import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:collection/collection.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter_svg/svg.dart';
import 'package:swipable_stack/swipable_stack.dart';

import '../constants.dart';
import '../forms/matched_screen.dart';
import '../models/language.dart';
import '../models/location.dart';
import '../models/user_profile.dart';
import '../services/auth/auth_service.dart';
import '../utils/math.dart';
import 'chat_page.dart';

class UserMatchingPage extends StatefulWidget {
  const UserMatchingPage({super.key});

  @override
  UserMatchingPageState createState() => UserMatchingPageState();
}

class UserMatchingPageState extends State<UserMatchingPage> {
  /// The current's user profile
  UserProfile? currentUserProfile;

  /// List with [all] user profiles
  List<UserProfile> userProfiles = [];

  /// List of user profiles to show.
  List<UserProfile> potentialUserProfiles = [];

  late final SwipableStackController _controller;

  // get instance of firestore and auth
  final FirebaseFirestore _firestore = FirebaseFirestore.instance;
  final AuthService _authService = AuthService();

  void _listenController() => setState(() {});

  @override
  void initState() {
    super.initState();
    _controller = SwipableStackController()..addListener(_listenController);
    _fetchUserProfiles();
  }

  @override
  void dispose() {
    _controller
      ..removeListener(_listenController)
      ..dispose();
    super.dispose();
  }

  Future<void> _fetchUserProfiles() async {
    final String currentUserId = _authService.getCurrentUser()!.uid;
    List<UserProfile> allUsers = [];
    List<UserProfile> showProfiles = [];

    final usersSnapshot = await FirebaseFirestore.instance
        .collection(Constants.dbCollectionUsers)
        .get();

    // Fetch the list of profiles the current user has already swiped
    final QuerySnapshot swipesSnapshot = await FirebaseFirestore.instance
        .collection(Constants.dbCollectionUsers)
        .doc(currentUserId)
        .collection(Constants.dbCollectionSwipes)
        .get();

    final Set<String> likedUserIds = swipesSnapshot.docs
        .where((doc) => doc[Constants.dbFieldSwipesLike] == true)
        .map((doc) => doc.id)
        .toSet();

    final DateTime thresholdDate =
        DateTime.now().subtract(const Duration(hours: 24));
    final Set<String> dislikedUserIds = swipesSnapshot.docs
        .where((doc) =>
            doc[Constants.dbFieldSwipesLike] == false &&
            (doc[Constants.dbFieldSwipesTimestamp] as Timestamp)
                .toDate()
                .isAfter(thresholdDate))
        .map((doc) => doc.id)
        .toSet();

    for (var userDoc in usersSnapshot.docs) {
      final languagesSnapshot = await userDoc.reference
          .collection(Constants.dbCollectionLanguages)
          .get();

      // get languages
      final languages = languagesSnapshot.docs.map((doc) {
        final data = doc.data();
        return Language(
          code: data['code'],
          name: data['name'],
          nativeName: data['nativeName'],
          iconFile: data['iconFile'],
        );
      }).toList();

      // get locations
      final locationsSnapshot = await userDoc.reference
          .collection(Constants.dbCollectionLocations)
          .get();
      final mainDoc = locationsSnapshot.docs
          .firstWhereOrNull((doc) => doc.id == Constants.dbDocMainLocation);
      final secondaryDoc = locationsSnapshot.docs
          .firstWhereOrNull((doc) => doc.id == Constants.dbDocSecondLocation);
      final locations = {
        Constants.dbDocMainLocation:
            mainDoc != null ? _createLocationFromDoc(mainDoc.data()) : null,
        Constants.dbDocSecondLocation: secondaryDoc != null
            ? _createLocationFromDoc(secondaryDoc.data())
            : null,
      };

      // create userProfile including the data above
      UserProfile userProfile = UserProfile.fromDocument(userDoc);
      userProfile.locations.addAll(locations);
      userProfile.languages.addAll(languages);

      // add profiles accordingly
      allUsers.add(userProfile);
      // Exclude (1) the current user's profile, (2) the already liked profiles
      // and (3) users that were disliked less than 24 hours ago
      if (userDoc.id != currentUserId &&
          !likedUserIds.contains(userDoc.id) &&
          !dislikedUserIds.contains(userDoc.id)) {
        showProfiles.add(userProfile);
      }
    } // end for

    setState(() {
      userProfiles = allUsers;
      potentialUserProfiles = showProfiles;
      currentUserProfile =
          allUsers.firstWhereOrNull((x) => x.uid == currentUserId);
    });
  }

  MyLocation? _createLocationFromDoc(Map<String, dynamic>? data) {
    if (data == null || data.isEmpty) return null;

    return MyLocation(
      street: data[Constants.dbFieldLocationStreet],
      country: data[Constants.dbFieldLocationCountry],
      administrativeArea: data[Constants.dbFieldLocationArea],
      locality: data[Constants.dbFieldLocationLocality],
      subLocality: data[Constants.dbFieldLocationSubLocality],
      postalCode: data[Constants.dbFieldLocationPostalCode],
      latitude: data[Constants.dbFieldLocationLatitude],
      longitude: data[Constants.dbFieldLocationLongitude],
    );
  }

  void _swipeLeft() {
    _controller.next(
        swipeDirection: SwipeDirection.left, duration: Durations.extralong1);
  }

  void _swipeRight() {
    _controller.next(
        swipeDirection: SwipeDirection.right, duration: Durations.extralong4);
  }

  void _skip() {
    _controller.next(
        swipeDirection: SwipeDirection.up, duration: Durations.long4);
  }

  /// Save swipe status to database
  Future<void> _saveSwipeAction(
      String swipedUserId, SwipeDirection direction) async {
    await _firestore
        .collection(Constants.dbCollectionUsers)
        .doc(_authService.getCurrentUser()!.uid)
        .collection(Constants.dbCollectionSwipes)
        .doc(swipedUserId) // UserID instead of autogenerated ID
        .set(
      {
        Constants.dbFieldSwipesSwipedId: swipedUserId,
        Constants.dbFieldSwipesLike: direction == SwipeDirection.right,
        Constants.dbFieldSwipesTimestamp: FieldValue.serverTimestamp(),
      },
    );
  }

  UserProfile _getUserProfile(String userId) {
    return userProfiles.firstWhere((x) => x.uid == userId);
  }

  /// Check whether the swiped user has also swiped to the right
  Future<void> _checkForMatch(String swipedUserId) async {
    String currentUserId = _authService.getCurrentUser()!.uid;

    final QuerySnapshot matchSnapshot = await _firestore
        .collection(Constants.dbCollectionUsers)
        .doc(swipedUserId)
        .collection(Constants.dbCollectionSwipes)
        .where(Constants.dbFieldSwipesSwipedId, isEqualTo: currentUserId)
        .where(Constants.dbFieldSwipesLike, isEqualTo: true)
        .get();

    if (matchSnapshot.docs.isNotEmpty) {
      // save match for both users
      // using set method (with UserID) instead of add (with autogenerated ID)
      final matchesCurrentUser = _firestore
          .collection(Constants.dbCollectionUsers)
          .doc(currentUserId)
          .collection(Constants.dbCollectionMatches);
      final matchesSwipedUser = _firestore
          .collection(Constants.dbCollectionUsers)
          .doc(swipedUserId)
          .collection(Constants.dbCollectionMatches);

      await matchesCurrentUser.doc(swipedUserId).set({
        'otherUserId': swipedUserId,
        'timestamp': FieldValue.serverTimestamp(),
      });

      await matchesSwipedUser.doc(currentUserId).set({
        'otherUserId': currentUserId,
        'timestamp': FieldValue.serverTimestamp(),
      });

      //
      // TODO Notify other user?
      //
      showMatchedScreen(currentUserId, swipedUserId);

      // Remove matched user from the list of potential users
      potentialUserProfiles.removeWhere((x) => x.uid == swipedUserId);
    }
  }

  showMatchedScreen(String currentUserId, String swipedUserId) {
    UserProfile currentUser = _getUserProfile(currentUserId);
    UserProfile swipedUser = _getUserProfile(swipedUserId);

    Navigator.push(
      context,
      MaterialPageRoute(
        builder: (context) => MatchedScreen(
          currentUserName: currentUser.name,
          otherUserName: swipedUser.name,
          currentUserImageUrl: currentUser.profilePictureUrl ?? '',
          otherUserImageUrl: swipedUser.profilePictureUrl ?? '',
          onMessageButtonPressed: () {
            Navigator.pop(context); // Close the MatchedScreen
            Navigator.push(
              context,
              MaterialPageRoute(
                builder: (context) => ChatPage(
                  receiverEmail: swipedUser.email,
                  receiverID: swipedUser.uid,
                ),
              ),
            );
          },
          onContinueButtonPressed: () {
            Navigator.pop(context); // Close the MatchedScreen
          },
        ),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    if (potentialUserProfiles.isEmpty) {
      return Scaffold(
        appBar: AppBar(title: const Text('Find your Match')),
        body: Center(
          child: Padding(
            padding: const EdgeInsets.all(16.0),
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                const Icon(Icons.person_search, size: 64),
                const SizedBox(height: 20),
                // Loading...
                if (userProfiles.isEmpty) ...[
                  const CircularProgressIndicator(),
                  const SizedBox(height: 20),
                  const Text(
                    'Loading data, please wait...',
                    style: TextStyle(fontWeight: FontWeight.bold, fontSize: 18),
                  ),
                ] else ...[
                  Text(
                    userProfiles.length > 1
                        ? 'No new profiles available yet.'
                        : 'No profiles available at the moment.',
                    style: const TextStyle(
                      fontWeight: FontWeight.bold,
                      fontSize: 18,
                    ),
                  ),
                  const SizedBox(height: 60),
                  const Text(
                    'Please check back later, perhaps tomorrow.',
                    textAlign: TextAlign.center,
                    style: TextStyle(fontWeight: FontWeight.bold, fontSize: 18),
                  ),
                ],
              ],
            ),
          ),
        ),
      );
    }

    return Scaffold(
      appBar: AppBar(title: const Text('Find your Match')),
      body: SafeArea(
        top: false,
        child: Stack(
          children: [
            Positioned.fill(
              child: Padding(
                padding: const EdgeInsets.all(8),
                child: SwipableStack(
                  detectableSwipeDirections: const {
                    SwipeDirection.right,
                    SwipeDirection.left,
                    SwipeDirection.up,
                  },
                  controller: _controller,
                  stackClipBehaviour: Clip.none,
                  swipeAnchor: SwipeAnchor.bottom,
                  // item count +1 for additional end page
                  itemCount: potentialUserProfiles.length + 1,
                  onSwipeCompleted: (index, direction) {
                    //
                    // Swipe logic
                    //
                    String swipedUserId =
                        potentialUserProfiles[_controller.currentIndex].id;
                    if (direction == SwipeDirection.right) {
                      _saveSwipeAction(swipedUserId, SwipeDirection.right);
                      _checkForMatch(swipedUserId);
                    } else if (direction == SwipeDirection.left) {
                      _saveSwipeAction(swipedUserId, SwipeDirection.left);
                    }
                  },
                  horizontalSwipeThreshold: 0.8,
                  verticalSwipeThreshold: 0.8,
                  builder: (context, properties) {
                    if (properties.index == potentialUserProfiles.length) {
                      return Center(
                        child: _buildLastCard(), // last card
                      );
                    }

                    final userProfile = potentialUserProfiles[
                        properties.index % potentialUserProfiles.length];
                    return Container(
                      alignment: Alignment.center,
                      decoration: BoxDecoration(
                        borderRadius: BorderRadius.circular(25.0),
                        color: Colors.blue,
                      ),
                      child: Stack(
                        children: [
                          _buildUserCard(userProfile),
                          if (properties.stackIndex == 0 &&
                              properties.direction != null)
                            CardOverlay(
                              swipeProgress: properties.swipeProgress,
                              direction: properties.direction!,
                            ),
                        ],
                      ),
                    );
                  },
                ),
              ),
            ),
            _buildSwipeButtons(),
          ],
        ),
      ),
    );
  }

  Widget _buildUserCard(UserProfile userProfile) {
    String? profileImageUrl = userProfile.profilePictureUrl;

    int age = calcAge(userProfile.born);
    String ageInfo = age > 0 ? ' ($age)' : '';

    // Sort the languages according to the given order below
    List<Language> sortedLanguages = List.from(userProfile.languages);
    sortedLanguages.sort((a, b) {
      if (a.code == 'de') return -1; // German first
      if (b.code == 'de') return 1; // German first
      if (a.code == 'en') return -1; // English second
      if (b.code == 'en') return 1; // English second
      return a.name.compareTo(b.name); // All others by name ascending
    });

    String shortDist =
        shortestDistanceBetweenUsers(currentUserProfile!, userProfile)
            .toStringAsFixed(0);

    return Card(
      child: Padding(
        padding: const EdgeInsets.all(16.0),
        child: SingleChildScrollView(
          child: Column(
            mainAxisSize: MainAxisSize.min,
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              if (kDebugMode)
                Center(
                  child: Text(
                    userProfile.email,
                    style: const TextStyle(fontSize: 12),
                  ),
                ),

              Center(
                child: CircleAvatar(
                  radius: 50,
                  backgroundImage:
                      ((profileImageUrl != null && profileImageUrl.isNotEmpty))
                          ? NetworkImage(profileImageUrl)
                          : null,
                  child: (profileImageUrl == null || profileImageUrl.isEmpty)
                      ? const Icon(Icons.person_pin, size: 50)
                      : null,
                ),
              ),
              const SizedBox(height: 8),
              Center(
                child: Text('${userProfile.name}$ageInfo',
                    style: const TextStyle(fontSize: 24)),
              ),
              const SizedBox(height: 8),
              Text(
                'Would like to team up with someone who has experience in '
                '${userProfile.skillsSought.map((x) => x.displayName).join(', ')}.',
              ),
              Text(
                'He/She brings skills and experience in '
                '${userProfile.skills.map((x) => x.displayName).join(', ')}',
              ),
              Text(
                'and is willing to commit in '
                '${userProfile.availability.commitmentText}.',
              ),
              Text(
                'Lives in ${userProfile.locations[Constants.dbDocMainLocation]?.toString() ?? 'N/A'}'
                ' and ${userProfile.locations[Constants.dbDocSecondLocation]?.toString() ?? 'N/A'}'
                ' which is only/about $shortDist km away from you.',
              ),
              const SizedBox(height: 8),
              const Row(
                children: [
                  Text('Spoken languages '),
                  Expanded(child: Divider()),
                ],
              ),
              const SizedBox(height: 4),
              Wrap(
                children: sortedLanguages.map(
                  (language) {
                    return Row(
                      mainAxisSize: MainAxisSize.min,
                      children: [
                        SvgPicture.asset(
                          language.iconFile,
                          height: 12.0,
                        ),
                        const SizedBox(width: 4.0),
                        Text(language.name),
                        // Space between each language icon pair
                        const SizedBox(width: 8.0),
                      ],
                    );
                  },
                ).toList(),
              ),

              //Text('Risk type: ${userProfile.risk.displayName}'),
            ],
          ),
        ),
      ),
    );
  }

  Widget _buildLastCard() {
    return Padding(
      padding: const EdgeInsets.all(16.0),
      child: SingleChildScrollView(
        child: Column(
          // Show reached end message and restart button
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Icon(Icons.person_search, size: 64),
            const SizedBox(height: 20),
            const Text('You\'ve viewed all available profiles.',
                textAlign: TextAlign.center,
                style: TextStyle(fontSize: 24, fontWeight: FontWeight.bold)),
            const SizedBox(height: 60),
            const Text(
                'Would you like to do another run and see the remaining profiles again?',
                textAlign: TextAlign.center,
                style: TextStyle(fontSize: 24, fontWeight: FontWeight.bold)),
            const SizedBox(height: 20),
            ElevatedButton(
              onPressed: () {
                setState(() {
                  // Restart swiping from the beginning
                  _controller.currentIndex = 0;
                });
              },
              child: const Text('Another run'),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildSwipeButtons() {
    return Positioned(
      bottom: 16,
      left: 0,
      right: 0,
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: [
          FloatingActionButton(
            heroTag: 'myFABUndo',
            tooltip: 'Undo last action',
            shape: const CircleBorder(),
            onPressed: () {
              _controller.rewind(duration: Durations.extralong4);
            },
            child: const Icon(Icons.undo),
          ),
          SizedBox(
            width: 72,
            height: 72,
            child: FloatingActionButton(
              heroTag: 'myFABSwipeLeft',
              shape: const CircleBorder(),
              onPressed: _swipeLeft,
              child: Stack(
                // to deal with icons inner transparency
                alignment: Alignment.center,
                children: [
                  Container(
                    width: 48.0,
                    height: 48.0,
                    decoration: const BoxDecoration(
                      color: Colors.white70,
                      shape: BoxShape.circle,
                    ),
                  ),
                  const Icon(Icons.cancel, color: Colors.red, size: 72),
                ],
              ),
            ),
          ),
          SizedBox(
            width: 72,
            height: 72,
            child: FloatingActionButton(
              heroTag: 'myFABSwipeRight',
              shape: const CircleBorder(),
              onPressed: _swipeRight,
              child: Stack(
                // to deal with icons inner transparency
                alignment: Alignment.center,
                children: [
                  Container(
                    width: 48.0,
                    height: 48.0,
                    decoration: const BoxDecoration(
                      color: Colors.white70,
                      shape: BoxShape.circle,
                    ),
                  ),
                  const Icon(Icons.check_circle, color: Colors.green, size: 72),
                ],
              ),
            ),
          ),
          FloatingActionButton(
            tooltip: 'Skip profile',
            heroTag: 'myFABSkip',
            shape: const CircleBorder(),
            onPressed: _skip,
            child: const Icon(Icons.skip_next),
          ),
        ],
      ),
    );
  }
}

class CardOverlay extends StatelessWidget {
  final double swipeProgress;
  final SwipeDirection direction;

  const CardOverlay({
    super.key,
    required this.swipeProgress,
    required this.direction,
  });

  @override
  Widget build(BuildContext context) {
    return Positioned.fill(
      bottom: 300,
      child: Opacity(
        opacity: swipeProgress.abs().clamp(0.0, 1.0),
        child: Align(
          alignment: direction == SwipeDirection.right
              ? Alignment.centerLeft
              : (direction == SwipeDirection.left
                  ? Alignment.centerRight
                  : Alignment.center),
          child: Icon(
            direction == SwipeDirection.right
                ? Icons.thumb_up
                : (direction == SwipeDirection.left ? Icons.thumb_down : null),
            size: 100,
            color: direction == SwipeDirection.right
                ? Colors.green
                : (direction == SwipeDirection.left ? Colors.red : Colors.blue),
          ),
        ),
      ),
    );
  }
}