#!/usr/bin/env bash
# Debian 13 KDE Wayland — macOS-style three-finger drag on bcm5974 trackpads.
# Source: https://github.com/lmr97/linux-3-finger-drag
set -Eeuo pipefail

if (( EUID == 0 )); then
  echo 'Run as your desktop user, without sudo.' >&2
  echo 'The script will request sudo only for system-wide changes.' >&2
  exit 1
fi

command -v sudo >/dev/null || { echo 'sudo is required.' >&2; exit 1; }
command -v systemctl >/dev/null || { echo 'systemd is required.' >&2; exit 1; }
if ! grep -qs 'bcm5974' /proc/bus/input/devices; then
  echo 'Warning: bcm5974 trackpad not detected; this setup targets Apple bcm5974.' >&2
  read -r -p 'Continue anyway? [y/N] ' reply
  [[ "$reply" =~ ^[Yy]$ ]] || exit 1
fi

sudo -v
sudo apt-get update
sudo apt-get install -y git build-essential pkg-config libudev-dev libevdev-dev curl ca-certificates acl

# rustup is installed per user so that Cargo does not run as root.
if ! command -v cargo >/dev/null 2>&1; then
  echo 'Installing Rust via rustup (official installer)...'
  curl --proto '=https' --tlsv1.2 -fsSL https://sh.rustup.rs -o "${TMPDIR:-/tmp}/rustup-3fd-$$.sh"
  sh "${TMPDIR:-/tmp}/rustup-3fd-$$.sh" -y --profile minimal
  rm -f "${TMPDIR:-/tmp}/rustup-3fd-$$.sh"
fi
export PATH="$HOME/.cargo/bin:$PATH"
command -v cargo >/dev/null || { echo 'Cargo is not available.' >&2; exit 1; }

source_dir="$HOME/linux-3-finger-drag"
if [[ -d "$source_dir/.git" ]]; then
  echo "Using existing checkout: $source_dir"
else
  [[ ! -e "$source_dir" ]] || { echo "Path exists but is not a git checkout: $source_dir" >&2; exit 1; }
  git clone https://github.com/lmr97/linux-3-finger-drag.git "$source_dir"
fi

cd "$source_dir"
# Pin the version used successfully on this machine, if its tag exists.
if git rev-parse -q --verify 'refs/tags/v2.0.0' >/dev/null; then
  git checkout --detach v2.0.0
elif git rev-parse -q --verify 'refs/tags/2.0.0' >/dev/null; then
  git checkout --detach 2.0.0
else
  echo 'Warning: no local v2.0.0 tag; building the existing checkout.' >&2
fi
cargo build --release
[[ -x target/release/linux-3-finger-drag ]] || { echo 'Expected binary not found.' >&2; exit 1; }
sudo install -m 0755 target/release/linux-3-finger-drag /usr/local/bin/linux-3-finger-drag

mkdir -p "$HOME/.config/linux-3-finger-drag" "$HOME/.config/systemd/user"
config="$HOME/.config/linux-3-finger-drag/3fd-config.json"
if [[ ! -e "$config" ]]; then
  cat > "$config" <<'JSON'
{
  "acceleration": 1.0,
  "dragEndDelay": 0,
  "logFile": "stdout",
  "logLevel": "info",
  "entryDebounce": 50,
  "probeDelay": 15,
  "pressGrace": 75
}
JSON
else
  echo "Keeping existing config: $config"
fi

# Match the device by name, not by unstable /dev/input/eventN.
# OWNER is used instead of RUN+=setfacl because the latter failed after reboot.
udev_rule='/etc/udev/rules.d/70-linux-3-finger-drag.rules'
rule_tmp="$(mktemp)"
trap 'rm -f "$rule_tmp"' EXIT
cat > "$rule_tmp" <<EOF_RULE
# Apple bcm5974 touchpad and uinput access for the desktop user.
ACTION=="add|change", SUBSYSTEM=="input", KERNEL=="event*", ATTRS{name}=="bcm5974", OWNER="$(id -un)", MODE="0600"
ACTION=="add|change", SUBSYSTEM=="misc", KERNEL=="uinput", OWNER="$(id -un)", MODE="0600"
EOF_RULE
sudo install -m 0644 "$rule_tmp" "$udev_rule"

sudo modprobe uinput
printf 'uinput\n' | sudo tee /etc/modules-load.d/three-finger-drag.conf >/dev/null
sudo udevadm control --reload-rules
sudo udevadm trigger --action=change --subsystem-match=input --sysname-match='event*'
sudo udevadm trigger --action=change --subsystem-match=misc --sysname-match=uinput || true

cat > "$HOME/.config/systemd/user/three-finger-drag.service" <<'SERVICE'
[Unit]
Description=macOS-like Three Finger Drag for Apple Trackpad
After=graphical-session.target
PartOf=graphical-session.target

[Service]
Type=exec
ExecStart=/usr/local/bin/linux-3-finger-drag
Restart=on-failure
RestartSec=2

[Install]
WantedBy=graphical-session.target
SERVICE

systemctl --user daemon-reload
systemctl --user enable three-finger-drag.service
systemctl --user restart three-finger-drag.service

echo
echo '== Three-Finger Drag status =='
systemctl --user --no-pager --full status three-finger-drag.service || true
echo
echo 'If permission errors appear, reboot and check:'
echo '  journalctl --user -u three-finger-drag.service -b --no-pager -n 50'