#!/bin/bash
# Generate HTML header
#
#  Copyright (C) 2019 Mike Gerwitz
#
#  This program is free software: you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation, either version 3 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
# The header is mostly static but contains a dynamic page type and title.
##

set -euo pipefail

declare -ri EX_USAGE=64


# Generate header by populating @PAGE_{TITLE,TYPE}@.  If no title is given,
# then the title will be completely omitted.  If provided, it will have an
# em dash delimiter appended, with whitespace on both sides for visual
# clarity (contrary to my usual typographical conventions).
main()
{
  local -r type=${1?Missing type}
  local -r title_orig=${2:-}

  local -r title=${title_orig/&/\\&amp;}

  [[ $type =~ ^[a-z]+$ ]] || {
    echo 'error: type must be an all-lowercase word'
    exit $EX_USAGE
  }

  [[ ! $title =~ \# ]] || {
    echo "error: title must not contain \`#'"
    exit $EX_USAGE
  }

  sed "s#@PAGE_TITLE@#$title${title:+ \\&mdash; }#g
       s#@PAGE_TYPE@#$type#g
       /<style>/rinline.css" \
      src/header.tpl.htm
}

main "$@"