#! /bin/sh
# vim:set fdm=marker:
set -euf

Server='htgen-plain/1.0'

## htgen --serve {{{
case $# in
  (1)
    case "$1" in
      (--serve)
        HTGEN_HOST="${HTGEN_HOST-0.0.0.0}"
        HTGEN_PORT="${HTGEN_PORT-42380}"
        TCPSERVER_OPTS='-c 423 -t 2 -D'
        echo "#### $Server $HTGEN_HOST:$HTGEN_PORT" >&2
        exec tcpserver $TCPSERVER_OPTS "$HTGEN_HOST" "$HTGEN_PORT" "$0"
        ## this should not happen...
        exit 23
    esac
esac
## }}}

## reply_404 {{{
reply_404() {
  cat<<EOF
HTTP/1.0 404 Not Found
Content-Type: text/plain; charset=UTF-8
Server: $Server
Connection: close
Content-Length: 0

EOF
}
## }}}

## date. {{{
#date=`date --rfc-3339=ns`
date="`date '+%Y-%m-%d %H:%M:%S'`"
cat>&2<<EOF

# ${TCPREMOTEHOST-}[$TCPREMOTEIP]:$TCPREMOTEPORT connected at $date over $PROTO
EOF
## }}}
## Parse Request-Line. {{{
read Request_Line
eval "$(echo "$Request_Line" | sed -rn '
  s^([a-zA-Z]+) ([a-zA-Z0-9?&+*/.-]+) HTTP/([0-9]+\.[0-9]+)\r$\
     Request_Line="&"\
     Method="\1"\
     Request_URI="\2"\
     HTTP_Version="\3"\
   p;t;i\
     Request_Line= # invalid request
')"
#echo "Request-Line: $Request_Line" >&2
# cat>&2<<EOF
# Request_Line='$Request_Line'
# Method='$Method'
# Request_URI='$Request_URI'
# HTTP_Version='$HTTP_Version'
# EOF

## debug
cat>&2<<EOF
$Method $Request_URI HTTP/$HTTP_Version
EOF
## }}}
## Parse HTTP-Headers. {{{
# TODO support https://tools.ietf.org/html/rfc7230#section-3.2.4, obs-fold?
# TODO allow headers to appear multiple times
k=
v=
while read -r line; do
  line=${line%
}
  case $line in
    '')
      break
      ;;
    [A-Za-z][0-9A-Za-z-]*:*)
      k=${line%%:*}
      k=${k//-/_}
      k=${k,,}
      k=req_$k
      v=${line#*: }
      v=${v## }
      printf '%s=%s\n' "$k" "$v" >&2
      export "$k=$v"
      ;;
  esac
done
unset k v

echo >&2
## }}}

find_item() {
  if test ${#1} -ge 7; then
    set -- "$(find "$STATEDIR/items" -type f -mindepth 1 -maxdepth 1 \
        -regex "$STATEDIR/items/$1[0-9A-Za-z]*$")"
    if test $(printf '%s' "$1" | wc -l) = 1; then
      echo "$1"
      return 0
    fi
  fi
  return 1
}

# run server: STATEDIR=/tmp/htgen-state HTGEN_PORT=1080 ./htgen --serve
# paste: echo lol | curl http://localhost:1080 -d @-
case "$Method $Request_URI" in
  "GET /"[0-9a-z]*)
      if item=$(find_item ${Request_URI:1}); then
        printf 'HTTP/1.1 200 OK\r\n'
        printf 'Content-Type: %s\r\n' "$(file -ib $item)"
        printf 'Server: %s\r\n' "$Server"
        printf 'Connection: close\r\n'
        printf 'Content-Length: %d\r\n' $(wc -c < $item)
        printf '\r\n'
        cat $item
        exit
      fi
    ;;
  "POST /")
    content=$(mktemp -t htgen.$$.content.XXXXXXXX)
    trap "rm $content >&2" EXIT

    case ${req_expect-} in 100-continue)
      printf 'HTTP/1.1 100 Continue\r\n\r\n'
    esac

    head -c $req_content_length > $content

    sha256=$(sha256sum -b $content | cut -d\  -f1)
    base32=$(nix-hash --to-base32 --type sha256 $sha256)
    item=$STATEDIR/items/$base32
    ref=http://$req_host/$base32

    if ! test -e $item; then
      mkdir -v -p $STATEDIR/items >&2
      cp -v $content $item >&2
    fi

    if item=$(find_item ${base32:0:7}); then
      ref=$(echo "$ref"; echo "http://$req_host/${base32:0:7}")
    fi

    printf 'HTTP/1.1 200 OK\r\n'
    printf 'Content-Type: text/plain; charset=UTF-8\r\n'
    printf 'Server: %s\r\n' "$Server"
    printf 'Connection: close\r\n'
    printf 'Content-Length: %d\r\n' $(expr ${#ref} + 1)
    printf '\r\n'
    printf '%s\n' "$ref"

    exit
  ;;
esac

reply_404
exit