R/map-txt.R

In dipsaus: A Dipping Sauce for Data Analysis and Visualizations

TextMap <- R6::R6Class(
  classname = 'TextMap',
  inherit = FileMap,
  portable = TRUE,
  cloneable = TRUE,
  public = list(

    `@set` = function(key, value, signature){
      # If new key, then no-harm as there is no writing
      # self$`@remove`(key)

      # Generate filename from key
      encoded_key <- safe_urlencode(key)
      # signature is already hashed

      # save value
      fpath <- file.path(private$db_dir, encoded_key)

      tf <- tempfile()
      on.exit({ unlink(tf) })

      yaml::write_yaml(value, file = tf)
      file.copy(from = tf, to = fpath, overwrite = TRUE)

      file.copy(from = private$header_file, to = tf, overwrite = TRUE)

      write.table(
        data.frame(Key = encoded_key, Hash = signature),
        file = tf,
        sep = '|',
        append = TRUE,
        quote = FALSE,
        row.names = FALSE,
        col.names = FALSE
      )
      file.copy(from = tf, to = private$header_file, overwrite = TRUE)

      # write.table(
      #   data.frame(Key = encoded_key, Hash = signature),
      #   file = private$header_file,
      #   sep = '|',
      #   append = TRUE,
      #   quote = FALSE,
      #   row.names = FALSE,
      #   col.names = FALSE
      # )

      return( signature )
    },

    get = function(key, missing_default){
      ekey <- safe_urlencode(key)
      fpath <- file.path(private$db_dir, ekey)
      if( file.exists(fpath) ){
        yaml::read_yaml(fpath)
      }else{
        if(missing(missing_default)){ missing_default <- self$missing_default }
        missing_default
      }
    },

    initialize = function(path){
      path <- dir_create(path)
      private$root_path <- path
      private$db_dir <- dir_create(file.path(path, 'MAP-YAMLDB'))
      header_file <- file.path(path, 'MAP-YAMLHEAD')
      if( !file.exists(header_file) ){
        header_file <- file_create(header_file)
        writeLines('Key|Hash', con = header_file)
      }
      private$header_file <- header_file
      self$lockfile <- file.path(path, 'MAP-YAMLLOCK')
    }
  )
)