[Feature request] add selfhosted webinterface for jdownloader

[milahu]

Idea

the java gui is too ugly / too heavy for my taste
and the VNC tunnel does not make it better

so i scraped the webapp at my.jdownloader.org
and made it work on localhost in my myjdownloader
to get a selfhosted webinterface for jdownloader

see also
My.JDownloader over localhost
local web interface on LAN

one problem is that my.jdownloader.org is closed-source
so this would require some maintenance to keep it working

im running jdownloader in bubblewrap
which is more lightweight than docker

jdownloader-install-and-run.sh

#!/usr/bin/env bash

dir="$(dirname "$0")"

src="https://github.com/milahu/jdownloader-installed"

# TODO better? ~/.cache? ~/.local? ~/.jdownloader?
dst="$HOME/.config/jdownloader"

if ! [ -e "$dst" ]; then
  echo "creating $dst"
  git clone --depth=1 "$src" "$dst"
else
  echo "keeping $dst"
fi

# patch jdownloader
# dont require MyJDownloader login for headless mode
# so we can run our own MyJDownloader service
"$dir"/jdownloader-patch-core.sh "$dst"

# https://my.jdownloader.org/developers/
# My.JDownloader API Documentation
# Pro Tip: It's possible to access the JDownloader API directly (Bypass our server)
# by enabling the so called 'Deprecated API' in the Advanced Options.
# -> jd will listen on port 3128 -> http://localhost:3128/help
cfg="$dst"/cfg/org.jdownloader.api.RemoteAPIConfig.json
if [ "$(cat "$cfg" | jq -r .deprecatedapienabled)" = "false" ]; then
  cat "$cfg" | jq -c '. * { "deprecatedapienabled": true }' | sponge "$cfg"
fi

jre=$(nix-build --no-out-link '<nixpkgs>' -A jre)

bubblewrap=$(nix-build --no-out-link '<nixpkgs>' -A bubblewrap)

a=($bubblewrap/bin/bwrap)

# FIXME add only required /nix/store paths
a+=(--ro-bind /nix /nix)

# TODO better
a+=(--proc /proc)
a+=(--dev /dev)
a+=(--unshare-pid) # ?
a+=(--new-session) # ?
a+=(--unshare-all)
a+=(--share-net)
a+=(--ro-bind /etc/resolv.conf /etc/resolv.conf)
a+=(--die-with-parent)
#a+=(--dir /run/user/$UID) # tmpfs
#a+=(--dir "$dst") # give access to JDownloader.jar etc
a+=(--bind "$dst" "$dst") # give access to JDownloader.jar etc
a+=(--bind "$HOME/Downloads/jdownloader" "/output") # give access to JDownloader.jar etc
#a+=()

a+=($jre/bin/java)

# see also
# https://aur.archlinux.org/cgit/aur.git/tree/JDownloaderHeadless?h=jdownloader2
# headless mode requires username and password in
# $dst/cfg/org.jdownloader.api.myjdownloader.MyJDownloaderSettings.json
a+=(-Djava.awt.headless=true)

a+=(-jar "$dst/JDownloader.jar")

# no. with "-norestart" jd does not restart after update
#a+=(-norestart)

set -x
exec "${a[@]}"

running jdownloader in headless mode
without a my.jdownloader.org account
requires binary patching of the Core.jar file

jdownloader-patch-core.sh

#!/usr/bin/env bash

# patch jdownloader
# dont require MyJDownloader login for headless mode

# based on
# https://github.com/NixOS/nixpkgs/pull/136998/files#r720864456

set -eux

recaf=$(NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link '<nixpkgs>' -A nur.repos.milahu.recaf-bin)
export PATH="$recaf/bin:$PATH"

now=$(date --utc +%Y%m%dT%H%M%SZ)

jdownloader_path="$HOME/.config/jdownloader"
if [ $# != 0 ]; then
  jdownloader_path="$1"
fi

jar_path="$jdownloader_path/Core.jar"
bak_jar_path="$jar_path.bak.$now"

class="org/jdownloader/api/myjdownloader/MyJDownloaderController"
method="isAlwaysConnectRequired()Z"

# note: no whitespace in paths
temp_base=/run/user/$UID/recaf-jdownloader-MyJDownloaderController-isAlwaysConnectRequired
asm_path=$temp_base.asm
recaf_script_path=$temp_base.recaf
temp_jar_path=$temp_base.patched.jar

# disassemble the method to patch
cat >$recaf_script_path <<EOF
disassemble --destination=$asm_path $class $method
EOF
recaf --input="$jar_path" --script=$recaf_script_path

# check if method is patched
if ! grep -q INVOKESTATIC $asm_path; then
  echo "patch was already applied"
  # cleanup
  # TODO trap exit
  rm $recaf_script_path
  rm $asm_path
  exit
fi

# patch the assembly code
# -INVOKESTATIC org/appwork/utils/Application.isHeadless()Z
# -IRETURN
# +EXPR return false;
sed -i '/INVOKESTATIC/d; s/IRETURN/EXPR return false;/' $asm_path

# assemble the patched method
cat >$recaf_script_path <<EOF
assemble $class $method $asm_path
export $temp_jar_path
EOF
recaf --input="$jar_path" --script=$recaf_script_path

echo "replacing $jar_path"
mv "$jar_path" "$bak_jar_path"
mv $temp_jar_path "$jar_path"

# cleanup
# TODO trap exit
rm $recaf_script_path
rm $asm_path