facebookcomments.r

library("RCurl")
library("rjson")
library("plyr")
library("stringr")


# Returns json from url of Json

get.json.from.url <- function(url) {
    # Need certificate for https downloading
    raw.data <- getURL(url, cainfo = "http://curl.haxx.se/ca/cacert.pem")
    res <- fromJSON(raw.data)
    return(res)
}

# Returns Facebook comments id from URL of blog post

get.fb.comments.id <- function(url) {
    uri <- paste("https://graph.facebook.com/comments/?ids=", url, sep = "")
    res <- get.json.from.url(uri)
    idstring <- res[[url]]$comments$data[[1]]$id
    id <- str_split(idstring, "_")[[1]][1]
    return(id)
}


# From the the URL of a post with Facebook commments, recursively grabs FB comments until there are no
# more comments. It returns list a that contains two data.frames: one with parent comments, the other
# contains replies (FB comments only have two levels)

get.comments <- function(url = NULL, allcomments = NULL, first.time = TRUE) {
    if (first.time == TRUE) {
        commentsid <- get.fb.comments.id(url)
        url <- paste("https://graph.facebook.com/", commentsid, "/comments", sep = "")
    }
    res <- get.json.from.url(url)
    
    parentcomments <- ldply(res$data, function(x) data.frame(id = x$id, fromname = x$from$name, fromid = x$from$id,
    message = x$message, created_time = x$created_time, likes = ifelse(is.null(x$likes), 0, x$likes),
    count = ifelse(is.null(x$comments$count), 0, x$comments$count)))
    
    replies <- ldply(res$data, function(x) (data.frame(ldply(x$comments$data, function(y) y$id), ldply(x$comments$data,
    function(y) y$from$name), ldply(x$comments$data, function(y) y$from$id), ldply(x$comments$data,
    function(y) y$message), ldply(x$comments$data, function(y) y$created_time))))
    
    coltitles <- c("reply.id", "reply.fromname", "reply.fromid", "reply.message", "reply.created_time")
    
    if (length(replies) == length(coltitles)) {
        names(replies) <- coltitles
    }
    
    if (first.time == TRUE) {
        allcomments <- list(parentcomments, replies)
    } else {
        somecomments <- list(parentcomments, replies)
        allcomments[[1]] <- rbind(allcomments[[1]], somecomments[[1]])
        allcomments[[2]] <- rbind(allcomments[[2]], somecomments[[2]])
    }
    print(dim(allcomments[[1]]))
    print(dim(allcomments[[2]]))
    
    if (is.null(res$paging$"next") == FALSE) {
        get.comments(res$paging$"next", allcomments, FALSE)
    } else {
        return(allcomments)
    }
}

# Example URL
url <- "http://blog.netflix.com/2011/09/explanation-and-some-reflections.html"

## Example usage of comments function
comments <- get.comments(url)