import { createHash, randomUUID } from 'node:crypto';
import { ErrorCode, McpError } from './errors.js';
export interface TextResourceEntry {
uri: string;
name: string;
mimeType: string;
text: string;
hash: string;
}
export interface ResourceStore {
putText(params: {
name: string;
mimeType?: string;
text: string;
}): TextResourceEntry;
getText(uri: string): TextResourceEntry;
clear(): void;
}
interface ResourceStoreOptions {
maxEntries: number;
maxTotalBytes: number;
maxEntryBytes: number;
}
const DEFAULT_RESOURCE_STORE_OPTIONS: ResourceStoreOptions = {
maxEntries: 64,
maxTotalBytes: 25 * 1024 * 1024,
maxEntryBytes: 10 * 1024 * 1024,
};
function estimateBytes(text: string): number {
return Buffer.byteLength(text, 'utf8');
}
function computeSha256(text: string): string {
return createHash('sha256').update(text, 'utf8').digest('hex');
}
export function createInMemoryResourceStore(
options: Partial<ResourceStoreOptions> = {}
): ResourceStore {
const resolved: ResourceStoreOptions = {
...DEFAULT_RESOURCE_STORE_OPTIONS,
...options,
};
const byUri = new Map<string, TextResourceEntry>();
const insertionOrder: string[] = [];
let totalBytes = 0;
function evictOldest(): void {
const uri = insertionOrder.shift();
if (!uri) return;
const existing = byUri.get(uri);
if (!existing) return;
totalBytes -= estimateBytes(existing.text);
byUri.delete(uri);
}
function enforceLimits(): void {
while (insertionOrder.length > resolved.maxEntries) evictOldest();
while (totalBytes > resolved.maxTotalBytes) {
if (insertionOrder.length === 0) break;
evictOldest();
}
}
function putText(params: {
name: string;
mimeType?: string;
text: string;
}): TextResourceEntry {
const mimeType = params.mimeType ?? 'text/plain';
const entryBytes = estimateBytes(params.text);
if (entryBytes > resolved.maxEntryBytes) {
throw new McpError(
ErrorCode.E_TOO_LARGE,
`Resource too large to cache (${entryBytes} bytes)`
);
}
const id = randomUUID();
const uri = `fs-context://result/${id}`;
const hash = computeSha256(params.text);
const entry: TextResourceEntry = {
uri,
name: params.name,
mimeType,
text: params.text,
hash,
};
byUri.set(uri, entry);
insertionOrder.push(uri);
totalBytes += entryBytes;
enforceLimits();
if (!byUri.has(uri)) {
throw new McpError(
ErrorCode.E_TOO_LARGE,
'Resource cache full: entry evicted immediately'
);
}
return entry;
}
function getText(uri: string): TextResourceEntry {
const existing = byUri.get(uri);
if (!existing) {
throw new McpError(ErrorCode.E_NOT_FOUND, `Resource not found: ${uri}`);
}
return existing;
}
function clear(): void {
byUri.clear();
insertionOrder.length = 0;
totalBytes = 0;
}
return { putText, getText, clear };
}
