feat: adds Vicente's implementation of CsvDataLoader (code-differently#303)

* feat: CsvDataLoader implementation

* fix: Implementation for CsvDataLoader that handles null (or blank) elements.

* fix: removing line that wasn't used in CsvDataLoader

* feat: Initial implementation of readGuests()

* chore: removing repetitive sysout's (logging).

* chore: formatting, spotlessApply, delogging.

* feat: added getCheckedOutItems()

* chore: Correcting functionality and encapsulating.

* fix: MapToInt wasn't handling null pointer exception

* chore: Removing main method

* fix: undo changes to LibraryCsvDataLoaderTest

* feat: Handling null pointer exception

* fix: revert LibraryCsvDataLoaderTest.java to original state

* fix: gradle spotlessApply CsvDataLoader.java

Author: VicenteVigueras

lesson_12/io/io_app/src/main/java/com/codedifferently/lesson12/factory/vicentevigueras/CsvDataLoader.java

@@ -0,0 +1,132 @@
+package com.codedifferently.lesson12.factory.vicentevigueras;
+
+import com.codedifferently.lesson12.factory.LibraryCsvDataLoader;
+import com.codedifferently.lesson12.models.CheckoutModel;
+import com.codedifferently.lesson12.models.LibraryDataModel;
+import com.codedifferently.lesson12.models.LibraryGuestModel;
+import com.codedifferently.lesson12.models.MediaItemModel;
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.stereotype.Service;
+
+/**
+ * @author vscode
+ */
+@Service
+public class CsvDataLoader implements LibraryCsvDataLoader {
+
+  @Override
+  public LibraryDataModel loadData() throws IOException {
+    // Create object named model that is an instance of LibraryDataModel
+    var model = new LibraryDataModel();
+    // Creates a list and loads with everything inside of file path
+    model.mediaItems = readMediaItems("csv/media_items.csv");
+    model.guests = readGuests("csv/guests.csv");
+    Map<String, List<CheckoutModel>> checkoutsByGuestEmail =
+        getCheckedOutItems("csv/checked_out_items.csv");
+    for (var guest : model.guests) {
+      var checkouts = checkoutsByGuestEmail.get(guest.email);
+      if (checkouts == null) {
+        checkouts = new ArrayList<>();
+      }
+      guest.checkedOutItems = checkouts;
+    }
+
+    return model;
+  }
+
+  // Read data after loading it.
+  private List<MediaItemModel> readMediaItems(String filePath) throws IOException {
+    String[] eachLine = getFileContent(filePath).split("\n");
+
+    var items = new ArrayList<MediaItemModel>();
+
+    for (int i = 1; i < eachLine.length; i++) {
+      String[] parts = eachLine[i].split(",", -1);
+      var item = new MediaItemModel();
+
+      // Parse as proper data types
+      // if else statements to handle empty spots
+      item.type = parts[0];
+      item.id = UUID.fromString(parts[1]);
+      item.title = parts[2];
+      if (parts.length > 3) {
+        item.isbn = parts[3];
+      }
+      if (parts.length > 4) {
+        item.authors = Arrays.asList(parts[4]);
+      }
+      if (parts.length > 5) {
+        item.pages = Integer.parseInt(parts[5].isEmpty() ? "0" : parts[5]);
+      }
+      if (parts.length > 6) {
+        item.runtime = Integer.parseInt(parts[6].isEmpty() ? "0" : parts[6]);
+      }
+      if (parts.length > 7) {
+        item.edition = parts[7];
+      }
+      items.add(item);
+    }
+    return items;
+  }
+
+  private List<LibraryGuestModel> readGuests(String filePath) throws IOException {
+    String[] eachLine = getFileContent(filePath).split("\n");
+
+    var guests = new ArrayList<LibraryGuestModel>();
+
+    for (int i = 1; i < eachLine.length; i++) {
+      String[] parts = eachLine[i].split(",", -1);
+      var guest = new LibraryGuestModel();
+      guest.type = parts[0];
+      guest.name = parts[1];
+      guest.email = parts[2];
+      guests.add(guest);
+    }
+    return guests;
+  }
+
+  private Map<String, List<CheckoutModel>> getCheckedOutItems(String filePath) throws IOException {
+    String fileContent = getFileContent(filePath);
+
+    Map<String, List<CheckoutModel>> checkedOutItems = new HashMap<>();
+    String[] eachLine = fileContent.split("\n");
+
+    for (int i = 1; i < eachLine.length; i++) {
+      // separate elements
+      String[] parts = eachLine[i].split(",", -1);
+
+      // read parts of the line
+      String email = parts[0];
+
+      CheckoutModel newCheckoutModel = new CheckoutModel();
+      newCheckoutModel.itemId = UUID.fromString(parts[1]);
+      newCheckoutModel.dueDate = Instant.parse(parts[2]);
+
+      List<CheckoutModel> existingCheckoutModel = checkedOutItems.get(email);
+      // validate there is not checkout items in the map
+      if (existingCheckoutModel == null) {
+        existingCheckoutModel = new ArrayList<>();
+      }
+      existingCheckoutModel.add(newCheckoutModel);
+      // store full thing in the map
+      checkedOutItems.put(email, existingCheckoutModel);
+    }
+
+    return checkedOutItems;
+  }
+
+  private String getFileContent(String filePath) throws IOException {
+    File myResource = new ClassPathResource(filePath).getFile();
+    return new String(Files.readAllBytes(myResource.toPath()));
+  }
+}