Add opt-in client-side API caching for safe GET requests

[Copilot]

This adds a client-side caching layer to the Axios-based Mempool client without changing default behavior: caching remains off unless the caller explicitly enables it. The implementation is scoped to safe/idempotent GETs, isolates cache entries by client configuration, and avoids caching authorization-bearing requests unless the caller deliberately opts into an isolated store.

• Cache model

  • Adds cache configuration to mempoolJS(...) with:
    • enabled
    • ttlMs (number or function)
    • maxEntries
    • store
    • allowAuthorizedRequests
    • shouldCache
  • Keeps caching disabled by default.
  • Exposes client.cache.clear() only when caching is enabled.

• Storage + isolation

  • Adds a bounded in-memory default store for browser/Node usage.
  • Adds mempoolJS.createMemoryCacheStore() for explicit isolated stores.
  • Keys are normalized and include client/baseURL context so separate hosts/networks/configurations do not share entries accidentally.
  • Absolute URLs are also isolated from each other when using shared stores.

• Request behavior

  • Caches only GET requests.
  • Never caches POST/mutation requests.
  • Coalesces concurrent identical GET misses into a single upstream request.
  • Applies TTL expiry and evicts old entries from the bounded memory store.
  • Does not cache failures.
  • Preserves Axios response shape for cache hits, including request.

• Security guards

  • Skips caching by default for requests carrying authorization, cookie, proxy-authorization, set-cookie, x-api-key, or auth.
  • Allows those requests only when the caller explicitly enables them and provides a store configuration intended for isolation.
  • Omits sensitive header values from cache keys.

• Docs

  • Updates README.md with cache configuration examples, TTL guidance, limitations, and security notes.

Example:

import mempoolJS from '@mempool/mempool.js';

const client = mempoolJS({
  hostname: 'mempool.space',
  cache: {
    enabled: true,
    ttlMs: 30_000,
    maxEntries: 100,
  },
});

const tx = await client.bitcoin.transactions.getTx({ txid: '...' });

await client.cache?.clear();

[Micfinch]

@copilot please fix the merge conflicts in this pull request.

[Copilot]

@copilot please fix the merge conflicts in this pull request.

Fixed in 8d661ff. I merged the latest main into this branch, resolved the src/index.ts conflict, and validated the merged result with the build plus targeted cache/default/address tests.

[Micfinch]

@copilot please fix the merge conflicts in this pull request.

[Micfinch]

@copilot please fix the merge conflicts in this pull request.

[Micfinch]

@copilot please fix the merge conflicts in this pull request.

[Copilot]

@copilot please fix the merge conflicts in this pull request.

Fixed in e504801. I merged the latest main into this branch, resolved the src/services/api/index.ts conflict, and validated the merged result with the build plus targeted cache/default/address checks.

[Copilot]

@copilot please fix the merge conflicts in this pull request.

The pull request is currently mergeable and I do not see any remaining merge conflicts to resolve.

@copilot please fix the merge conflicts in this pull request.

The pull request is currently mergeable and I do not see any remaining merge conflicts to resolve.