R/dvQuery.r

In leeper/dvn: Access to Dataverse 3 APIs

dvQuery <- function(verb, query = NULL, dv = getOption('dvn'), browser=FALSE, ...){
	# Data Sharing API workhorse query function
	if(!verb %in% c("metadataSearchFields", "metadataSearch", "metadataFormatsAvailable", "metadata", "downloadInfo", "download"))
		warning("API query verb not recognized")
	if(is.null(dv) || dv=="")
		stop("Must specify Dataverse URL as 'dv'")
	else{
		https <- substring(dv,1,5)
		if(!https=="https")
			stop("API query must use https")
		slash <- substring(dv,nchar(dv),nchar(dv))
		if(!slash=="/")
			dv <- paste(dv,"/",sep="")
	}
	url <- paste(dv,"api/",verb,sep="")
	if(!is.null(query))
		url <- paste(url,query,sep="/")
	if(browser)
		browseURL(url)
	else{
	    user <- getOption('dvn.user')
	    pwd <- getOption('dvn.pwd')
	    if(!user=='' && !pwd=='')
	    	userpwd <- paste(user,pwd,sep=':')
	    else
	    	userpwd <- NULL
	    xml <- getURL(url, followlocation = 1L, httpauth=1L, userpwd=userpwd,
	                       ssl.verifypeer = 0L, ssl.verifyhost = 2L,
                           cainfo = system.file("CurlSSL", "cacert.pem", package = "RCurl"), ...)
	    if('html' %in% names(xmlChildren(xmlParse(xml)))){
            temp <- htmlTreeParse(xml,useInternalNodes=TRUE)
            out <- 
            c(xpathApply(temp,'//title/text()',xmlValue)[[1]],
              xpathApply(temp,'//h1/text()',xmlValue)[[1]],
              unlist(xpathApply(temp,'//p/text()',xmlValue)))
            message('Operation failed with the following response:\n',paste(out,'\n',collapse='\n'))
            return(NULL)
        }
        else
            return(xml)
	}
}