#!/usr/bin/env bash

## Author: Abidán Brito
## This script builds GNU Emacs 29 with support for native elisp compilation,
## libjansson (C JSON library), pure GTK and mailutils.

# Exit on error and print out commands before executing them.
set -euxo pipefail 

# Let's set the number of jobs to something reasonable; keep 2 cores
# free to avoid choking the computer during compilation.
JOBS=`nproc --ignore=2`

# Clone repo locally and get into it.
git clone --depth 1 --branch emacs-29 git://git.savannah.gnu.org/emacs.git
pushd emacs

# Get essential dependencies.
sudo apt install -y build-essential \
    texinfo \
    libgnutls28-dev \
    libjpeg-dev \
    libpng-dev \
    libtiff5-dev \
    libgif-dev \
    libxpm-dev \
    libncurses-dev \
    #libncurses5-dev \
    libgtk-3-dev \
    libtree-sitter-dev \
    libmagick++-dev \
    #libwebkit2gtk-4.0-dev \

# Get dependencies for gcc-10 and the build process.
sudo apt update -y
sudo apt install -y gcc-10 \
    g++-10 \
    libgccjit0 \
    libgccjit-10-dev \
    autoconf \

# Get dependencies for fast JSON.
sudo apt install -y libjansson4 libjansson-dev

# Get GNU Mailutils (protocol-independent mail framework).
sudo apt install -y mailutils

# Enable source packages and get dependencies for whatever 
# Emacs version Ubuntu supports by default.
#
# Taken from here:
# https://www.masteringemacs.org/article/speed-up-emacs-libjansson-native-elisp-compilation
#sudo sed -i 's/# deb-src/deb-src/' /etc/apt/sources.list \
#    && apt update \
#    && apt build-dep -y emacs

# Stop debconf from complaining about postfix nonsense.
DEBIAN_FRONTEND=noninteractive

# Needed for compiling libgccjit or we'll get cryptic error messages.
export CC=/usr/bin/gcc-10 CXX=/usr/bin/g++-10

# Configure and run.
#
# Compiler flags:
# -O2 -> Turn on a bunch of optimization flags. There's also -O3, but it increases
#        the instruction cache footprint, which may end up reducing performance.
# -pipe -> Reduce temporary files to the minimum.
# -mtune=native -> Optimize code for the local machine (under ISA constraints).
# -march=native -> Enable all instruction subsets supported by the local machine.
# -fomit-frame-pointer -> Small functions don't need a frame pointer (optimization).
# https://lemire.me/blog/2018/07/25/it-is-more-complicated-than-i-thought-mtune-march-in-gcc/
#
# NOTE(abi): binaries should go to /usr/local/bin by default.
./autogen.sh \
    && ./configure \
    --with-native-compilation \     # use the libgccjit native compiler
    --with-pgtk \                   # better font rendering
    --with-x-toolkit=gtk3 \         # widgets toolkit
    --with-tree-sitter \            # syntax parsing
    --with-wide-int \               # larger file size limit
    --with-json \                   # fast JSON
    --with-gnutls \                 # TLS/SSL
    --with-mailutils \              # e-mail
    --without-pop \                 # no pop3 (insecure channels)
    --with-cairo \                  # vector graphics backend
    --with-imagemagick \            # raster images backend
    
    CFLAGS="-O2 -pipe -mtune=native -march=native -fomit-frame-pointer"
    
    # Other interesting compilation options:
    #
    #--prefix=""            # output binaries location
    #--with-x-toolkit=lucid # supposedly more stable
    #--with-xwidgets
    #--with-modules
    #--without-dbus
    
# Build.
#
# NOTE(abi): NATIVE_FULL_AOT=1 ensures native compilation ahead-of-time for all
#            elisp files included in the distribution.
make -j${JOBS} NATIVE_FULL_AOT=1 \
    && sudo make install

# Return to the original path.
popd