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* @fileoverview Base European Parliament API Client
*
* Shared HTTP infrastructure for all EP API sub-clients:
* LRU caching, token-bucket rate limiting, timeout/retry logic,
* and structured audit/performance instrumentation.
*
* **ISMS Policies:**
* - SC-002 (Secure Coding Standards)
* - PE-001 (Performance Standards)
* - AU-002 (Audit Logging and Monitoring)
* - DP-001 (Data Protection and GDPR Compliance)
*
* @module clients/ep/baseClient
* @see https://github.com/Hack23/ISMS-PUBLIC/blob/main/Secure_Development_Policy.md
*/
import { fetch } from 'undici';
import { LRUCache } from 'lru-cache';
import { RateLimiter } from '../../utils/rateLimiter.js';
import { withRetry, withTimeoutAndAbort, TimeoutError } from '../../utils/timeout.js';
import { performanceMonitor } from '../../utils/performance.js';
import { DEFAULT_RATE_LIMIT_PER_MINUTE, DEFAULT_API_URL, USER_AGENT } from '../../config.js';
// ─── URL Validation (SSRF prevention) ────────────────────────────────────────
/** Exact hostnames that must never be used as API endpoints. */
const BLOCKED_HOSTS_EXACT = new Set(['localhost', '0.0.0.0', '::1']);
/**
* Patterns matching private / link-local / loopback / IPv6-mapped-IPv4 address
* prefixes. All patterns are tested against the bracket-stripped hostname.
*
* IPv6-mapped IPv4 patterns use the normalised hex form that the WHATWG URL
* parser emits (e.g. `::ffff:127.0.0.1` → `::ffff:7f00:1`).
*/
const BLOCKED_HOST_PATTERNS = [
/^fe[89ab][0-9a-f]:/i, // IPv6 link-local fe80::/10
/^f[cd][0-9a-f]{2}:/i, // IPv6 unique-local fc00::/7
/^::ffff:7f/i, // IPv6-mapped 127.x.x.x loopback
/^::ffff:a[0-9a-f]{2}:/i, // IPv6-mapped 10.x.x.x RFC-1918
/^::ffff:ac1[0-9a-f]:/i, // IPv6-mapped 172.16-31.x.x RFC-1918
/^::ffff:c0a8:/i, // IPv6-mapped 192.168.x.x RFC-1918
/^::ffff:a9fe:/i, // IPv6-mapped 169.254.x.x link-local
/^127\./, // IPv4 loopback 127.0.0.0/8
/^169\.254\./, // IPv4 link-local 169.254.0.0/16
/^10\./, // RFC-1918 10.0.0.0/8
/^172\.(1[6-9]|2\d|3[01])\./, // RFC-1918 172.16.0.0/12
/^192\.168\./, // RFC-1918 192.168.0.0/16
];
/**
* Returns true when `host` is a loopback, link-local, or RFC-1918 address that
* MUST NOT be used as an API endpoint (SSRF prevention).
* @private
*/
function isBlockedHost(host: string): boolean {
return BLOCKED_HOSTS_EXACT.has(host) || BLOCKED_HOST_PATTERNS.some(p => p.test(host));
}
/**
* Validates an EP API base URL to prevent SSRF via environment variable or
* constructor argument poisoning.
*
* Enforces HTTPS-only and blocks requests to localhost, loopback addresses
* (127.0.0.0/8), and known internal IP ranges (link-local 169.254.x.x,
* RFC-1918 10.x.x.x / 172.16-31.x.x / 192.168.x.x, and their IPv6-mapped
* IPv4 equivalents), as well as IPv6 loopback/link-local/unique-local ranges.
*
* @param url - The URL string to validate
* @param label - Label used in error messages (defaults to `'EP_API_URL'`)
* @returns The validated URL string (unchanged)
* @throws {Error} If the URL uses a non-HTTPS scheme or targets an internal host
*
* @security SSRF Prevention – ISMS Policy: SC-002, NE-001
*/
export function validateApiUrl(url: string, label = 'EP_API_URL'): string {
let parsed: URL;
try {
parsed = new URL(url);
} catch {
throw new Error(`${label} is not a valid URL`);
}
if (parsed.protocol !== 'https:') {
throw new Error(`${label} must use HTTPS protocol`);
}
// In the Node.js WHATWG URL API, .hostname includes the surrounding brackets
// for IPv6 addresses (e.g. new URL('https://[::1]/').hostname === '[::1]').
// Strip them before pattern matching so both IPv4 and IPv6 patterns are
// applied to the bare address string without brackets.
// Also strip a single trailing dot so the FQDN form "localhost." is treated
// identically to "localhost" (both resolve to loopback).
const rawHost = parsed.hostname.replace(/\.$/, '');
const host = rawHost.startsWith('[') && rawHost.endsWith(']')
? rawHost.slice(1, -1)
: rawHost;
if (isBlockedHost(host)) {
throw new Error(`${label} must not point to internal or loopback addresses`);
}
return url;
}
// ─── Default configuration constants ─────────────────────────────────────────
/** Default base URL for European Parliament Open Data Portal API v2 — derived from centralized config */
export const DEFAULT_EP_API_BASE_URL = DEFAULT_API_URL;
/** Default HTTP request timeout in milliseconds (10 seconds) */
export const DEFAULT_REQUEST_TIMEOUT_MS = 10_000;
/** Whether automatic retry on transient failures is enabled by default */
export const DEFAULT_RETRY_ENABLED = true;
/** Default maximum number of retry attempts for failed requests */
export const DEFAULT_MAX_RETRIES = 2;
/** Default base retry delay in milliseconds (exponential backoff starting point) */
export const DEFAULT_RETRY_BASE_DELAY_MS = 1_000;
/** Default maximum retry delay in milliseconds (caps exponential backoff growth) */
export const DEFAULT_RETRY_MAX_DELAY_MS = 30_000;
/** Default cache time-to-live in milliseconds (15 minutes) */
export const DEFAULT_CACHE_TTL_MS = 900_000;
/** Default maximum number of entries in the LRU response cache */
export const DEFAULT_MAX_CACHE_SIZE = 500;
/** Default rate limit token bucket size (requests per interval) — derived from centralized config */
export const DEFAULT_RATE_LIMIT_TOKENS = DEFAULT_RATE_LIMIT_PER_MINUTE;
/** Default rate limit interval unit */
export const DEFAULT_RATE_LIMIT_INTERVAL = 'minute' as const;
/** Maximum allowed response body size in bytes (10 MiB, 10×1024×1024) to prevent memory exhaustion */
export const DEFAULT_MAX_RESPONSE_BYTES = 10_485_760;
// ─── Exported error class ─────────────────────────────────────────────────────
/**
* API Error thrown when European Parliament API requests fail.
*
* @example
* ```typescript
* throw new APIError('EP API request failed: Not Found', 404, { endpoint: '/meps/999999' });
* ```
* @public
*/
export class APIError extends Error {
constructor(
message: string,
public statusCode?: number,
public details?: unknown
) {
super(message);
this.name = 'APIError';
}
}
// ─── Interfaces ───────────────────────────────────────────────────────────────
/**
* JSON-LD response format from EP API.
* @internal
*/
export interface JSONLDResponse<T = Record<string, unknown>>
extends Record<string, unknown> {
data: T[];
'@context': unknown[];
}
/**
* Configuration options for EP API clients.
* @internal
*/
export interface EPClientConfig {
/** Base URL for European Parliament API. @default DEFAULT_EP_API_BASE_URL */
baseURL?: string;
/** Cache time-to-live in milliseconds. @default 900000 */
cacheTTL?: number;
/** Maximum number of entries in LRU cache. @default 500 */
maxCacheSize?: number;
/** Custom rate limiter instance. */
rateLimiter?: RateLimiter;
/** Request timeout in milliseconds. @default 10000 */
timeoutMs?: number;
/** Enable automatic retry on transient failures. @default true */
enableRetry?: boolean;
/** Maximum number of retry attempts. @default 2 */
maxRetries?: number;
/** Maximum allowed response body size in bytes. @default 10485760 (10 MiB) */
maxResponseBytes?: number;
}
/**
* Pre-built shared resources passed from a facade to its sub-clients
* so they all operate on the same cache and rate-limiter bucket.
* @internal
*/
export interface EPSharedResources {
cache: LRUCache<string, Record<string, unknown>>;
rateLimiter: RateLimiter;
baseURL: string;
timeoutMs: number;
enableRetry: boolean;
maxRetries: number;
maxResponseBytes: number;
/** Shared cache hit/miss counters so all sub-clients contribute to aggregate stats. */
cacheCounters: { hits: number; misses: number };
}
// ─── Base client ──────────────────────────────────────────────────────────────
/**
* Base class for European Parliament API sub-clients.
*
* Holds the shared HTTP machinery: LRU cache, token-bucket rate limiter,
* timeout/abort controller, and retry logic. Sub-clients extend this class
* and call the protected `get()` helper for all HTTP requests.
*
* @class BaseEPClient
*/
export class BaseEPClient {
/** LRU cache for API responses. */
protected readonly cache: LRUCache<string, Record<string, unknown>>;
/** European Parliament API base URL. */
protected readonly baseURL: string;
/** Token bucket rate limiter. */
protected readonly rateLimiter: RateLimiter;
/** Request timeout in milliseconds. */
protected readonly timeoutMs: number;
/** Enable automatic retry on transient failures. */
protected readonly enableRetry: boolean;
/** Maximum number of retry attempts. */
protected readonly maxRetries: number;
/** Maximum allowed response body size in bytes. */
protected readonly maxResponseBytes: number;
/** Shared cache hit/miss counters (shared via EPSharedResources when used as sub-client). */
private readonly cacheCounters: { hits: number; misses: number };
/**
* Resolves all EPClientConfig options to their final values with defaults applied.
* Extracted to keep constructor complexity within limits.
* @private
*/
private static resolveConfig(config: EPClientConfig): {
baseURL: string;
cacheTTL: number;
maxCacheSize: number;
rateLimiter: RateLimiter;
timeoutMs: number;
enableRetry: boolean;
maxRetries: number;
maxResponseBytes: number;
} {
const rawBaseURL = config.baseURL ?? DEFAULT_EP_API_BASE_URL;
// Validate baseURL to prevent SSRF when sub-clients are instantiated directly
validateApiUrl(rawBaseURL, 'config.baseURL');
// Ensure baseURL always ends with '/' so that relative endpoints resolve correctly
// e.g. new URL('meps', 'https://host/api/v2') would drop 'v2' without the trailing slash
const baseURL = rawBaseURL.endsWith('/') ? rawBaseURL : `${rawBaseURL}/`;
return {
baseURL,
cacheTTL: config.cacheTTL ?? DEFAULT_CACHE_TTL_MS,
maxCacheSize: config.maxCacheSize ?? DEFAULT_MAX_CACHE_SIZE,
rateLimiter:
config.rateLimiter ??
new RateLimiter({
tokensPerInterval: DEFAULT_RATE_LIMIT_TOKENS,
interval: DEFAULT_RATE_LIMIT_INTERVAL,
}),
timeoutMs: config.timeoutMs ?? DEFAULT_REQUEST_TIMEOUT_MS,
enableRetry: config.enableRetry ?? DEFAULT_RETRY_ENABLED,
maxRetries: config.maxRetries ?? DEFAULT_MAX_RETRIES,
maxResponseBytes: config.maxResponseBytes ?? DEFAULT_MAX_RESPONSE_BYTES,
};
}
/**
* Creates a BaseEPClient.
*
* When `shared` is provided the constructor reuses those pre-built resources
* instead of allocating new ones; this is the mechanism used by the facade to
* ensure all sub-clients share one cache and one rate-limiter.
*
* @param config - Client configuration (used when `shared` is absent)
* @param shared - Pre-built shared resources (passed by facade to sub-clients)
*/
constructor(config: EPClientConfig = {}, shared?: EPSharedResources) {
if (shared !== undefined) {
this.cache = shared.cache;
this.rateLimiter = shared.rateLimiter;
this.baseURL = shared.baseURL;
this.timeoutMs = shared.timeoutMs;
this.enableRetry = shared.enableRetry;
this.maxRetries = shared.maxRetries;
this.maxResponseBytes = shared.maxResponseBytes;
this.cacheCounters = shared.cacheCounters;
} else {
const cfg = BaseEPClient.resolveConfig(config);
this.baseURL = cfg.baseURL;
this.cache = new LRUCache<string, Record<string, unknown>>({
max: cfg.maxCacheSize,
ttl: cfg.cacheTTL,
allowStale: false,
updateAgeOnGet: true,
});
this.rateLimiter = cfg.rateLimiter;
this.timeoutMs = cfg.timeoutMs;
this.enableRetry = cfg.enableRetry;
this.maxRetries = cfg.maxRetries;
this.maxResponseBytes = cfg.maxResponseBytes;
this.cacheCounters = { hits: 0, misses: 0 };
}
}
// ─── HTTP infrastructure ────────────────────────────────────────────────────
/**
* Builds the full request URL from endpoint + optional params.
* @private
*/
private buildRequestUrl(
endpoint: string,
params?: Record<string, unknown>
): URL {
const url = new URL(endpoint, this.baseURL);
if (params === undefined) return url;
for (const [key, value] of Object.entries(params)) {
if (value === undefined || value === null) continue;
let str: string;
if (typeof value === 'string') {
str = value;
} else if (typeof value === 'number' || typeof value === 'boolean') {
str = String(value);
} else {
str = JSON.stringify(value);
}
url.searchParams.append(key, str);
}
return url;
}
/**
* Returns true when an error should trigger a retry.
*
* Retries on:
* - 429 Too Many Requests (rate-limited by EP API; exponential backoff applied)
* - 5xx Server Errors (transient server failures)
* - Network / unknown errors
*
* Does NOT retry on 4xx client errors (except 429).
* @private
*/
private shouldRetryRequest(error: unknown): boolean {
Iif (error instanceof TimeoutError) return false;
if (error instanceof APIError) {
const code = error.statusCode ?? 500;
return code === 429 || code >= 500;
}
// JSON parse errors (SyntaxError) are generally not retried, but
// "Unexpected end of JSON input" indicates a truncated response body
// (e.g. the EP API's own server-side timeout cut the stream short).
// These are transient and often succeed on retry.
if (error instanceof SyntaxError) {
return error.message.includes('Unexpected end of JSON input');
}
return true;
}
/**
* Parses a byte buffer as JSON-LD. Returns an empty JSON-LD shape for
* zero-byte bodies (the EP API sends these for out-of-range offsets).
* Non-empty bodies must contain valid JSON; any `SyntaxError` is allowed
* to propagate so callers (including single-entity endpoints) fail fast
* instead of receiving a misleading empty-list shape.
* @private
*/
private static parseJsonLdBytes(bytes: Uint8Array): JSONLDResponse {
if (bytes.byteLength === 0) {
return { data: [], '@context': [] };
}
return JSON.parse(new TextDecoder().decode(bytes)) as JSONLDResponse;
}
/**
* Reads the response body as a stream, enforcing the response size cap.
* Used as a fallback when the `content-length` header is absent (e.g. chunked
* transfer encoding). Accumulates all chunks and parses the result as JSON.
* @private
*/
private async readStreamedBody<T>(response: Response): Promise<T> {
const reader = (response.body as ReadableStream<Uint8Array> | null)?.getReader();
if (!reader) {
return response.json() as Promise<T>;
}
const chunks: Uint8Array[] = [];
let totalBytes = 0;
let readerReleased = false;
try {
for (;;) {
const result = await reader.read();
if (result.done) break;
const { value } = result;
totalBytes += value.byteLength;
if (totalBytes > this.maxResponseBytes) {
reader.releaseLock();
readerReleased = true;
await (response.body as ReadableStream<Uint8Array> | null)?.cancel();
throw new APIError(
`EP API response too large: exceeds limit of ${String(this.maxResponseBytes)} bytes`,
413
);
}
chunks.push(value);
}
} finally {
if (!readerReleased) {
reader.releaseLock();
}
}
const combined = new Uint8Array(totalBytes);
let offset = 0;
for (const chunk of chunks) {
combined.set(chunk, offset);
offset += chunk.byteLength;
}
return BaseEPClient.parseJsonLdBytes(combined) as T;
}
/**
* Treats a truly empty body as an empty JSON-LD shape; invalid JSON for
* non-empty bodies is surfaced as an error.
* @private
*/
private static async parseResponseJson<T>(response: Response): Promise<T> {
// Use text + JSON.parse instead of response.json() so we can distinguish
// between an actually empty body and malformed JSON content.
const raw = await response.text();
// Empty or whitespace-only body — mirror the behaviour used for
// `content-length: 0` responses and return a minimal JSON-LD shape so
// callers see an empty `data` array instead of a parse error.
if (raw.length === 0 || /^\s*$/.test(raw)) {
return { data: [], '@context': [] } as unknown as T;
}
// Non-empty body must be valid JSON; let any SyntaxError propagate so
// callers are aware of malformed API responses.
return JSON.parse(raw) as T;
}
/**
* Executes the HTTP fetch with timeout/abort support and response size guard.
* @private
*/
private async fetchWithTimeout<T>(url: URL, endpoint: string): Promise<T> {
return withTimeoutAndAbort(
async (signal) => {
const response = await fetch(url.toString(), {
headers: {
Accept: 'application/ld+json',
'User-Agent': USER_AGENT,
},
signal,
});
if (!response.ok) {
throw new APIError(
`EP API request failed: ${response.statusText}`,
response.status
);
}
// Guard against oversized responses to prevent memory exhaustion.
const contentLength = response.headers.get('content-length');
if (contentLength !== null) {
const bytes = Number.parseInt(contentLength, 10);
// Non-finite / negative values (e.g. garbled header) are treated as
// "no content-length" and fall through to readStreamedBody() which
// enforces the byte cap incrementally.
if (Number.isFinite(bytes) && bytes >= 0) {
// Empty body (content-length: 0) — the EP API returns this for
// out-of-range offsets or when no data exists. Return a minimal
// JSON-LD shape so callers get an empty `data` array instead of a
// JSON parse error.
Iif (bytes === 0) {
await response.body?.cancel();
return { data: [], '@context': [] } as unknown as T;
}
if (bytes > this.maxResponseBytes) {
// Cancel/drain the body before throwing so the underlying TCP
// connection can be returned to the pool and reused.
await response.body?.cancel();
throw new APIError(
`EP API response too large: ${String(bytes)} bytes exceeds limit of ${String(this.maxResponseBytes)} bytes`,
413
);
}
return BaseEPClient.parseResponseJson<T>(response);
}
}
// No content-length header (chunked encoding) — stream the body and
// enforce the cap incrementally so oversized responses are aborted
// before they are fully buffered in memory.
return this.readStreamedBody<T>(response);
},
this.timeoutMs,
`EP API request to ${endpoint} timed out after ${String(this.timeoutMs)}ms`
);
}
/**
* Wraps a fetch call with the configured retry policy.
* @private
*/
private async fetchWithRetry<T>(url: URL, endpoint: string): Promise<T> {
return withRetry(
() => this.fetchWithTimeout<T>(url, endpoint),
{
maxRetries: this.enableRetry ? this.maxRetries : 0,
retryDelayMs: DEFAULT_RETRY_BASE_DELAY_MS,
maxDelayMs: DEFAULT_RETRY_MAX_DELAY_MS,
shouldRetry: (error) => this.shouldRetryRequest(error),
}
);
}
/**
* Converts a caught error to a typed {@link APIError}.
* @private
*/
private toAPIError(error: unknown, endpoint: string): APIError {
if (error instanceof TimeoutError) {
return new APIError(
`EP API request to ${endpoint} timed out after ${String(this.timeoutMs)}ms`,
408
);
}
if (error instanceof APIError) return error;
return new APIError(
`EP API request error: ${error instanceof Error ? error.message : 'Unknown error'}`,
undefined,
error
);
}
/**
* Executes a cached, rate-limited GET request to the EP API.
*
* @template T - Expected response type (extends `Record<string, unknown>`)
* @param endpoint - API endpoint path (relative to `baseURL`)
* @param params - Optional query parameters
* @returns Promise resolving to the typed API response
* @throws {APIError} On HTTP errors, network failures, or parse failures
* @protected
*/
protected async get<T extends Record<string, unknown>>(
endpoint: string,
params?: Record<string, unknown>
): Promise<T> {
// Consume one rate-limit token; waits asynchronously up to 5 s before giving up
const rlResult = await this.rateLimiter.removeTokens(1);
Iif (!rlResult.allowed) {
throw new APIError(
`Rate limit exceeded. Retry after ${String(rlResult.retryAfterMs)}ms`,
429,
{ retryAfterMs: rlResult.retryAfterMs, remainingTokens: rlResult.remainingTokens }
);
}
const cacheKey = this.getCacheKey(endpoint, params);
// Cache hit path
const cacheStart = performance.now();
const cached = this.cache.get(cacheKey);
if (cached !== undefined) {
this.cacheCounters.hits++;
performanceMonitor.recordDuration('ep_api_cache_hit', performance.now() - cacheStart);
return cached as T;
}
this.cacheCounters.misses++;
const url = this.buildRequestUrl(endpoint, params);
const requestStart = performance.now();
try {
const data = await this.fetchWithRetry<T>(url, endpoint);
performanceMonitor.recordDuration('ep_api_request', performance.now() - requestStart);
this.cache.set(cacheKey, data);
return data;
} catch (error) {
performanceMonitor.recordDuration('ep_api_request_failed', performance.now() - requestStart);
throw this.toAPIError(error, endpoint);
}
}
/**
* Generates a deterministic cache key.
* @param endpoint - API endpoint path
* @param params - Optional query parameters
* @returns JSON string used as cache key
* @private
*/
private getCacheKey(
endpoint: string,
params?: Record<string, unknown>
): string {
return JSON.stringify({ endpoint, params });
}
// ─── Public cache helpers ───────────────────────────────────────────────────
/**
* Clears all entries from the LRU cache.
* @public
*/
clearCache(): void {
this.cache.clear();
}
/**
* Returns cache statistics for monitoring and debugging.
* @returns `{ size, maxSize, hitRate, hits, misses }`
* @public
*/
getCacheStats(): { size: number; maxSize: number; hitRate: number; hits: number; misses: number } {
const { hits, misses } = this.cacheCounters;
const total = hits + misses;
return {
size: this.cache.size,
maxSize: this.cache.max,
hitRate: total > 0 ? hits / total : 0,
hits,
misses,
};
}
}
|