feat: adds Sherllin's lesson 12 LibraryCsvDataLoader (#308)

* feat: submitting lesson 12

* feat: completed map, tweaked methods and ran tests to parse data

* feat: lesson 12; updated correct relative path

Author: SherllinT

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

@@ -0,0 +1,130 @@
+package com.codedifferently.lesson12.factory.sherllin;
+
+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.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+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;
+
+@Service
+public class CsvDataLoader implements LibraryCsvDataLoader {
+
+  @Override
+  public LibraryDataModel loadData() {
+    // Read media items
+    List<MediaItemModel> mediaItems = readMediaItems("csv/media_items.csv");
+
+    // Read guests
+    List<LibraryGuestModel> guests = readGuests("csv/guests.csv");
+
+    // Read checked-out items
+    Map<String, List<CheckoutModel>> checkoutsByGuestEmail =
+        readCheckoutItems("csv/checked_out_items.csv");
+
+    for (LibraryGuestModel guest : guests) {
+      List<CheckoutModel> checkouts =
+          checkoutsByGuestEmail.getOrDefault(guest.email, new ArrayList<>());
+      guest.checkedOutItems = checkouts;
+    }
+
+    // Construct LibraryDataModel instance with initialized fields
+    LibraryDataModel libraryDataModel = new LibraryDataModel();
+    libraryDataModel.mediaItems = mediaItems;
+    libraryDataModel.guests = guests;
+
+    return libraryDataModel;
+  }
+
+  private List<MediaItemModel> readMediaItems(String filePath) {
+    try (var reader =
+        new BufferedReader(new FileReader(new ClassPathResource(filePath).getFile()))) {
+      var items = new ArrayList<MediaItemModel>();
+      String line;
+      boolean isFirstLine = true;
+      while ((line = reader.readLine()) != null) {
+        if (isFirstLine) {
+          isFirstLine = false;
+          continue;
+        }
+        var parts = line.split(",");
+        var item = new MediaItemModel();
+        item.type = parts[0];
+        item.id = UUID.fromString(parts[1]);
+        item.title = parts[2];
+        item.isbn = parts[3];
+        item.authors = Arrays.asList(parts[4].split(","));
+        item.pages = parts.length > 5 && !parts[5].isEmpty() ? Integer.parseInt(parts[5]) : 0;
+        item.runtime = parts.length > 6 && !parts[6].isEmpty() ? Integer.parseInt(parts[6]) : 0;
+        item.edition = parts.length > 7 ? parts[7] : "";
+        items.add(item);
+      }
+      return items;
+    } catch (IOException e) {
+      throw new RuntimeException("Failed to read media items", e);
+    }
+  }
+
+  private List<LibraryGuestModel> readGuests(String filePath) {
+    try (var reader =
+        new BufferedReader(new FileReader(new ClassPathResource(filePath).getFile()))) {
+      var items = new ArrayList<LibraryGuestModel>();
+      String line;
+      boolean isFirstLine = true;
+      while ((line = reader.readLine()) != null) {
+        if (isFirstLine) {
+          isFirstLine = false;
+          continue;
+        }
+        var parts = line.split(",");
+        var item = new LibraryGuestModel();
+        item.type = parts[0];
+        item.name = parts[1];
+        item.email = parts[2];
+        items.add(item);
+      }
+      return items;
+    } catch (IOException e) {
+      throw new RuntimeException("Failed to read guests", e);
+    }
+  }
+
+  private Map<String, List<CheckoutModel>> readCheckoutItems(String filePath) {
+    try (var reader =
+        new BufferedReader(new FileReader(new ClassPathResource(filePath).getFile()))) {
+      var checkoutMap = new HashMap<String, List<CheckoutModel>>();
+      String line;
+      boolean isFirstLine = true;
+      while ((line = reader.readLine()) != null) {
+        if (isFirstLine) {
+          isFirstLine = false;
+          continue;
+        }
+        var parts = line.split(",");
+        var checkoutModel = new CheckoutModel();
+        checkoutModel.itemId = UUID.fromString(parts[1]);
+        checkoutModel.dueDate = Instant.parse(parts[2]);
+
+        List<CheckoutModel> checkoutModels = checkoutMap.getOrDefault(parts[0], new ArrayList<>());
+
+        checkoutModels.add(checkoutModel);
+
+        checkoutMap.put(parts[0], checkoutModels);
+      }
+      return checkoutMap;
+    } catch (IOException e) {
+      throw new RuntimeException("Failed to read checkout items", e);
+    }
+  }
+}