app.R

library(shiny)
library(shinyjs) #to easily run javascript
library(shinyBS) #shiny bootstrap; show error dialogs

### Set up a LinkedIn application first
### To do this, go to https://linkedin.com/developers
### Create an application, and set up the redirect URL to your Shiny application
### Go to products and activate Sign in with LinkedIn
ClientID <- "XXXXXXXXXXX" # see the Auth page for your app at https://linkedin.com/developers
ClientSecret <- "XXXXXXXXXX"
RedirectURL <- "https://rfaelens.shinyapps.io/linkedin/"

## See https://docs.microsoft.com/nl-be/linkedin/shared/authentication/authorization-code-flow
ui <- fluidPage(
    shinyjs::useShinyjs(),
    titlePanel("Linkedin fetch profile demo"),
    shinyBS::bsAlert("alert"),
    sidebarLayout(
        sidebarPanel(
            shinyjs::disabled(
                actionButton("fetch", "Fetch profile data")
            )
        ),
        mainPanel(
           verbatimTextOutput("profile")
        )
    )
)

redirectToLogin <- function(redirect_uri) {
    url <- httr::parse_url("https://www.linkedin.com/oauth/v2/authorization")
    url$query <- list(
        response_type = "code",
        client_id = ClientID,
        redirect_uri = redirect_uri,
        state = "SHOULD_BE_RANDOM",
        scope="r_liteprofile"
    )
    url <- httr::build_url(url)
    shinyjs::runjs(paste0("window.location = '", url, "'"))
}

getAccessToken <- function(AuthCode, redirect_uri) {
    res <- httr::POST("https://www.linkedin.com/oauth/v2/accessToken",
               body=list(
                   grant_type="authorization_code",
                   code = AuthCode,
                   redirect_uri	= redirect_uri,
                   client_id = ClientID,
                   client_secret = ClientSecret
               ),
               encode = "form")
    httr::content(res, as="parsed")
}

getProfile <- function(access_token) {
    res <- httr::GET("https://api.linkedin.com/v2/me",
              httr::add_headers(`Authorization`=paste0("Bearer ", access_token))
    )
    httr::content(res, as="parsed")
}

server <- function(input, output, session) {
    data <- reactiveValues(auth_code=NULL)
    observeEvent(session$clientData, {
        query <- parseQueryString(session$clientData$url_search)
        ### Any time LinkedIn redirects the user back to us, then the 'state' is filled in
        if(!is.null(query$state)) {
            message("User logged in to LinkedIn")
            
            ## This is a response from LinkedIn
            if(!is.null(query$error)) {
                shinyBS::createAlert(session, "alert", content=query$error_description, title = query$error)
            } else {
                data$auth_code <- query$code
                shinyBS::createAlert(session, "alert", content=query$code, title="Received auth_code")
                shinyjs::enable("fetch")
            }
        } else {
            message("User not logged in, redirecting...")
            redirectToLogin(RedirectURL)
        }
    })
    observeEvent(input$fetch,{
                AuthCode <- data$auth_code
                res <- getAccessToken(AuthCode, RedirectURL)
                data$profile <- getProfile(res$access_token)
    })
    
    output$profile <- renderPrint({
        data$profile
    })
}

# Run the application 
shinyApp(ui = ui, server = server)