Dataset <- R6Class(
  classname = "lgb.Dataset",
  cloneable = FALSE,
  public = list(
    
    # Finalize will free up the handles
    finalize = function() {
      
      # Check the need for freeing handle
      if (!lgb.is.null.handle(private$handle)) {
        
        # Freeing up handle
        lgb.call("LGBM_DatasetFree_R", ret = NULL, private$handle)
        private$handle <- NULL
        
      }
      
    },
    
    # Initialize will create a starter dataset
    initialize = function(data,
                          params = list(),
                          reference = NULL,
                          colnames = NULL,
                          categorical_feature = NULL,
                          predictor = NULL,
                          free_raw_data = TRUE,
                          used_indices = NULL,
                          info = list(),
                          ...) {
      
      # Check for additional parameters
      additional_params <- list(...)
      
      # Create known attributes list
      INFO_KEYS <- c("label", "weight", "init_score", "group")
      
      # Check if attribute key is in the known attribute list
      for (key in names(additional_params)) {
        
        # Key existing
        if (key %in% INFO_KEYS) {
          
          # Store as info
          info[[key]] <- additional_params[[key]]
          
        } else {
          
          # Store as param
          params[[key]] <- additional_params[[key]]
          
        }
        
      }
      
      # Check for dataset reference
      if (!is.null(reference)) {
        if (!lgb.check.r6.class(reference, "lgb.Dataset")) {
          stop("lgb.Dataset: Can only use ", sQuote("lgb.Dataset"), " as reference")
        }
      }
      
      # Check for predictor reference
      if (!is.null(predictor)) {
        if (!lgb.check.r6.class(predictor, "lgb.Predictor")) {
          stop("lgb.Dataset: Only can use ", sQuote("lgb.Predictor"), " as predictor")
        }
      }
      
      # Setup private attributes
      private$raw_data <- data
      private$params <- params
      private$reference <- reference
      private$colnames <- colnames

      private$categorical_feature <- categorical_feature
      private$predictor <- predictor
      private$free_raw_data <- free_raw_data
      private$used_indices <- used_indices
      private$info <- info
      
    },
    
    create_valid = function(data,
                            info = list(),
                            ...) {
      
      # Create new dataset
      ret <- Dataset$new(data,
                         private$params,
                         self,
                         private$colnames,
                         private$categorical_feature,
                         private$predictor,
                         private$free_raw_data,
                         NULL,
                         info,
                         ...)
      
      # Return ret
      return(ret)
      
    },
    
    # Dataset constructor
    construct = function() {
      
      # Check for handle null
      if (!lgb.is.null.handle(private$handle)) {
        return(self)
      }
      
      # Get feature names
      cnames <- NULL
      if (is.matrix(private$raw_data) || is(private$raw_data, "dgCMatrix")) {
        cnames <- colnames(private$raw_data)
      }
      
      # set feature names if not exist
      if (is.null(private$colnames) && !is.null(cnames)) {
        private$colnames <- as.character(cnames)
      }
      
      # Get categorical feature index
      if (!is.null(private$categorical_feature)) {
        
        # Check for character name
        if (typeof(private$categorical_feature) == "character") {
          
            cate_indices <- as.list(match(private$categorical_feature, private$colnames) - 1)
            
            # Provided indices, but some indices are not existing?
            if (sum(is.na(cate_indices)) > 0) {
              stop("lgb.self.get.handle: supplied an unknown feature in categorical_feature: ", sQuote(private$categorical_feature[is.na(cate_indices)]))
            }
            
          } else {
            
            # Check if more categorical features were output over the feature space
            if (max(private$categorical_feature) > length(private$colnames)) {
              stop("lgb.self.get.handle: supplied a too large value in categorical_feature: ", max(private$categorical_feature), " but only ", length(private$colnames), " features")
            }
            
            # Store indices as [0, n-1] indexed instead of [1, n] indexed
            cate_indices <- as.list(private$categorical_feature - 1)
            
          }
        
        # Store indices for categorical features
        private$params$categorical_feature <- cate_indices
        
      }
      
      # Check has header or not
      has_header <- FALSE
      if (!is.null(private$params$has_header) || !is.null(private$params$header)) {
        if (tolower(as.character(private$params$has_header)) == "true" || tolower(as.character(private$params$header)) == "true") {
          has_header <- TRUE
        }
      }
      
      # Generate parameter str
      params_str <- lgb.params2str(private$params)
      
      # Get handle of reference dataset
      ref_handle <- NULL
      if (!is.null(private$reference)) {
        ref_handle <- private$reference$.__enclos_env__$private$get_handle()
      }
      handle <- lgb.new.handle()
      
      # Not subsetting
      if (is.null(private$used_indices)) {
        
        # Are we using a data file?
        if (is.character(private$raw_data)) {
          
          handle <- lgb.call("LGBM_DatasetCreateFromFile_R",
                             ret = handle,
                             lgb.c_str(private$raw_data),
                             params_str,
                             ref_handle)
          
        } else if (is.matrix(private$raw_data)) {
          
          # Are we using a matrix?
          handle <- lgb.call("LGBM_DatasetCreateFromMat_R",
                             ret = handle,
                             private$raw_data,
                             nrow(private$raw_data),
                             ncol(private$raw_data),
                             params_str,
                             ref_handle)
          
        } else if (is(private$raw_data, "dgCMatrix")) {
          
          # Are we using a dgCMatrix (sparsed matrix column compressed)
          handle <- lgb.call("LGBM_DatasetCreateFromCSC_R",
                             ret = handle,
                             private$raw_data@p,
                             private$raw_data@i,
                             private$raw_data@x,
                             length(private$raw_data@p),
                             length(private$raw_data@x),
                             nrow(private$raw_data),
                             params_str,
                             ref_handle)
          
        } else {
          
          # Unknown data type
          stop("lgb.Dataset.construct: does not support constructing from ", sQuote(class(private$raw_data)))
          
        }
        
      } else {
        
        # Reference is empty
        if (is.null(private$reference)) {
          stop("lgb.Dataset.construct: reference cannot be NULL for constructing data subset")
        }
        
        # Construct subset
        handle <- lgb.call("LGBM_DatasetGetSubset_R",
                           ret = handle,
                           ref_handle,
                           private$used_indices,
                           length(private$used_indices),
                           params_str)
        
      }
      
      # Setup class and private type
      class(handle) <- "lgb.Dataset.handle"
      private$handle <- handle
      
      # Set feature names
      if (!is.null(private$colnames)) {
        self$set_colnames(private$colnames)
      }

      # Load init score if requested
      if (!is.null(private$predictor) && is.null(private$used_indices)) {
        
        # Setup initial scores
        init_score <- private$predictor$predict(private$raw_data, rawscore = TRUE, reshape = TRUE)
        
        # Not needed to transpose, for is col_marjor
        init_score <- as.vector(init_score)
        private$info$init_score <- init_score
        
      }
      
      # Should we free raw data?
      if (isTRUE(private$free_raw_data)) {
        private$raw_data <- NULL
      }
      
      # Get private information
      if (length(private$info) > 0) {
        
        # Set infos
        for (i in seq_along(private$info)) {
          
          p <- private$info[i]
          self$setinfo(names(p), p[[1]])
          
        }
        
      }
      
      # Get label information existence
      if (is.null(self$getinfo("label"))) {
        stop("lgb.Dataset.construct: label should be set")
      }
      
      # Return oneself
      return(self)
      
    },
    
    # Dimension function
    dim = function() {
      
      # Check for handle
      if (!lgb.is.null.handle(private$handle)) {
        
        num_row <- 0L
        num_col <- 0L
        
        # Get numeric data and numeric features
        c(lgb.call("LGBM_DatasetGetNumData_R", ret = num_row, private$handle),
          lgb.call("LGBM_DatasetGetNumFeature_R", ret = num_col, private$handle))
        
      } else if (is.matrix(private$raw_data) || is(private$raw_data, "dgCMatrix")) {
        
        # Check if dgCMatrix (sparse matrix column compressed)
        dim(private$raw_data)
        
      } else {
        
        # Trying to work with unknown dimensions is not possible
        stop("dim: cannot get dimensions before dataset has been constructed, please call lgb.Dataset.construct explicitly")
        
      }
      
    },
    
    # Get column names
    get_colnames = function() {
      
      # Check for handle
      if (!lgb.is.null.handle(private$handle)) {
        
        # Get feature names and write them
        cnames <- lgb.call.return.str("LGBM_DatasetGetFeatureNames_R", private$handle)
        private$colnames <- as.character(base::strsplit(cnames, "\t")[[1]])
        private$colnames
        
      } else if (is.matrix(private$raw_data) || is(private$raw_data, "dgCMatrix")) {
        
        # Check if dgCMatrix (sparse matrix column compressed)
        colnames(private$raw_data)
        
      } else {
        
        # Trying to work with unknown dimensions is not possible
        stop("dim: cannot get dimensions before dataset has been constructed, please call lgb.Dataset.construct explicitly")
        
      }
      
    },
    
    # Set column names
    set_colnames = function(colnames) {
      
      # Check column names non-existence
      if (is.null(colnames)) {
        return(self)
      }
      
      # Check empty column names
      colnames <- as.character(colnames)
      if (length(colnames) == 0) {
        return(self)
      }
      
      # Write column names
      private$colnames <- colnames
      if (!lgb.is.null.handle(private$handle)) {
        
        # Merge names with tab separation
        merged_name <- paste0(as.list(private$colnames), collapse = "\t")
        lgb.call("LGBM_DatasetSetFeatureNames_R",
                 ret = NULL,
                 private$handle,
                 lgb.c_str(merged_name))
        
      }
      
      # Return self
      return(self)
      
    },
    
    # Get information
    getinfo = function(name) {
      
      # Create known attributes list
      INFONAMES <- c("label", "weight", "init_score", "group")
      
      # Check if attribute key is in the known attribute list
      if (!is.character(name) || length(name) != 1 || !name %in% INFONAMES) {
        stop("getinfo: name must one of the following: ", paste0(sQuote(INFONAMES), collapse = ", "))
      }
      
      # Check for info name and handle
      if (is.null(private$info[[name]]) && !lgb.is.null.handle(private$handle)) {
        
        # Get field size of info
        info_len <- 0L
        info_len <- lgb.call("LGBM_DatasetGetFieldSize_R",
                             ret = info_len,
                             private$handle,
                             lgb.c_str(name))
        
        # Check if info is not empty
        if (info_len > 0) {
          
          # Get back fields
          ret <- NULL
          ret <- if (name == "group") {
            integer(info_len) # Integer
          } else {
            numeric(info_len) # Numeric
          }
          
          ret <- lgb.call("LGBM_DatasetGetField_R",
                          ret = ret,
                          private$handle,
                          lgb.c_str(name))
          
          private$info[[name]] <- ret
          
        }
      }
      
      private$info[[name]]
      
    },
    
    # Set information
    setinfo = function(name, info) {
      
      # Create known attributes list
      INFONAMES <- c("label", "weight", "init_score", "group")
      
      # Check if attribute key is in the known attribute list
      if (!is.character(name) || length(name) != 1 || !name %in% INFONAMES) {
        stop("setinfo: name must one of the following: ", paste0(sQuote(INFONAMES), collapse = ", "))
      }
      
      # Check for type of information
      info <- if (name == "group") {
        as.integer(info) # Integer
      } else {
        as.numeric(info) # Numeric
      }
      
      # Store information privately
      private$info[[name]] <- info
      
      if (!lgb.is.null.handle(private$handle) && !is.null(info)) {
        
        if (length(info) > 0) {
          
          lgb.call("LGBM_DatasetSetField_R",
                   ret = NULL,
                   private$handle,
                   lgb.c_str(name),
                   info,
                   length(info))
          
        }
        
      }
      
      # Return self
      return(self)
      
    },
    
    # Slice dataset
    slice = function(idxset, ...) {
      
      # Perform slicing
      Dataset$new(NULL,
                  private$params,
                  self,
                  private$colnames,
                  private$categorical_feature,
                  private$predictor,
                  private$free_raw_data,
                  idxset,
                  NULL,
                  ...)
      
    },
    
    # Update parameters
    update_params = function(params) {
      
      # Parameter updating
      private$params <- modifyList(private$params, params)
      self
      
    },
    
    # Set categorical feature parameter
    set_categorical_feature = function(categorical_feature) {
      
      # Check for identical input
      if (identical(private$categorical_feature, categorical_feature)) {
        return(self)
      }
      
      # Check for empty data
      if (is.null(private$raw_data)) {
        stop("set_categorical_feature: cannot set categorical feature after freeing raw data,
          please set ", sQuote("free_raw_data = FALSE"), " when you construct lgb.Dataset")
      }
      
      # Overwrite categorical features
      private$categorical_feature <- categorical_feature
      
      # Finalize and return self
      self$finalize()
      return(self)
      
    },
    
    # Set reference
    set_reference = function(reference) {
      
      # Set known references
      self$set_categorical_feature(reference$.__enclos_env__$private$categorical_feature)
      self$set_colnames(reference$get_colnames())
      private$set_predictor(reference$.__enclos_env__$private$predictor)
      
      # Check for identical references
      if (identical(private$reference, reference)) {
        return(self)
      }
      
      # Check for empty data
      if (is.null(private$raw_data)) {
        
        stop("set_reference: cannot set reference after freeing raw data,
          please set ", sQuote("free_raw_data = FALSE"), " when you construct lgb.Dataset")
        
      }
      
      # Check for non-existing reference
      if (!is.null(reference)) {
        
        # Reference is unknown
        if (!lgb.check.r6.class(reference, "lgb.Dataset")) {
          stop("set_reference: Can only use lgb.Dataset as a reference")
        }
        
      }
      
      # Store reference
      private$reference <- reference
      
      # Finalize and return self
      self$finalize()
      return(self)
      
    },
    
    # Save binary model
    save_binary = function(fname) {
      
      # Store binary data
      self$construct()
      lgb.call("LGBM_DatasetSaveBinary_R",
               ret = NULL,
               private$handle,
               lgb.c_str(fname))
      return(self)
    }
    
  ),
  private = list(
    handle = NULL,
    raw_data = NULL,
    params = list(),
    reference = NULL,
    colnames = NULL,
    categorical_feature = NULL,
    predictor = NULL,
    free_raw_data = TRUE,
    used_indices = NULL,
    info = NULL,
    
    # Get handle
    get_handle = function() {
      
      # Get handle and construct if needed
      if (lgb.is.null.handle(private$handle)) {
        self$construct()
      }
      private$handle
      
    },
    
    # Set predictor
    set_predictor = function(predictor) {
      
      # Return self is identical predictor
      if (identical(private$predictor, predictor)) {
        return(self)
      }
      
      # Check for empty data
      if (is.null(private$raw_data)) {
        stop("set_predictor: cannot set predictor after free raw data,
          please set ", sQuote("free_raw_data = FALSE"), " when you construct lgb.Dataset")
      }
      
      # Check for empty predictor
      if (!is.null(predictor)) {
        
        # Predictor is unknown
        if (!lgb.check.r6.class(predictor, "lgb.Predictor")) {
          stop("set_predictor: Can only use lgb.Predictor as predictor")
        }
        
      }
      
      # Store predictor
      private$predictor <- predictor
      
      # Finalize and return self
      self$finalize()
      return(self)
      
    }
    
  )
)

#' Construct lgb.Dataset object
#'
#' Construct lgb.Dataset object from dense matrix, sparse matrix
#' or local file (that was created previously by saving an \code{lgb.Dataset}).
#'
#' @param data a \code{matrix} object, a \code{dgCMatrix} object or a character representing a filename
#' @param params a list of parameters
#' @param reference reference dataset
#' @param colnames names of columns
#' @param categorical_feature categorical features
#' @param free_raw_data TRUE for need to free raw data after construct
#' @param info a list of information of the lgb.Dataset object
#' @param ... other information to pass to \code{info} or parameters pass to \code{params}
#' 
#' @return constructed dataset
#' 
#' @examples
#' \dontrun{
#' library(lightgbm)
#' data(agaricus.train, package = "lightgbm")
#' train <- agaricus.train
#' dtrain <- lgb.Dataset(train$data, label = train$label)
#' lgb.Dataset.save(dtrain, "lgb.Dataset.data")
#' dtrain <- lgb.Dataset("lgb.Dataset.data")
#' lgb.Dataset.construct(dtrain)
#' }
#' 
#' @export
lgb.Dataset <- function(data,
                        params = list(),
                        reference = NULL,
                        colnames = NULL,
                        categorical_feature = NULL,
                        free_raw_data = TRUE,
                        info = list(),
                        ...) {
  
  # Create new dataset
  Dataset$new(data,
              params,
              reference,
              colnames,
              categorical_feature,
              NULL,
              free_raw_data,
              NULL,
              info,
              ...)
  
}

#' Construct validation data
#' 
#' Construct validation data according to training data
#' 
#' @param dataset \code{lgb.Dataset} object, training data
#' @param data a \code{matrix} object, a \code{dgCMatrix} object or a character representing a filename
#' @param info a list of information of the lgb.Dataset object
#' @param ... other information to pass to \code{info}.
#' 
#' @return constructed dataset
#' 
#' @examples
#' \dontrun{
#' library(lightgbm)
#' data(agaricus.train, package = "lightgbm")
#' train <- agaricus.train
#' dtrain <- lgb.Dataset(train$data, label = train$label)
#' data(agaricus.test, package = "lightgbm")
#' test <- agaricus.test
#' dtest <- lgb.Dataset.create.valid(dtrain, test$data, label = test$label)
#' }
#' 
#' @export
lgb.Dataset.create.valid <- function(dataset, data, info = list(), ...) {
  
  # Check if dataset is not a dataset
  if (!lgb.is.Dataset(dataset)) {
    stop("lgb.Dataset.create.valid: input data should be an lgb.Dataset object")
  }
  
  # Create validation dataset
  dataset$create_valid(data, info, ...)
  
}

#' Construct Dataset explicitly
#' 
#' @param dataset Object of class \code{lgb.Dataset}
#' 
#' @examples
#' \dontrun{
#' library(lightgbm)
#' data(agaricus.train, package = "lightgbm")
#' train <- agaricus.train
#' dtrain <- lgb.Dataset(train$data, label = train$label)
#' lgb.Dataset.construct(dtrain)
#' }
#' 
#' @export
lgb.Dataset.construct <- function(dataset) {
  
  # Check if dataset is not a dataset
  if (!lgb.is.Dataset(dataset)) {
    stop("lgb.Dataset.construct: input data should be an lgb.Dataset object")
  }
  
  # Construct the dataset
  dataset$construct()
  
}

#' Dimensions of an lgb.Dataset
#' 
#' Returns a vector of numbers of rows and of columns in an \code{lgb.Dataset}.
#' @param x Object of class \code{lgb.Dataset}
#' @param ... other parameters
#' 
#' @return a vector of numbers of rows and of columns
#' 
#' @details
#' Note: since \code{nrow} and \code{ncol} internally use \code{dim}, they can also
#' be directly used with an \code{lgb.Dataset} object.
#' 
#' @examples
#' \dontrun{
#' library(lightgbm)
#' data(agaricus.train, package = "lightgbm")
#' train <- agaricus.train
#' dtrain <- lgb.Dataset(train$data, label = train$label)
#' 
#' stopifnot(nrow(dtrain) == nrow(train$data))
#' stopifnot(ncol(dtrain) == ncol(train$data))
#' stopifnot(all(dim(dtrain) == dim(train$data)))
#' }
#' 
#' @rdname dim
#' @export
dim.lgb.Dataset <- function(x, ...) {
  
  # Check if dataset is not a dataset
  if (!lgb.is.Dataset(x)) {
    stop("dim.lgb.Dataset: input data should be an lgb.Dataset object")
  }
  
  # Return dimensions
  x$dim()
  
}

#' Handling of column names of \code{lgb.Dataset}
#'
#' Only column names are supported for \code{lgb.Dataset}, thus setting of
#' row names would have no effect and returned row names would be NULL.
#'
#' @param x object of class \code{lgb.Dataset}
#' @param value a list of two elements: the first one is ignored
#'        and the second one is column names
#'
#' @details
#' Generic \code{dimnames} methods are used by \code{colnames}.
#' Since row names are irrelevant, it is recommended to use \code{colnames} directly.
#'
#' @examples
#' \dontrun{
#' library(lightgbm)
#' data(agaricus.train, package = "lightgbm")
#' train <- agaricus.train
#' dtrain <- lgb.Dataset(train$data, label = train$label)
#' lgb.Dataset.construct(dtrain)
#' dimnames(dtrain)
#' colnames(dtrain)
#' colnames(dtrain) <- make.names(1:ncol(train$data))
#' print(dtrain, verbose = TRUE)
#' }
#' 
#' @rdname dimnames.lgb.Dataset
#' @export
dimnames.lgb.Dataset <- function(x) {
  
  # Check if dataset is not a dataset
  if (!lgb.is.Dataset(x)) {
    stop("dimnames.lgb.Dataset: input data should be an lgb.Dataset object")
  }
  
  # Return dimension names
  list(NULL, x$get_colnames())
  
}

#' @rdname dimnames.lgb.Dataset
#' @export
`dimnames<-.lgb.Dataset` <- function(x, value) {
  
  # Check if invalid element list
  if (!is.list(value) || length(value) != 2L) {
    stop("invalid ", sQuote("value"), " given: must be a list of two elements")
  }
  
  # Check for unknown row names
  if (!is.null(value[[1L]])) {
    stop("lgb.Dataset does not have rownames")
  }
  
  # Check for second value missing
  if (is.null(value[[2]])) {
    
    # No column names
    x$set_colnames(NULL)
    return(x)
    
  }
  
  # Check for unmatching column size
  if (ncol(x) != length(value[[2]])) {
    stop("can't assign ", sQuote(length(value[[2]])), " colnames to an lgb.Dataset with ", sQuote(ncol(x)), " columns")
  }
  
  # Set column names properly, and return
  x$set_colnames(value[[2]])
  x
  
}

#' Slice a dataset
#' 
#' Get a new \code{lgb.Dataset} containing the specified rows of
#' orginal lgb.Dataset object
#' 
#' @param dataset Object of class "lgb.Dataset"
#' @param idxset a integer vector of indices of rows needed
#' @param ... other parameters (currently not used)
#' @return constructed sub dataset
#' 
#' @examples
#' \dontrun{
#' library(lightgbm)
#' data(agaricus.train, package = "lightgbm")
#' train <- agaricus.train
#' dtrain <- lgb.Dataset(train$data, label = train$label)
#' 
#' dsub <- lightgbm::slice(dtrain, 1:42)
#' labels <- lightgbm::getinfo(dsub, "label")
#' }
#' 
#' @export
slice <- function(dataset, ...) {
  UseMethod("slice")
}

#' @rdname slice
#' @export
slice.lgb.Dataset <- function(dataset, idxset, ...) {
  
  # Check if dataset is not a dataset
  if (!lgb.is.Dataset(dataset)) {
    stop("slice.lgb.Dataset: input dataset should be an lgb.Dataset object")
  }
  
  # Return sliced set
  dataset$slice(idxset, ...)
  
}

#' Get information of an lgb.Dataset object
#' 
#' @param dataset Object of class \code{lgb.Dataset}
#' @param name the name of the information field to get (see details)
#' @param ... other parameters
#' @return info data
#' 
#' @details
#' The \code{name} field can be one of the following:
#' 
#' \itemize{
#'     \item \code{label}: label lightgbm learn from ;
#'     \item \code{weight}: to do a weight rescale ;
#'     \item \code{group}: group size
#'     \item \code{init_score}: initial score is the base prediction lightgbm will boost from ;
#' }
#' 
#' @examples
#' \dontrun{
#' library(lightgbm)
#' data(agaricus.train, package = "lightgbm")
#' train <- agaricus.train
#' dtrain <- lgb.Dataset(train$data, label = train$label)
#' lgb.Dataset.construct(dtrain)
#' 
#' labels <- lightgbm::getinfo(dtrain, "label")
#' lightgbm::setinfo(dtrain, "label", 1 - labels)
#' 
#' labels2 <- lightgbm::getinfo(dtrain, "label")
#' stopifnot(all(labels2 == 1 - labels))
#' }
#' 
#' @export
getinfo <- function(dataset, ...) {
  UseMethod("getinfo")
}

#' @rdname getinfo
#' @export
getinfo.lgb.Dataset <- function(dataset, name, ...) {
  
  # Check if dataset is not a dataset
  if (!lgb.is.Dataset(dataset)) {
    stop("getinfo.lgb.Dataset: input dataset should be an lgb.Dataset object")
  }
  
  # Return information
  dataset$getinfo(name)
  
}

#' Set information of an lgb.Dataset object
#' 
#' @param dataset Object of class "lgb.Dataset"
#' @param name the name of the field to get
#' @param info the specific field of information to set
#' @param ... other parameters
#' @return passed object
#' 
#' @details
#' The \code{name} field can be one of the following:
#' 
#' \itemize{
#'     \item \code{label}: label lightgbm learn from ;
#'     \item \code{weight}: to do a weight rescale ;
#'     \item \code{init_score}: initial score is the base prediction lightgbm will boost from ;
#'     \item \code{group}.
#' }
#' 
#' @examples
#' \dontrun{
#' library(lightgbm)
#' data(agaricus.train, package = "lightgbm")
#' train <- agaricus.train
#' dtrain <- lgb.Dataset(train$data, label = train$label)
#' lgb.Dataset.construct(dtrain)
#' 
#' labels <- lightgbm::getinfo(dtrain, "label")
#' lightgbm::setinfo(dtrain, "label", 1 - labels)
#' 
#' labels2 <- lightgbm::getinfo(dtrain, "label")
#' stopifnot(all.equal(labels2, 1 - labels))
#' }
#' 
#' @export
setinfo <- function(dataset, ...) {
  UseMethod("setinfo")
}

#' @rdname setinfo
#' @export
setinfo.lgb.Dataset <- function(dataset, name, info, ...) {
  
  # Check if dataset is not a dataset
  if (!lgb.is.Dataset(dataset)) {
    stop("setinfo.lgb.Dataset: input dataset should be an lgb.Dataset object")
  }
  
  # Set information
  dataset$setinfo(name, info)
}

#' Set categorical feature of \code{lgb.Dataset}
#' 
#' @param dataset object of class \code{lgb.Dataset}
#' @param categorical_feature categorical features
#' 
#' @return passed dataset
#' 
#' @examples
#' \dontrun{
#' library(lightgbm)
#' data(agaricus.train, package = "lightgbm")
#' train <- agaricus.train
#' dtrain <- lgb.Dataset(train$data, label = train$label)
#' lgb.Dataset.save(dtrain, "lgb.Dataset.data")
#' dtrain <- lgb.Dataset("lgb.Dataset.data")
#' lgb.Dataset.set.categorical(dtrain, 1:2)
#' }
#' 
#' @rdname lgb.Dataset.set.categorical
#' @export
lgb.Dataset.set.categorical <- function(dataset, categorical_feature) {
  
  # Check if dataset is not a dataset
  if (!lgb.is.Dataset(dataset)) {
    stop("lgb.Dataset.set.categorical: input dataset should be an lgb.Dataset object")
  }
  
  # Set categoricals
  dataset$set_categorical_feature(categorical_feature)
  
}

#' Set reference of \code{lgb.Dataset}
#' 
#' If you want to use validation data, you should set reference to training data
#' 
#' @param dataset object of class \code{lgb.Dataset}
#' @param reference object of class \code{lgb.Dataset}
#' 
#' @return passed dataset
#' 
#' @examples
#' \dontrun{
#' library(lightgbm)
#' data(agaricus.train, package ="lightgbm")
#' train <- agaricus.train
#' dtrain <- lgb.Dataset(train$data, label = train$label)
#' data(agaricus.test, package = "lightgbm")
#' test <- agaricus.test
#' dtest <- lgb.Dataset(test$data, test = train$label)
#' lgb.Dataset.set.reference(dtest, dtrain)
#' }
#' 
#' @rdname lgb.Dataset.set.reference
#' @export
lgb.Dataset.set.reference <- function(dataset, reference) {
  
  # Check if dataset is not a dataset
  if (!lgb.is.Dataset(dataset)) {
    stop("lgb.Dataset.set.reference: input dataset should be an lgb.Dataset object")
  }
  
  # Set reference
  dataset$set_reference(reference)
}

#' Save \code{lgb.Dataset} to a binary file
#' 
#' @param dataset object of class \code{lgb.Dataset}
#' @param fname object filename of output file
#' 
#' @return passed dataset
#' 
#' @examples
#' 
#' \dontrun{
#' library(lightgbm)
#' data(agaricus.train, package = "lightgbm")
#' train <- agaricus.train
#' dtrain <- lgb.Dataset(train$data, label = train$label)
#' lgb.Dataset.save(dtrain, "data.bin")
#' }
#' 
#' @rdname lgb.Dataset.save
#' @export
lgb.Dataset.save <- function(dataset, fname) {
  
  # Check if dataset is not a dataset
  if (!lgb.is.Dataset(dataset)) {
    stop("lgb.Dataset.set: input dataset should be an lgb.Dataset object")
  }
  
  # File-type is not matching
  if (!is.character(fname)) {
    stop("lgb.Dataset.set: fname should be a character or a file connection")
  }
  
  # Store binary
  dataset$save_binary(fname)
}