#' Run EnrichR on SCE object
 #' @details 

 #' EnrichR works by querying the specified \code{features} to its online 
 #' databases, thus it requires the Internet connection. 

 #' 
 #' Available \code{db} options could be shown by running 
 #' \code{enrichR::listEnrichrDbs()$libraryName}

 #' 
 #' This function checks for the existence of features in the SCE object. When 
 #' \code{features} do not have a match in \code{rownames(inSCE)}, users may 
 #' try to specify \code{by} to pass the check. 
 #' 

 #' EnrichR expects gene symbols/names as the input (i.e. Ensembl ID might not 
 #' work). When specified \code{features} are not qualified for this, users may 
 #' try to specify \code{featureName} to change the identifier type to pass to 
 #' EnrichR. 

 #' @param inSCE A \linkS4class{SingleCellExperiment} object.

 #' @param features Character vector, selected genes for enrichment analysis. 

 #' @param analysisName A string that identifies each specific analysis.

 #' @param db Character vector. Selected database name(s) from the enrichR 

 #' database list. If \code{NULL} then EnrichR will be run on all the available 
 #' databases on the enrichR database. See details. Default \code{NULL}
 #' @param by Character. From where should we find the \code{features}? 
 #' \code{"rownames"} for from \code{rownames(inSCE)}, otherwise, from a column
 #' of feature metadata (\code{rowData(inSCE)[[by]]}). See details. Default 
 #' \code{"rownames"}.
 #' @param featureName Character. Indicates the actual feature identifiers to be
 #' passed to EnrichR. Can be \code{"rownames"}, a column in feature metadata 
 #' (\code{rowData(inSCE)[[featureName]]}), or a character vector with its length
 #' equals to \code{nrow(inSCE)}. See details. Default \code{"rownames"}.

 #' @return Updates \code{inSCE} metadata with a data.frame of enrichment terms 
 #' overlapping in the respective databases along with p-values, z-scores etc.

 #' @export

 #' @seealso \code{\link{getEnrichRResult}}

 #' @examples

 #' data("mouseBrainSubsetSCE")

 #' if (Biobase::testBioCConnection()) {
 #'   mouseBrainSubsetSCE <- runEnrichR(mouseBrainSubsetSCE, features = "Cmtm5", 
 #'                                     db = "GO_Cellular_Component_2017",
 #'                                     analysisName = "analysis1")
 #' }
 #' 

 runEnrichR <- function(inSCE, 

                        features,
                        analysisName,
                        db = NULL,
                        by = "rownames",
                        featureName = NULL) {

   if (!inherits(inSCE, "SingleCellExperiment")) {
     stop("inSCE has to inherit from SingleCellExperiment object.")
   }

   if (is.null(analysisName)) {
     stop("Have to specify analysisName.")
   }

   if (by == "rownames") {
     if (!all(features %in% rownames(inSCE))) {
       stop("Not all features found in `rownames(inSCE)`.")

     }

     allFeatures <- rownames(inSCE)
   } else {
     if (!by %in% names(SummarizedExperiment::rowData(inSCE))) {
       stop("`by` not found in rowData(inSCE).")
     }
     if (!all(features %in% SummarizedExperiment::rowData(inSCE)[[by]])) {
       stop("Not all features found in `rowData(inSCE)$",by,"`.")
     }
     allFeatures <- SummarizedExperiment::rowData(inSCE)[[by]]
   }
   if (!is.null(featureName)) {
     featureIdx <- allFeatures %in% features
     if (length(featureName) == 1) {
       if (featureName == "rownames") {
         features <- rownames(inSCE)[featureIdx]
       } else if (featureName %in% names(SummarizedExperiment::rowData(inSCE))) {
         features <- SummarizedExperiment::rowData(inSCE[featureIdx,])[[featureName]]
       } else {
         stop("featureName not found in `rowData(inSCE)`.")
       }
     } else if (length(featureName) == nrow(inSCE)) {
       features <- featureName[featureIdx]
     } else {
       stop("Invalid featureName specification.")

     }
   }

   internetConnection <- suppressWarnings(Biobase::testBioCConnection())
   #check for internet connection
   if (!internetConnection){
     stop("Please connect to the Internet and continue..")
   }

   err <- tryCatch(
     {
       attachNamespace("enrichR")
     },
     error = function(e) {}
   )
   #options(enrichR.base.address = "https://maayanlab.cloud/Enrichr/")
   #options(enrichR.live = TRUE)

   temp_db <- enrichR::listEnrichrDbs()
   enrdb <- temp_db$libraryName

   #test for db existing

   if (is.null(db)){
     db <- enrdb
   } else if (!all(db %in% enrdb)){
     db.notFound <- db[!db %in% enrdb]
     stop("database ", paste(db.notFound, collapse = ", "), " do not exist.")

   }

   enriched <- enrichR::enrichr(features, db)

   enriched <- data.frame(data.table::rbindlist(enriched, use.names = TRUE,
                                                fill = TRUE,
                                                idcol = "Database_selected"))
   
   enriched$link <- vapply(enriched$Database_selected, function(x){
     temp_db$link[temp_db$libraryName %in% x]
   }, FUN.VALUE = character(1))
   
   #sort the results based on p-values
   enriched <- enriched[order(enriched$P.value, decreasing = FALSE), ]
   
   #round the numeric values to their 7th digit
   #nums <- vapply(enriched, is.numeric, FUN.VALUE = logical(1))
   #enriched[, nums] <- round(enriched[, nums], digits = 7)
   

   getEnrichRResult(inSCE, analysisName) <- list(result = enriched,
                                                 param = list(
                                                   features = features,
                                                   by = by,
                                                   db = db
                                                 )) 

   return(inSCE)
 }

 #' @title Get or Set EnrichR Result
 #' @rdname getEnrichRResult
 #' @param inSCE A \linkS4class{SingleCellExperiment} object.

 #' @param analysisName A string that identifies each specific analysis

 #' @param value The EnrichR result table
 #' @return For getter method, a data.frame of the EnrichR result;
 #' For setter method, \code{inSCE} with EnrichR results updated.
 #' @export
 #' @seealso \code{\link{runEnrichR}}
 #' @examples 
 #' data("mouseBrainSubsetSCE")

 #' if (Biobase::testBioCConnection()) {
 #'   mouseBrainSubsetSCE <- runEnrichR(mouseBrainSubsetSCE, features = "Cmtm5", 
 #'                                     db = "GO_Cellular_Component_2017",
 #'                                     analysisName = "analysis1")
 #'   result <- getEnrichRResult(mouseBrainSubsetSCE, "analysis1")
 #' }
 setGeneric("getEnrichRResult<-", function(inSCE, analysisName, value) 

   standardGeneric("getEnrichRResult<-"))

 #' @rdname getEnrichRResult
 #' @export

 setGeneric("getEnrichRResult", function(inSCE, analysisName) 

   standardGeneric("getEnrichRResult"))

 #' @rdname getEnrichRResult
 #' @export
 setMethod("getEnrichRResult", 
           "SingleCellExperiment", 

           function(inSCE, analysisName){
             if (!"runEnrichR" %in% names(S4Vectors::metadata(inSCE)$sctk)) {
               stop("EnrichR analysis not performed yet. ",
                    "Please run `runEnrichR()`")
             }
             if (!analysisName %in% names(S4Vectors::metadata(inSCE)$sctk$runEnrichR)) {
               stop('"', analysisName, '" not found in EnrichR analysis names.')
             }
             return(S4Vectors::metadata(inSCE)$sctk$runEnrichR[[analysisName]])

           })
 
 #' @rdname getEnrichRResult
 #' @export
 setReplaceMethod("getEnrichRResult", 
                  c("SingleCellExperiment"), 

                  function(inSCE, analysisName, value) {

                    if (is.null(analysisName)) {
                      stop("Have to specify analysisName.")
                    }

                    S4Vectors::metadata(inSCE)$sctk$runEnrichR[[analysisName]] <- value

                    return(inSCE)

                  })