✏️ Exercices : Testabilité et doublures

/**
 * A service able to manage simple data persistence (in a "NoSQL-like" fashion).
 * Data is managed in collections, each collection containing a set of Record objects.
 * Record objects can be stored or loaded from a collection.
 */
interface DataStorage {	

    /**
     * Store a record in a specified collection of the data storage service.
     * 
     * @param collection The name of the collection where to store the record.
     * @param record     The record to store.
     */
	void storeRecord(String collection, Record record);

    /**
     * Load all records from a specified collection of the data storage service.
     * 
     * @param collection The name of the collection.
     * @return All records currently stored in the collection.
     */
	List<Record> loadRecords(String collection);
}

/**
 * A key-value structure to store data.
 * Each record is a set of key-value pairs of strings.
 * Example of record with two key-value pairs : 
 *    [ { "name" : "alpha" }, { "color" : "red" } ]
 */
class Record {

    /**
     * Construct an empty record.
     */
	public Record() {};

    /**
     * Set a value in the record.
     * If the provided key already exists, change the value associated with the key.
     * If the provided key does not exist, create a new key-value pair in the record.
     * 
     * @param key The key of the value to set.
     * @param value The value to set.
     */
	public void setValue(String key, String value) { … }

    /**
     * Retrieve a value associated with a key in the record.
     * If the key does not exist, null is returned.
     * 
     * @param key The key for which the value must be retrieved.
     * @return The value associated with the key if it exists, 'null' otherwise.
     */
	public String getValue(String key)  { … }

    /**
     * Compare two records, considered equal if they contain the exact same set of key/value pairs.
     * 
     * @param other The object to compare to.
     * @return true if other is a Record and contain the same key/value pairs as the caller.
     */
    @Override
    public boolean equals(Object other) { … }
}

/**
 * An implementation of the DataStorage service using a MongoDB backend.
 */
class MongoDBStorage implements DataStorage {
	
    /**
     * Constructor for the MongoDBStorage class. 
     * When the object is constructed, a network connection is created with the specified MongoDB server.
     * 
     * @param host The IP address of the MongoDB server to use.
     * @param port The listening port of he MongoDB server to use.
     */
	public MongoDBStorage(String host, int port) { … }
    
    …
}

/**
 * Address book service, to store and manage contacts.
 * Requires a DataStorage object to deal with data persistence.
 */
class SimpleAddressBook {
	
	private DataStorage dataStorage;

	/**
	 * Constructor for the SimpleAddressBook service.
     * 
	 * @param dataStorage the DataStorage object to use for loading
	                      and storing persistent address book data.
	 */
	public SimpleAddressBook(DataStorage dataStorage) {
		this.dataStorage = dataStorage;
	}
	
	/**
	 * Create and add a new contact in the address book.
	 * 
	 * @param firstName   The first name of the contact.
	 * @param lastName    The last name of the contact.
	 * @param phoneNumber The phone number of the contact.
	 * @param address     The postal address of the contact.
	 * @throws ExistingContactException if a contact with the same phone number 
     *                                  already exists in the address book.
	 *
	 */
	public void addContact(String firstName, String lastName, String phoneNumber, String address) 
	                       throws ExistingContactException {
		for (Record contact : this.dataStorage.loadRecords("contacts")) {
			if (contact.getValue("phone_number").equals(phoneNumber)) 
				throw new ExistingContactException();
		}
		Record newContact = new Record();
		newContact.setValue("first_name", firstName);
		newContact.setValue("last_name", lastName);
		newContact.setValue("phone_number", phoneNumber);
		newContact.setValue("address", address);
		this.dataStorage.storeRecord("contacts", newContact);
	}
}

/**
 * Required data types.
 */

public record Bakery (String name, Coordinates coordinates, boolean isOrganic) {}
public record Coordinates (float latitude, float longitude) {
    public static computeDistanceBetween(Coordinates c1, Coordinates c2) { … }
}

/**
 * To retrieve the current coordinates of the user.
 */
public interface LocalizationModule {
    Coordinates getCurrentCoordinates();
    String getCurrentCityName();
}

/**
 * To ask a server about the bakeries in a given city.
 */
public interface BakeryServerConnector {
    List<Bakery> getBakeriesIn(String city);
}

/**
 * Available working implementations of LocalizationModule and BakeryServerConnector (not shown but exist).
 */
public class PhoneLocalizationModule implements LocalizationModule { … }
public class WebsocketBakeryServerConnector implements BakeryServerConnector { … }

/**
 * Main class of the FindMyBakery app being developped.
 */
public class FindMyBakeryApp {
    /**
     * Find the best bakery the closest from the current location.
     * An organic bakery always comes before a non-organic bakery.
     */
    public Bakery findBestNearestBakery() {
        LocalizationModule localizationModule = new PhoneLocalizationModule();
        BakeryServerConnector bakeryServer = new WebsocketBakeryServerConnector("https://api.findmybakery/socket");
        Coordinates currentCoordinates = localizationModule.getCurrentCoordinates();
        Bakery best = null;
        for (Bakery candidateBakery : bakeryServer.getBakeriesIn(localizationModule.getCurrentCityName())) 
            if (best == null || (!best.isOrganic() && candidateBakery.isOrganic())
                 || (Coordinates.computeDistanceBetween(best.getCoordinates(), currentCoordinates) 
                    > Coordinates.computeDistanceBetween(candidateBakery.getCoordinates(), currentCoordinates))) 
                best = candidateBakery;
        return best;
    }
}