#!/usr/bin/env bash
# Install the GCC 16 cross compiler over the GCC 13.2.0 one, in every
# location the build actually reads a compiler from.
#
# There are three such locations, and all three must agree or the build
# picks up a mixed toolchain:
#
#   1. prefix/<target>/gcc-install/   - the GCC half of the prefix
#   2. prefix/<target>/sysroot/       - the merged prefix (gcc+rust+clang)
#   3. ~/.redoxer/<target>/toolchain/ - HIGHEST PRIORITY. src/cook/script.rs
#      prepends this to PATH last, so it wins over both prefix paths for
#      every recipe. Missing this one silently leaves recipes on GCC 13.
#
# Reversible: the GCC 13 components are moved aside to a timestamped
# backup dir rather than deleted, and --restore puts them back.
#
# Run local/scripts/build-gcc16-cross.sh first.
set -euo pipefail

ROOT=$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)
TARGET=x86_64-unknown-redox
NEWGCC=16.1.0
OLDGCC=13.2.0
SRC="$ROOT/build/gcc16-install"
PREFIX_GCC="$ROOT/prefix/$TARGET/gcc-install"
PREFIX_SYSROOT="$ROOT/prefix/$TARGET/sysroot"
REDOXER="$HOME/.redoxer/$TARGET/toolchain"
BACKUP="$ROOT/build/gcc13-backup"

# GCC's <cstdlib> does `using ::strtold` before relibc's cbindgen trailer has
# declared it, so the C++ wrapper must pull in <stdlib.h> explicitly. mk/prefix.mk
# does this with a sed, but that sed is NOT idempotent -- the current GCC 13
# toolchain has the comment block appended 17 times from repeated `make prefix`
# runs. The guard below makes it apply exactly once.
patch_cstdlib() {
    local f="$1"
    [ -f "$f" ] || return 0
    grep -q "Red Bear: relibc declares strtold" "$f" && return 0
    sed -i '/^#include_next <stdlib.h>$/a\\n// Red Bear: relibc declares strtold via cbindgen trailer.\n// The explicit include ensures ::strtold is visible when the\n// C++ wrapper processes its using-directives below.\n#include <stdlib.h>' "$f"
    echo "    patched strtold: $f"
}

# Move GCC's own components out of a tree without disturbing the rust/clang/
# relibc files that share it.
evict_old() {
    local dst="$1" tag="$2"
    local bk="$BACKUP/$tag"
    mkdir -p "$bk"
    for p in "bin/$TARGET-gcc-$OLDGCC" \
             "lib/gcc/$TARGET/$OLDGCC" \
             "libexec/gcc/$TARGET/$OLDGCC" \
             "$TARGET/include/c++/$OLDGCC"; do
        if [ -e "$dst/$p" ]; then
            mkdir -p "$bk/$(dirname "$p")"
            mv "$dst/$p" "$bk/$p"
        fi
    done
    for so in "$dst/$TARGET/lib/"libstdc++.so.6.0.* ; do
        [ -e "$so" ] || continue
        mkdir -p "$bk/$TARGET/lib"
        mv "$so" "$bk/$TARGET/lib/"
    done
}

install_into() {
    local dst="$1" tag="$2"
    [ -d "$dst" ] || { echo "  skip $tag (not present)"; return 0; }
    echo "  -> $tag: $dst"
    evict_old "$dst" "$tag"
    # Driver, cc1/cc1plus, target headers and libs.
    cp -a "$SRC/bin/." "$dst/bin/"
    mkdir -p "$dst/lib/gcc/$TARGET" "$dst/libexec/gcc/$TARGET"
    cp -a "$SRC/lib/gcc/$TARGET/$NEWGCC" "$dst/lib/gcc/$TARGET/"
    cp -a "$SRC/libexec/gcc/$TARGET/$NEWGCC" "$dst/libexec/gcc/$TARGET/"
    mkdir -p "$dst/$TARGET/include/c++"
    cp -a "$SRC/$TARGET/include/c++/$NEWGCC" "$dst/$TARGET/include/c++/"
    cp -a "$SRC/$TARGET/lib/." "$dst/$TARGET/lib/"
    for c in "$dst/$TARGET/include/c++/$NEWGCC/cstdlib"; do patch_cstdlib "$c"; done
}

if [ "${1:-}" = "--restore" ]; then
    [ -d "$BACKUP" ] || { echo "no backup at $BACKUP" >&2; exit 1; }
    for tag in gcc-install sysroot redoxer; do
        case $tag in
            gcc-install) dst="$PREFIX_GCC" ;;
            sysroot)     dst="$PREFIX_SYSROOT" ;;
            redoxer)     dst="$REDOXER" ;;
        esac
        [ -d "$BACKUP/$tag" ] || continue
        echo "restoring $tag"
        cp -a "$BACKUP/$tag/." "$dst/"
    done
    echo "GCC $OLDGCC restored. Re-run without --restore to go back to $NEWGCC."
    exit 0
fi

[ -x "$SRC/bin/$TARGET-gcc" ] || {
    echo "FATAL: $SRC not built. Run local/scripts/build-gcc16-cross.sh" >&2; exit 1; }
[ -e "$SRC/$TARGET/lib/libstdc++.so.6" ] || {
    echo "FATAL: $SRC has no shared libstdc++. The desktop stack links" >&2
    echo "       libstdc++.so.6 (readelf -d libQt6Core.so), so a static-only" >&2
    echo "       toolchain cannot build it." >&2; exit 1; }

echo "Installing GCC $NEWGCC (backup of $OLDGCC -> $BACKUP)"
rm -rf "$BACKUP"
install_into "$PREFIX_GCC"     gcc-install
install_into "$PREFIX_SYSROOT" sysroot
install_into "$REDOXER"        redoxer

echo
echo "Verifying the compiler each recipe will actually invoke:"
PATH="$REDOXER/bin:$PREFIX_SYSROOT/bin:$PATH" "$TARGET-gcc" --version | head -1
PATH="$REDOXER/bin:$PREFIX_SYSROOT/bin:$PATH" "$TARGET-g++" -std=c++23 -x c++ -c - -o /dev/null <<'EOF'
#include <version>
#ifndef __cpp_lib_ranges_to_container
#error ranges::to missing
#endif
int main(){}
EOF
echo "C++23 ranges::to: OK"
echo "Revert with: $0 --restore"