R/goesaodc_openScanFile.R

In MazamaScience/MazamaSatelliteUtils: Utilities for Working with Model and Satellite Data as Rasters

#' @export
#' 
#' @title Open a GOES AOD netCDF file
#' 
#' @description Opens a NetCDF file and returns the \code{nc} handle. By 
#' default, the directory specified with \code{setSatelliteDataDir()} is 
#' searched for the file.
#' 
#' @details
#' Errors generated by `nc_open()` are not handled and will pass through to the
#' console or calling function.
#' 
#' @param filename Name of scan file.
#' @param dataDir Data directory containing \code{filename}. Defaults to 
#' \code{getSatelliteDataDir()}.
#' 
#' @return NetCDF \code{ncdf4} handle.
#' 
#' @seealso \code{\link{getSatelliteDataDir}}
#' 
#' @examples
#' \dontrun{
#' library(MazamaSatelliteUtils)
#' setSatelliteDataDir("~/Data/Satellite")
#' 
#' scanFile <- goesaodc_downloadScanFiles(
#'   satID = "G16", 
#'   datetime = "2019-09-06 18:00", 
#'   timezone = "UTC"
#' )
#' 
#' goesaodc_openScanFile(scanFile)
#' }

goesaodc_openScanFile <- function(
  filename = NULL,
  dataDir = getSatelliteDataDir()
) {
  
  # ----- Validate parameters --------------------------------------------------
  
  MazamaCoreUtils::stopIfNull(filename)
  
  if ( length(filename) == 0 )
    stop("Param 'filename' must be a single filename or a list of filenames")
  
  # ----- Open nc handle -------------------------------------------------------
  
  if ( length(filename) == 1 ) {
    
    nc <- goesaodc_openSingleScanFile(filename, dataDir)
    
  } else {
    
    nc <- list()
    
    for ( fn in filename ) {
      
      # Create a label for this file in the list
      label <- 
        fn %>%
        goesaodc_convertFilenameToDatetime() %>%
        MazamaCoreUtils::timeStamp(unit = "sec", timezone = "UTC")
      
      nc[[label]] <- goesaodc_openSingleScanFile(fn, dataDir)
      
    }
    
  }
  
  # ----- Return ---------------------------------------------------------------
  
  return(nc)
  
}

# Internal helper function
goesaodc_openSingleScanFile <- function(
  filename = NULL,
  dataDir = getSatelliteDataDir()
) {
  
  # Check if internal package file is being used
  if ( stringr::str_detect(filename, "extdata") ) { 
    fullPath <- filename
  } else {
    fullPath <- file.path(dataDir, filename)
  }
  
  if ( !file.exists(fullPath) )
    stop(paste0("Cannot find ", fullPath))
  
  nc <- ncdf4::nc_open(fullPath)
  
  return(nc)
  
}