R dropbox persistency

R_dropbox_persistency.R

library(rdrop2)

## This script uses both local storage and dropbox to store files. When saving, the file is saved in both locations.
## When loading, the file is first looked for locally, and if not found, is looked for on dropbox.
## Could be used in services such as shinyapps in which you don't have access to persistent storage on the machine.
## Note that you have to authenticate your dropbox API before using rdrop2's methods.

## Global param to set dropbox interface on/off
USE_DROPBOX <<- T

## Writes a data frame to dropbox.
## similar to write.csv(...)
saveDfToDropbox <- function(df,folder = "data",filename,...){
  filepath <- paste0(folder,"/",filename)
  write.csv(x = df, file = filepath,row.names=FALSE,na="",...)
  if(USE_DROPBOX){
    saveFileToDropbox(filepath,folder = folder)
  }
}

## Copies a file from the local machine to dropbox
saveFileToDropbox <- function(filepath,folder = "data") {
  # Upload the file to Dropbox
  drop_upload(filepath, dest = folder)
}

## same as read.csv(...)
loadFromDropbox <- function(filepath,localpath = getwd(),...) {
  if(file.exists(filepath)){
    data <- read.csv(file = filepath,...)
  } else{
    if(USE_DROPBOX && fileExistsOnDropbox(filepath)){
      data <- drop_read_csv(file = filepath,dest = localpath,...)
    } else{
      data <- NULL
    }
  }
  if(is.null(data)){
    return(data.frame())
  }
  data
}

## Checks if a file exists at a specific path
## same as file.exists(...)
fileExistsOnDropbox <- function(filepath){
  if(USE_DROPBOX){
    drop_exists(filepath)
  } else{
    file.exists(filepath)
  }
}

## Lists all the files in a specific path
## same as list.files()
listFilesDropbox <- function(path){
  if(USE_DROPBOX){
    files <- drop_dir(path)
    files.list <- gsub(path,"",files$path)
    files.list <- gsub("/","",files.list)
  } else{
    files.list <- list.files(paste0(getwd(),"/",path))
  }
  files.list
  
}