implement DBI interface

ropensci#48

DESCRIPTION

@@ -25,3 +25,5 @@ Suggests:
     xml2,
     readxl,
     maptools
+Depends:
+    DBI

R/dbi.R

@@ -0,0 +1,234 @@
+## DBI Interface
+
+setClass("CKANDriver", representation("DBIDriver"))
+
+setMethod("dbUnloadDriver", "CKANDriver",
+          def = function(drv, ...) invisible(NULL),
+          valueClass = "logical"
+          )
+
+setMethod("dbGetInfo", "CKANDriver",
+          def = function(dbObj, ...) {
+            cat(sprintf("DBI Interface for CKAN\n"))
+          }
+          )
+
+setMethod("summary", "CKANDriver",
+          def = function(object, ...) dbGetInfo(object, ...)
+          )
+
+##
+## Class: DBIConnection
+##
+setClass("CKANConnection", representation("DBIConnection", "url" = "character"))
+
+setMethod("initialize", "CKANConnection", function(.Object, url, ...) {
+  .Object@url <- url
+  .Object
+})
+
+setMethod("dbConnect", "CKANDriver",
+          def = function(drv, url, ...) new("CKANConnection", url),
+          valueClass = "CKANConnection"
+          )
+
+## clone a connection
+setMethod("dbConnect", "CKANConnection",
+          def = function(drv, ...) drv,
+          valueClass = "CKANConnection"
+          )
+
+setMethod("dbDisconnect", "CKANConnection",
+          def = function(conn, ...) invisible(TRUE),
+          valueClass = "logical"
+          )
+
+setClass("CKANResult", representation("DBIResult", value = "list"))
+
+setMethod("initialize", "CKANResult", function(.Object, value, ...) {
+  .Object@value <- value
+  .Object
+})
+
+setMethod("dbSendQuery",
+          signature(conn = "CKANConnection", statement = "character"),
+          def = function(conn, statement,...) {
+            retval <- ds_search_sql(statement, url = conn@url, as = "table")
+            new("CKANResult", value = retval)
+          },
+          valueClass = "CKANResult"
+          )
+
+
+setMethod("dbGetQuery",
+          signature(conn = "CKANConnection", statement = "character"),
+          def = function(conn, statement, ...) {
+            retval <- dbSendQuery(conn, statement, ...)
+            retval@value$records
+          }
+          )
+
+setMethod("dbGetException", "CKANConnection",
+          def = function(conn, ...) {
+              list()
+          },
+          valueClass = "list"
+          )
+
+setMethod("dbGetInfo", "CKANConnection",
+          def = function(dbObj, ...) {
+            cat(sprintf("url: %s\n", dbObj@url))
+          }
+          )
+
+setMethod("dbListResults", "CKANConnection",
+          def = function(conn, ...) dbGetInfo(conn, "rsId")[[1]]
+          )
+
+setMethod("summary", "CKANConnection",
+          def = function(object, ...) dbGetInfo(object)
+          )
+
+## convenience methods
+setMethod("dbListTables", "CKANConnection",
+          def = function(conn, ...){
+              stop("TODO: dbListTables")
+          },
+          valueClass = "character"
+          )
+
+setMethod("dbReadTable", signature(conn="CKANConnection", name="character"),
+          def = function(conn, name, ...) {
+            sql <- sprintf('SELECT * FROM "%s"', name)
+            dbGetQuery(conn, sql)
+          },
+          valueClass = "data.frame"
+          )
+
+setMethod("dbWriteTable",
+          signature(conn="CKANConnection", name="character", value="data.frame"),
+          def = function(conn, name, value, ...){
+              stop("(dbWriteTable) This interface is read-only currently")
+          },
+          valueClass = "logical"
+          )
+
+setMethod("dbExistsTable",
+          signature(conn="CKANConnection", name="character"),
+          def = function(conn, name, ...){
+            stop("TODO: dbExistsTable")
+          },
+          valueClass = "logical"
+          )
+
+setMethod("dbRemoveTable",
+          signature(conn="CKANConnection", name="character"),
+          def = function(conn, name, ...){
+              stop("(dbRemoveTable) This interface is read-only currently")
+          },
+          valueClass = "logical"
+          )
+
+## return field names (no metadata)
+setMethod("dbListFields",
+          signature(conn="CKANConnection", name="character"),
+          def = function(conn, name, ...){
+              stop("TODO: dbListFields")
+          },
+          valueClass = "character"
+          )
+
+
+setMethod("dbCallProc", "CKANConnection",
+          def = function(conn, ...) {
+            stop("TODO: dbCallProc")
+          }
+          )
+
+setMethod("dbCommit", "CKANConnection",
+          def = function(conn, ...) {
+            stop("TODO: dbCommit")
+          }
+          )
+
+setMethod("dbRollback", "CKANConnection",
+          def = function(conn, ...) {
+            stop("TODO: dbRollback")
+          }
+          )
+
+setMethod("dbClearResult", "CKANResult",
+          def = function(res, ...) {
+            TRUE
+          },
+          valueClass = "logical"
+          )
+
+setMethod("fetch", signature(res="CKANResult", n="numeric"),
+          def = function(res, n, ...){
+              stop("TODO: fetch")
+          },
+          valueClass = "data.frame"
+          )
+
+setMethod("fetch",
+          signature(res="CKANResult", n="missing"),
+          def = function(res, n, ...){
+              res@value$records
+          },
+          valueClass = "data.frame"
+          )
+
+setMethod("dbGetInfo", "CKANResult",
+          def = function(dbObj, ...) {
+            dbObj@value[-1]
+          },
+          valueClass = "list"
+          )
+
+setMethod("dbGetStatement", "CKANResult",
+          def = function(res, ...){
+              dbGetInfo(res)$sql
+          },
+          valueClass = "character"
+          )
+
+setMethod("dbListFields",
+          signature(conn="CKANResult", name="missing"),
+          def = function(conn, name, ...){
+              dbGetInfo(res)$fields
+          },
+          valueClass = "character"
+          )
+
+setMethod("dbColumnInfo", "CKANResult",
+          def = function(res, ...) dbListFields(res, ...),
+          valueClass = "data.frame"
+          )
+
+setMethod("dbGetRowsAffected", "CKANResult",
+          def = function(res, ...) stop("TODO: dbGetRowsAffected"),
+          valueClass = "numeric"
+          )
+
+setMethod("dbGetRowCount", "CKANResult",
+          def = function(res, ...) nrow(res@value$records),
+          valueClass = "numeric"
+          )
+
+setMethod("dbHasCompleted", "CKANResult",
+          def = function(res, ...) TRUE,
+          valueClass = "logical"
+          )
+
+setMethod("dbGetException", "CKANResult",
+          def = function(conn, ...){
+              list()
+          },
+          valueClass = "list"    ## TODO: should be a DBIException?
+          )
+
+setMethod("summary", "CKANResult",
+          def = function(object, ...) stop("TODO: summary.CKANResult")
+          )
+