Flutter keyword-based search chatbot

Introduction:

This chatbot operates by matching user input with a set of predefined questions and responses. It utilizes a list of French and English prepositions and pronouns to filter out non-essential words from the user’s query, making it more efficient in finding relevant answers.

This chatbot does not use a sophisticated machine learning or AI model. Instead, it relies on simple text processing and keyword matching. Here are the key elements of its model:

• Predefined Question-Answer Pairs: A dictionary containing possible questions and their corresponding answers.
• Tokenization: Splitting the input text into words.
• Lemmatization: Reduce inflectional forms to base form
• Filtering: Removing common prepositions and pronouns to focus on the main content words.
• Matching: Comparing the filtered query with the predefined questions and scoring based on word intersections.
• UI Components: Flutter widgets to handle user input, display questions and answers and even relevant answers so it can help you more, and manage the state of the conversation.

Benefits:

1. Offline Functionality:

• This chatbot can operate entirely offline as it doesn’t rely on any cloud-based services or APIs, ensuring that it is accessible even without an internet connection.
• Enhanced privacy and security since no data is transmitted over the internet.

1. Cost Efficiency:

• Being a locally run application, it doesn’t incur any costs associated with cloud-based AI services or APIs.
• No subscription fees or usage costs typically associated with online generative chatbots.

1. Simplicity and Speed:

• The simple keyword matching algorithm ensures quick responses without the computational overhead of large-scale AI models.
• Easy to maintain and extend by simply adding more question-answer pairs to the predefined list.

Technical guide:

The code I am sharing it with you below is a single user interface so i let the creativity to you to access it from any where within your application by navigation buttons..

User interfaces:

• press on “En” to change language
• press on the answer to see it fully

Code :

I wrote the variables and functions with meaningful names to enhance readability. Additionally, I included many comments throughout the code to help explain the procedures and improve understanding.
NB: Please do not hesitate to contact me for any question.

Here is the code:

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const ChatScreen(),
    );
  }
}

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

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

class _ChatScreenState extends State<ChatScreen> {
  String searchWord = '';
  List<String> answerResults = [];
  List<String> questionResults = [];
  bool isEnglish = true;
// List of adverbs, pronouns, and prepositions in English
  final List<String> adverbPronounsPrepositions = [
    "i",
    "you",
    "he",
    "she",
    "it",
    "we",
    "they",
    "me",
    "you",
    "him",
    "her",
    "it",
    "us",
    "them",
    "mine",
    "yours",
    "his",
    "hers",
    "its",
    "ours",
    "theirs",
    "this",
    "that",
    "the",
    "theses",
    "those",
    "is",
    "are",
    "about",
    "above",
    "across",
    "after",
    "against",
    "along",
    "among",
    "around",
    "at",
    "before",
    "behind",
    "below",
    "beneath",
    "beside",
    "between",
    "beyond",
    "by",
    "down",
    "during",
    "except",
    "for",
    "from",
    "in",
    "inside",
    "into",
    "like",
    "near",
    "of",
    "off",
    "on",
    "over",
    "through",
    "to",
    "toward",
    "under",
    "up",
    "with",
    "without",
    "where",
    "when",
    'why',
    "how",
    "how much",
    "how many",
    "who",
    "what",
    "which",
    "such",
    "so"
  ];

// List of adverbs, pronouns, and prepositions in French

  final List<String> adverbPrenomPrepositions = [
    "je",
    "tu",
    "il",
    "elle",
    "ils",
    "elles",
    "nous",
    "vous",
    "à",
    "chez",
    "dans",
    "de",
    "depuis",
    "durant",
    "en",
    "entre",
    "jusqu'à",
    "par",
    "pour",
    "sans",
    "sous",
    "sur",
    "vers",
    "avec",
    "avant",
    "après",
    "pendant",
    "derrière",
    "devant",
    "contre",
    "entre",
    "auprès",
    "au",
    "aux",
    "du",
    "des",
    "vos",
    "nos",
    "votre",
    "notre",
    "l",
    "que",
    "comment",
    'combien',
    "comme ",
    "sont",
    "quoi",
    "qui",
    "quand",
    "ou",
    "quel",
    "quels",
    "quelle",
    "quelles",
    "lequel",
    "laquelle",
    "lesquels",
    "lesquelles",
    "le",
    "la",
    "les",
    "un",
    "une"
  ];

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        appBar: AppBar(
            backgroundColor: Colors.grey.shade300,
            actions: [
              TextButton(
                  onPressed: () => setState(() {
                        isEnglish = !isEnglish;
                        questionResults = [];
                        answerResults = [];
                        searchWord = "";
                      }),
                  child: Text(isEnglish ? "En" : "Fr"))
            ],
            leading: InkWell(
                onTap: (() => Navigator.pop(context)),
                child: const Icon(Icons.arrow_back)),
            centerTitle: true,
            title: const Text('Chatbot')),
        body: Column(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          mainAxisSize: MainAxisSize.max,
          children: [
            Expanded(
                child: questionResults.isNotEmpty
                    ? ListView.builder(
                        itemCount: questionResults.length,
                        itemBuilder: (context, index) {
                          return ListTile(
                            title: Align(
                              alignment: Alignment.topRight,
                              child: Container(
                                padding: const EdgeInsets.all(5),
                                decoration: const BoxDecoration(
                                    color: Colors.black,
                                    borderRadius:
                                        BorderRadius.all(Radius.circular(10))),
                                child: Text(
                                  questionResults[index],
                                  style: const TextStyle(
                                      fontWeight: FontWeight.w400,
                                      color: Colors.white,
                                      fontSize: 16),
                                ),
                              ),
                            ),
                            subtitle: Align(
                              alignment: Alignment.topLeft,
                              child: Container(
                                  margin:
                                      const EdgeInsets.only(top: 10, right: 40),
                                  decoration: BoxDecoration(
                                    color: Colors.grey.shade200,
                                    borderRadius: const BorderRadius.all(
                                        Radius.circular(10)),
                                  ),
                                  padding: const EdgeInsets.all(5.0),
                                  child: Text(
                                    answerResults[index],
                                    overflow: TextOverflow.ellipsis,
                                    maxLines: 2,
                                    style: const TextStyle(
                                        fontWeight: FontWeight.w400,
                                        color: Colors.black,
                                        fontSize: 16),
                                  )),
                            ),
                            onTap: () => showValue(questionResults[index]),
                          );
                        },
                      )
                    : Center(
                        child: Text(isEnglish
                            ? "please specify your question.... "
                            : "veuillez préciser votre question s'il vous plait..."),
                      )),
            Padding(
              padding: const EdgeInsets.all(10.0),
              child: Row(
                  mainAxisAlignment: MainAxisAlignment.center,
                  crossAxisAlignment: CrossAxisAlignment.end,
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    Expanded(
                      child: TextField(
                        textAlign: TextAlign.left,
                        decoration: InputDecoration(
                          border: OutlineInputBorder(
                            borderSide: const BorderSide(
                              color: Colors.black,
                            ),
                            borderRadius: BorderRadius.circular(10.0),
                          ),
                          contentPadding: const EdgeInsets.all(10.0),
                          filled: true,
                          fillColor: Colors.grey.shade200,
                          labelText: isEnglish
                              ? 'ask your question'
                              : 'posez vos question',
                        ),
                        onChanged: (value) {
                          setState(() {
                            searchWord = value;
                          });
                        },
                      ),
                    ),
                    IconButton(
                      color: Colors.black,
                      onPressed: () => search(searchWord),
                      icon: const Icon(
                        Icons.send,
                      ),
                    ),
                  ]),
            ),
          ],
        ),
      ),
    );
  }

// dispaly full answer 
  void showValue(String key) {
    showDialog(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          title: Text(key),
          content: Text(
            isEnglish
                ? enQuestionsAndResponses[key]!
                : frQuestionsAndResponses[key]!,
            style: const TextStyle(fontSize: 12),
          ),
          actions: <Widget>[
            TextButton(
              child: Text(isEnglish ? 'Close' : "Fermer"),
              onPressed: () {
                Navigator.of(context).pop();
              },
            ),
          ],
        );
      },
    );
  }

  void search(String word) {
    List<Map<String, dynamic>> matches = [];

    // Remove adverbPrenomPrepositions from the search word
    List<String> searchWords = word
        .toLowerCase()
        .replaceAll(RegExp(r"[-'?]"), ' ')
        .replaceAll(RegExp(r"[êéè]"), 'e')
        .trim()
        .split(' ')
        .where((word) {
      if (isEnglish) {
        return !adverbPronounsPrepositions.contains(word);
      } else {
        return !adverbPrenomPrepositions.contains(word);
      }
    }).map((word) {
      if (isEnglish) {
        return word.endsWith('s')
            ? word.substring(0, word.length - 1)
            : word.endsWith('ly') || word.endsWith('ed')
                ? word.substring(0, word.length - 2)
                : word.endsWith('ing')
                    ? word.substring(0, word.length - 3)
                    : word;
      } else {
        return word.endsWith('s') || word.endsWith('z') || word.endsWith('r')
            ? word.substring(0, word.length - 1)
            : word;
      }
    }).toList();
    print("search $searchWords");

    (isEnglish ? enQuestionsAndResponses : frQuestionsAndResponses)
        .forEach((key, value) {
      // Split key into words and remove punctuation and adverbPrenomPrepositions
      List<String> questionWords = key
          .toLowerCase()
          .replaceAll(RegExp(r"[-'?]"), ' ')
          .replaceAll(RegExp(r"[êéè]"), 'e')
          .trim()
          .split(' ')
          .where((word) {
        if (isEnglish) {
          return !adverbPronounsPrepositions.contains(word);
        } else {
          return !adverbPrenomPrepositions.contains(word);
        }
      }).map((word) {
        if (isEnglish) {
          return word.endsWith('s')
              ? word.substring(0, word.length - 1)
              : word.endsWith('ly') || word.endsWith('ed')
                  ? word.substring(0, word.length - 2)
                  : word.endsWith('ing')
                      ? word.substring(0, word.length - 3)
                      : word;
        } else {
          return word.endsWith('s') || word.endsWith('z') || word.endsWith('r')
              ? word.substring(0, word.length - 1)
              : word;
        }
      }).toList();

      int score = intersect(questionWords, searchWords).length;

      if (score > 0) {
        matches.add({'question': key, 'answer': value, 'score': score});
      }
    });

    // Sort matches by score in descending order
    matches.sort((a, b) => b['score'].compareTo(a['score']));

    setState(() {
      questionResults =
          matches.map((match) => match['question'] as String).toList();
      answerResults =
          matches.map((match) => match['answer'] as String).toList();
    });
  }

  List<String> intersect(List<String> p1, List<String> p2) {
    List<String> answer = [];

    print('p1 : $p1');
    print('p2 : $p2');
    for (String word1 in p1) {
      for (String word2 in p2) {
        if (word1 == word2 || word1.contains(word2)) {
          // If a match is found, add it to the answer list
          answer.add(word1);
        }
      }
    }
    return answer;
  }

  Map<String, String> frQuestionsAndResponses = {
    "Qui êtes-vous ?":
        "Nous sommes Viamobile, un établissement de paiement en ligne agréé par la banque centrale.",
    "Que faites-vous ?":
        "Nous proposons des services financiers sécurisés tels que l'envoi, la réception et le transfert d'argent à tout moment et en tout lieu. Nous avons également de nombreux partenaires auprès desquels vous pouvez régler vos factures.",
    "D'où pouvez-vous envoyer ou recevoir de l'argent ?":
        "Vous pouvez envoyer de l'argent, recevoir des paiements et régler vos factures via nos agents présents dans chaque région. Si vous souhaitez localiser un agent près de chez vous, cliquez sur le bouton ci-dessous.",
    "Quels services offrez-vous ?":
        "Nous offrons des services de paiement mobile, de transfert d'argent et de paiement de factures.",
    "Comment contacter le support client ?":
        "Vous pouvez contacter notre support client via l'application ou par téléphone au numéro indiqué sur notre site.",
    "Quels sont vos partenaires ?":
        "Nos partenaires incluent des banques locales, des entreprises de télécommunications et des points de vente au détail.",
    "Comment sécurisez-vous vos transactions ?":
        "Nous utilisons des technologies de cryptage avancées pour garantir la sécurité de vos transactions.",
    "Quels sont les frais pour vos services ?":
        "Les frais pour nos services varient en fonction du type de transaction et sont affichés de manière transparente avant chaque opération.",
    "Puis-je utiliser vos services à l'international ?":
        "Oui, nos services sont disponibles à l'international dans les pays où nous avons des partenaires.",
    "Comment ouvrir un compte ?":
        "Pour ouvrir un compte, téléchargez notre application, suivez les étapes d'inscription et vérifiez votre identité.",
    "Quels documents sont nécessaires pour l'inscription ?":
        "Vous aurez besoin d'une pièce d'identité valide et d'un justificatif de domicile pour vous inscrire.",
    "Comment effectuer un transfert d'argent ?":
        "Pour effectuer un transfert d'argent, sélectionnez l'option 'Transfert' dans l'application, entrez les détails du bénéficiaire et confirmez la transaction.",
    "Puis-je annuler un transfert ?":
        "Les transferts peuvent être annulés dans un délai d'une heure après la confirmation, sous réserve des conditions de notre politique d'annulation.",
    "Que faire en cas de problème avec une transaction ?":
        "En cas de problème avec une transaction, contactez immédiatement notre support client pour assistance.",
    "Comment consulter l'historique des transactions ?":
        "Vous pouvez consulter l'historique de vos transactions dans la section 'Historique' de notre application.",
  };

  Map<String, String> enQuestionsAndResponses = {
    "Who are you?":
        "We are Viamobile, an online payment institution authorized by the central bank.",
    "What do you do?":
        "We offer secure financial services such as sending, receiving, and transferring money at any time and from anywhere. We also have many partners where you can pay your bills.",
    "Where can you send or receive money from?":
        "You can send money, receive payments, and pay your bills via our agents present in every region. If you want to locate an agent near you, click the button below.",
    "What services do you offer?":
        "We offer mobile payment services, money transfer, and bill payment.",
    "How to contact customer support?":
        "You can contact our customer support via the app or by phone at the number indicated on our website.",
    "Who are your partners?":
        "Our partners include local banks, telecommunications companies, and retail outlets.",
    "How do you secure your transactions?":
        "We use advanced encryption technologies to ensure the security of your transactions.",
    "What are the fees for your services?":
        "The fees for our services vary depending on the type of transaction and are transparently displayed before each operation.",
    "Can I use your services internationally?":
        "Yes, our services are available internationally in countries where we have partners.",
    "How to open an account?":
        "To open an account, download our app, follow the registration steps, and verify your identity.",
    "What documents are needed for registration?":
        "You will need a valid ID and proof of address to register.",
    "How to make a money transfer?":
        "To make a money transfer, select the 'Transfer' option in the app, enter the recipient's details, and confirm the transaction.",
    "Can I cancel a transfer?":
        "Transfers can be canceled within one hour after confirmation, subject to the conditions of our cancellation policy.",
    "What to do in case of a problem with a transaction?":
        "In case of a problem with a transaction, contact our customer support immediately for assistance.",
    "How to check transaction history?":
        "You can check your transaction history in the 'History' section of our app."
  };
}

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