feat: adds Rich's Lesson12 CSVDataLoader (#305)

* feat: Lesson12 CSVDataLoader - failing 2 tests.

* fix: altered file paths

* fix: fixes code to make all tests now work

* chore: refactors filepath code to be more succinct

Author: RichHawkins

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

@@ -0,0 +1,121 @@
+package com.codedifferently.lesson12.factory.richhawkins;
+
+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 com.opencsv.CSVReader;
+import com.opencsv.exceptions.CsvException;
+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() {
+    var model = new LibraryDataModel();
+    model.mediaItems = readMediaItems(("csv/media_items.csv"));
+    model.guests = readGuests(("csv/guests.csv"));
+    Map<String, List<CheckoutModel>> checkoutsByGuestEmail =
+        getCheckedOutItems(("csv/checked_out_items.csv"));
+
+    // Combine checkouts with guests
+    for (LibraryGuestModel guest : model.guests) {
+      List<CheckoutModel> checkouts = checkoutsByGuestEmail.get(guest.email);
+      if (checkouts != null) {
+        guest.checkedOutItems = checkouts;
+      } else {
+        guest.checkedOutItems = new ArrayList<>();
+      }
+    }
+
+    model.guests.forEach(guest -> {});
+
+    return model;
+  }
+
+  private List<MediaItemModel> readMediaItems(String filePath) {
+    List<MediaItemModel> items = new ArrayList<>();
+    try (CSVReader reader =
+        new CSVReader(
+            new FileReader(new ClassPathResource(filePath).getFile()))) { // Skip the header
+      String[] header = reader.readNext();
+      String[] line;
+      while ((line = reader.readNext()) != null) {
+        MediaItemModel item = new MediaItemModel();
+        item.type = line[0];
+        item.id = UUID.fromString(line[1]);
+        item.title = line[2];
+        item.isbn = line[3];
+        item.authors = Arrays.asList(line[4].split("\\s*,\\s*"));
+        // checks for empty index and if empty sets to 0
+        if (line[5].equals("")) item.pages = 0;
+        else item.pages = Integer.parseInt(line[5]);
+        // checks for empty index and sets it to 0 if empty
+        if (line[6].equals("")) item.pages = 0;
+        else item.pages = Integer.parseInt(line[6]);
+        item.edition = line[7];
+        items.add(item);
+      }
+    } catch (IOException e) {
+      throw new RuntimeException("Failed to read CSV file", e);
+    } catch (CsvException e) {
+      throw new RuntimeException("Error parsing CSV file", e);
+    }
+    return items;
+  }
+
+  private List<LibraryGuestModel> readGuests(String filePath) {
+    List<LibraryGuestModel> guests = new ArrayList<>();
+    try (CSVReader reader =
+        new CSVReader(
+            new FileReader(new ClassPathResource(filePath).getFile()))) { // Skip the header
+      String[] header = reader.readNext();
+      String[] line;
+      while ((line = reader.readNext()) != null) {
+        LibraryGuestModel guest = new LibraryGuestModel();
+        guest.type = line[0];
+        guest.name = line[1];
+        guest.email = line[2];
+        guests.add(guest);
+      }
+    } catch (IOException e) {
+      throw new RuntimeException("Failed to read CSV file", e);
+    } catch (CsvException e) {
+      throw new RuntimeException("Error parsing CSV file", e);
+    }
+    return guests;
+  }
+
+  private Map<String, List<CheckoutModel>> getCheckedOutItems(String filePath) {
+    Map<String, List<CheckoutModel>> checkoutsByGuestEmail = new HashMap<>();
+    try (CSVReader reader =
+        new CSVReader(new FileReader(new ClassPathResource(filePath).getFile()))) {
+      // Skip the header
+      String[] header = reader.readNext();
+      String[] line;
+      while ((line = reader.readNext()) != null) {
+        String email = line[0];
+        CheckoutModel item = new CheckoutModel();
+        item.itemId = UUID.fromString(line[1]);
+        item.dueDate = Instant.parse(line[2]);
+        checkoutsByGuestEmail.computeIfAbsent(email, k -> new ArrayList<>()).add(item);
+      }
+    } catch (IOException e) {
+      throw new RuntimeException("Failed to read checked out items", e);
+    } catch (CsvException e) {
+      throw new RuntimeException("Error parsing CSV file", e);
+    }
+    return checkoutsByGuestEmail;
+  }
+}