@helia/verified-fetch/src/index.ts

A fetch-like API for obtaining verified & trustless IPFS content on the web

/**
 * @packageDocumentation
 *
 * `@helia/verified-fetch` provides a [fetch](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API)-like API for retrieving content from the [IPFS](https://ipfs.tech/) network.
 *
 * All content is retrieved in a [trustless manner](https://www.techopedia.com/definition/trustless), and the integrity of all bytes are verified by comparing hashes of the data.
 *
 * By default, providers for CIDs are found using [delegated routing endpoints](https://docs.ipfs.tech/concepts/public-utilities/#delegated-routing).
 *
 * Data is retrieved using the following strategies:
 * - Directly from providers, using [Bitswap](https://docs.ipfs.tech/concepts/bitswap/) over WebSockets and WebRTC if available.
 * - Directly from providers exposing a [trustless gateway](https://specs.ipfs.tech/http-gateways/trustless-gateway/) over HTTPS.
 * - As a fallback, if no providers reachable from a browser are found, data is retrieved using recursive gateways, e.g. `trustless-gateway.link` which can be configured.
 *
 * This is a marked improvement over `fetch` which offers no such protections and is vulnerable to all sorts of attacks like [Content Spoofing](https://owasp.org/www-community/attacks/Content_Spoofing), [DNS Hijacking](https://en.wikipedia.org/wiki/DNS_hijacking), etc.
 *
 * A `verifiedFetch` function is exported to get up and running quickly, and a `createVerifiedFetch` function is also available that allows customizing the underlying [Helia](https://ipfs.github.io/helia/) node for complete control over how content is retrieved.
 *
 * Browser-cache-friendly [Response](https://developer.mozilla.org/en-US/docs/Web/API/Response) objects are returned which should be instantly familiar to web developers.
 *
 * Learn more in the [announcement blog post](https://blog.ipfs.tech/verified-fetch/) and check out the [ready-to-run example](https://github.com/ipfs-examples/helia-examples/tree/main/examples/helia-browser-verified-fetch).
 *
 * You may use any supported resource argument to fetch content:
 *
 * - [CID](https://multiformats.github.io/js-multiformats/classes/cid.CID.html) instance
 * - IPFS URL
 * - IPNS URL
 *
 * @example Getting started
 *
 * ```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 *
 * const resp = await verifiedFetch('ipfs://bafy...')
 *
 * const json = await resp.json()
 *```
 *
 * @example Using a CID instance to fetch JSON
 *
 * ```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 * import { CID } from 'multiformats/cid'
 *
 * const cid = CID.parse('bafyFoo') // some json file
 * const response = await verifiedFetch(cid)
 * const json = await response.json()
 * ```
 *
 * @example Using IPFS protocol to fetch an image
 *
 * ```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 *
 * const response = await verifiedFetch('ipfs://bafyFoo') // CID for some image file
 * const blob = await response.blob()
 * const image = document.createElement('img')
 * image.src = URL.createObjectURL(blob)
 * document.body.appendChild(image)
 * ```
 *
 * @example Using IPNS protocol to stream a big file
 *
 * ```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 *
 * const response = await verifiedFetch('ipns://mydomain.com/path/to/very-long-file.log')
 * const bigFileStreamReader = await response.body?.getReader()
 * ```
 *
 * ## Configuration
 *
 * ### Custom HTTP gateways and routers
 *
 * Out of the box `@helia/verified-fetch` uses a default set of [trustless gateways](https://specs.ipfs.tech/http-gateways/trustless-gateway/) for fetching blocks and [HTTP delegated routers](https://specs.ipfs.tech/routing/http-routing-v1/) for performing routing tasks - looking up peers, resolving/publishing [IPNS](https://docs.ipfs.tech/concepts/ipns/) names, etc.
 *
 * It's possible to override these by passing `gateways` and `routers` keys to the `createVerifiedFetch` function:
 *
 * @example Configuring gateways and routers
 *
 * ```typescript
 * import { createVerifiedFetch } from '@helia/verified-fetch'
 *
 * const fetch = await createVerifiedFetch({
 *   gateways: ['https://trustless-gateway.link'],
 *   routers: ['http://delegated-ipfs.dev']
 * })
 *
 * const resp = await fetch('ipfs://bafy...')
 *
 * const json = await resp.json()
 *```
 *
 * ### Usage with customized Helia
 *
 * For full control of how `@helia/verified-fetch` fetches content from the distributed web you can pass a preconfigured Helia node to `createVerifiedFetch`.
 *
 * The [helia](https://www.npmjs.com/package/helia) module is configured with a libp2p node that is suited for decentralized applications, alternatively [@helia/http](https://www.npmjs.com/package/@helia/http) is available which uses HTTP gateways for all network operations.
 *
 * You can see variations of Helia and js-libp2p configuration options at <https://ipfs.github.io/helia/interfaces/helia.HeliaInit.html>.
 *
 * ```typescript
 * import { trustlessGateway } from '@helia/block-brokers'
 * import { createHeliaHTTP } from '@helia/http'
 * import { delegatedHTTPRouting, httpGatewayRouting } from '@helia/routers'
 * import { createVerifiedFetch } from '@helia/verified-fetch'
 *
 * const fetch = await createVerifiedFetch(
 *   await createHeliaHTTP({
 *     blockBrokers: [
 *       trustlessGateway()
 *     ],
 *     routers: [
 *       delegatedHTTPRouting('http://delegated-ipfs.dev'),
 *       httpGatewayRouting({
 *         gateways: ['https://mygateway.example.net', 'https://trustless-gateway.link']
 *       })
 *     ]
 *   })
 * )
 *
 * const resp = await fetch('ipfs://bafy...')
 *
 * const json = await resp.json()
 * ```
 *
 * ### Custom content-type parsing
 *
 * By default, if the response can be parsed as JSON, `@helia/verified-fetch` sets the `Content-Type` header as `application/json`, otherwise it sets it as `application/octet-stream` - this is because the `.json()`, `.text()`, `.blob()`, and `.arrayBuffer()` methods will usually work as expected without a detailed content type.
 *
 * If you require an accurate content-type you can provide a `contentTypeParser` function as an option to `createVerifiedFetch` to handle parsing the content type.
 *
 * The function you provide will be called with the first chunk of bytes from the file and should return a string or a promise of a string.
 *
 * @example Customizing content-type parsing
 *
 * ```typescript
 * import { createVerifiedFetch } from '@helia/verified-fetch'
 * import { fileTypeFromBuffer } from 'file-type'
 *
 * const fetch = await createVerifiedFetch({
 *   gateways: ['https://trustless-gateway.link'],
 *   routers: ['http://delegated-ipfs.dev']
 * }, {
 *   contentTypeParser: async (bytes) => {
 *     // call to some magic-byte recognition library like magic-bytes, file-type, or your own custom byte recognition
 *     const result = await fileTypeFromBuffer(bytes)
 *     return result?.mime
 *   }
 * })
 * ```
 *
 * ### Custom DNS resolvers
 *
 * If you don't want to leak DNS queries to the default resolvers, you can provide your own list of DNS resolvers to `createVerifiedFetch`.
 *
 * Note that you do not need to provide both a DNS-over-HTTPS and a DNS-over-JSON resolver, and you should prefer `dnsJsonOverHttps` resolvers for usage in the browser for a smaller bundle size. See https://github.com/ipfs/helia/tree/main/packages/ipns#example---using-dns-json-over-https for more information.
 *
 * @example Customizing DNS resolvers
 *
 * ```typescript
 * import { createVerifiedFetch } from '@helia/verified-fetch'
 * import { dnsJsonOverHttps, dnsOverHttps } from '@multiformats/dns/resolvers'
 *
 * const fetch = await createVerifiedFetch({
 *   gateways: ['https://trustless-gateway.link'],
 *   routers: ['http://delegated-ipfs.dev'],
 *   dnsResolvers: [
 *     dnsJsonOverHttps('https://my-dns-resolver.example.com/dns-json'),
 *     dnsOverHttps('https://my-dns-resolver.example.com/dns-query')
 *   ]
 * })
 * ```
 *
 * @example Customizing DNS per-TLD resolvers
 *
 * DNS resolvers can be configured to only service DNS queries for specific
 * TLDs:
 *
 * ```typescript
 * import { createVerifiedFetch } from '@helia/verified-fetch'
 * import { dnsJsonOverHttps, dnsOverHttps } from '@multiformats/dns/resolvers'
 *
 * const fetch = await createVerifiedFetch({
 *   gateways: ['https://trustless-gateway.link'],
 *   routers: ['http://delegated-ipfs.dev'],
 *   dnsResolvers: {
 *     // this resolver will only be used for `.com` domains (note - this could
 *     // also be an array of resolvers)
 *     'com.': dnsJsonOverHttps('https://my-dns-resolver.example.com/dns-json'),
 *     // this resolver will be used for everything else (note - this could
 *     // also be an array of resolvers)
 *     '.': dnsOverHttps('https://my-dns-resolver.example.com/dns-query')
 *   }
 * })
 * ```
 * ### Custom Hashers
 *
 * By default, `@helia/verified-fetch` supports `sha256`, `sha512`, and `identity` hashers.
 *
 * If you need to use a different hasher, you can provide a [custom `hasher` function](https://multiformats.github.io/js-multiformats/interfaces/hashes_interface.MultihashHasher.html) as an option to `createVerifiedFetch`.
 *
 * @example Passing a custom hashing function
 *
 * ```typescript
 * import { createVerifiedFetch } from '@helia/verified-fetch'
 * import { blake2b256 } from '@multiformats/blake2/blake2b'
 *
 * const verifiedFetch = await createVerifiedFetch({
 *   gateways: ['https://ipfs.io'],
 *   hashers: [blake2b256]
 * })
 *
 * const resp = await verifiedFetch('ipfs://cid-using-blake2b256')
 * ```
 *
 * ### IPLD codec handling
 *
 * IPFS supports several data formats (typically referred to as codecs) which are included in the CID. `@helia/verified-fetch` attempts to abstract away some of the details for easier consumption.
 *
 * #### DAG-PB
 *
 * [DAG-PB](https://ipld.io/docs/codecs/known/dag-pb/) is the codec we are most likely to encounter, it is what [UnixFS](https://github.com/ipfs/specs/blob/main/UNIXFS.md) uses under the hood.
 *
 * ##### Using the DAG-PB codec as a Blob
 *
 * ```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 *
 * const res = await verifiedFetch('ipfs://Qmfoo')
 * const blob = await res.blob()
 *
 * console.info(blob) // Blob { size: x, type: 'application/octet-stream' }
 * ```
 *
 * ##### Using the DAG-PB codec as an ArrayBuffer
 *
 * ```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 *
 * const res = await verifiedFetch('ipfs://Qmfoo')
 * const buf = await res.arrayBuffer()
 *
 * console.info(buf) // ArrayBuffer { [Uint8Contents]: < ... >, byteLength: x }
 * ```
 *
 * ##### Using the DAG-PB codec as a stream
 *
 * ```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 *
 * const res = await verifiedFetch('ipfs://Qmfoo')
 * const reader = res.body?.getReader()
 *
 * if (reader == null) {
 *   throw new Error('Could not create reader from response body')
 * }
 *
 * while (true) {
 *   const next = await reader.read()
 *
 *   if (next?.done === true) {
 *     break
 *   }
 *
 *   if (next?.value != null) {
 *     console.info(next.value) // Uint8Array(x) [ ... ]
 *   }
 * }
 * ```
 *
 * ##### Content-Type
 *
 * When fetching `DAG-PB` data, the content type will be set to `application/octet-stream` unless a custom content-type parser is configured.
 *
 * #### JSON
 *
 * The JSON codec is a very simple codec, a block parseable with this codec is a JSON string encoded into a `Uint8Array`.
 *
 * ##### Using the JSON codec
 *
 * ```typescript
 * import * as json from 'multiformats/codecs/json'
 *
 * const block = new TextEncoder().encode('{ "hello": "world" }')
 * const obj = json.decode(block)
 *
 * console.info(obj) // { hello: 'world' }
 * ```
 *
 * ##### Content-Type
 *
 * When the `JSON` codec is encountered, the `Content-Type` header of the response will be set to `application/json`.
 *
 * ### DAG-JSON
 *
 * [DAG-JSON](https://ipld.io/docs/codecs/known/dag-json/) expands on the `JSON` codec, adding the ability to contain [CID](https://docs.ipfs.tech/concepts/content-addressing/)s which act as links to other blocks, and byte arrays.
 *
 * `CID`s and byte arrays are represented using special object structures with a single `"/"` property.
 *
 * Using `DAG-JSON` has two important caveats:
 *
 * 1. Your `JSON` structure cannot contain an object with only a `"/"` property, as it will be interpreted as a special type.
 * 2. Since `JSON` has no technical limit on number sizes, `DAG-JSON` also allows numbers larger than `Number.MAX_SAFE_INTEGER`. JavaScript requires use of `BigInt`s to represent numbers larger than this, and `JSON.parse` does not support them, so precision will be lost.
 *
 * Otherwise this codec follows the same rules as the `JSON` codec.
 *
 * ##### Using the DAG-JSON codec
 *
 * ```typescript
 * import * as dagJson from '@ipld/dag-json'
 *
 * const block = new TextEncoder().encode(`{
 *   "hello": "world",
 *   "cid": {
 *     "/": "baeaaac3imvwgy3zao5xxe3de"
 *   },
 *   "buf": {
 *     "/": {
 *       "bytes": "AAECAwQ"
 *     }
 *   }
 * }`)
 *
 * const obj = dagJson.decode(block)
 *
 * console.info(obj)
 * // {
 * // hello: 'world',
 * // cid: CID(baeaaac3imvwgy3zao5xxe3de),
 * // buf: Uint8Array(5) [ 0, 1, 2, 3, 4 ]
 * // }
 * ```
 *
 * ##### Content-Type
 *
 * When the `DAG-JSON` codec is encountered in the requested CID, the `Content-Type` header of the response will be set to `application/json`.
 *
 * `DAG-JSON` data can be parsed from the response by using the `.json()` function, which will return `CID`s/byte arrays as plain `{ "/": ... }` objects:
 *
 * ```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 * import * as dagJson from '@ipld/dag-json'
 *
 * const res = await verifiedFetch('ipfs://bafyDAGJSON')
 *
 * // either:
 * const obj = await res.json()
 * console.info(obj.cid) // { "/": "baeaaac3imvwgy3zao5xxe3de" }
 * console.info(obj.buf) // { "/": { "bytes": "AAECAwQ" } }
 * ```
 *
 * Alternatively, it can be decoded using the `@ipld/dag-json` module and the `.arrayBuffer()` method, in which case you will get `CID` objects and `Uint8Array`s:
 *
 *```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 * import * as dagJson from '@ipld/dag-json'
 *
 * const res = await verifiedFetch('ipfs://bafyDAGJSON')
 *
 * // or:
 * const obj = dagJson.decode<any>(await res.arrayBuffer())
 * console.info(obj.cid) // CID(baeaaac3imvwgy3zao5xxe3de)
 * console.info(obj.buf) // Uint8Array(5) [ 0, 1, 2, 3, 4 ]
 * ```
 *
 * #### DAG-CBOR
 *
 * [DAG-CBOR](https://ipld.io/docs/codecs/known/dag-cbor/) uses the [Concise Binary Object Representation](https://cbor.io/) format for serialization instead of JSON.
 *
 * This supports more data types in a safer way than JSON and is smaller on the wire to boot so is usually preferable to JSON or DAG-JSON.
 *
 * ##### Content-Type
 *
 * Not all data types supported by `DAG-CBOR` can be successfully turned into JSON and back into the same binary form.
 *
 * When a decoded block can be round-tripped to JSON, the `Content-Type` will be set to `application/json`. In this case the `.json()` method on the `Response` object can be used to obtain an object representation of the response.
 *
 * When it cannot, the `Content-Type` will be `application/octet-stream` - in this case the `@ipld/dag-json` module must be used to deserialize the return value from `.arrayBuffer()`.
 *
 * ##### Detecting JSON-safe DAG-CBOR
 *
 * If the `Content-Type` header of the response is `application/json`, the `.json()` method may be used to access the response body in object form, otherwise the `.arrayBuffer()` method must be used to decode the raw bytes using the `@ipld/dag-cbor` module.
 *
 * ```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 * import * as dagCbor from '@ipld/dag-cbor'
 *
 * const res = await verifiedFetch('ipfs://bafyDagCborCID')
 * let obj
 *
 * if (res.headers.get('Content-Type') === 'application/json') {
 *   // DAG-CBOR data can be safely decoded as JSON
 *   obj = await res.json()
 * } else {
 *   // response contains non-JSON friendly data types
 *   obj = dagCbor.decode(await res.arrayBuffer())
 * }
 *
 * console.info(obj) // ...
 * ```
 *
 * ## The `Accept` header
 *
 * The `Accept` header can be passed to override certain response processing, or to ensure that the final `Content-Type` of the response is the one that is expected.
 *
 * If the final `Content-Type` does not match the `Accept` header, or if the content cannot be represented in the format dictated by the `Accept` header, or you have configured a custom content type parser, and that parser returns a value that isn't in the accept header, a [406: Not Acceptable](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/406) response will be returned:
 *
 * ```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 *
 * const res = await verifiedFetch('ipfs://bafyJPEGImageCID', {
 *   headers: {
 *     accept: 'image/png'
 *   }
 * })
 *
 * console.info(res.status) // 406 - the image was a JPEG but we specified PNG as the accept header
 * ```
 *
 * It can also be used to skip processing the data from some formats such as `DAG-CBOR` if you wish to handle decoding it yourself:
 *
 * ```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 *
 * const res = await verifiedFetch('ipfs://bafyDAGCBORCID', {
 *   headers: {
 *     accept: 'application/octet-stream'
 *   }
 * })
 *
 * console.info(res.headers.get('accept')) // application/octet-stream
 * const buf = await res.arrayBuffer() // raw bytes, not processed as JSON
 * ```
 *
 * ## Redirects
 *
 * If a requested URL contains a path component, that path component resolves to
 * a UnixFS directory, but the URL does not have a trailing slash, one will be
 * added to form a canonical URL for that resource, otherwise the request will
 * be resolved as normal.
 *
 * ```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 *
 * const res = await verifiedFetch('ipfs://bafyfoo/path/to/dir')
 *
 * console.info(res.url) // ipfs://bafyfoo/path/to/dir/
 * ```
 *
 * It's possible to prevent this behavior and/or handle a redirect manually
 * through use of the [redirect](https://developer.mozilla.org/en-US/docs/Web/API/fetch#redirect)
 * option.
 *
 * @example Redirect: follow
 *
 * This is the default value and is what happens if no value is specified.
 *
 * ```typescript
 * import { verifiedFetch } from '@helia/verified-fetch'
 *
 * const res = await verifiedFetch('ipfs://bafyfoo/path/to/dir', {
 *   redirect: 'follow'
 * })
 *
 * console.info(res.status) // 200
 * console.info(res.url) // ipfs://bafyfoo/path/to/dir/
 * console.info(res.redirected) // true
 * ```
 *
 * @example Redirect: error
 *
 * This causes a `TypeError` to be thrown if a URL would cause a redirect.
 *
 * ```typescript
 *
 * import { verifiedFetch } from '@helia/verified-fetch'
 *
 * const res = await verifiedFetch('ipfs://bafyfoo/path/to/dir', {
 *   redirect: 'error'
 * })
 * // throw TypeError('Failed to fetch')
 * ```
 *
 * @example Redirect: manual
 *
 * Manual redirects allow the user to process the redirect. A [301](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/301)
 * is returned, and the location to redirect to is available as the "location"
 * response header.
 *
 * This differs slightly from HTTP fetch which returns an opaque response as the
 * browser itself is expected to process the redirect and hide all details from
 * the user.
 *
 * ```typescript
 *
 * import { verifiedFetch } from '@helia/verified-fetch'
 *
 * const res = await verifiedFetch('ipfs://bafyfoo/path/to/dir', {
 *   redirect: 'manual'
 * })
 *
 * console.info(res.status) // 301
 * console.info(res.url) // ipfs://bafyfoo/path/to/dir
 * console.info(res.redirected) // false
 * console.info(res.headers.get('location')) // ipfs://bafyfoo/path/to/dir/
 * ```
 *
 * ## Comparison to fetch
 *
 * This module attempts to act as similarly to the `fetch()` API as possible.
 *
 * [The `fetch()` API](https://developer.mozilla.org/en-US/docs/Web/API/fetch) takes two parameters:
 *
 * 1. A [resource](https://developer.mozilla.org/en-US/docs/Web/API/fetch#resource)
 * 2. An [options object](https://developer.mozilla.org/en-US/docs/Web/API/fetch#options)
 *
 * ### Resource argument
 *
 * This library supports the following methods of fetching web3 content from IPFS:
 *
 * 1. IPFS protocol: `ipfs://<cidv0>` & `ipfs://<cidv1>`
 * 2. IPNS protocol: `ipns://<peerId>` & `ipns://<publicKey>` & `ipns://<hostUri_Supporting_DnsLink_TxtRecords>`
 * 3. CID instances: An actual CID instance `CID.parse('bafy...')`
 *
 * As well as support for pathing & params for items 1 & 2 above according to [IPFS - Path Gateway Specification](https://specs.ipfs.tech/http-gateways/path-gateway) & [IPFS - Trustless Gateway Specification](https://specs.ipfs.tech/http-gateways/trustless-gateway/). Further refinement of those specifications specifically for web-based scenarios can be found in the [Web Pathing Specification IPIP](https://github.com/ipfs/specs/pull/453).
 *
 * If you pass a CID instance, it assumes you want the content for that specific CID only, and does not support pathing or params for that CID.
 *
 * ### Options argument
 *
 * This library does not plan to support the exact Fetch API options object, as some of the arguments don't make sense. Instead, it will only support options necessary to meet [IPFS specs](https://specs.ipfs.tech/) related to specifying the resultant shape of desired content.
 *
 * Some of those header specifications are:
 *
 * 1. https://specs.ipfs.tech/http-gateways/path-gateway/#request-headers
 * 2. https://specs.ipfs.tech/http-gateways/trustless-gateway/#request-headers
 * 3. https://specs.ipfs.tech/http-gateways/subdomain-gateway/#request-headers
 *
 * Where possible, options and Helia internals will be automatically configured to the appropriate codec & content type based on the `verified-fetch` configuration and `options` argument passed.
 *
 * Known Fetch API options that will be supported:
 *
 * 1. `signal` - An AbortSignal that a user can use to abort the request.
 * 2. `redirect` - A string that specifies the redirect type. One of `follow`, `error`, or `manual`. Defaults to `follow`. Best effort to adhere to the [Fetch API redirect](https://developer.mozilla.org/en-US/docs/Web/API/fetch#redirect) parameter.
 * 3. `headers` - An object of headers to be sent with the request. Best effort to adhere to the [Fetch API headers](https://developer.mozilla.org/en-US/docs/Web/API/fetch#headers) parameter.
 *     - `accept` - A string that specifies the accept header. Relevant values:
 *         - [`vnd.ipld.raw`](https://www.iana.org/assignments/media-types/application/vnd.ipld.raw). (default)
 *         - [`vnd.ipld.car`](https://www.iana.org/assignments/media-types/application/vnd.ipld.car)
 *         - [`vnd.ipfs.ipns-record`](https://www.iana.org/assignments/media-types/application/vnd.ipfs.ipns-record)
 * 4. `method` - A string that specifies the HTTP method to use for the request. Defaults to `GET`. Best effort to adhere to the [Fetch API method](https://developer.mozilla.org/en-US/docs/Web/API/fetch#method) parameter.
 * 5. `body` - An object that specifies the body of the request. Best effort to adhere to the [Fetch API body](https://developer.mozilla.org/en-US/docs/Web/API/fetch#body) parameter.
 * 6. `cache` - Will basically act as `force-cache` for the request. Best effort to adhere to the [Fetch API cache](https://developer.mozilla.org/en-US/docs/Web/API/fetch#cache) parameter.
 *
 * Non-Fetch API options that will be supported:
 *
 * 1. `onProgress` - Similar to Helia `onProgress` options, this will be a function that will be called with a progress event. Supported progress events are:
 *     - `helia:verified-fetch:error` - An error occurred during the request.
 *     - `helia:verified-fetch:request:start` - The request has been sent
 *     - `helia:verified-fetch:request:complete` - The request has been sent
 *     - `helia:verified-fetch:request:error` - An error occurred during the request.
 *     - `helia:verified-fetch:request:abort` - The request was aborted prior to completion.
 *     - `helia:verified-fetch:response:start` - The initial HTTP Response headers have been set, and response stream is started.
 *     - `helia:verified-fetch:response:complete` - The response stream has completed.
 *     - `helia:verified-fetch:response:error` - An error occurred while building the response.
 *
 * Some in-flight specs (IPIPs) that will affect the options object this library supports in the future can be seen at https://specs.ipfs.tech/ipips, a subset are:
 *
 * 1. [IPIP-0412: Signaling Block Order in CARs on HTTP Gateways](https://specs.ipfs.tech/ipips/ipip-0412/)
 * 2. [IPIP-0402: Partial CAR Support on Trustless Gateways](https://specs.ipfs.tech/ipips/ipip-0402/)
 * 3. [IPIP-0386: Subdomain Gateway Interop with _redirects](https://specs.ipfs.tech/ipips/ipip-0386/)
 * 4. [IPIP-0328: JSON and CBOR Response Formats on HTTP Gateways](https://specs.ipfs.tech/ipips/ipip-0328/)
 * 5. [IPIP-0288: TAR Response Format on HTTP Gateways](https://specs.ipfs.tech/ipips/ipip-0288/)
 *
 * ### Response types
 *
 * This library's purpose is to return reasonably representable content from IPFS. In other words, fetching content is intended for leaf-node content -- such as images/videos/audio & other assets, or other IPLD content (with link) -- that can be represented by https://developer.mozilla.org/en-US/docs/Web/API/Response#instance_methods. The content type you receive back will depend upon the CID you request as well as the `Accept` header value you provide.
 *
 * All content we retrieve from the IPFS network is obtained via an AsyncIterable, and will be set as the [body of the HTTP Response](https://developer.mozilla.org/en-US/docs/Web/API/Response/Response#body) via a [`ReadableStream`](https://developer.mozilla.org/en-US/docs/Web/API/Streams_API/Using_readable_streams#consuming_a_fetch_as_a_stream) or other efficient method that avoids loading the entire response into memory or getting the entire response from the network before returning a response to the user.
 *
 * If your content doesn't have a mime-type or an [IPFS spec](https://specs.ipfs.tech), this library will not support it, but you can use the [`helia`](https://github.com/ipfs/helia) library directly for those use cases. See [Unsupported response types](#unsupported-response-types) for more information.
 *
 * #### Handling response types
 *
 * For handling responses we want to follow conventions/abstractions from Fetch API where possible:
 *
 * - For JSON, assuming you abstract any differences between dag-json/dag-cbor/json/and json-file-on-unixfs, you would call `.json()` to get a JSON object.
 * - For images (or other web-relevant asset) you want to add to the DOM, use `.blob()` or `.arrayBuffer()` to get the raw bytes.
 * - For plain text in utf-8, you would call `.text()`
 * - For streaming response data, use something like `response.body.getReader()` to get a [`ReadableStream`](https://developer.mozilla.org/en-US/docs/Web/API/Streams_API/Using_readable_streams#consuming_a_fetch_as_a_stream).
 *
 * #### Unsupported response types
 *
 * - Returning IPLD nodes or DAGs as JS objects is not supported, as there is no currently well-defined structure for representing this data in an [HTTP Response](https://developer.mozilla.org/en-US/docs/Web/API/Response). Instead, users should request `aplication/vnd.ipld.car` or use the [`helia`](https://github.com/ipfs/helia) library directly for this use case.
 * - Others? Open an issue or PR!
 *
 * ### Response headers
 *
 * This library will set the [HTTP Response](https://developer.mozilla.org/en-US/docs/Web/API/Response) headers to the appropriate values for the content type according to the appropriate [IPFS Specifications](https://specs.ipfs.tech/).
 *
 * Some known header specifications:
 *
 * - https://specs.ipfs.tech/http-gateways/path-gateway/#response-headers
 * - https://specs.ipfs.tech/http-gateways/trustless-gateway/#response-headers
 * - https://specs.ipfs.tech/http-gateways/subdomain-gateway/#response-headers
 *
 * #### Server Timing headers
 *
 * By default, we do not include [Server Timing](https://developer.mozilla.org/en-US/docs/Web/API/Performance_API/Server_timing) headers in responses. If you want to include them, you can pass an
 * `withServerTiming` option to the `createVerifiedFetch` function to include them in all future responses. You can
 * also pass the `withServerTiming` option to each fetch call to include them only for that specific response.
 *
 * See PR where this was added, https://github.com/ipfs/helia-verified-fetch/pull/164, for more information.
 *
 * ### Possible Scenarios that could cause confusion
 *
 * #### Attempting to fetch the CID for content that does not make sense
 *
 * If you request `bafybeiaysi4s6lnjev27ln5icwm6tueaw2vdykrtjkwiphwekaywqhcjze`, which points to the root of the en.wikipedia.org mirror, a response object does not make sense.
 *
 * ### Errors
 *
 * Known Errors that can be thrown:
 *
 * 1. `TypeError` - If the resource argument is not a string, CID, or CID string.
 * 2. `TypeError` - If the options argument is passed and not an object.
 * 3. `TypeError` - If the options argument is passed and is malformed.
 * 4. `AbortError` - If the content request is aborted due to user aborting provided AbortSignal. Note that this is a `AbortError` from `@libp2p/interface` and not the standard `AbortError` from the Fetch API.
 *
 * ## Extensibility
 *
 * Verified‑fetch can now be extended to alter how it handles requests by using plugins.
 * Plugins are classes that extend the `BasePlugin` class and implement the `VerifiedFetchPlugin`
 * interface. They are instantiated with `PluginOptions` when the `VerifiedFetch` class is created.
 *
 * ### Plugin Interface
 *
 * Each plugin must implement two methods:
 *
 * - **`canHandle(context: PluginContext): boolean`**
 *   Inspects the current `PluginContext` (which includes the CID, path, query, accept header, etc.)
 *   and returns `true` if the plugin can operate on the current state of the request.
 *
 * - **`handle(context: PluginContext): Promise<Response | null>`**
 *   Performs the plugin’s work. It may:
 *     - **Return a final `Response`**: This stops the pipeline immediately.
 *     - **Return `null`**: This indicates that the plugin has only partially processed the request
 *       (for example, by performing path walking or decoding) and the pipeline should continue.
 *    - **Throw a `PluginError`**: This logs a non-fatal error and continues the pipeline.
 *    - **Throw a `PluginFatalError`**: This logs a fatal error and stops the pipeline immediately.
 *
 * ### Plugin Pipeline
 *
 * Plugins are executed in a chain (a **plugin pipeline**):
 *
 * 1. **Initialization:**
 *    - The `VerifiedFetch` class is instantiated with a list of plugins.
 *    - When a request is made via the `fetch` method, the resource and options are parsed to
 *      create a mutable `PluginContext` object.
 *
 * 2. **Pipeline Execution:**
 *    - The pipeline repeatedly checks, up to a maximum number of passes (default = 3), which plugins
 *      are currently able to handle the request by calling each plugin’s `canHandle()` method.
 *    - Plugins that have not yet been called in the current run and return `true` for `canHandle()`
 *      are invoked in sequence.
 *      - If a plugin returns a final `Response` or throws a `PluginFatalError`, the pipeline immediately
 *        stops and that response is returned.
 *      - If a plugin returns `null`, it may have updated the context (for example, by
 *        performing path walking), other plugins that said they `canHandle` will run.
 *    - If no plugin modifies the context (i.e. no change to `context.modified`) and no final response is
 *      produced after iterating through all plugins, the pipeline exits and a default “Not Supported”
 *      response is returned.
 *
 *    **Diagram of the Plugin Pipeline:**
 *
 * ```mermaid
 * flowchart TD
 *     A[Resource & Options] --> B[Parse into PluginContext]
 *     B --> C[Plugin Pipeline]
 *     subgraph IP[Iterative Passes max 3 passes]
 *       C1[Check canHandle for each plugin]
 *       C2[Call handle on ready plugins]
 *       C3[Update PluginContext if partial work is done]
 *       C1 --> C2
 *       C2 --> C3
 *     end
 *     C --> IP
 *     IP --> D[Final Response]
 * ```
 *
 * 3. **Finalization:**
 *    - After the pipeline completes, the resulting response & context is processed (e.g. headers such as ETag,
 *      Cache‑Control, and Content‑Disposition are set) and returned.
 *
 * Please see the original discussion on extensibility in [Issue #167](https://github.com/ipfs/helia-verified-fetch/issues/167).
 *
 * ---
 *
 * ### Non-default plugins provided by this library
 *
 * #### `dir-index-html-plugin`
 *
 * This plugin is used to serve dag-pb/unixfs without an `index.html` child as HTML directory listing of the content requested.
 *
 * #### `dag-cbor-html-preview-plugin`
 *
 * This plugin is used to serve the requested dag-cbor object as HTML when the Accept header includes `text/html`.
 *
 * @example Using the plugins
 *
 * ```typescript
 * import { createVerifiedFetch } from '@helia/verified-fetch'
 * import { dagCborHtmlPreviewPluginFactory, dirIndexHtmlPluginFactory } from '@helia/verified-fetch/plugins'
 * import { createHelia } from 'helia'
 *
 * const helia = await createHelia()
 * const fetch = await createVerifiedFetch(helia, {
 *   plugins: [dagCborHtmlPreviewPluginFactory, dirIndexHtmlPluginFactory, ]
 * })
 * ```
 *
 * ### Extending Verified‑Fetch with Custom Plugins
 *
 * To add your own plugin:
 *
 * 1. **Extend the BasePlugin:**
 *
 *    Create a new class that extends `BasePlugin` and implements:
 *
 *    - `canHandle(context: PluginContext): boolean`
 *    - `handle(context: PluginContext): Promise<Response | null>`
 *
 * @example custom plugin
 *
 *    ```typescript
 *    import { BasePlugin } from '@helia/verified-fetch'
 *    import type { PluginContext, VerifiedFetchPluginFactory, PluginOptions } from '@helia/verified-fetch'
 *
 *    export class MyCustomPlugin extends BasePlugin {
 *      id = 'my-custom-plugin' // Required: must be unique unless you want to override one of the default plugins.
 *
 *      // Optionally, list any codec codes your plugin supports:
 *      codes = [] //
 *
 *      canHandle(context: PluginContext): boolean {
 *        // Only handle requests if the Accept header matches your custom type
 *        // Or check context for pathDetails, custom values, etc...
 *        return context.accept === 'application/vnd.my-custom-type'
 *      }
 *
 *      async handle(context: PluginContext): Promise<Response | null> {
 *        // Perform any partial processing here, e.g., modify the context:
 *        context.customProcessed = true;
 *
 *        // If you are ready to finalize the response:
 *        return new Response('Hello, world!', {
 *          status: 200,
 *          headers: {
 *            'Content-Type': 'text/plain'
 *          }
 *        });
 *
 *        // Or, if further processing is needed by another plugin, simply return null.
 *      }
 *    }
 *    export const myCustomPluginFactory: VerifiedFetchPluginFactory = (opts: PluginOptions) => new MyCustomPlugin(opts)
 *    ```
 *
 * 2. **Integrate Your Plugin:**
 *
 *    Add your custom plugin to Verified‑Fetch’s plugin list when instantiating Verified‑Fetch:
 *
 * @example Integrate custom plugin
 *
 *    ```typescript
 *    import { createVerifiedFetch, type VerifiedFetchPluginFactory } from '@helia/verified-fetch'
 *    import { createHelia } from 'helia'
 *
 *    const helia = await createHelia()
 *    const plugins: VerifiedFetchPluginFactory[] = [
 *      // myCustomPluginFactory
 *    ]
 *
 *    const fetch = await createVerifiedFetch(helia, { plugins })
 *    ```
 *
 * ---
 *
 * ### Error Handling in the Plugin Pipeline
 *
 * Verified‑Fetch distinguishes between two types of errors thrown by plugins:
 *
 * - **PluginError (Non‑Fatal):**
 *   - Use this when your plugin encounters an issue that should be logged but does not prevent the pipeline
 *     from continuing.
 *   - When a plugin throws a `PluginError`, the error is logged and the pipeline continues with the next plugin.
 *
 * - **PluginFatalError (Fatal):**
 *   - Use this when a critical error occurs that should immediately abort the request.
 *   - When a plugin throws a `PluginFatalError`, the pipeline immediately terminates and the provided error
 *     response is returned.
 *
 * @example Plugin error Handling
 *
 * ```typescript
 * import { PluginError, PluginFatalError } from '@helia/verified-fetch'
 *
 * // async handle(context: PluginContext): Promise<Response | null> {
 * const recoverable = Math.random() > 0.5 // Use more sophisticated logic here ;)
 * if (recoverable === true) {
 *   throw new PluginError('MY_CUSTOM_WARNING', 'A non‑fatal issue occurred', {
 *     details: {
 *       someKey: 'Additional details here'
 *     }
 *   });
 * }
 *
 * if (recoverable === false) {
 *   throw new PluginFatalError('MY_CUSTOM_FATAL', 'A critical error occurred', {
 *     response: new Response('Something happened', { status: 500 })  // Required: supply your own error response
 *   });
 * }
 *
 *   // Otherwise, continue processing...
 * // }
 * ```
 *
 * ### How the Plugin Pipeline Works
 *
 * - **Shared Context:**
 *   A mutable `PluginContext` is created for each request. It includes the parsed CID, path, query parameters,
 *   accept header, and any other metadata. Plugins can update this context as they perform partial work (for example,
 *   by doing path walking or decoding).
 *
 * - **Iterative Processing:**
 *   The pipeline repeatedly checks which plugins can currently handle the request by calling `canHandle(context)`.
 *   - Plugins that perform partial processing update the context and return `null`, allowing subsequent passes by other plugins.
 *   - Once a plugin is ready to finalize the response, it returns a final `Response` and the pipeline terminates.
 *
 * - **No Strict Ordering:**
 *   Plugins are invoked based solely on whether they can handle the current state of the context.
 *   This means you do not have to specify a rigid order, each plugin simply checks the context and acts if appropriate.
 *
 * - **Error Handling:**
 *   - A thrown `PluginError` is considered non‑fatal and is logged, allowing the pipeline to continue.
 *   - A thrown `PluginFatalError` immediately stops the pipeline and returns the error response.
 *
 * For a detailed explanation of the pipeline, please refer to the discussion in [Issue #167](https://github.com/ipfs/helia-verified-fetch/issues/167).
 */

import { bitswap, trustlessGateway } from '@helia/block-brokers'
import { createDelegatedRoutingV1HttpApiClient } from '@helia/delegated-routing-v1-http-api-client'
import { httpGatewayRouting, libp2pRouting } from '@helia/routers'
import { dns } from '@multiformats/dns'
import { createHelia } from 'helia'
import { createLibp2p } from 'libp2p'
import { getLibp2pConfig } from './utils/libp2p-defaults.js'
import { VerifiedFetch as VerifiedFetchClass } from './verified-fetch.js'
import type { VerifiedFetchPluginFactory } from './plugins/types.js'
import type { ContentTypeParser } from './types.js'
import type { GetBlockProgressEvents, Helia, Routing } from '@helia/interface'
import type { ResolveDNSLinkProgressEvents } from '@helia/ipns'
import type { Libp2p, ServiceMap } from '@libp2p/interface'
import type { DNSResolvers, DNS } from '@multiformats/dns'
import type { DNSResolver } from '@multiformats/dns/resolvers'
import type { HeliaInit } from 'helia'
import type { ExporterProgressEvents } from 'ipfs-unixfs-exporter'
import type { Libp2pOptions } from 'libp2p'
import type { CID } from 'multiformats/cid'
import type { ProgressEvent, ProgressOptions } from 'progress-events'
/**
 * The types for the first argument of the `verifiedFetch` function.
 */
export type Resource = string | CID

export interface ResourceDetail {
  resource: Resource
}

export interface CIDDetail {
  cid: CID
  path: string
}

export interface CIDDetailError extends CIDDetail {
  error: Error
}

export interface VerifiedFetch {
  (resource: Resource, options?: VerifiedFetchInit): Promise<Response>
  start(): Promise<void>
  stop(): Promise<void>
}

/**
 * Instead of passing a Helia instance, you can pass a list of gateways and
 * routers, and a HeliaHTTP instance will be created for you.
 */
export interface CreateVerifiedFetchInit {
  gateways: string[]
  routers?: string[]

  /**
   * In order to parse DNSLink records, we need to resolve DNS queries. You can
   * pass a list of DNS resolvers that we will provide to the @helia/ipns
   * instance for you. You must construct them using the `dnsJsonOverHttps` or
   * `dnsOverHttps` functions exported from `@helia/ipns/dns-resolvers`.
   *
   * We use cloudflare and google's dnsJsonOverHttps resolvers by default.
   *
   * @default [dnsJsonOverHttps('https://cloudflare-dns.com/dns-query'),dnsJsonOverHttps('https://dns.google/resolve')]
   */
  dnsResolvers?: DNSResolver[] | DNSResolvers

  /**
   * By default sha256, sha512 and identity hashes are supported for
   * retrieval operations. To retrieve blocks by CIDs using other hashes
   * pass appropriate MultihashHashers here.
   */
  hashers?: HeliaInit['hashers']

  /**
   * By default we will not connect to any HTTP Gateways providers over local or
   * loopback addresses, this is because they are typically running on remote
   * peers that have published private addresses by mistake.
   *
   * Pass `true` here to connect to local Gateways as well, this may be useful
   * in testing environments.
   *
   * @default false
   */
  allowLocal?: boolean

  /**
   * By default we will not connect to any gateways over HTTP addresses,
   * requiring HTTPS connections instead. This is because it will cause
   * "mixed-content" errors to appear in the console when running in secure
   * browser contexts.
   *
   * Pass `true` here to connect to insecure Gateways as well, this may be
   * useful in testing environments.
   *
   * @default false
   */
  allowInsecure?: boolean

  /**
   * We will instantiate a libp2p node for you, but if you want to override the libp2p configuration,
   * you can pass it here.
   *
   * **WARNING**: We use Object.assign to merge the default libp2p configuration from Helia with the one you pass here,
   * which results in a shallow merge. If you need a deep merge, you should do it yourself before passing the
   * configuration here.
   */
  libp2pConfig?: Partial<Libp2pOptions<ServiceMap>>
}

export interface CreateVerifiedFetchOptions {
  /**
   * A function to handle parsing content type from bytes. The function you
   * provide will be passed the first set of bytes we receive from the network,
   * and should return a string that will be used as the value for the
   * `Content-Type` header in the response.
   *
   * @default undefined
   */
  contentTypeParser?: ContentTypeParser

  /**
   * Blockstore sessions are cached for reuse with requests with the same
   * base URL or CID. This parameter controls how many to cache. Once this limit
   * is reached older/less used sessions will be evicted from the cache.
   *
   * @default 100
   */
  sessionCacheSize?: number

  /**
   * How long each blockstore session should stay in the cache for.
   *
   * @default 60000
   */
  sessionTTLms?: number

  /**
   * Whether to include server-timing headers in responses. This option can be overridden on a per-request basis.
   *
   * @default false
   * @see https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Server-Timing
   */
  withServerTiming?: boolean

  /**
   * Plugins to use with the verified-fetch instance. Note that we have a set of default plugins that are always used.
   * If you want to replace one of the default plugins, you can do so by passing a plugin with the same name.
   */
  plugins?: VerifiedFetchPluginFactory[]
}

export type { ContentTypeParser } from './types.js'

export type BubbledProgressEvents =
  // unixfs-exporter
  ExporterProgressEvents |
  // helia blockstore
  GetBlockProgressEvents |
  // ipns
  ResolveDNSLinkProgressEvents

export type VerifiedFetchProgressEvents =
  ProgressEvent<'verified-fetch:request:start', CIDDetail> |
  ProgressEvent<'verified-fetch:request:info', string> |
  ProgressEvent<'verified-fetch:request:progress:chunk', CIDDetail> |
  ProgressEvent<'verified-fetch:request:end', CIDDetail> |
  ProgressEvent<'verified-fetch:request:error', CIDDetailError>

/**
 * Options for the `fetch` function returned by `createVerifiedFetch`.
 *
 * This interface contains all the same fields as the [options object](https://developer.mozilla.org/en-US/docs/Web/API/fetch#options)
 * passed to `fetch` in browsers, plus an `onProgress` option to listen for
 * progress events.
 */
export interface VerifiedFetchInit extends RequestInit, ProgressOptions<BubbledProgressEvents | VerifiedFetchProgressEvents> {
  /**
   * If true, try to create a blockstore session - this can reduce overall
   * network traffic by first querying for a set of peers that have the data we
   * wish to retrieve. Subsequent requests for data using the session will only
   * be sent to those peers, unless they don't have the data, in which case
   * further peers will be added to the session.
   *
   * Sessions are cached based on the CID/IPNS name they attempt to access. That
   * is, requests for `https://qmfoo.ipfs.localhost/bar.txt` and
   * `https://qmfoo.ipfs.localhost/baz.txt` would use the same session, if this
   * argument is true for both fetch requests.
   *
   * @default true
   */
  session?: boolean

  /**
   * By default we will not connect to any HTTP Gateways providers over local or
   * loopback addresses, this is because they are typically running on remote
   * peers that have published private addresses by mistake.
   *
   * Pass `true` here to connect to local Gateways as well, this may be useful
   * in testing environments.
   *
   * @default false
   */
  allowLocal?: boolean

  /**
   * By default we will not connect to any gateways over HTTP addresses,
   * requiring HTTPS connections instead. This is because it will cause
   * "mixed-content" errors to appear in the console when running in secure
   * browser contexts.
   *
   * Pass `true` here to connect to insecure Gateways as well, this may be
   * useful in testing environments.
   *
   * @default false
   */
  allowInsecure?: boolean

  /**
   * Whether to include server-timing headers in the response for an individual request.
   *
   * @default false
   * @see https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Server-Timing
   */
  withServerTiming?: boolean
}

/**
 * Create and return a Helia node
 */
export async function createVerifiedFetch (init?: Helia | CreateVerifiedFetchInit, options?: CreateVerifiedFetchOptions): Promise<VerifiedFetch> {
  let libp2p: Libp2p<any> | undefined
  if (!isHelia(init)) {
    const dns = createDns(init?.dnsResolvers)

    const libp2pConfig = getLibp2pConfig()
    libp2pConfig.dns = dns

    const delegatedRouters = init?.routers ?? ['https://delegated-ipfs.dev']
    for (let index = 0; index < delegatedRouters.length; index++) {
      const routerUrl = delegatedRouters[index]
      libp2pConfig.services[`delegatedRouting${index}`] = () => createDelegatedRoutingV1HttpApiClient(routerUrl)
    }
    // merge any passed options from init.libp2pConfig into libp2pConfig if it exists
    if (init?.libp2pConfig != null) {
      Object.assign(libp2pConfig, init.libp2pConfig)
    }
    libp2p = await createLibp2p(libp2pConfig)

    const blockBrokers = [
      bitswap()
    ]
    const routers: Array<Partial<Routing>> = [
      libp2pRouting(libp2p)
    ]
    if (init?.gateways == null || init.gateways.length > 0) {
      // if gateways is null, or set to a non-empty array, use trustless gateways.
      blockBrokers.push(trustlessGateway({ allowInsecure: init?.allowInsecure, allowLocal: init?.allowLocal }))
      routers.push(httpGatewayRouting({ gateways: init?.gateways ?? ['https://trustless-gateway.link'] }))
    }

    init = await createHelia({
      libp2p,
      blockBrokers,
      dns,
      routers,
      hashers: init?.hashers
    })
    init.logger.forComponent('helia:verified-fetch').trace('created verified-fetch with libp2p config: %j', libp2pConfig)
  }

  const verifiedFetchInstance = new VerifiedFetchClass({ helia: init }, options)
  async function verifiedFetch (resource: Resource, options?: VerifiedFetchInit): Promise<Response> {
    return verifiedFetchInstance.fetch(resource, options)
  }
  verifiedFetch.start = verifiedFetchInstance.start.bind(verifiedFetchInstance)
  verifiedFetch.stop = verifiedFetchInstance.stop.bind(verifiedFetchInstance)

  return verifiedFetch
}

export { verifiedFetch } from './singleton.js'
export * from './plugins/index.js'

function isHelia (obj: any): obj is Helia {
  // test for the presence of known Helia properties, return a boolean value
  return obj?.blockstore != null &&
    obj?.datastore != null &&
    obj?.gc != null &&
    obj?.stop != null &&
    obj?.start != null
}

function createDns (resolvers?: DNSResolver[] | DNSResolvers): DNS | undefined {
  if (resolvers == null) {
    return
  }

  if (Array.isArray(resolvers)) {
    return dns({
      resolvers: {
        '.': resolvers
      }
    })
  }

  return dns({ resolvers })
}