R/classes.R

In chainsawriot/weiborr: A Simple Sina Weibo Client

## reference: http://open.weibo.com/wiki/%E5%B8%B8%E8%A7%81%E8%BF%94%E5%9B%9E%E5%AF%B9%E8%B1%A1%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84

## proposed S3 classes:
## 1. weibo_user
## 2. weibo_status
## 3. multiple_weibo_users
## 4. multiple_weibo_statuses
## 5. weibo_error

make_class <- function(x, which_class) {
    class(x) <- append(class(x), which_class)
    return(x)
}

#' @export
to_df <- function(obj, ...) {
    UseMethod("to_df", obj)
}


## weibo_status

#' @export
print.multiple_weibo_statuses <- function(obj) {
    cat("Collection of", length(obj), "weibo status(es).\n")
}

#' @export
print.weibo_status <- function(obj) {
    if (nchar(obj$text) > 10) {
        preview <- paste0(substr(obj$text, 1, 10), "...")
    } else {
        preview <- obj$text
    }
    cat("Weibo status: ", obj$mid, ". Preview:", preview, "\n")
    if (!is.null(obj$retweeted_status)) {
        cat("A retweet of weibo status: ", obj$mid, "\n")
    }
}


gen_multiple_weibo_statuses <- function(res) {
    if (!"statuses" %in% (names(res))) {
        stop("Not a API result from a 'statuses/...' query.")
    }
    res$statuses <- plyr::llply(res$statuses, make_weibo_status)
    res$statuses <- make_class(res$statuses, "multiple_weibo_statuses")
    return(res)
}

make_weibo_status <- function(obj) {
    if (!is.null(obj$user)) {
        obj$user <- make_class(obj$user, "weibo_user")
    }
    if (!is.null(obj$retweeted_status)) {
        obj$retweeted_status <- make_weibo_status(obj$retweeted_status)
    }
    obj <- make_class(obj, "weibo_status")
    return(obj)
}

fields_to_extract <- c("created_at", "mid", "text", "truncated", "source", "in_reply_to_status_id", "in_reply_to_user_id", "in_reply_to_screen_name", "pic_urls", "geo", "user", "retweeted_status", "reposts_count", "comments_count", "attitudes_count", "isLongText")

extract_tweet <- function(weibo_status, fields = fields_to_extract) {
    s_status <- weibo_status[names(weibo_status) %in% fields]
    s_status$geo <- ifelse(is.null(s_status$geo), NA, paste0(s_status$geo$coordinates[[1]], ",", s_status$geo$coordinates[[2]]))
    s_status$user <- s_status$user$id
    s_status$retweeted_status <- ifelse(is.null(s_status$retweeted_status), NA, s_status$retweeted_status$mid)
    s_status$pic_urls <- ifelse(length(s_status$pic_urls) == 0, NA, paste(sapply(s_status$pic_urls, function(x) x$thumbnail_pic), collapse = ","))
    return(as.data.frame.list(s_status, stringsAsFactors = FALSE))
}

#' @export
to_df.weibo_status <- function(obj, level = "tweets") {
    if (level == "tweets") {
        return(extract_tweet(obj, fields_to_extract))
    }
}

#' @export
to_df.multiple_weibo_statuses <- function(obj, level = "tweets") {
    if (level == "tweets") {
        return(plyr::ldply(obj, to_df))
    }
    if (level == "retweets") {
        retweets <- plyr::llply(Filter(function(x) !is.null(x$retweeted_status), obj), function(x) x$retweeted_status)
        return(plyr::ldply(retweets, to_df))
    }
    if (level == "users") {
        ori_users <- plyr::llply(obj, function(x) x$user)
        rt_users <- plyr::llply(Filter(function(x) !is.null(x$retweeted_status), obj), function(x) x$retweeted_status$user)
        all_users <- Filter(function(x) !is.null(x), append(ori_users, rt_users))
        return(unique(plyr::ldply(all_users, to_df)))
    }
}

## weibo_user and multiple_weibo_users

#' @export
print.multiple_weibo_users <- function(obj) {
    cat("Collection of", length(obj), "weibo user(s).\n")
}

#' @export
print.weibo_user <- function(obj) {
    if (!"status" %in% names(obj)) {
        cat("Weibo user: id", obj$id, ".\n")
    } else {
        cat("Weibo user: id", obj$id, ". With embeded status.\n")
    }
}

#' @export
to_df.weibo_user <- function(obj) {
    if (!'status' %in% names(obj)) {
        return(as.data.frame.list(obj, stringsAsFactors = FALSE))
    } else {
        warning("Status in the weibo_user object removed.")
        return(as.data.frame.list(obj[names(obj) != "status"], stringsAsFactors = FALSE))
    }
}

#' @export
to_df.multiple_weibo_users <- function(obj) {
    return(plyr::ldply(obj, to_df))
}

gen_multiple_weibo_users <- function(res) {
    if (!"users" %in% (names(res))) {
        stop("Not a API result from a 'friendships/...' query.")
    }
    res$users <- plyr::llply(res$users, function(x) make_class(x, "weibo_user"))
    res$users <- make_class(res$users, "multiple_weibo_users")
    return(res)
}

#### weibo_error

#' @export
print.weibo_error <- function(obj) {
    cat("Weibo error, error code:", obj$error_code, ".\n")
}