namespace eval ::PackageDownloader {
  #
  # NOTE: This procedure sets up the default values for all URN configuration
  #       parameters used by the package downloader client.  If the force
  #       argument is non-zero, any existing values will be overwritten and
  #       set back to their default values.
  #
  proc setupDownloadServerVars { force } {
    #
    # NOTE: The URN, relative to the base URI, where the Package Signing Key
    #       may be downloaded.
    #
    variable openPgpKeyUrn; # DEFAULT: pkg_key

    if {$force || ![info exists openPgpKeyUrn]} then {

    variable logoutUrn; # DEFAULT: pkgd_logout

    if {$force || ![info exists logoutUrn]} then {
      set logoutUrn pkgd_logout
    }
  }

  #
  # NOTE: This procedure sets up the default values for all version
  #       configuration parameters used by the package downloader client.
  #       If the force argument is non-zero, any existing values will be
  #       overwritten and set back to their default values.
  #
  proc setupDownloadVersionVars { force } {
    #
    # NOTE: The name of the branch where the package files should be fetched
    #       from.
    #
    variable branchName; # DEFAULT: trunk

    if {$force || ![info exists branchName]} then {
      set branchName trunk
    }
  }

  #
  # NOTE: This procedure sets up the default values for all URI configuration
  #       parameters used by the package downloader client.  If the force
  #       argument is non-zero, any existing values will be overwritten and
  #       set back to their default values.
  #
  proc setupDownloadUriVars { force } {

    #
    # NOTE: The URI where the list of supported platforms for a single
    #       package may be found.
    #
    variable platformsUri; # DEFAULT: ${baseUri}/${platformsUrn}?...

    if {$force || ![info exists platformsUri]} then {
      set platformsUri {${baseUri}/${platformsUrn}?download&name=${branchName}}
    }

    #
    # NOTE: The URI where a single package file may be found.  This file will
    #       belong to a specific version of one package.
    #
    variable downloadUri; # DEFAULT: ${baseUri}/${downloadUrn}?...

    if {$force || ![info exists downloadUri]} then {
      set downloadUri [appendArgs \
          {${baseUri}/${downloadUrn}?download&ci=${branchName}&} \
          {[uriEscape filename $fileName]}]
    }

    #
    # NOTE: The URI where a logout request should be sent.  This should
    #       return a payload indicating that the logout was successful.
    #

      set loginUrn [appendArgs pkgd_login_ $serverId]
      set downloadUrn [appendArgs pkgd_file_ $serverId]
      set logoutUrn [appendArgs pkgd_logout_ $serverId]
    } else {
      #
      # NOTE: Forcibly reset URN variables to their default values.
      #
      setupDownloadServerVars true
    }
  }

  #
  # NOTE: This procedure modifies the version variables used by the package
  #       downloader client so that a specific version will be used.  The
  #       versionId argument must consist only of hexadecimal characters.
  #
  # <public>
  proc useVersionId { {versionId ""} } {
    variable branchName

    if {[string length $versionId] > 0 && \
        ![regexp -nocase -- {^[0-9A-F]*$} $versionId]} then {
      error "version Id must be hexadecimal"
    }

    if {[string length $versionId] > 0} then {
      #
      # NOTE: Set the variables to values that should cause the specified
      #       version Id to be used (assume the version Id itself is valid
      #       and active).
      #
      set branchName $versionId; # TODO: Translations here?
    } else {
      #
      # NOTE: Forcibly reset the variables to their default values.
      #
      setupDownloadVersionVars true
    }
  }

  #
  # NOTE: This procedure escapes a single name/value pair for use in a URI
  #       query string.  The name argument is the name of the parameter.
  #       The value argument is the value of the parameter.

  #       directory on the package file server and may be an empty string.
  #       The fileNames argument is the list of file names to be downloaded.
  #       The usePgp argument should be non-zero when an OpenPGP signature
  #       needs to be verified for the downloaded file.
  #
  proc downloadAllPlatforms { language version packageName fileNames usePgp } {
    variable baseUri
    variable branchName
    variable platformsUri
    variable platformsUrn
    variable temporaryRootDirectory

    set temporaryDirectory [file join \
        $temporaryRootDirectory [appendArgs \
        pkgd_plat_ [::PackageRepository::getUniqueSuffix]]]

  #       file should be written.  The usePgp argument should be non-zero when
  #       the OpenPGP signature file needs to be verified for the downloaded
  #       file.
  #
  proc downloadOneFile {
          language version platform fileName localFileName usePgp } {
    variable baseUri
    variable branchName
    variable downloadUri
    variable downloadUrn

    #
    # NOTE: First, build the full relative file name to download from
    #       the remote package repository.
    #

  #
  # NOTE: Setup the variables, within this namespace, used by this script.
  #
  setupDownloadVars [info script]

  #
  # NOTE: Setup the server, version, and URI variables, in this namespace,
  #       that are used by this script.
  #
  setupDownloadServerVars false
  setupDownloadVersionVars false
  setupDownloadUriVars false

  #
  # NOTE: If necessary, add the package persistence root directory to the
  #       auto-path for the current language.  This will only be done if
  #       it falls outside of the existing auto-path.
  #
  variable persistentRootDirectory