#!/bin/sh
#
# A posix sh CGI script (yeah, that's right) to update the daily
# code for CharmBypass. This is not useful to you unless you
# host CharmBypass on a public web server and are insane.
#
# Fail on the first error.
set -e
# The CGI spec says that the current working directory SHOULD be set
# to the directory containing the script. Well, that's not always what
# happens. It's true in apache...
INDEX_HTML=$(pwd)/../index.html
# But not in python's server.http
[ -f "${INDEX_HTML}" ] || INDEX_HTML=$(pwd)/index.html
# Die with an error. The first argument, an HTTP status code, is
# returned as the Status. The second argument, an error message, is
# printed after setting the Content-type to text/plain. Finally, we
# cease execution.
die() {
echo "Status: ${1}"
echo "Content-type: text/plain"
echo ""
echo "${2}"
exit 1
}
# Redirect to the given URL; return a 302 status, and send the
# necessary location header.
redirect() {
echo "Status: 302"
echo "Location: ${1}"
echo ""
exit
}
# Parse and return the daily code from the index.html file.
# This relies on "implementation details" within the HTML;
# namely, the field name and its value must appear next
# to each other on the same line.
parse_code() {
sed -n \
-e 's/.*name="code" value="\([A-Za-z0-9]\{2\}\)".*/\1/p' \
"${INDEX_HTML}" \
| head -n 1
}
# Update (replace) the daily code in the index.html file. The first
# argument is the new code to use. This relies on "implementation
# details" within the HTML; namely, the field name and its value must
# appear next to each other on the same line.
update_code() {
_new_code="${1}"
_find='name="code" value="[a-zA-Z0-9]\{0,2\}"'
_replace="name=\"code\" value=\"${_new_code}\""
_tmp=$(mktemp)
# The "-i" flag to sed isn't POSIX, and worse, it tries to use a
# temp file in CWD. We don't want to make the parent directory
# writable because then this script is writable.
sed -e "s/${_find}/${_replace}/g" "${INDEX_HTML}" > "${_tmp}"
# mv would also recreate the file here, so cp/rm instead.
cp "${_tmp}" "${INDEX_HTML}"
rm "${_tmp}"
}
# Display the "update code" form and exit.
display_code_form() {
echo "Content-type: text/html"
echo ""
cat <<-EOF
CharmBypass: got that transit equity