#!/bin/sh -eu
# vim: set ts=4 sw=4 et:

BODY_TX_TIMEOUT=${BODY_TX_TIMEOUT:-3}
REQUEST_TIMEOUT=${REQUEST_TIMEOUT:-$((BODY_TX_TIMEOUT + 3))}

fin() {
	printf "HTTP/1.1 %d \r\n" "$1" >&4
	printf "Content-Type: text/plain;charset=utf-8\r\n" >&4
	printf "Content-Length: %d\r\n" "${#2}" >&4
	printf "Access-Control-Allow-Origin: *\r\n" >&4
	printf "\r\n" >&4
	printf "%s" "$2" >&4
	[ "$1" -eq 200 ] && exit 0
	exit 1
}

if test ! "${1:-}" = "client"; then
	export MAX_BODY=${MAX_BODY:-65536}
	PORT=${PORT:-20021}

	usage() {
		cat <<EOF >&2
Usage: $0 filter_cmd | ...

Read and filter points from a HTTP POST request.
For example from http://sol.alinkspace.org/web-sign
The filter command is called for every HTTP Post request
This command should output the points it accepts to stdout or exit with an error code
The accepted points are put on stdin for further processing

Examples:
    
    $0 lk filter query "hello:[#:pub]:/world//*" | lk f

    $0 lk filter one-of domain test | LKDB=$HOME/test lk save 

    $0 lk filter fset -- ":[#:test]:[kv**:friends]"  > ./friends.spool

NOTE: The input CAN contain multiple points. use lk filter --limit 1 ... to disallow.

PORT=$PORT
MAX_BODY=$MAX_BODY
REQUEST_TIMEOUT=$REQUEST_TIMEOUT
BODY_TX_TIMEOUT=$BODY_TX_TIMEOUT

Error: $1
EOF
		exit 1
	}

	command -v lk >/dev/null || usage "missing lk binary"

	echo "Accepting HTTP POST requests on port: ${PORT}" >&2

	# store cmd & arguments so we can call it later with ... | xargs -a $fargv $fcmd
	if [ "${1+isset}" = isset ]; then
		export fcmd="${1:-cat}"
		command -v "$fcmd" >/dev/null || usage "unknown cmd $fcmd"
		shift
		if [ "${1+isset}" = isset ]; then
			export fargv="$(mktemp)"
			printf '%s\0' "$@" >"$fargv"
		fi
		printf "filtering using: %s %s" "$fcmd" "$*" >&2
	fi

	cleanup() {
		trap '' TERM
		kill -- -$$ || echo already closing
		exit 0
	}
	trap 'cleanup' TERM INT

	# start receiving - run this script in client mode
	socat tcp-listen:$PORT,fork exec:"timeout $REQUEST_TIMEOUT \"$0\" client",fdout=4
	cleanup
fi

read -r HEAD
case "$HEAD" in
"POST"*) ;;
*) fin 404 "method not supported" ;;
esac

CONTENT_LEN=0
for i in $(seq 1 32); do
	read -r line || fin 500 "bad header"
	line="${line%?}"
	case "$line" in
	"Content-Length: "*[!0-9]*) fin 418 "Teabag available on request" ;;
	"Content-Length: "*) CONTENT_LEN="${line#Content-Length: }" ;;
	"") break ;;
	*) [ "$i" -eq 32 ] && fin 500 "too many headers" ;;
	esac
done

if ! [ "$CONTENT_LEN" -gt 68 ] || ! [ "$CONTENT_LEN" -le "$MAX_BODY" ]; then
	fin 500 "expects between 68 and 65536 bytes"
fi

read_body() {
	timeout "$BODY_TX_TIMEOUT" dd count=1 bs="$CONTENT_LEN" status=none
}

filter() {
	case "${fcmd:+FILTER}_${fargv:+FARGV}" in
	"_") cat - ;;
	"FILTER_") $fcmd || fin 401 "not accepted" && exit ;;
	"FILTER_FARGV") xargs -a "$fargv" -0 "$fcmd" || fin 401 "not accepted" && exit ;;
	esac
}

ack_point() {
	lk link http-rx::/ack -t ack --forward /stdout --write "[point:http-reply]/fd:4" || false
}

read_body | filter | ack_point || fin 500 "Server pipe error"