#!/usr/bin/env bash
set -euo pipefail

EMACS_VER="${EMACS_VER:-30.2}"

TARBALL="emacs-${EMACS_VER}.tar.gz"
URL="https://ftp.gnu.org/gnu/emacs/${TARBALL}"
SRC_DIR="emacs-${EMACS_VER}"

install_deps() {
  echo "==> Installing build dependencies (Debian/Ubuntu)"
  sudo apt update
  sudo apt install -y \
    build-essential \
    autoconf \
    texinfo \
    curl \
    libsystemd-dev \
    libmailutils-dev \
    libtree-sitter-dev \
    libxml2-dev \
    libjansson-dev \
    libsqlite3-dev \
    libgnutls28-dev \
    libncurses-dev \
    pkg-config
}

echo "==> Building Emacs ${EMACS_VER} (nox-style) under /usr/local"

install_deps

if [[ -e "${SRC_DIR}" ]]; then
  echo "Error: source directory '${SRC_DIR}' already exists."
  echo "Please remove it first, or build a different version."
  exit 1
fi

if [[ ! -f "${TARBALL}" ]]; then
  echo "==> Downloading ${URL}"
  curl -fLO "${URL}"
else
  echo "==> Reusing existing tarball ${TARBALL}"
fi

echo "==> Extracting ${TARBALL}"
tar xf "${TARBALL}"

cd "${SRC_DIR}"

echo "==> Configuring Emacs ${EMACS_VER}"
./configure \
  --prefix=/usr/local \
  --with-libsystemd \
  --with-pop=yes \
  --enable-locallisppath="/etc/emacs:/usr/local/share/emacs/${EMACS_VER}/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/${EMACS_VER}/site-lisp" \
  --without-sound \
  --without-gconf \
  --with-mailutils \
  --with-native-compilation=no \
  --with-x=no \
  --without-gsettings \
  --with-tree-sitter \
  --with-xml2

echo "==> Building Emacs ${EMACS_VER}"
make -j"$(nproc)"

cat <<EOF

Build finished successfully.

Next step:
  cd ${PWD}
  sudo make install

Optional verification before install:
  ./src/emacs --version

EOF