import 'dart:async';
import 'package:flutter/material.dart';
import 'package:path/path.dart';
import 'package:sqflite/sqflite.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized(); // Required to initialize widgets before db operations
  final database = await openDatabase(
    // Set the path to the database. Using the `path` package is recommended to ensure
    // the database path is correctly set on all platforms.
    join(await getDatabasesPath(), 'doggie_database.db'),
    
    // When the database is first created, create a table to store dogs.
    onCreate: (db, version) {
      return db.execute(
        'CREATE TABLE dogs(id INTEGER PRIMARY KEY, name TEXT, age INTEGER)',
      );
    },
    
    // Set the version. This is important for future migrations.
    version: 1,
  );

  // Define a Dog class with fields corresponding to the table columns
  class Dog {
    final int id;
    final String name;
    final int age;

    Dog({
      required this.id,
      required this.name,
      required this.age,
    });

    // Convert a Dog into a Map. The keys must correspond to the column names in the database.
    Map<String, Object?> toMap() {
      return {
        'id': id,
        'name': name,
        'age': age,
      };
    }

    @override
    String toString() {
      return 'Dog{id: $id, name: $name, age: $age}';
    }
  }

  // Insert a Dog into the database.
  Future<void> insertDog(Dog dog) async {
    // Get a reference to the database.
    final db = await database;

    // Insert the Dog into the correct table.
    // `conflictAlgorithm` means replacing the existing record in case of a conflict.
    await db.insert(
      'dogs',
      dog.toMap(),
      conflictAlgorithm: ConflictAlgorithm.replace,
    );
  }

  // A method that retrieves all the dogs from the dogs table.
  Future<List<Dog>> dogs() async {
    // Get a reference to the database.
    final db = await database;

    // Query the table for all the Dogs.
    final List<Map<String, dynamic>> maps = await db.query('dogs');

    // Convert the List<Map<String, dynamic> into a List<Dog>.
    return List.generate(maps.length, (i) {
      return Dog(
        id: maps[i]['id'],
        name: maps[i]['name'],
        age: maps[i]['age'],
      );
    });
  }

  // Update a Dog's data by ID.
  Future<void> updateDog(Dog dog) async {
    // Get a reference to the database.
    final db = await database;

    // Update the given Dog.
    await db.update(
      'dogs',
      dog.toMap(),
      // Ensure that the Dog has the matching id to be updated.
      where: 'id = ?',
      // Pass the Dog's id as a whereArg to prevent SQL injection.
      whereArgs: [dog.id],
    );
  }

  // Delete a Dog from the database by ID.
  Future<void> deleteDog(int id) async {
    // Get a reference to the database.
    final db = await database;

    // Remove the Dog from the database.
    await db.delete(
      'dogs',
      // Use a `where` clause to delete a specific dog.
      where: 'id = ?',
      // Pass the Dog's id as a whereArg to prevent SQL injection.
      whereArgs: [id],
    );
  }

  // Using the database with some example operations.
  var fido = Dog(id: 0, name: 'Fido', age: 35);

  // Insert Fido into the database.
  await insertDog(fido);

  // Print the list of dogs (including Fido).
  print(await dogs());

  // Update Fido's age and update him in the database.
  fido = Dog(id: fido.id, name: fido.name, age: fido.age + 7);
  await updateDog(fido);

  // Print the updated list of dogs.
  print(await dogs());

  // Delete Fido from the database.
  await deleteDog(fido.id);

  // Print the list of dogs (empty since Fido is deleted).
  print(await dogs());
}