import 'dart:convert';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_svg/flutter_svg.dart';

import '../components/location_dialog.dart';
import '../components/my_button.dart';
import '../constants.dart';
import '../enumerations.dart';
import '../forms/skills_form.dart';
import '../models/language.dart';
import '../models/language_setting.dart';
import '../models/location.dart';
import '../services/auth/auth_service.dart';
import '../utils/helper_dialogs.dart';
import '../utils/math.dart';

class UserDataPage extends StatefulWidget {
  final bool isRegProcess;
  final bool isEditMode;

  const UserDataPage(
      {super.key, required this.isRegProcess, required this.isEditMode});

  @override
  State<UserDataPage> createState() => _UserDataPageState();
}

class _UserDataPageState extends State<UserDataPage> {
  MyLocation? _mainLocation;
  MyLocation? _secondaryLocation;

  List<LanguageSetting> languagesList = [];
  final List<Language> _selectedLanguages = [];

  final FirebaseFirestore _firestore = FirebaseFirestore.instance;
  final AuthService _authService = AuthService();

  int? _selectedYear;
  int? _yearFromDb;
  Gender genderView = Gender.none;
  int _genderFromDb = 0;
  List<Language> _languagesFromDb = [];
  MyLocation? _mainLocationFromDb;
  MyLocation? _secondaryLocationFromDb;
  bool _secondLocationExists = false;

  @override
  void initState() {
    super.initState();

    // load settings from database
    _fetchSettings();
  }

  Future<void> _fetchSettings() async {
    try {
      String currentUserId = _authService.getCurrentUser()!.uid;

      // Fetch user document fields (email, uid, gender, ...) from database
      DocumentSnapshot userSnapshot = await _firestore
          .collection(Constants.dbCollectionUsers)
          .doc(currentUserId)
          .get();

      if (!userSnapshot.exists || userSnapshot.data() == null) {
        return; // should not happen, user entry should exist
      }

      Map<String, dynamic> userFields =
          userSnapshot.data() as Map<String, dynamic>;

      // Extract gender and birth year
      if (userFields.containsKey(Constants.dbFieldUsersGender)) {
        _genderFromDb = userSnapshot[Constants.dbFieldUsersGender];
      }
      if (userFields.containsKey(Constants.dbFieldUsersYearBorn)) {
        _yearFromDb = userSnapshot[Constants.dbFieldUsersYearBorn];
      }

      // Fetch locations
      QuerySnapshot locationSnapshot = await _firestore
          .collection(Constants.dbCollectionUsers)
          .doc(currentUserId)
          .collection(Constants.dbCollectionLocations)
          .get();

      MyLocation userLoc;
      for (var doc in locationSnapshot.docs) {
        userLoc = MyLocation(
          street: doc[Constants.dbFieldLocationStreet],
          country: doc[Constants.dbFieldLocationCountry],
          administrativeArea: doc[Constants.dbFieldLocationArea],
          locality: doc[Constants.dbFieldLocationLocality],
          subLocality: doc[Constants.dbFieldLocationSubLocality],
          postalCode: doc[Constants.dbFieldLocationPostalCode],
          latitude: doc[Constants.dbFieldLocationLatitude],
          longitude: doc[Constants.dbFieldLocationLongitude],
        );
        if (doc.id == Constants.dbDocMainLocation) {
          _mainLocationFromDb = userLoc;
        } else if (doc.id == Constants.dbDocSecondLocation) {
          _secondaryLocationFromDb = userLoc;
          _secondLocationExists = true;
        }
      }

      // Fetch languages
      QuerySnapshot languagesSnapshot = await _firestore
          .collection(Constants.dbCollectionUsers)
          .doc(currentUserId)
          .collection(Constants.dbCollectionLanguages)
          .get();

      List<Language> userLanguages = [];
      for (var doc in languagesSnapshot.docs) {
        //languages.add(Language.fromDocument(doc));
        userLanguages.add(Language(
          code: doc.id, // aka doc['code'],
          name: doc['name'],
          nativeName: doc['nativeName'],
          iconFile: doc['iconFile'],
        ));
      }
      setState(() {
        genderView = Gender.values[_genderFromDb];
        _selectedYear = _yearFromDb;
        _languagesFromDb = userLanguages;
        _mainLocation = _mainLocationFromDb;
        _secondaryLocation = _secondaryLocationFromDb;
      });

      // Load data from JSON file when the widget initializes
      loadLanguagesFromJson();
    } catch (error) {
      _showSnackBar('Error fetching settings: $error');
    }
  }

  /// Loads the languages to display
  Future<void> loadLanguagesFromJson() async {
    // Load JSON data from assets
    String jsonData = await rootBundle.loadString(Constants.pathLanguagesJson);
    // Parse JSON into a list of objects
    List<dynamic> jsonList = await json.decode(jsonData);

    // Create LanguageSetting objects from JSON data
    languagesList = jsonList.map((item) {
      Language language = Language(
        code: item['code'],
        name: item['name'],
        nativeName: item['nativeName'],
        iconFile: item['iconFile'],
      );
      return LanguageSetting(
        language: language,
        isSelected: _languagesFromDb.any(
          (language) => language.code == item['code'],
        ),
      );
    }).toList();

    // Update the UI after loading data
    setState(() {
      if (_selectedLanguages.isEmpty) {
        _selectedLanguages.addAll(_languagesFromDb);
      }
    });
  }

  Future<bool> saveUserData(BuildContext context) async {
    try {
      // Get userID from auth service
      String currentUserID = _authService.getCurrentUser()!.uid;

      // Get references to the current users Firebase collections
      DocumentReference userRef =
          _firestore.collection(Constants.dbCollectionUsers).doc(currentUserID);
      CollectionReference languagesRef =
          userRef.collection(Constants.dbCollectionLanguages);
      CollectionReference locationsRef =
          userRef.collection(Constants.dbCollectionLocations);

      if (_selectedYear != _yearFromDb) {
        await userRef.update(
          {Constants.dbFieldUsersYearBorn: _selectedYear},
        );
        // update local value
        _yearFromDb = _selectedYear;
      }

      // Update Gender in database - only if value has changed
      if (_genderFromDb != genderView.index) {
        await userRef.update(
          {Constants.dbFieldUsersGender: genderView.index},
        );
        // update local value
        _genderFromDb = genderView.index;
      }

      // Save locations
      if (_mainLocation != _mainLocationFromDb) {
        if (_mainLocation != null) {
          // Update existing user document with new locations
          await locationsRef
              .doc(Constants.dbDocMainLocation)
              .set(_mainLocation!.toMap());
        }
      }

      if (_secondaryLocation != _secondaryLocationFromDb) {
        if (_secondaryLocation != null) {
          await locationsRef
              .doc(Constants.dbDocSecondLocation)
              .set(_secondaryLocation!.toMap())
              .then((value) => {
                    // update local values
                    _secondaryLocationFromDb = _secondaryLocation,
                    _secondLocationExists = true
                  });
        } else if (_secondLocationExists) {
          // secondLocationExists but is null here -> delete secondary in DB
          await locationsRef.doc(Constants.dbDocSecondLocation).delete().then(
                (doc) => {
                  // update local values
                  _secondaryLocationFromDb = null,
                  _secondLocationExists = false
                },
                onError: (e) => _showSnackBar('Error updating document: $e'),
              );
        }
      }

      // Save Languages - only if selected values changed
      if (_selectedLanguages.isEmpty) {
        _showSnackBar('No language selected');
        return false;
      } else if (_languagesFromDb.length != _selectedLanguages.length ||
          _selectedLanguages
              .any((element) => !_languagesFromDb.contains(element))) {
        // Loop through each Language object and save it to the collection
        for (int i = 0; i < _selectedLanguages.length; i++) {
          // Convert Language object to a map and add the map to the collection,
          // using .doc(myID).set() instead of .add() to avoid duplicates.
          await languagesRef
              .doc(_selectedLanguages[i].code)
              .set(_selectedLanguages[i].toMap());
        }
        // update local variable (only if selection is not empty)
        _languagesFromDb.clear();
        _languagesFromDb.addAll(_selectedLanguages);

        // List to store language codes from the provided list
        List<String> languageCodes =
            _selectedLanguages.map((language) => language.code).toList();
        // Clean up languages that were not part of the provided list
        await deleteUnusedDocuments(languagesRef, languageCodes);
      }

      return true;
    } catch (e) {
      _showSnackBar(e.toString());
      return false;
    }
  }

  /// Deletes documents from collection that are not part of the provided list
  Future<void> deleteUnusedDocuments(
      CollectionReference refCollection, List<String> idsToKeep) async {
    // Fetch the existing documents from the database
    QuerySnapshot snapshot = await refCollection.get();

    // Loop through each document in the collection
    for (QueryDocumentSnapshot doc in snapshot.docs) {
      String documentId = doc.id;
      // If the language code is not in the provided list, delete the document
      if (!idsToKeep.contains(documentId)) {
        await doc.reference.delete();
      }
    }
  }

  void updateSelectedGender(Set<Gender> newSelection) {
    setState(() {
      // By default there is only a single segment that can be
      // selected at one time, so its value is always the first
      // item in the selected set.
      genderView = newSelection.first;
    });
  }

  // Function to show location dialog
  void _showLocationDialog(bool isPrimary) {
    showDialog(
      context: context,
      builder: (BuildContext context) {
        return LocationDialog(
          onLocationSelected: (location) {
            setState(() {
              if (isPrimary) {
                _mainLocation = location;
              } else {
                _secondaryLocation = location;
              }
            });
          },
        );
      },
    );
  }

  /// Method to remove secondary location
  void _removeSecondaryLocation() {
    setState(() {
      _secondaryLocation = null;
    });
  }

  void _saveButtonClicked(BuildContext context) async {
    bool success = await saveUserData(context);
    if (context.mounted) {
      if (success) {
        if (widget.isRegProcess) {
          Navigator.push(
            context,
            MaterialPageRoute(
              builder: (context) => SkillsForm(
                isRegProcess: widget.isRegProcess,
                skillsSought: false,
                isEditMode: false,
              ),
            ),
          );
        } else {
          if (widget.isEditMode == true) {
            // pass data back to caller
            Map<String, MyLocation?> locations = {
              if (_mainLocation != null)
                Constants.dbDocMainLocation: _mainLocation,
              if (_secondaryLocation != null)
                Constants.dbDocSecondLocation: _secondaryLocation,
            };

            Navigator.pop(context, {
              Constants.dbFieldUsersYearBorn: _selectedYear,
              Constants.dbFieldUsersGender: genderView,
              Constants.dbCollectionLanguages: _languagesFromDb,
              Constants.dbCollectionLocations: locations,
            });
          } else {
            Navigator.pop(context);
          }
        }
      } else {
        _showSnackBar('Failed to save user data.');
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    if (languagesList.isEmpty) {
      return const Center(child: CircularProgressIndicator());
    } else {
      return Scaffold(
        appBar: AppBar(
          title:
              Text('${widget.isRegProcess ? 'User Data' : 'Edit your data'} '),
          centerTitle: true,
          actions: [
            if (widget.isRegProcess)
              IconButton(
                onPressed: () {
                  AuthService().signOut();
                },
                icon: const Icon(Icons.logout),
              )
          ],
        ),
        body: Padding(
          padding: const EdgeInsets.all(16.0),
          child: ListView(
            children: [
              if (widget.isRegProcess) ...[
                const SizedBox(height: 10),
                const Text(
                  'Please fill in the following fields to proceed with the registration process.',
                  style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
                ),
                const SizedBox(height: 20),
                const Divider(),
              ],
              const SizedBox(height: 10),
              const Text(
                'Location',
                style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
              ),
              const SizedBox(height: 20),
              // Display selected main location
              const Text(
                'Main Location:',
                style: TextStyle(fontWeight: FontWeight.bold),
              ),
              if (_mainLocation != null) ...[
                Text(_mainLocation!.toString()),
                const SizedBox(height: 10),
              ] else ...[
                const Text('n/a'),
                const SizedBox(height: 10),
              ],
              // Button to set main location
              Center(
                child: ElevatedButton(
                  onPressed: () {
                    _showLocationDialog(true);
                  },
                  child: Text(_mainLocation != null
                      ? 'Change Main Location'
                      : 'Set Main Location'),
                ),
              ),
              const SizedBox(height: 20),
              // Display selected secondary location
              if (_secondaryLocation != null) ...[
                const Text(
                  'Secondary Location:',
                  style: TextStyle(fontWeight: FontWeight.bold),
                ),
                Text(_secondaryLocation!.toString()),
                const SizedBox(height: 10),
              ],
              if (_mainLocation != null) ...[
                // Button to set secondary location
                Center(
                  child: ElevatedButton(
                    onPressed: () {
                      _showLocationDialog(false);
                    },
                    child: Text(_secondaryLocation != null
                        ? 'Change Secondary Location'
                        : 'Add Secondary Location'),
                  ),
                ),
              ],
              // Display selected secondary location or remove button
              if (_secondaryLocation != null) ...[
                const SizedBox(height: 12),
                Center(
                  child: ElevatedButton(
                    onPressed: _removeSecondaryLocation,
                    child: const Text('Remove Secondary Location'),
                  ),
                ),
              ],
              const SizedBox(height: 20),
              const Text(
                'Age',
                style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
              ),
              Row(
                children: [
                  const Padding(padding: EdgeInsets.symmetric(horizontal: 8)),
                  Text(_selectedYear != null
                      ? '${calcAge(_selectedYear)} years old'
                      : 'undefined age'),
                  const SizedBox(width: 20),
                  DropdownMenu(
                    initialSelection: _selectedYear,
                    onSelected: (int? newValue) {
                      setState(() {
                        _selectedYear = newValue;
                      });
                    },
                    dropdownMenuEntries: List.generate(50, (index) {
                      return DropdownMenuEntry<int>(
                        value: DateTime.now().year - 16 - index,
                        label: '${DateTime.now().year - 16 - index}',
                      );
                    }),
                    label: const Text('birth year'),
                  ),
                ],
              ),
              const SizedBox(height: 20),
              Text(
                'Gender (${genderView.name} selected)',
                style:
                    const TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
              ),
              Center(
                child: SegmentedButton<Gender>(
                  style: SegmentedButton.styleFrom(
                    selectedBackgroundColor: Colors.blue,
                  ),
                  segments: const <ButtonSegment<Gender>>[
                    ButtonSegment<Gender>(
                      value: Gender.none,
                      label: Text('none'),
                    ),
                    ButtonSegment<Gender>(
                      value: Gender.male,
                      label: Text('male'),
                    ),
                    ButtonSegment<Gender>(
                      value: Gender.female,
                      label: Text('female'),
                    ),
                    ButtonSegment<Gender>(
                      value: Gender.divers,
                      label: Text('diverse'),
                    ),
                  ],
                  selected: <Gender>{genderView},
                  showSelectedIcon: false,
                  onSelectionChanged: updateSelectedGender,
                ),
              ),
              const SizedBox(height: 20),
              const Divider(),
              Text(
                'Language: (${_selectedLanguages.length} selected)',
                style:
                    const TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
              ),
              ...languagesList.map(buildSingleCheckbox), // ... spread operator
              const Divider(),
              Padding(
                padding: const EdgeInsets.all(8.0),
                child: MyButton(
                  text: widget.isRegProcess ? 'Save and continue' : 'Save',
                  onTap: () {
                    _saveButtonClicked(context);
                  },
                ),
              ),
            ],
          ),
        ),
      );
    }
  }

  Widget buildSingleCheckbox(LanguageSetting languageSetting) => buildCheckbox(
        languageSetting: languageSetting,
        onClicked: () {
          setState(() {
            final newValue = !languageSetting.isSelected;
            languageSetting.isSelected = newValue;

            if (languageSetting.isSelected &&
                !_selectedLanguages.contains(languageSetting.language)) {
              _selectedLanguages.add(languageSetting.language);
            } else if (languageSetting.isSelected == false) {
              _selectedLanguages.removeWhere(
                  (element) => element.code == languageSetting.language.code);
            }
          });
        },
      );

  Widget buildCheckbox({
    required LanguageSetting languageSetting,
    required VoidCallback onClicked,
  }) =>
      ListTile(
        tileColor: Theme.of(context).colorScheme.secondary,
        onTap: onClicked,
        leading: SizedBox(
          width: 48,
          height: 32,
          child: SvgPicture.asset(
            languageSetting.language.iconFile,
          ),
        ),
        title: Text(
          languageSetting.language.nativeName,
          style: const TextStyle(fontSize: 20, fontWeight: FontWeight.bold),
        ),
        subtitle: Text(languageSetting.language.name),
        trailing: Checkbox(
          value: languageSetting.isSelected,
          onChanged: (value) => onClicked(),
        ),
      );

  void _showSnackBar(String message) {
    showErrorSnackBar(context, message);
  }
}