background.js

/// <reference path="./types.ts" />

// @ts-check

'use strict'

/** @param {string}str */
const strToUint8Array = str => new TextEncoder().encode(str)

/** @param {Uint8Array}uint8Array */
const uint8ArrayToStr = uint8Array => new TextDecoder('utf-8').decode(uint8Array)

const createPostUri = 'https://www.linkedin.com/voyager/api/contentcreation/normShares'

/** @type {Map<string, EventRequestObjWithBodyCreatePost>} */
const requestJar = new Map()

/** @param {EventRequestObjWithBodyCreatePost['requestBodyJson']} requestBodyJson */
const transformRequestBodyJson = requestBodyJson => {
  requestBodyJson.commentaryV2.text = 'Hola senior'
}

chrome.webRequest.onBeforeRequest.addListener(
  /** @param {EventRequestObjWithBodyCreatePost} details */
  details => {
    if (details.method !== 'POST') return

    console.log(`[${details.requestId}] request: `, details)

    let jsonBody
    try {
      const rawTextBody = details.requestBody.raw
        .map(data => String.fromCharCode.apply(null, new Uint8Array(data.bytes)))
        .join('')
      jsonBody = JSON.parse(rawTextBody)
    } catch (err) {
      throw new Error(`Failed to parse JSON request body - ${err.message}`)
    }
    details.requestBodyJson = jsonBody

    console.log(`[${details.requestId}] jsonBody: `, jsonBody)
    requestJar.set(details.requestId, details)
  },
  {
    urls: [createPostUri]
  },
  ['requestBody', 'blocking']
)

chrome.webRequest.onBeforeSendHeaders.addListener(
  /** @param {EventRequestObjWithHeaders} details */
  details => {
    if (details.method !== 'POST') return

    console.log(`[${details.requestId}] details: `, details)
    // Convert `{ name: 'name', value: 'value' }` to `{ [name: string]: string }`
    const headers = /** @type {Record<string, string>} */ (
      details.requestHeaders.reduce((acc, cur) => {
        acc[cur.name] = cur.value
        return acc
      }, {})
    )

    console.log(`[${details.requestId}] headers: `, headers)

    const transformedRequestBodyJson = transformRequestBodyJson(requestJar.get(details.requestId).requestBodyJson)
    console.log(`[${details.requestId}] transformedRequestBodyJson: `, transformedRequestBodyJson)
    ;(async () => {
      const res = await fetch(createPostUri, {
        // credentials: 'include',
        method: 'POST',
        body: strToUint8Array(JSON.stringify(transformedRequestBodyJson)),
        headers
      }).then(res => res.text())
      console.log('res', res)
    })()

    return { cancel: true }
  },
  { urls: [createPostUri] },
  ['requestHeaders', 'extraHeaders', 'blocking']
)

types.d.ts

declare var chrome: any

type EventRequestObj = {
  frameId: number
  initiator: string
  method: string
  parentFrameId: number
  requestId: string
  tabId: number
  timeStamp: number
  type: string
  url: string
}

type EventRequestObjWithBody = EventRequestObj & {
  requestBody: { raw: [{ bytes: Uint8Array }] }
  requestBodyJson: unknown
}
type EventRequestObjWithHeaders = EventRequestObj & { requestHeaders: { name: string; value: string }[] }

type CreatePostBody = {
  visibleToConnectionsOnly: boolean
  externalAudienceProviders: []
  commentaryV2: { text: string; attributes: [] }
  origin: string
  allowedCommentersScope: string
  media: []
}

type EventRequestObjWithBodyCreatePost = EventRequestObjWithBody & { requestBodyJson: CreatePostBody }