Feat: adds mekhi's csvdataloader (#324)

* Feat: Added mekhi csvdataloader

* Feat: added loader update

---------

Co-authored-by: “Mekhi” <“[email protected] config --global user.email “[email protected]>

Author: 00USER1X

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

@@ -0,0 +1,114 @@
+package com.codedifferently.lesson12.factory.mekhiloader;
+
+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.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.Collections;
+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;
+
+@Service("LibraryCsvDataLoader")
+public class CsvDataLoader implements LibraryCsvDataLoader {
+
+  private static final int MEDIA_ITEM_FIELDS_COUNT = 8;
+
+  private static final String MEDIA_ITEMS_FILE_PATH = "csv/media_items.csv";
+  private static final String GUESTS_FILE_PATH = "csv/guests.csv";
+  private static final String CHECKED_OUT_ITEMS_FILE_PATH = "csv/checked_out_items.csv";
+
+  @Override
+  public LibraryDataModel loadData() {
+    LibraryDataModel libraryData = new LibraryDataModel();
+
+    libraryData.guests = readGuestList(GUESTS_FILE_PATH);
+    libraryData.mediaItems = readMediaItems(MEDIA_ITEMS_FILE_PATH);
+    Map<String, List<CheckoutModel>> checkoutsByGuestEmail =
+        readCheckedOutByEmail(CHECKED_OUT_ITEMS_FILE_PATH);
+
+    for (var guest : libraryData.guests) {
+      var checkouts = checkoutsByGuestEmail.getOrDefault(guest.email, Collections.emptyList());
+      guest.checkedOutItems = new ArrayList<>(checkouts);
+    }
+
+    return libraryData;
+  }
+
+  public List<MediaItemModel> readMediaItems(String path) {
+    try (var reader = Files.newBufferedReader(Path.of(new ClassPathResource(path).getURI()))) {
+      var items = new ArrayList<MediaItemModel>();
+      String line;
+      reader.readLine();
+      while ((line = reader.readLine()) != null) {
+        var parts = line.split(",", MEDIA_ITEM_FIELDS_COUNT);
+        var item = new MediaItemModel();
+
+        item.type = parts[0];
+        item.id = UUID.fromString(parts[1]);
+        item.title = parts[2];
+        item.isbn = parts[3];
+        item.authors = List.of(parts[4]);
+
+        item.pages = parts[5].isEmpty() ? 0 : Integer.parseInt(parts[5]);
+        item.runtime = parts[6].isEmpty() ? 0 : Integer.parseInt(parts[6]);
+        item.edition = parts[7];
+
+        items.add(item);
+      }
+      return items;
+    } catch (IOException e) {
+      throw new RuntimeException("Failed to read media items from: " + path, e);
+    }
+  }
+
+  private List<LibraryGuestModel> readGuestList(String path) {
+    try (var reader = Files.newBufferedReader(Path.of(new ClassPathResource(path).getURI()))) {
+      var guests = new ArrayList<LibraryGuestModel>();
+      String line;
+      reader.readLine();
+      while ((line = reader.readLine()) != null) {
+        var parts = line.split(",");
+        var guest = new LibraryGuestModel();
+
+        guest.type = parts[0];
+        guest.name = parts[1];
+        guest.email = parts[2];
+
+        guests.add(guest);
+      }
+      return guests;
+    } catch (IOException e) {
+      throw new RuntimeException("Failed to read guest list from: " + path, e);
+    }
+  }
+
+  private Map<String, List<CheckoutModel>> readCheckedOutByEmail(String path) {
+    try (var reader = Files.newBufferedReader(Path.of(new ClassPathResource(path).getURI()))) {
+      var checkedOutItems = new HashMap<String, List<CheckoutModel>>();
+      String line;
+      reader.readLine();
+      while ((line = reader.readLine()) != null) {
+        var parts = line.split(",");
+        var item = new CheckoutModel();
+
+        item.itemId = UUID.fromString(parts[1]);
+        item.dueDate = Instant.parse(parts[2]);
+
+        checkedOutItems.computeIfAbsent(parts[0], k -> new ArrayList<>()).add(item);
+      }
+      return checkedOutItems;
+    } catch (IOException e) {
+      throw new RuntimeException("Failed to read checked out items from: " + path, e);
+    }
+  }
+}