#!/bin/sh

# first choice is curl(1), should be OK for Linux
if command -v curl >/dev/null 2>&1; then
  __download () {
    curl -sL "$1"
  }
# second is fetch(1), for FreeBSD
elif command -v fetch >/dev/null 2>&1; then
  __download () {
    fetch -q -o - "$1"
  }
# last comes ftp(1), which does far more than its name implies (OpenBSD only)
elif [ "$(uname -s)" = OpenBSD ] && command -v ftp >/dev/null 2>&1; then
  __download () {
    ftp -o - "$1"
  }
else
  printf '%s\n' "Oh no! You don't seem to have curl(1) or fetch(1)" >&2
  printf '%s\n' "I'm cowardly exiting" >&2
  exit 4
fi

# We find magnet links
__magnet () {
  __download "$1" | grep -Eo 'magnet:\?[^"<> ]+'
}

# We find absolute torrent links
__abs_torrent () {
  __download "$1" | grep -Eo 'href="?[^"]+\.torrent' | grep -Eo '[^"=]+\.torrent'
}

__root_torrent () {
  _domain="$(printf '%s\n' "$1" | grep -Eo 'https?://[^/]+')"
  __download "$1" |
   grep -Eo 'href="?[^"]+\.torrent' |
   grep -Eo '[^"=]+\.torrent' |
   while read -r _root_link; do
     printf '%s/%s\n' "$_domain" "$_root_link"
   done
}

# We find relative links to the torrents and generate an absolute link
__rel_torrent () {
  _page="$1"
  __download "$_page" | grep -Eo 'href="?[^"]+\.torrent' |
   grep -Eo '[^"=]+\.torrent' |
    while read -r _rel_link; do
      printf '%s%s\n' "$_page" "$_rel_link"
    done
  unset _page _rel_link
}

# Archlinux
__magnet 'https://www.archlinux.org/download/'

# Debian
for _arch in amd64 i386 ; do
  # Installation media
  for _medium in 'cd' 'dvd'; do
    __rel_torrent "https://cdimage.debian.org/debian-cd/current/$_arch/bt-$_medium/"
  done
  # Live CD
  __rel_torrent "https://cdimage.debian.org/debian-cd/current-live/$_arch/bt-hybrid/"
done

# devuan
__magnet "https://www.devuan.org/get-devuan"

# Ubuntu
__abs_torrent 'https://ubuntu.com/download/alternative-downloads'

# openSUSE
# Doesn't provide torrents anymore!

# Linux Mint
# It's not trivial to get a page with the latest torrents

# Fedora
# Doesn't seem to provide torrents..?

# Elementary
__magnet 'https://elementary.io'

# CentOS
# It's not trivial to get a page with the latest torrents

# ReactOS
# Uses sourceforge to distribute its isos

# Kali
# https://www.kali.org/downloads/ forces gzip encoding. I'm not dealing with
# this crap. Learn how to configure your webserver.

# KDE Neon
# Doesn't seem to provide torrents..?

# Mageia
__magnet "http://www.mageia.org/en/downloads/alternative/"

# tails
__rel_torrent 'https://tails.boum.org/torrents/files/'

# FreeBSD
__magnet "https://wiki.freebsd.org/Torrents"

# Solus
__abs_torrent "https://getsol.us/download/"

# Parrot
for _version in security home; do
  __abs_torrent "https://parrotsec.org/${_version}-edition/"
done

# lubuntu
__abs_torrent "https://lubuntu.me/downloads/"

# slackware
__root_torrent "http://www.slackware.com/getslack/torrents.php"