import 'dart:math';
import 'package:flutter/foundation.dart' show kDebugMode, debugPrint;
import '../enumerations.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

  // distance between latitudes and longitudes
  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) {
  // weights
  const double distanceWeight = 0.55;
  const double skillWeight = 0.25;
  const double availabilityWeight = 0.065;
  const double visionWeight = 0.04;
  const double riskWeight = 0.035;
  const double workWeight = 0.025;
  const double cultureWeight = 0.02;
  const double communicationWeight = 0.015;

  if (kDebugMode) {
    double weightSum = (distanceWeight +
        skillWeight +
        availabilityWeight +
        visionWeight +
        riskWeight +
        workWeight +
        cultureWeight +
        communicationWeight);
    if (weightSum != 1) {
      debugPrint(
          'DEBUG Info --> calculateMatchScore : Weights Sum $weightSum != 1');
    }
  }

  // Score on locations distance
  double distance = shortestDistanceBetweenUsers(currentUser, otherUser);
  double distanceScore = _distanceToPercentage(distance);

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

  int skillsSought = currentUser.skillsSought.length;
  int skillsOffered = otherUser.skills.length;

  // Idea: Calculate sum of matching skills divided by amount of skills listed.
  // As each list can have up to 3 skills max, this gives the following equation
  // with 3 skills: 0 1/3 2/3 3/3; with 2 skills: 0 1/2 2/2; with 1 skill: 0 1.
  // In total this will result in a total of 5 different states:
  // [0], [1/3], [1/2], [2/3], and [1].

  double valueSought = matchingSkillsSought / skillsSought;
  int scoreSought;
  if (valueSought == 1) {
    scoreSought = 4;
  } else if (valueSought == 2 / 3) {
    scoreSought = 3;
  } else if (valueSought == 1 / 2) {
    scoreSought = 2;
  } else if (valueSought == 1 / 3) {
    scoreSought = 1;
  } else {
    scoreSought = 0;
  }

  double valueOffered = matchingSkillsOffered / skillsOffered;
  int scoreOffered;
  if (valueOffered == 1) {
    scoreOffered = 4;
  } else if (valueOffered == 2 / 3) {
    scoreOffered = 3;
  } else if (valueOffered == 1 / 2) {
    scoreOffered = 2;
  } else if (valueOffered == 1 / 3) {
    scoreOffered = 1;
  } else {
    scoreOffered = 0;
  }

  int skillsScore = scoreSought + scoreOffered; // 8 points max

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

  if (currentAvail == AvailabilityOption.flexible ||
      otherAvail == AvailabilityOption.flexible ||
      currentAvail == otherAvail) {
    availabilityScore = 3;
  } else {
    int availabilityDifference = (currentAvail.index - otherAvail.index).abs();
    availabilityScore = 3 - availabilityDifference;
  }

  // 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
  int riskScore = 0;
  if (currentUser.risk == otherUser.risk) {
    riskScore = 1;
  }

  // Score on CorporateCulture
  int cultureScore = 0;
  if (currentUser.culture == otherUser.culture) {
    cultureScore = 1;
  }

  // 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 = (distanceWeight * distanceScore / 100) +
      (skillWeight * skillsScore / 8) +
      (availabilityWeight * availabilityScore / 3) +
      (visionWeight * visionScore / 4) +
      (workWeight * workScore / 4) +
      (riskWeight * riskScore) +
      (cultureWeight * cultureScore) +
      (communicationWeight * communicationScore);

  return totalScore * 100;
}

double _distanceToPercentage(double distance) {
  // Self predefined data points
  final List<double> distances = [0, 5, 50, 100, 200];
  final List<double> percentages = [100, 99.5, 95, 90, 50];

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

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

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

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