#!/usr/bin/env bash
# bollux: a bash gemini client or whatever
# Author: Case Duckworth <acdw@acdw.net>
# License: MIT
# Version: -0.8

set -euo pipefail

### constants ###
PRGN="${0##*/}"                # program name
DLDR="${BOLLUX_DOWNDIR:-.}"    # where to download
LOGL="${BOLLUX_LOGLEVEL:-3}"   # log level
MAXR="${BOLLUX_MAXREDIR:-5}"   # max redirects
PORT="${BOLLUX_PORT:-1965}"    # port number
PROT="${BOLLUX_PROTO:-gemini}" # protocol
RDRS=0                         # redirects

# LOGLEVELS:
# 0 - application fatal error
# 1 - application warning
# 2 - response error
# 3 - response logging
# 4 - application logging
# 5 - diagnostic

### utility functions ###
# a better echo
put() { printf '%s\n' "$*"; }

# conditionally log events to stderr
# lower = more important
log() { # log [LEVEL] [<] MESSAGE
	case "$1" in
	[0-5])
		lvl="$1"
		shift
		;;
	*) lvl=4 ;;
	esac

	output="$*"
	if ((lvl < LOGL)); then
		if (($# == 0)); then
			while IFS= read -r line; do
				output="$output${output:+$'\n'}$line"
			done
		fi
		printf '\e[3%dm%s\e[0m:\t%s\n' "$((lvl + 1))" "$PRGN" "$output" >&2
	fi
}

# halt and catch fire
die() { # die [EXIT-CODE] MESSAGE
	case "$1" in
	[0-9]*)
		ec="$1"
		shift
		;;
	*) ec=1 ;;
	esac

	log 0 "$*"
	exit "$ec"
}

# fail if something isn't installed
require() { hash "$1" 2>/dev/null || die 127 "Requirement '$1' not found."; }

# trim a string
trim() { sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//'; }

# stubs for when things aren't implemented (fully)
NOT_IMPLEMENTED() { die 200 "NOT IMPLEMENTED!!!"; }
NOT_FULLY_IMPLEMENTED() { log 1 "NOT FULLY IMPLEMENTED!!!"; }

### gemini ###
# normalize a gemini address
# example.com => gemini://example.com/
_address() { # _address URL
	addr="$1"
	[[ "$addr" != *://* ]] && addr="$PROT://$addr"
	trim <<<"$addr"
}

# return only the server part from an address, with the port added
# gemini://example.com/path/to/file => example.com:1965
_server() {
	serv="$(_address "$1")" # normalize first
	serv="${serv#*://}"
	serv="${serv%%/*}"
	if [[ "$serv" != *:* ]]; then
		serv="$serv:$PORT"
	fi
	trim <<<"$serv"
}

# request a gemini page
# by default, extract the server from the url
request() { # request [-s SERVER] URL
	case "$1" in
	-s)
		serv="$(_server "$2")"
		addr="$(_address "$3")"
		;;
	*)
		serv="$(_server "$1")"
		addr="$(_address "$1")"
		;;
	esac

	log 5 "serv: $serv"
	log 5 "addr: $addr"

	t="$(mktemp)"

	sslcmd=(openssl s_client -crlf -ign_eof -quiet -connect "$serv")
	log "${sslcmd[@]}"
	"${sslcmd[@]}" <<<"$addr" 2>"$t"

	((LOGL > 4)) && cat "$t"
	rm "$t"
}

# handle the response
# cf. gemini://gemini.circumlunar.space/docs/spec-spec.txt
handle() { # handle URL < RESPONSE
	url="$(_address "$1")"
	resp="$(cat)"
	head="$(sed 1q <<<"$resp")"
	body="$(sed 1d <<<"$resp")"

	code="$(awk '{print $1}' <<<"$head")"
	meta="$(awk '{for(i=2;i<=NF;i++)printf "%s ",$i;printf "\n"}' <<<"$head")"

	log 5 "[$code]	$meta"

	case "$code" in
	1*) # INPUT
		log 3 "Input"
		put "$meta"
		read -rep "? "
		bollux "$url?$REPLY"
		;;
	2*) # SUCCESS
		log 3 "Success"
		case "$code" in
		20) log 5 "- OK" ;;
		21) log 5 "- End of client certificate session" ;;
		*) log 2 "- Unknown response code: '$code'." ;;
		esac
		display <<<"$body"
		;;
	3*) # REDIRECT
		log 3 "Redirecting"
		case "$code" in
		30) log 5 "- Temporary" ;;
		31) log 5 "- Permanent" ;;
		*) log 2 "- Unknown response code: '$code'." ;;
		esac
		((RDRS+=1))
		((RDRS > MAXR)) && die "$code" "Too many redirects!"
		bollux "$meta"
		;;
	4*) # TEMPORARY FAILURE
		log 2 "Temporary failure"
		case "$code" in
		41) log 5 "- Server unavailable" ;;
		42) log 5 "- CGI error" ;;
		43) log 5 "- Proxy error" ;;
		44) log 5 "- Rate limited" ;;
		*) log 2 "- Unknown response code: '$code'." ;;
		esac
		exit "$code"
		;;
	5*) # PERMANENT FAILURE
		log 2 "Permanent failure"
		case "$code" in
		51) log 5 "- Not found" ;;
		52) log 5 "- No longer available" ;;
		53) log 5 "- Proxy request refused" ;;
		59) log 5 "- Bad request" ;;
		*) log 2 "- Unknown response code: '$code'." ;;
		esac
		exit "$code"
		;;
	6*) # CLIENT CERT REQUIRED
		log 2 "Client certificate required"
		case "$code" in
		61) log 5 "- Transient cert requested" ;;
		62) log 5 "- Authorized cert required" ;;
		63) log 5 "- Cert not accepted" ;;
		64) log 5 "- Future cert rejected" ;;
		65) log 5 "- Expired cert rejected" ;;
		*) log 2 "- Unknown response code: '$code'." ;;
		esac
		exit "$code"
		;;
	*) # ???
		die "$code" "Unknown response code: '$code'."
		;;
	esac
}

# display the page
display() { # display <<< STRING
	# normalize line endings to "\n"
	awk 'BEGIN{RS=""}{gsub("\r\n?","\n");print}'
	# TODO: use less with linking and stuff
	# less -R -p'^=>' +g
	# lesskey:
	# l /=>\n # highlight links
	# o pipe \n open_url # open the link on the top line
	# u shell select_url % # shows a selection prompt for all urls (on screen? file?)
	# Q exit 1  # for one of these, show a selection prompt for urls
	# q exit 0  # for the other, just quit
	###
	# also look into the prompt, the filename, and input preprocessor
	# ($LESSOPEN, $LESSCLOSE)
}

### main entry point ###
bollux() {
	if (($# == 1)); then
		url="$1"
	else
		read -rp "GO> " url
	fi

	log 5 "url : $url"
	log 5 "addr: $(_address "$url")"
	log 5 "serv: $(_server "$url")"

	request "$url" | handle "$url"
}

if [[ "${BASH_SOURCE[0]}" == "$0" ]]; then
	# requirements here -- so they're only checked once
	require openssl

	bollux "$@"
fi