#26 - Kotlin

Author: eulogioep

Roadmap/26 - SOLID SRP/kotlin/eulogioep.kt

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+/*
+ * Principio de Responsabilidad Única (SRP)
+ * 
+ * El Principio de Responsabilidad Única es el primer principio de SOLID y establece que una clase
+ * debe tener una, y solo una, razón para cambiar. En otras palabras, una clase debe tener una
+ * única responsabilidad bien definida.
+ *
+ * Este principio promueve la modularidad, facilita el mantenimiento y mejora la legibilidad del código.
+ * Cuando una clase tiene múltiples responsabilidades, se vuelve más difícil de entender, modificar y probar.
+ */
+
+// Definiciones de datos comunes
+data class Book(val title: String, val author: String, var availableCopies: Int)
+data class User(val name: String, val id: String, val email: String)
+data class Loan(val user: User, val book: Book)
+
+// Versión que no cumple con SRP
+class LibraryWithoutSRP {
+    private val books = mutableListOf<Book>()
+    private val users = mutableListOf<User>()
+    private val loans = mutableListOf<Loan>()
+
+    fun addBook(title: String, author: String, copies: Int) {
+        books.add(Book(title, author, copies))
+    }
+
+    fun registerUser(name: String, id: String, email: String) {
+        users.add(User(name, id, email))
+    }
+
+    fun loanBook(userId: String, bookTitle: String) {
+        val user = users.find { it.id == userId }
+        val book = books.find { it.title == bookTitle }
+        if (user != null && book != null && book.availableCopies > 0) {
+            loans.add(Loan(user, book))
+            book.availableCopies--
+        }
+    }
+
+    fun returnBook(userId: String, bookTitle: String) {
+        val loan = loans.find { it.user.id == userId && it.book.title == bookTitle }
+        if (loan != null) {
+            loans.remove(loan)
+            loan.book.availableCopies++
+        }
+    }
+}
+
+// Versión refactorizada que cumple con SRP
+class BookManager {
+    private val books = mutableListOf<Book>()
+
+    fun addBook(title: String, author: String, copies: Int) {
+        books.add(Book(title, author, copies))
+    }
+
+    fun findBook(title: String): Book? = books.find { it.title == title }
+}
+
+class UserManager {
+    private val users = mutableListOf<User>()
+
+    fun registerUser(name: String, id: String, email: String) {
+        users.add(User(name, id, email))
+    }
+
+    fun findUser(id: String): User? = users.find { it.id == id }
+}
+
+class LoanManager {
+    private val loans = mutableListOf<Loan>()
+
+    fun loanBook(user: User, book: Book) {
+        if (book.availableCopies > 0) {
+            loans.add(Loan(user, book))
+            book.availableCopies--
+        }
+    }
+
+    fun returnBook(user: User, book: Book) {
+        val loan = loans.find { it.user == user && it.book == book }
+        if (loan != null) {
+            loans.remove(loan)
+            book.availableCopies++
+        }
+    }
+}
+
+class Library(
+    private val bookManager: BookManager,
+    private val userManager: UserManager,
+    private val loanManager: LoanManager
+) {
+    fun addBook(title: String, author: String, copies: Int) {
+        bookManager.addBook(title, author, copies)
+    }
+
+    fun registerUser(name: String, id: String, email: String) {
+        userManager.registerUser(name, id, email)
+    }
+
+    fun loanBook(userId: String, bookTitle: String) {
+        val user = userManager.findUser(userId)
+        val book = bookManager.findBook(bookTitle)
+        if (user != null && book != null) {
+            loanManager.loanBook(user, book)
+        }
+    }
+
+    fun returnBook(userId: String, bookTitle: String) {
+        val user = userManager.findUser(userId)
+        val book = bookManager.findBook(bookTitle)
+        if (user != null && book != null) {
+            loanManager.returnBook(user, book)
+        }
+    }
+}
+
+// Uso del sistema refactorizado
+fun main() {
+    val bookManager = BookManager()
+    val userManager = UserManager()
+    val loanManager = LoanManager()
+    val library = Library(bookManager, userManager, loanManager)
+
+    library.addBook("1984", "George Orwell", 5)
+    library.registerUser("EulogioEP", "001", "eulogioep@email.com")
+    library.loanBook("001", "1984")
+    library.returnBook("001", "1984")
+}