feat: implement database-backed student management with MySQL and add persistence strategies

lab2/README.md

@@ -5,6 +5,74 @@
 
 ```mermaid
 classDiagram
+    class PersistenceStrategy {
+        + load(filename : String) : Raise
+        + save(filename : String, students : Students) : Raise
+    }
+
+    class StudentsListBase {
+        + initialize(filename : String)
+        + load_from_file() : Raise
+        + save_to_file() : Raise
+        + get_student_by_id(id : String) : Student
+        + get_k_n_student_short_list(k : Int, n : Int, data_list = nil) : List<Student>
+        + sort_students() : List<Student>
+        + add_student(student : Student) : Student
+        + update_student_by_id(id : Int, new_stodent : Student) : Bool
+        + delete_student_by_id(id : Int)
+        + get_student_short_count() : Int
+    }
+
+    class StudentsListDB {
+        + initialize()
+        + get_student_by_id(id : Int) : nil | Student
+        + get_k_n_student_short_list(k : Int, n : Int) : List<Student>
+        + add_student(student : Student) : Student
+        + update_student_by_id(id : Int, new_student : Student)
+        + delete_student_by_id(id : Int)
+        + get_student_short_count() : Int
+        - row_to_student(row : Student)
+        - escape(value : any)
+    }
+
+    class JSONPersistenceStrategy {
+        + load(filename : String) : List<>
+        + save(filename : String, students : List<Student>)
+        - student_to_hash(student : Student)
+        - hash_to_student(hash : String)
+    }
+
+    class TXTPersistenceStrategy {
+        + load(filename : String) : List<>
+        + save(filename : String, students : List<Student>)
+    }
+
+    class YAMLPersistenceStrategy {
+        + load(filename : String) : List<>
+        + save(filename : String, students : List<Student>)
+        - student_to_hash(student : Student)
+        - hash_to_student(hash : String)
+    }
+
+    class StudentsList {
+        + initialize(filename : String, persistence_strategy)
+        + load() : self
+        + save() : self
+        + get_student_by_id(id : Int) : Student
+        + get_k_n_student_short_list(k : Int, n : Int, data_list = nil) : DataListStudentShort
+        + sort_students() : List<Student>
+        add_student(student : Student) : Student
+        + update_student_by_id(id : Int, new_student : Student) : Bool
+        + delete_student_by_id(id : Int) : Bool
+        + get_student_short_count() : Int
+    }
+
+    class DatabaseConnection {
+        + initialize()
+        + client()
+        + query(sql : String)
+    }
+
     class BinarySearchTree {
         - root : Node
         + add(student : Student) : void
@@ -81,6 +149,12 @@ classDiagram
 
     BinarySearchTree o-- Node
     Node o-- Student
+    StudentsListBase o-- Student
+    StudentsListDB o-- DatabaseConnection
+    DatabaseConnection <.. Singleton
+    JSONPersistenceStrategy o-- PersistenceStrategy
+    TXTPersistenceStrategy o-- PersistenceStrategy
+    YAMLPersistenceStrategy o-- PersistenceStrategy
     Person <|-- Student
     Person <|-- StudentShort
     Student <.. StudentRepository

lab2/compose.yml

@@ -0,0 +1,20 @@
+version: '3.8'
+
+services:
+  mysql:
+    image: mysql:8.0
+    container_name: mysql_container
+    restart: unless-stopped
+    environment:
+      MYSQL_ROOT_PASSWORD: rootpassword
+      MYSQL_DATABASE: project_db
+      MYSQL_USER: project_user
+      MYSQL_PASSWORD: project_password
+    ports:
+      - "3306:3306"
+    volumes:
+      - mysql_data:/var/lib/mysql
+      - ./db/migrations:/docker-entrypoint-initdb.d  # Автоматическая инициализация базы (скрипты миграций)
+
+volumes:
+  mysql_data:

lab2/db/migrations/001_create_student_table.sql

@@ -0,0 +1,11 @@
+CREATE TABLE IF NOT EXISTS student (
+  id INT AUTO_INCREMENT PRIMARY KEY,
+  git VARCHAR(255) NOT NULL,
+  surname VARCHAR(100) NOT NULL,
+  name VARCHAR(100) NOT NULL,
+  patronymic VARCHAR(100) NOT NULL,
+  birth_date DATE NOT NULL,
+  phone VARCHAR(20),
+  telegram VARCHAR(50),
+  email VARCHAR(100)
+);

lab2/db/migrations/002_insert_student_data.sql

@@ -0,0 +1,4 @@
+INSERT INTO student (git, surname, name, patronymic, birth_date, phone, telegram, email)
+VALUES 
+  ('https://github.com/example', 'Иванов', 'Иван', 'Иванович', '2000-01-01', '+123456789', '@telegram', 'email@example.com'),
+  ('https://github.com/example2', 'Петров', 'Петр', 'Петрович', '1999-05-15', '+987654321', '@petrov', 'petrov@example.com');

lab2/db_connection.rb

@@ -0,0 +1,23 @@
+require 'mysql2'
+require 'singleton'
+
+class DatabaseConnection
+  include Singleton
+
+  def initialize
+    @client = Mysql2::Client.new(
+      host: 'localhost',
+      username: 'project_user',
+      password: 'project_password',
+      database: 'project_db'
+    )
+  end
+
+  def client
+    @client
+  end
+
+  def query(sql)
+    @client.query(sql)
+  end
+end

lab2/providers/students_list_db.rb

@@ -0,0 +1,101 @@
+require_relative '../db_connection'
+require_relative '../student'
+require_relative '../student_short'
+require_relative '../data_list_student_short'
+require 'date'
+
+class StudentsListDB
+  def initialize
+    @db = DatabaseConnection.instance
+  end
+
+  # Получить объект Student по ID.
+  def get_student_by_id(id)
+    result = @db.query("SELECT * FROM student WHERE id = #{id} LIMIT 1")
+    row = result.first
+    row ? row_to_student(row) : nil
+  end
+
+  # Получить список из k студентов (страница n) в виде объекта DataList.
+  def get_k_n_student_short_list(k, n)
+    offset = (n - 1) * k
+    results = @db.query("SELECT * FROM student ORDER BY surname, name, patronymic LIMIT #{k} OFFSET #{offset}")
+    student_shorts = results.map { |row| StudentShort.from_student(row_to_student(row)) }
+    DataListStudentShort.new(student_shorts)
+  end
+
+  # Добавить объект Student в БД (ID формируется автоматически).
+  def add_student(student)
+    sql = <<~SQL
+      INSERT INTO student (git, surname, name, patronymic, birth_date, phone, telegram, email)
+      VALUES (
+        '#{escape(student.git)}',
+        '#{escape(student.surname)}',
+        '#{escape(student.name)}',
+        '#{escape(student.patronymic)}',
+        '#{student.birth_date}',
+        #{student.phone ? "'#{escape(student.phone)}'" : "NULL"},
+        #{student.telegram ? "'#{escape(student.telegram)}'" : "NULL"},
+        #{student.email ? "'#{escape(student.email)}'" : "NULL"}
+      )
+    SQL
+
+    @db.query(sql)
+    new_id = @db.query("SELECT LAST_INSERT_ID() as id").first['id']
+    student.id = new_id.to_s
+    student
+  end
+
+  # Обновить студента по ID.
+  def update_student_by_id(id, new_student)
+    sql = <<~SQL
+      UPDATE student SET 
+        git = '#{escape(new_student.git)}',
+        surname = '#{escape(new_student.surname)}',
+        name = '#{escape(new_student.name)}',
+        patronymic = '#{escape(new_student.patronymic)}',
+        birth_date = '#{new_student.birth_date}',
+        phone = #{new_student.phone ? "'#{escape(new_student.phone)}'" : "NULL"},
+        telegram = #{new_student.telegram ? "'#{escape(new_student.telegram)}'" : "NULL"},
+        email = #{new_student.email ? "'#{escape(new_student.email)}'" : "NULL"}
+      WHERE id = #{id}
+    SQL
+
+    @db.query(sql)
+    @db.client.affected_rows > 0
+  end
+
+  # Удалить студента по ID.
+  def delete_student_by_id(id)
+    @db.query("DELETE FROM student WHERE id = #{id}")
+    @db.client.affected_rows > 0
+  end
+
+  # Получить количество студентов.
+  def get_student_short_count
+    result = @db.query("SELECT COUNT(*) as count FROM student")
+    result.first['count']
+  end
+
+  private
+
+  # Преобразование строки результата в объект Student.
+  def row_to_student(row)
+    Student.new(
+      id:         row['id'].to_s,
+      git:        row['git'],
+      surname:    row['surname'],
+      name:       row['name'],
+      patronymic: row['patronymic'],
+      birth_date: Date.parse(row['birth_date'].to_s),
+      phone:      row['phone'],
+      telegram:   row['telegram'],
+      email:      row['email']
+    )
+  end
+
+  # Простой метод для экранирования строк (на практике лучше использовать подготовленные выражения).
+  def escape(value)
+    @db.client.escape(value.to_s)
+  end
+end

lab2/student.rb

@@ -17,6 +17,20 @@ class Student < Person
     self.birth_date = birth_date
   end
 
+  def self.new_from_hash(hash)
+    new(
+      id:         hash[:id] || hash['id'],
+      git:        hash[:git] || hash['git'],
+      surname:    hash[:surname] || hash['surname'],
+      name:       hash[:name] || hash['name'],
+      patronymic: hash[:patronymic] || hash['patronymic'],
+      birth_date: hash[:birth_date].is_a?(Date) ? hash[:birth_date] : Date.parse(hash[:birth_date].to_s),
+      phone:      hash[:phone] || hash['phone'],
+      telegram:   hash[:telegram] || hash['telegram'],
+      email:      hash[:email] || hash['email']
+    )
+  end
+
   def self.from_string(student_string)
     parts = student_string.split('|').map(&:strip)
     raise ArgumentError, 'Invalid student string format' if parts.size < 7

lab2/tests/test_select_db.rb

@@ -0,0 +1,18 @@
+require_relative '../db_connection'
+require_relative '../providers/students_list_db'
+
+students_db = StudentsListDB.new
+
+# Пример: получение студента с ID = 1
+student = students_db.get_student_by_id(1)
+puts student ? student.get_info : "Студент не найден"
+
+# Пример: получение второй страницы по 2 записи (если записей достаточно)
+data_list = students_db.get_k_n_student_short_list(2, 2)
+puts "Количество студентов: #{students_db.get_student_short_count}"
+data_table = data_list.get_data
+
+(0...data_table.rows_count).each do |row|
+  row_data = (0...data_table.columns_count).map { |col| data_table.item(row, col) }
+  puts row_data.join(" | ")
+end