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import { EventEmitter } from 'node:events'

import crypto from 'node:crypto'

import bl from 'bl'

/**

* @typedef {Object} CreateHandlerOptions

* @property {string} path

* @property {string} secret

* @property {string | string[]} [events]

*/

/**

* @typedef {Object} WebhookEvent

* @property {string} event - The event type (e.g. 'push', 'issues')

* @property {string} id - The delivery ID from X-Github-Delivery header

* @property {any} payload - The parsed JSON payload

* @property {string} [protocol] - The request protocol

* @property {string} [host] - The request host header

* @property {string} url - The request URL

* @property {string} path - The matched handler path

*/

/**

* @param {string} url

* @param {CreateHandlerOptions | CreateHandlerOptions[]} arr

* @returns {CreateHandlerOptions}

*/

function findHandler (url, arr) {

if (!Array.isArray(arr)) {

return arr

}

let ret = arr[0]

for (let i = 0; i < arr.length; i++) {

if (url === arr[i].path) {

ret = arr[i]

}

}

return ret

}

/**

* @param {CreateHandlerOptions} options

*/

function checkType (options) {

if (typeof options !== 'object') {

throw new TypeError('must provide an options object')

}

if (typeof options.path !== 'string') {

throw new TypeError("must provide a 'path' option")

}

if (typeof options.secret !== 'string') {

throw new TypeError("must provide a 'secret' option")

}

}

/**

* @param {CreateHandlerOptions | CreateHandlerOptions[]} initOptions

* @returns {EventEmitter & {(req: import('node:http').IncomingMessage, res: import('node:http').ServerResponse, callback: (err?: Error) => void): void, sign(data: string | Buffer): string, verify(signature: string, data: string | Buffer): boolean}}

*/

function create (initOptions) {

/** @type {CreateHandlerOptions} */

let options

if (Array.isArray(initOptions)) {

for (let i = 0; i < initOptions.length; i++) {

checkType(initOptions[i])

}

} else {

checkType(initOptions)

}

// @ts-ignore - handler is a callable EventEmitter via setPrototypeOf

Object.setPrototypeOf(handler, EventEmitter.prototype)

// @ts-ignore

EventEmitter.call(handler)

handler.sign = sign

handler.verify = verify

// @ts-ignore

return handler

/**

* @param {string | Buffer} data

* @returns {string}

*/

function sign (data) {

return `sha1=${crypto.createHmac('sha1', options.secret).update(data).digest('hex')}`

}

/**

* @param {string} signature

* @param {string | Buffer} data

* @returns {boolean}

*/

function verify (signature, data) {

const sig = Buffer.from(signature)

const signed = Buffer.from(sign(data))

if (sig.length !== signed.length) {

return false

}

return crypto.timingSafeEqual(sig, signed)

}

/**

* @param {import('node:http').IncomingMessage} req

* @param {import('node:http').ServerResponse} res

* @param {(err?: Error) => void} callback

*/

function handler (req, res, callback) {

/** @type {string[] | undefined} */

let events

options = findHandler(/** @type {string} */ (req.url), initOptions)

if (typeof options.events === 'string' && options.events !== '*') {

events = [options.events]

} else if (Array.isArray(options.events) && options.events.indexOf('*') === -1) {

events = options.events

}

if (req.url !== options.path || req.method !== 'POST') {

return callback()

}

/**

* @param {string} msg

*/

function hasError (msg) {

res.writeHead(400, { 'content-type': 'application/json' })

res.end(JSON.stringify({ error: msg }))

const err = new Error(msg)

// @ts-ignore - handler has EventEmitter prototype

handler.emit('error', err, req)

callback(err)

}

const sig = req.headers['x-hub-signature']

const event = req.headers['x-github-event']

const id = req.headers['x-github-delivery']

if (!sig) {

return hasError('No X-Hub-Signature found on request')

}

if (!event) {

return hasError('No X-Github-Event found on request')

}

if (!id) {

return hasError('No X-Github-Delivery found on request')

}

if (events && events.indexOf(/** @type {string} */ (event)) === -1) {

return hasError('X-Github-Event is not acceptable')

}

req.pipe(bl((err, data) => {

if (err) {

return hasError(err.message)

}

let obj

if (!verify(/** @type {string} */ (sig), data)) {

return hasError('X-Hub-Signature does not match blob signature')

}

try {

obj = JSON.parse(data.toString())

} catch (e) {

return hasError(/** @type {Error} */ (e).message)

}

res.writeHead(200, { 'content-type': 'application/json' })

res.end('{"ok":true}')

const emitData = {

event,

id,

payload: obj,

protocol: /** @type {any} */ (req).protocol,

host: req.headers.host,

url: req.url,

path: options.path

}

// @ts-ignore - handler has EventEmitter prototype

handler.emit(event, emitData)

// @ts-ignore - handler has EventEmitter prototype

handler.emit('*', emitData)

}))

}

}

export default create