R/query.R

In metadevpro/traitbaser: R package providing API access to Traitbase https://www.traitbase.info

#' Makes a query
#'
#' Executes a query on the server backend and returns data.
#'
#' @param resource The resource to query.
#' @param limit Limit the number of data rows to retrieve. If no specified, no limit applies.
#' @param skip Skip the first N data rows to retrieve. If no specified, no skip=0 is assumed.
#' @param conditions A set of conditions to constraint the query on the server side. Use the function \code{buildCondition()} to create the conditions.0
#' @param sort Criteria to sort the data returned. (Not yet implemented)
#' @param selectFields Select and filter the fields to retrieve (columns). (Not yet implemented)
#' @param distinct Provides a distict criteria. (Not yet implemented)
#' @param todataframe Should the output be tranformed to a data.frame

#'
#' @return Returns a dataframe with the returned data.
#' @export
#' @examples
#' \donttest{
#' cnx <- connect('http://www.traitbase.info')
#' off <- resource(cnx, 'species')
#'
#' res <- query(off)
#' query(off, conditions=buildCondition('species', '==', 'Bombus')  )
#' query(off, limit=2, skip=0)
#' query(off, limit=2, skip=2)
#' }

query <- function(resource, limit = -1, skip = 0, conditions = NULL, sort,
    selectFields, distinct, todataframe = TRUE) {
    urlbase <- httr::handle(resource[[1L]])
    aut <- httr::authenticate(resource[[2L]], resource[[3L]])

    query <- ""
    prefix <- "?"
    if (limit != -1) {
        query <- paste0(prefix, "limit=", limit)
        prefix <- "&"
    }
    if (skip != 0) {
        query <- paste0(query, prefix, "skip=", skip)
        prefix <- "&"
    }
    if (!is.null(conditions)) {
        query <- paste0(query, prefix, buildQueryConditions(conditions))
        prefix <- "&"
    }

    q1 <- httr::GET(handle = urlbase, config = aut, path = paste("api/",
        resource[[5]], query, sep = ""))
    dataQ1 <- httr::content(q1, type = "application/json")
    ## output
    if(todataframe){
        out <- toDataframe(dataQ1)
    } else {
        out <- dataQ1
    }
    return(out)
}