#!/usr/bin/env bash

set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
PROJECT_DIR="$SCRIPT_DIR"
SDK_DIR="$PROJECT_DIR/android-sdk"
NDK_DIR="$SDK_DIR/ndk/27.2.12479018"
TOOLBIN="$NDK_DIR/toolchains/llvm/prebuilt/linux-x86_64/bin"
TMP_DIR="$PROJECT_DIR/.tmp-android-build"
GIT_SRC_DIR="$TMP_DIR/git-src"
HOST_GIT_DIR="$PROJECT_DIR/build/host-git"
HOST_GIT_BINARY="$HOST_GIT_DIR/libgit.so"
ANDROID_JNI_DIR="$PROJECT_DIR/app/src/main/jniLibs"
ANDROID_API=24

log() {
  printf '\n[%s] %s\n' "compile-git" "$1"
}

require_path() {
  if [ ! -e "$1" ]; then
    echo "Required path not found: $1" >&2
    exit 1
  fi
}

require_tool() {
  if ! command -v "$1" >/dev/null 2>&1; then
    echo "Missing required tool: $1" >&2
    exit 1
  fi
}

ensure_git_source() {
  mkdir -p "$TMP_DIR"
  if [ ! -d "$GIT_SRC_DIR/.git" ]; then
    log "Cloning Git source"
    git clone --depth 1 https://github.com/git/git.git "$GIT_SRC_DIR"
  else
    log "Using existing Git source checkout"
  fi
}

common_git_make_args() {
  printf '%s\n' \
    NO_OPENSSL=YesPlease \
    NO_CURL=YesPlease \
    NO_EXPAT=YesPlease \
    NO_GETTEXT=YesPlease \
    NO_TCLTK=YesPlease \
    NO_PERL=YesPlease \
    NO_PYTHON=YesPlease \
    NO_INSTALL_HARDLINKS=YesPlease \
    NO_ICONV=YesPlease \
    NO_REGEX=NeedsStartEnd \
    HAVE_ALLOCA_H=YesPlease \
    HAVE_PATHS_H=YesPlease \
    HAVE_CLOCK_GETTIME=YesPlease \
    HAVE_CLOCK_MONOTONIC=YesPlease \
    HAVE_GETDELIM=YesPlease \
    FREAD_READS_DIRECTORIES=UnfortunatelyYes \
    CSPRNG_METHOD=
}

build_host_git() {
  log "Building Git for development host"
  cd "$GIT_SRC_DIR"
  make clean >/dev/null 2>&1 || true
  mapfile -t make_args < <(common_git_make_args)
  make -j"$(nproc 2>/dev/null || printf 4)" "${make_args[@]}" git

  mkdir -p "$HOST_GIT_DIR"
  cp git "$HOST_GIT_BINARY"
  chmod 755 "$HOST_GIT_BINARY"

  log "Host test Git binary: $HOST_GIT_BINARY"
  "$HOST_GIT_BINARY" --version
}

build_android_git_for_abi() {
  local abi="$1"
  local cc="$2"
  local output_dir="$ANDROID_JNI_DIR/$abi"

  require_path "$TOOLBIN/${cc}"

  log "Building Git for Android $abi"
  cd "$GIT_SRC_DIR"
  make clean >/dev/null 2>&1 || true
  mapfile -t make_args < <(common_git_make_args)
  make -j"$(nproc 2>/dev/null || printf 4)" \
    uname_S=Android \
    uname_O=Android \
    NO_PTHREADS=YesPlease \
    NO_LIBGEN_H=YesPlease \
    HAVE_DEV_TTY=YesPlease \
    CC="$cc" \
    AR=llvm-ar \
    RANLIB=llvm-ranlib \
    STRIP=llvm-strip \
    "${make_args[@]}" \
    git

  log "Validating Android $abi binary"
  file git
  readelf -h git | sed -n '1,12p'

  mkdir -p "$output_dir"
  llvm-strip -s git -o "$output_dir/libgit.so"
  chmod 755 "$output_dir/libgit.so"
  ls -lh "$output_dir/libgit.so"
}

build_android_git() {
  require_path "$NDK_DIR"
  export PATH="$TOOLBIN:$PATH"

  build_android_git_for_abi "arm64-v8a" "aarch64-linux-android${ANDROID_API}-clang"
  build_android_git_for_abi "armeabi-v7a" "armv7a-linux-androideabi${ANDROID_API}-clang"
  build_android_git_for_abi "x86" "i686-linux-android${ANDROID_API}-clang"
  build_android_git_for_abi "x86_64" "x86_64-linux-android${ANDROID_API}-clang"
}

print_usage() {
  cat <<EOF_USAGE
Usage: bash ./CompileGitForAllTargetPlatforms.sh [--host | --android | --all]

  --host     Compile Git for the development host and copy it to build/host-git/libgit.so
  --android  Cross-compile Git for Android ABIs served through Google Play
  --all      Compile both host and Android targets (default)
EOF_USAGE
}

main() {
  case "${1:---all}" in
    --host|--android|--all)
      ;;
    -h|--help)
      print_usage
      return
      ;;
    *)
      echo "Unknown argument: $1" >&2
      print_usage >&2
      exit 1
      ;;
  esac

  require_tool git
  require_tool make
  require_tool perl
  require_tool clang
  require_tool pkg-config
  require_tool readelf

  ensure_git_source

  case "${1:---all}" in
    --host)
      build_host_git
      ;;
    --android)
      build_android_git
      ;;
    --all)
      build_host_git
      build_android_git
      ;;
  esac
}

main "$@"