2; // semi match
  } else {
    workScore = 0; // no match
  }

  // Score on Risk
  RiskTolerance currentRisk = currentUser.risk;
  RiskTolerance otherRisk = currentUser.risk;
  int riskScore = 0;
  if (currentUser.risk == otherUser.risk) {
    riskScore = 3;
  } else {
    int riskDifference = (currentRisk.index - otherRisk.index).abs();
    riskScore = 3 - riskDifference;
  }

  // Score on CorporateCulture
  int cultureScore = 0;
  if (currentUser.culture == otherUser.culture) {
    cultureScore = 2;
  }

  // Score on Communication
  int communicationScore = 0;
  if (currentUser.communication == otherUser.communication) {
    communicationScore = 1;
  }

  // Calc total score. Sum of each score divided by its own max score value,
  // multiplied with its own weight.
  double totalScore = distanceScore +
      langScore +
      sectorScore +
      skillsScore +
      availabilityScore +
      riskScore +
      visionScore +
      workScore +
      cultureScore +
      communicationScore;

  return min(totalScore, 99.9);
}

double _distanceToPoints(double distance) {
  // Self predefined data points
  final List<double> distances = [0, 10, 100, 200, 500, 700, 1000];
  final List<double> points = [60, 55, 40, 20, 10, 5, 0];

  if (distance.isNaN || distance >= distances.last) {
    return points.last;
  } else if (distance <= distances[0]) {
    return points[0];
  }

  // Linear interpolation
  for (int i = 1; i < distances.length; i++) {
    if (distances[i] >= distance) {
      double x0 = distances[i - 1];
      double y0 = points[i - 1];
      double x1 = distances[i];
      double y1 = points[i];

      // Interpolate
      double result = y0 + (y1 - y0) * (distance - x0) / (x1 - x0);
      return result;
    }
  }

  // Fallback return value, though code should never reach here
  return points.last; // 50
}