#!/bin/sh

# rsstube - get RSS feed for YouTube channels and other sites
# Copyright (C) 2019
#
# 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
# 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 <https://www.gnu.org/licenses/>.

# run from absolute path of rsstube executable
cd `dirname "$(readlink -f "$0")"`


### UTILITIES
ERR='\033[1;31m'
WARN='\033[1;33m'
NC='\033[0m'

## for general output
notify() {
	if [[ ! -n "$quiet" ]]
	then
		output "${1}"
	fi
}

## for warning-level information, output in yellow
warn() {
	if [[ ! -n "$quiet" ]]
	then
		echo -e "${WARN}${1}${NC}"
	fi
}

## for errors. cannot be silenced, output in red
error() {
	echo -e "${ERR}${1}${NC}"
}

## fail to get feed, terminate program
fail() {
	error "Unable to get RSS feed."
	exit
}

## general output, no formatting
output() {
	echo "${1}"
}

## determine whether HTTP or HTTPS
## some sites may not support HTTPS
determine_protocol() {
	protocol=${url%//*}
	if [[ $protocol == $url ]]
	then
		protocol="http://"
	else
		protocol="${protocol}//"
	fi
}

## get domain of URL
get_domain() {
	domain=${url#*//}
	domain=${domain%%/*}
}

## attempt to get feed from URL only
## if successful, output feed and terminate
url_extract() {
	if [[ -f scripts/url-extractors/${site} ]]
	then
		source scripts/url-extractors/${site}
	fi

	if [[ -n $url_ext ]]
	then
		output $url_ext
		exit
	fi
}

## attempt to get feed from page data
## if successful, output feed and terminate
page_extract() {
	if [[ -f scripts/page-extractors/${site} ]]
	then
		source scripts/page-extractors/$site
	fi

	if [[ -n $page_ext ]]
	then
		output $page_ext
		exit
	fi
}


# get user arguments
source scripts/options

# determine site ("" if not supported)
source scripts/determine_site

# get protocol and domain
determine_protocol
get_domain

if [[ -n "$site" ]]
then
	notify "Site identified as $site"
fi

url_extract

if [[ -n $site ]]
then
	notify "Unable to get feed from URL alone."
fi


# if no page extractor exists or user has opted not to download page, don't download the page
if [[ $network == "false" ]] || [[ -n $site && ! -f scripts/page-extractors/${site} ]]
then
	fail
fi


# determine flags to pass to curl
args=" ${curl_args}"

vars=("proxy" "quiet")
for i in "${vars[@]}"
do
	if [[ -n "${!i}" ]]
	then
		args="$args ${!i}"
	fi
done

command="curl -L -i -D -$args $url"

notify "Downloading page..."
# download page with curl
content=`eval $command`


# check download for errors
source scripts/http_errors


# if unknown domain, try to determine if it uses known software
if [[ "$site" == "" ]]
then
	notify "Attempting to determine if site uses known software..."
	source scripts/determine_software
	if [[ -n "$site" ]]
	then
		notify "Software identified as $site"
		software_found="true"
	fi
fi

# try to extract feed from page
notify "Attempting to get feed from page..."
page_extract
notify "Unable to get feed from page."

# try to get feed from URL if we determined the software
if [[ -n $software_found ]]
then
	url_extract
	notify "Unable to get feed from URL based on software."
fi

# unable to get feed
fail