#!/bin/sh
# Installs Rewind VM from the latest GitHub release:
#
#   curl -fsSL https://rewindvm.dev/install | sh
#
# The command and the desktop app are unpacked under ~/.local/share/rewind
# and linked into ~/.local/bin. Running it again replaces both with the
# latest release. Settings, all optional:
#
#   REWIND_INSTALL_DIR  where the tarballs are unpacked (~/.local/share/rewind)
#   REWIND_BIN_DIR      where rewind and rewind-app are linked (~/.local/bin)
#   REWIND_NO_APP=1     install only the command
#   REWIND_WITH_DEBUG=1 also install the VM kernel's DWARF and source files
#                       for `rewind gdb`, 150 MB
#   REWIND_RELEASE_URL  where the release assets are, for testing a build
set -eu

RELEASE_URL=${REWIND_RELEASE_URL:-https://github.com/fzakaria/rewindvm/releases/latest/download}
INSTALL_DIR=${REWIND_INSTALL_DIR:-${XDG_DATA_HOME:-$HOME/.local/share}/rewind}
BIN_DIR=${REWIND_BIN_DIR:-$HOME/.local/bin}
CLI=rewind-x86_64-linux
APP=rewind-app-x86_64-linux
DEBUG=rewind-debug-x86_64-linux

say() {
  printf 'rewind install: %s\n' "$*" >&2
}

fail() {
  say "$*"
  exit 1
}

# Rewind runs Linux in KVM on x86_64 hosts only.
[ "$(uname -s)" = Linux ] || fail "Rewind VM needs Linux; this is $(uname -s)"
[ "$(uname -m)" = x86_64 ] || fail "Rewind VM needs x86_64; this is $(uname -m)"

if command -v curl >/dev/null 2>&1; then
  fetch() { curl -fsSL "$1"; }
elif command -v wget >/dev/null 2>&1; then
  fetch() { wget -qO- "$1"; }
else
  fail "needs curl or wget"
fi

# Each tarball unpacks to a directory of its own name, so a new release
# replaces the old one whole.
install_tarball() {
  name=$1
  say "downloading $name"
  staging=$(mktemp -d "$INSTALL_DIR/.install.XXXXXX")
  fetch "$RELEASE_URL/$name.tar.gz" | tar -xz -C "$staging"
  rm -rf "${INSTALL_DIR:?}/$name"
  mv "$staging/$name" "$INSTALL_DIR/$name"
  rmdir "$staging"
}

mkdir -p "$INSTALL_DIR" "$BIN_DIR"
install_tarball "$CLI"
ln -sf "$INSTALL_DIR/$CLI/bin/rewind" "$BIN_DIR/rewind"

# The kernel's debug symbols go next to the command, where its launcher
# looks for them.
if [ "${REWIND_WITH_DEBUG:-}" = 1 ]; then
  install_tarball "$DEBUG"
fi
if [ "${REWIND_NO_APP:-}" != 1 ]; then
  install_tarball "$APP"
  ln -sf "$INSTALL_DIR/$APP/bin/rewind-app" "$BIN_DIR/rewind-app"

  # The desktop entry and icon, so the app is in the desktop's launcher.
  # The entry names the app by its path: a desktop session's PATH often
  # lacks BIN_DIR.
  share=${XDG_DATA_HOME:-$HOME/.local/share}
  entry=surf.lunchtime.Rewind.desktop
  mkdir -p "$share/applications" "$share/icons/hicolor"
  sed "s|^Exec=rewind-app|Exec=$INSTALL_DIR/$APP/bin/rewind-app|" \
    "$INSTALL_DIR/$APP/share/applications/$entry" >"$share/applications/$entry"
  cp -R "$INSTALL_DIR/$APP/share/icons/hicolor/." "$share/icons/hicolor/"
fi

say "installed into $INSTALL_DIR, linked from $BIN_DIR"

# What is left for the user to do, if anything.
case ":$PATH:" in
  *":$BIN_DIR:"*) ;;
  *) say "add $BIN_DIR to your PATH" ;;
esac
if [ ! -r /dev/kvm ] || [ ! -w /dev/kvm ]; then
  say "/dev/kvm is not readable and writable by you; add yourself to the kvm group"
fi
if grep -q AuthenticAMD /proc/cpuinfo 2>/dev/null; then
  say "on AMD, run 'sudo rewind pmu enable' after each boot: https://rewindvm.dev/counter-time.html"
fi
say "try: rewind pmu status"