#!/usr/bin/env bash
#
# build-montauk-toolchain.sh — Build an <arch>-montauk cross compiler
# (Binutils + GCC) for MontaukOS userspace programs.
#
# Usage:  ./toolchain/build-montauk-toolchain.sh [x86_64|aarch64]
#         (or ARCH=aarch64 ./toolchain/build-montauk-toolchain.sh)
#
# Unlike the bare-metal x86_64-elf toolchain (build-toolchain.sh), this
# target knows the Montauk userspace ABI: it links static ET_EXEC
# binaries against the Montauk libc (crt1/crti/crtn + libc.a from
# programs/lib/libc), defaults to -mno-red-zone, forces 4 KiB segment
# alignment for the kernel ELF loader, and defines __montauk__.
#
# The toolchain is installed to toolchain/local/ and provides:
#   x86_64-montauk-gcc, x86_64-montauk-g++, x86_64-montauk-ld, etc.
#   (aarch64-montauk-* for ARCH=aarch64; both can live side by side).
#
# The target sysroot (libc headers + libs) is assembled into
# toolchain/sysroot/ (x86_64) or toolchain/sysroot-<arch>/ from
# programs/include/libc and programs/lib/libc.
# Re-run this script after changing libc headers or rebuilding libc to
# refresh the sysroot (the sysroot step always runs; compiler builds
# are skipped once installed).
#
# This script is idempotent — it skips steps whose output already exists.

set -euo pipefail

# ── Versions (kept in lockstep with build-toolchain.sh) ───────────────────────
BINUTILS_VERSION="2.43.1"
GCC_VERSION="14.2.0"
ARCH="${1:-${ARCH:-x86_64}}"
case "${ARCH}" in
    x86_64|aarch64) ;;
    *) echo "Unsupported architecture: ${ARCH}" >&2; exit 1 ;;
esac
TARGET="${ARCH}-montauk"

# ── Directories ───────────────────────────────────────────────────────────────
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
REPO_DIR="$(dirname "${SCRIPT_DIR}")"
PREFIX="${SCRIPT_DIR}/local"
SRC_DIR="${SCRIPT_DIR}/src"
BUILD_DIR="${SCRIPT_DIR}/build"
if [[ "${ARCH}" == x86_64 ]]; then
    SYSROOT="${SCRIPT_DIR}/sysroot"
    BUILD_SUFFIX=""
else
    SYSROOT="${SCRIPT_DIR}/sysroot-${ARCH}"
    BUILD_SUFFIX="-${ARCH}"
fi
PATCH_DIR="${SCRIPT_DIR}/patches"
FILES_DIR="${SCRIPT_DIR}/files"

BINUTILS_TARBALL="binutils-${BINUTILS_VERSION}.tar.xz"
GCC_TARBALL="gcc-${GCC_VERSION}.tar.xz"
BINUTILS_URL="https://ftp.gnu.org/gnu/binutils/${BINUTILS_TARBALL}"
GCC_URL="https://ftp.gnu.org/gnu/gcc/gcc-${GCC_VERSION}/${GCC_TARBALL}"

JOBS="$(nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || echo 4)"

# ── Color helpers ─────────────────────────────────────────────────────────────
bold()  { printf '\033[1m%s\033[0m\n' "$*"; }
green() { printf '\033[1;32m%s\033[0m\n' "$*"; }
red()   { printf '\033[1;31m%s\033[0m\n' "$*"; }

bold "=== Building ${TARGET} cross compiler ==="
bold "    Binutils ${BINUTILS_VERSION}  |  GCC ${GCC_VERSION}"
bold "    Install prefix: ${PREFIX}"
bold "    Sysroot:        ${SYSROOT}"
bold "    Parallel jobs:  ${JOBS}"
echo

export PATH="${PREFIX}/bin:${PATH}"

mkdir -p "${SRC_DIR}" "${BUILD_DIR}" "${PREFIX}"

# ── Download + extract sources (shared with build-toolchain.sh) ───────────────
download() {
    local url="$1" dest="$2"
    if [[ -f "${dest}" ]]; then
        bold "Already downloaded: $(basename "${dest}")"
    else
        bold "Downloading $(basename "${dest}")..."
        wget -q --show-progress -O "${dest}" "${url}"
    fi
}

extract() {
    local tarball="$1" name="$2"
    if [[ -d "${SRC_DIR}/${name}" ]]; then
        bold "Already extracted: ${name}"
    else
        bold "Extracting ${name}..."
        tar xf "${tarball}" -C "${SRC_DIR}"
    fi
}

download "${BINUTILS_URL}" "${SRC_DIR}/${BINUTILS_TARBALL}"
download "${GCC_URL}" "${SRC_DIR}/${GCC_TARBALL}"
extract "${SRC_DIR}/${BINUTILS_TARBALL}" "binutils-${BINUTILS_VERSION}"
extract "${SRC_DIR}/${GCC_TARBALL}" "gcc-${GCC_VERSION}"

if [[ ! -d "${SRC_DIR}/gcc-${GCC_VERSION}/gmp" ]]; then
    bold "Downloading GCC prerequisites..."
    (cd "${SRC_DIR}/gcc-${GCC_VERSION}" && ./contrib/download_prerequisites)
fi

# ── Apply Montauk target patches ──────────────────────────────────────────────
apply_patch() {
    local dir="$1" patch="$2"
    if grep -q "montauk" "${dir}/config.sub"; then
        bold "Already patched: $(basename "${dir}")"
    else
        bold "Patching $(basename "${dir}")..."
        patch -d "${dir}" -p1 < "${patch}"
    fi
}

# The AArch64 target is a second patch on top of the first.
apply_arch_patch() {
    local dir="$1" patch="$2" marker="$3"
    if grep -q "aarch64-\*-montauk" "${dir}/${marker}"; then
        bold "Already patched for aarch64: $(basename "${dir}")"
    else
        bold "Patching $(basename "${dir}") for aarch64..."
        patch -d "${dir}" -p1 < "${patch}"
    fi
}

apply_patch "${SRC_DIR}/binutils-${BINUTILS_VERSION}" "${PATCH_DIR}/binutils-${BINUTILS_VERSION}-montauk.patch"
apply_patch "${SRC_DIR}/gcc-${GCC_VERSION}" "${PATCH_DIR}/gcc-${GCC_VERSION}-montauk.patch"
apply_arch_patch "${SRC_DIR}/binutils-${BINUTILS_VERSION}" \
    "${PATCH_DIR}/binutils-${BINUTILS_VERSION}-montauk-aarch64.patch" bfd/config.bfd
apply_arch_patch "${SRC_DIR}/gcc-${GCC_VERSION}" \
    "${PATCH_DIR}/gcc-${GCC_VERSION}-montauk-aarch64.patch" gcc/config.gcc
cp "${FILES_DIR}/montauk.h" "${SRC_DIR}/gcc-${GCC_VERSION}/gcc/config/montauk.h"
cp "${FILES_DIR}/aarch64-montauk.h" "${SRC_DIR}/gcc-${GCC_VERSION}/gcc/config/aarch64/montauk.h"

# ── Assemble the target sysroot ───────────────────────────────────────────────
# usr/include — the Montauk libc headers (self-contained C; stddef/stdint/
#               stdarg come from GCC itself) plus the montauk/ SDK headers.
# usr/lib     — crt startup objects and the libc static library.
LIBC_DIR="${REPO_DIR}/programs/lib/libc"
if [[ "${ARCH}" != x86_64 ]]; then
    LIBC_DIR="${LIBC_DIR}/build-${ARCH}"
fi

# On a first build for a new architecture the libc cannot be compiled yet
# (it needs this compiler): the sysroot then holds only headers, which is
# all building GCC needs, and is completed once GCC exists.
assemble_sysroot() {
    bold "Assembling sysroot from programs/lib/libc..."
    local have_libc=1
    make -C "${REPO_DIR}/programs" libc ARCH="${ARCH}" >/dev/null 2>&1 || have_libc=0
    [[ -f "${LIBC_DIR}/liblibc.a" && -f "${LIBC_DIR}/crt1.o" ]] || have_libc=0

    rm -rf "${SYSROOT}"
    mkdir -p "${SYSROOT}/usr/include" "${SYSROOT}/usr/lib"
    cp -r "${REPO_DIR}/programs/include/libc/." "${SYSROOT}/usr/include/"
    cp -r "${REPO_DIR}/programs/include/montauk" "${SYSROOT}/usr/include/montauk"
    cp -r "${REPO_DIR}/programs/include/Api" "${SYSROOT}/usr/include/Api"
    # Freestanding C++ headers (<cstdint>, <type_traits>, <atomic>, ...) —
    # the subset the kernel and the in-tree programs build against. This is
    # NOT the whole C++ story: a hosted libstdc++ is built further down and
    # installs its own headers under ${PREFIX}/${TARGET}/include/c++.
    # That directory comes first on the include path and this one comes
    # last, so a plain g++ invocation gets the hosted headers and these are
    # shadowed. See "C++ standard library" in README.md.
    cp -r "${REPO_DIR}/kernel/freestnd-cxx-hdrs/${ARCH}/include/." "${SYSROOT}/usr/include/"
    if [[ ${have_libc} == 1 ]]; then
        cp "${LIBC_DIR}/crt1.o" "${LIBC_DIR}/crti.o" "${LIBC_DIR}/crtn.o" "${SYSROOT}/usr/lib/"
        cp "${LIBC_DIR}/liblibc.a" "${SYSROOT}/usr/lib/libc.a"
    else
        bold "libc not built yet - sysroot has headers only."
    fi
    # libm is an empty stand-in (math lives inside libc.a; the g++ driver
    # links -lm unconditionally). libstdc++ is copied from the toolchain
    # once built - the empty stand-in only bridges the first bootstrap.
    ar rcs "${SYSROOT}/usr/lib/libm.a"
    if [[ -f "${PREFIX}/${TARGET}/lib/libstdc++.a" ]]; then
        cp "${PREFIX}/${TARGET}/lib/libstdc++.a" "${SYSROOT}/usr/lib/libstdc++.a"
    else
        ar rcs "${SYSROOT}/usr/lib/libstdc++.a"
    fi
    green "Sysroot ready."
    return 0
}

assemble_sysroot

# ── Build Binutils ────────────────────────────────────────────────────────────
if [[ -x "${PREFIX}/bin/${TARGET}-ld" ]]; then
    bold "Binutils already installed — skipping."
else
    bold "Building Binutils ${BINUTILS_VERSION} for ${TARGET}..."
    rm -rf "${BUILD_DIR}/binutils-montauk${BUILD_SUFFIX}"
    mkdir -p "${BUILD_DIR}/binutils-montauk${BUILD_SUFFIX}"
    (
        cd "${BUILD_DIR}/binutils-montauk${BUILD_SUFFIX}"
        "${SRC_DIR}/binutils-${BINUTILS_VERSION}/configure" \
            --target="${TARGET}" \
            --prefix="${PREFIX}" \
            --with-sysroot="${SYSROOT}" \
            --disable-nls \
            --disable-werror
        make -j"${JOBS}"
        make install
    )
    green "Binutils installed."
fi

# ── Build GCC ─────────────────────────────────────────────────────────────────
# Hosted against the Montauk libc headers in the sysroot. Builds the
# compiler, libgcc, and a hosted libstdc++ (full STL: string/vector/map,
# exceptions, RTTI, iostream). libstdc++ is built gthr-single because
# the libc has no pthreads, so <thread>/<mutex> are absent and
# shared_ptr uses non-atomic refcounts. See README.md.
if [[ -x "${PREFIX}/bin/${TARGET}-gcc" ]]; then
    bold "GCC already installed — skipping."
else
    bold "Building GCC ${GCC_VERSION} for ${TARGET}..."
    rm -rf "${BUILD_DIR}/gcc-montauk${BUILD_SUFFIX}"
    mkdir -p "${BUILD_DIR}/gcc-montauk${BUILD_SUFFIX}"
    (
        cd "${BUILD_DIR}/gcc-montauk${BUILD_SUFFIX}"
        "${SRC_DIR}/gcc-${GCC_VERSION}/configure" \
            --target="${TARGET}" \
            --prefix="${PREFIX}" \
            --with-sysroot="${SYSROOT}" \
            --enable-languages=c,c++ \
            --disable-nls \
            --disable-shared \
            --disable-multilib \
            --disable-gcov \
            --with-gnu-as \
            --with-gnu-ld \
            --with-newlib \
            --enable-initfini-array \
            --disable-wchar_t \
            --disable-libstdcxx-pch
        make -j"${JOBS}" all-gcc
        make -j"${JOBS}" all-target-libgcc
        make install-gcc
        make install-target-libgcc
        make -j"${JOBS}" all-target-libstdc++-v3
        make install-target-libstdc++-v3
    )
    green "GCC and libstdc++ installed."
fi

# A first build for this architecture had no libc: complete the sysroot.
if [[ ! -f "${SYSROOT}/usr/lib/libc.a" ]] || [[ ! -s "${SYSROOT}/usr/lib/libstdc++.a" ]]; then
    assemble_sysroot
fi

# ── Done ──────────────────────────────────────────────────────────────────────
echo
green "=== ${TARGET} cross compiler ready ==="
"${PREFIX}/bin/${TARGET}-gcc" --version | head -1
"${PREFIX}/bin/${TARGET}-ld"  --version | head -1
echo
bold "Try it:"
bold "  echo 'int main(){return 0;}' > /tmp/t.c"
bold "  ${PREFIX}/bin/${TARGET}-gcc /tmp/t.c -o /tmp/t.elf"