refactor: organize backend by business responsibility

src/integrations/ncr/ncr-ratings.client.ts

@@ -0,0 +1,107 @@
+import { Injectable, ServiceUnavailableException } from '@nestjs/common';
+import { load } from 'cheerio';
+import { LRUCache } from 'lru-cache';
+
+const registryUrl = 'https://ratings.ru/ratings/issues/';
+export type NcrRating = {
+  agency: 'NCR';
+  value: string | null;
+  status: 'active' | 'withdrawn';
+  date: string;
+  sourceUrl: string;
+  observedAt: string;
+};
+
+@Injectable()
+export class NcrRatingsClient {
+  // Public registry contains no user data. Share one download across all issues.
+  private readonly cache = new LRUCache<
+    string,
+    Promise<Map<string, NcrRating>>
+  >({ max: 1, ttl: 6 * 60 * 60_000 });
+
+  async rating(isin: string): Promise<NcrRating | null> {
+    const key = isin.trim().toUpperCase();
+    if (!/^[A-Z]{2}[A-Z0-9]{9}\d$/.test(key)) return null;
+    let pending = this.cache.get('registry');
+    if (!pending) {
+      pending = this.registry().catch(() => {
+        // Bound outage traffic too; never present a failed download as no rating.
+        if (this.cache.get('registry') === pending)
+          this.cache.set('registry', pending, { ttl: 60_000 });
+        throw new ServiceUnavailableException({ code: 'NCR_UNAVAILABLE' });
+      });
+      this.cache.set('registry', pending);
+    }
+    return (await pending).get(key) ?? null;
+  }
+
+  private async registry(): Promise<Map<string, NcrRating>> {
+    const response = await fetch(registryUrl, {
+      signal: AbortSignal.timeout(10_000),
+    });
+    if (!response.ok) throw new Error('NCR unavailable');
+    const $ = load(await response.text());
+    const table = $('#issues-table');
+    const headings = table
+      .find('thead th')
+      .map((_, cell) => $(cell).text().trim())
+      .get();
+    if (
+      table.length !== 1 ||
+      headings.length !== 6 ||
+      headings[2] !== 'Рейтинг' ||
+      headings[3] !== 'ISIN' ||
+      headings[5] !== 'Дата'
+    )
+      throw new Error('NCR registry changed');
+    const observedAt = new Date().toISOString();
+    const result = new Map<string, NcrRating>();
+    table.find('tbody tr').each((_, row) => {
+      const cells = $(row).find('td');
+      if (cells.length !== 6) throw new Error('NCR row changed');
+      const isin = cells.eq(3).text().trim().toUpperCase();
+      // Unassigned issues cannot safely be matched to a held instrument.
+      if (!/^[A-Z]{2}[A-Z0-9]{9}\d$/.test(isin)) return;
+      const raw = cells.eq(2).text().replace(/\s+/g, ' ').trim();
+      const withdrawn = raw.toLowerCase() === 'рейтинг отозван';
+      if (
+        !withdrawn &&
+        !/^(AAA|AA[+-]?|A[+-]?|BBB[+-]?|BB[+-]?|B[+-]?|CCC[+-]?|CC|C|D)\.ru$/.test(
+          raw,
+        )
+      )
+        throw new Error('NCR rating changed');
+      const dateParts = /^(\d{2})\.(\d{2})\.(\d{4})$/.exec(
+        cells.eq(5).text().trim(),
+      );
+      const href = cells.eq(3).find('a').attr('href');
+      if (!dateParts || !href || !/^\/ratings\/issues\/\d+\/$/.test(href))
+        throw new Error('NCR identity missing');
+      const date = `${dateParts[3]}-${dateParts[2]}-${dateParts[1]}`;
+      if (
+        !Number.isFinite(Date.parse(date)) ||
+        new Date(date).toISOString().slice(0, 10) !== date
+      )
+        throw new Error('NCR date invalid');
+      const rating: NcrRating = {
+        agency: 'NCR',
+        value: withdrawn ? null : raw,
+        status: withdrawn ? 'withdrawn' : 'active',
+        date,
+        sourceUrl: `https://ratings.ru${href}`,
+        observedAt,
+      };
+      const previous = result.get(isin);
+      if (
+        previous &&
+        previous.date === date &&
+        (previous.value !== rating.value || previous.status !== rating.status)
+      )
+        throw new Error('NCR rating ambiguous');
+      if (!previous || previous.date < date) result.set(isin, rating);
+    });
+    if (!result.size) throw new Error('NCR registry empty');
+    return result;
+  }
+}