feat: add Dean's library data loader (code-differently#397)

Co-authored-by: Anthony D. Mays <[email protected]>

Author: dahw

lesson_10/libraries/src/loaders/dean_walston_loader.ts

@@ -0,0 +1,67 @@
+import csv from 'csv-parser';
+import fs from 'fs';
+import { Credit, MediaItem, MediaType, Role } from '../models/index.js';
+import { Loader } from './loader.js';
+
+export class DeanWalstonLoader implements Loader {
+  getLoaderName(): string {
+    return 'deanwalston';
+  }
+
+  async loadData(): Promise<MediaItem[]> {
+    const credits = await this.loadCredits();
+    const mediaItems = await this.loadMediaItems();
+
+    console.log(
+      `Loaded ${credits.length} credits and ${mediaItems.length} media items`,
+    );
+
+    // Combine credits with media items
+    const mediaItemsMap = new Map<string, MediaItem>();
+    
+    // Create a map of media items by ID for easy lookup
+    mediaItems.forEach(item => {
+      mediaItemsMap.set(item.getId(), item);
+    });
+
+    // Associate credits with their corresponding media items
+    credits.forEach(credit => {
+      const mediaItem = mediaItemsMap.get(credit.getMediaItemId());
+      if (mediaItem) {
+        mediaItem.addCredit(credit);
+      }
+    });
+
+    return [...mediaItemsMap.values()];
+  }
+
+  async loadMediaItems(): Promise<MediaItem[]> {
+    const mediaItems = [];
+    const readable = fs
+      .createReadStream('data/media_items.csv', 'utf-8')
+      .pipe(csv());
+    for await (const row of readable) {
+      const { id, title, type, year } = row;
+      // Parse the type as MediaType and year as number
+      const mediaType = type as MediaType;
+      const releaseYear = parseInt(year);
+      // Create MediaItem with empty credits initially (they'll be added later)
+      mediaItems.push(new MediaItem(id, title, mediaType, releaseYear, []));
+    }
+    return mediaItems;
+  }
+
+  async loadCredits(): Promise<Credit[]> {
+    const credits = [];
+    const readable = fs
+      .createReadStream('data/credits.csv', 'utf-8')
+      .pipe(csv());
+    for await (const row of readable) {
+      const { media_item_id, role, name } = row;
+      // Parse the role as Role enum
+      const roleEnum = role as Role;
+      credits.push(new Credit(media_item_id, name, roleEnum));
+    }
+    return credits;
+  }
+}

lesson_10/libraries/src/loaders/loaders.module.ts

@@ -2,10 +2,16 @@ import { Module } from '@nestjs/common';
 import { AnthonyMaysLoader } from './anthony_mays_loader.js';
 import { BenjaminScottLoader } from './benjamin_scott_loader.js';
 import { DanielBoyceLoader } from './daniel_boyce_loader.js';
+import { DeanWalstonLoader } from './dean_walston_loader.js';
 
 export const Loaders = Symbol.for('Loaders');
 
-const LOADER_PROVIDERS = [AnthonyMaysLoader, BenjaminScottLoader, DanielBoyceLoader];
+const LOADER_PROVIDERS = [
+  AnthonyMaysLoader,
+  BenjaminScottLoader,
+  DanielBoyceLoader,
+  DeanWalstonLoader,
+];
 
 @Module({
   providers: [