pre_upgrade() {
  # Owner preservation (compare post_upgrade)
  if [ -d /etc/webapps/matomo ]; then
    touch /etc/webapps/matomo/.owner.tmp
  fi
  if [ -d /usr/share/webapps/matomo/plugins ]; then
    touch /usr/share/webapps/matomo/plugins/.owner.tmp
    # We’ll chown -R /usr/share/webapps/matomo before getting to plugins, so
    # must move it to a different directory so we don’t accidentally chmod it!
    mv /usr/share/webapps/matomo/plugins/.owner.tmp /tmp/matomo-plugins-owner.tmp
  fi

  # The rest is 3.4.0-1 → 3.5.1-1 or later upgrade matters.
  if [ ! -L /usr/share/webapps/matomo/tmp ]; then
    # It’s a directory rather than a symlink: gotta be pre-3.5.1-1.
    install -dm700 /var/lib/webapps/matomo
    mv /usr/share/webapps/matomo/tmp /var/lib/webapps/matomo/tmp
    chown -R http:http /var/lib/webapps/matomo
    # No changes needed in /usr/share/webapps/matomo/config, it’ll upgrade cleanly.
    echo 'matomo 3.5.1-1 onward has some location and permissions changes to be aware'
    echo 'of. Everything necessary is moved to the new locations, so you have lost'
    echo 'nothing, and everything should continue to work just fine with no changes.'
    echo 'This is really just a FYI.'
    echo
    echo '- /usr/share/webapps/matomo/tmp is moved to /var/lib/webapps/matomo/tmp,'
    echo '  and a symlink left in its place.'
    echo
    echo '- Instead of copying global.ini.php to /etc/webapps/matomo/config.ini.php and'
    echo '  making a symlink to it in /usr/share/webapps/matomo/config, the entire'
    echo '  config directory is moved to /etc/webapps/matomo (*not* as'
    echo '  /etc/webapps/matomo/config) with a symlink in its place. Your config.ini.php'
    echo '  (which is in the same place as ever, /etc/webapps/matomo/config.ini.php)'
    echo '  is probably now rather bloated by comparison with that of a regular Matomo'
    echo '  installation, as it started as a copy of global.ini.php rather than empty.'
    echo
    echo '- The owner has changed for /usr/share/webapps/matomo: rather than http:http,'
    echo '  it’s now root:http, so that matomo itself can’t modify any of its own files.'
    echo '  Only the /var and /etc locations now, plus piwik.js and the plugins'
    echo '  directory, are writeable:'
    echo
    echo '  - /var/lib/webapps/matomo/tmp is owned by http:http because it’s essential'
    echo '    for the web server to be able to write there;'
    echo '  - /etc/webapps/matomo is owned by http:http so the installer can run;'
    echo '    but after that it need not be writeable; if you like, you can'
    echo '    `chown -R root:http /etc/webapps/matomo` for security);'
    echo '  - /usr/share/webapps/matomo/piwik.js is group-writeable because some plugins'
    echo '    want to add to it; you can `chmod g-w` it if you like, but I’m not sure if'
    echo '    that will persist across future upgrades.'
    echo '  - Actually I lied about ownership: /usr/share/webapps/matomo/plugins is'
    echo '    owned by http:http instead of root:http, so that you can add plugins from'
    echo '    the marketplace, upgrade them, and so forth. You can harden it with'
    echo '    `chown -R root:http /usr/share/webapps/matomo/plugins` if you like,'
    echo '    and this will persist across future upgrades.'
    echo
  fi
}


post_install() {
  chown -R root:http /usr/share/webapps/matomo
  chown -R http:http /usr/share/webapps/matomo/plugins
  chown -R http:http /etc/webapps/matomo
  chown -R http:http /var/lib/webapps/matomo
  echo 'matomo: you will need to hook matomo up in your http server somehow (the files'
  echo 'are in /usr/share/webapps/matomo), then go through its installer process.'
  echo 'After that, consider making the config and plugin directories read-only like'
  echo 'this (the directory owner changes will persist across matomo package upgrades):'
  echo
  echo '    chown -R root:http /etc/webapps/matomo'
  echo '    chown -R root:http /usr/share/webapps/matomo/plugins'
  echo
}


post_upgrade() {
  chown -R root:http /usr/share/webapps/matomo

  # This way, if the user did a `chown -R root:http` to make config files read-only,
  # we keep that owner after upgrade. (Yeah, it’s still not a great technique.)
  if [ -f /etc/webapps/matomo/.owner.tmp ]; then
    chown -R --reference=/etc/webapps/matomo/.owner.tmp /etc/webapps/matomo
    rm /etc/webapps/matomo/.owner.tmp
  else
    chown -R http:http /etc/webapps/matomo
  fi

  # Ditto on the plugins directory.
  if [ -f /tmp/matomo-plugins-owner.tmp ]; then
    chown -R --reference=/tmp/matomo-plugins-owner.tmp /usr/share/webapps/matomo/plugins
    rm /tmp/matomo-plugins-owner.tmp
  else
    chown -R http:http /usr/share/webapps/matomo/plugins
  fi

  # /var/lib/webapps/matomo: owner was set correctly in post_install or pre_upgrade,
  # and we don’t install any files to that directory, so no need to fiddle with it here.
}