#!/bin/bash
# Given social media links on stdin or as args, this extracts the link in the profile description, if any.

function verbose_echo {
	if [[ "${verbose}" ]]
	then
		echo "$@"
	fi
}

function fetch {
	verbose_echo "Fetching $1" >&2
	curl -sL --max-time 10 -A 'Mozilla/5.0 (Windows NT 6.1; rv:60.0) Gecko/20100101 Firefox/60.0' "$1"
}

function fetch_n_extract {
	url="$1"
	if [[ "${url}" == *'facebook.com/'* ]]
	then
		page="$(fetch "${url}")"
		if grep -qF '"tab_home"' <<<"${page}"
		then
			# Publicly accessible profile
			grep -Po '"website_url":\K"[^"]+"' <<<"${page}" | python3 -c 'import json, sys'$'\n''for line in sys.stdin:'$'\n'' print(json.loads(line))' | awk '!seen[$0]++'
		elif grep -qF 'id="pagelet_loggedout_sign_up"' <<< "${page}"
		then
			# Profile overview only
			grep -Po '<div\s([^<]*\s)?id\s*=\s*"pagelet_contact".*<div\s([^<]*\s)?id\s*=\s*"bottomContent"' <<<"${page}" | grep -Po 'href="https://l\.facebook\.com/l\.php\?u=\K[^&]+' | python3 -c 'import sys, urllib.parse; sys.stdout.write(urllib.parse.unquote(sys.stdin.read()))'
		fi
	elif [[ "${url}" == *'instagram.com/'* ]]
	then
		fetch "${url}" | grep -Po '"external_url":"\K[^"]+'
		sleep 3 # To avoid getting banned
	elif [[ "${url}" == *'twitter.com/'* ]]
	then
		fetch "${url}" | tr -d '\n' | grep -Po '<div\s+([^>]*\s)?class\s*=\s*"([^"]*\s)?ProfileHeaderCard-url(\s[^"]*)?">.*?</div>' | grep -Po '<a\s(?=([^>]*\s)?class\s*=\s*"([^"]*\s)?u-textUserColor(\s[^"]*)?")([^>]*\s)?title="\K[^"]+'
	elif [[ "${url}" == *'youtube.com/'* ]]
	then
		if [[ "${url}" == *'?'* ]]; then u="${url}&disable_polymer=1"; else u="${url}?disable_polymer=1"; fi
		fetch "${u}" | tr -d '\n' | grep -Po '<div\s([^>]*\s)?id\s*=\s*"header-links".*?</div>' | grep -Po 'href="/redirect\?([^"]*&(amp;)?)?q=\K[^&"]+' | python3 -c 'import sys, urllib.parse; sys.stdout.write(urllib.parse.unquote(sys.stdin.read()))'
	fi
}

verbose=
for arg in "$@"
do
	if [[ "${arg}" == '--verbose' || "${arg}" == '-v' ]]
	then
		verbose=1
		shift
	elif [[ "${arg}" == '--' ]]
	then
		shift
	else
		# Assume end of options
		break
	fi
done

{
	for arg in "$@"
	do
		echo "${arg}"
	done

	if [ ! -t 0 ]
	then
		cat
	fi
} | while read -r url
do
	if [[ "${url}" == '* '* ]]
	then
		url="${url:2}"
	fi
	fetch_n_extract "${url}"
done