#!/bin/bash
# ============================================================================
# DarkForge Linux — Phase 0: Environment Setup
# ============================================================================
# Purpose:  Set up the build environment, directory structure, and variables
#           needed for the cross-toolchain bootstrap.
# Inputs:   LFS - path to target partition (e.g., /mnt/darkforge)
# Outputs:  Environment variables, directory tree, lfs user
# Assumes:  Target partition is mounted at $LFS, running as root
# Ref:      LFS 13.0 Chapters 2-4
# ============================================================================

set -euo pipefail

# --- Configuration -----------------------------------------------------------
# These must be set before running this script.
# Override via environment or edit here.
LFS="${LFS:-/mnt/darkforge}"
LFS_TGT="x86_64-darkforge-linux-gnu"

# DarkForge hardware-specific flags (applied in native builds, NOT cross-compile)
DF_CFLAGS="-march=znver5 -O2 -pipe -fomit-frame-pointer"
DF_CXXFLAGS="${DF_CFLAGS}"
DF_MAKEFLAGS="-j32"
DF_LDFLAGS="-Wl,-O1,--as-needed"

# --- Verify mount point ------------------------------------------------------
if ! mountpoint -q "${LFS}" 2>/dev/null; then
    echo "ERROR: ${LFS} is not a mount point."
    echo "Run 000-setup-disk.sh first to create and mount the LFS filesystem,"
    echo "or mount a partition manually: mount /dev/<partition> ${LFS}"
    exit 1
fi

echo "=== DarkForge Phase 0: Environment Setup ==="
echo "LFS=${LFS}"
echo "LFS_TGT=${LFS_TGT}"

# --- Create directory structure -----------------------------------------------
echo ">>> Creating directory structure..."
mkdir -pv "${LFS}/sources"
mkdir -pv "${LFS}/tools"
mkdir -pv "${LFS}"/{etc,var,usr/{bin,lib,sbin}}

# Create /lib64 symlink for x86_64
case $(uname -m) in
    x86_64) mkdir -pv "${LFS}/lib64" ;;
esac

# Symlinks for unified /usr layout (LFS 13.0 style)
for dir in bin lib sbin; do
    ln -sfv "usr/${dir}" "${LFS}/${dir}" 2>/dev/null || true
done

# Set sticky bit on sources directory
chmod -v a+wt "${LFS}/sources"

# --- Create lfs user (if not exists) ------------------------------------------
echo ">>> Setting up 'lfs' build user..."
if ! id lfs &>/dev/null; then
    groupadd lfs
    useradd -s /bin/bash -g lfs -m -k /dev/null lfs
    echo "Created 'lfs' user."
else
    echo "'lfs' user already exists."
fi

# Grant lfs ownership of build directories
chown -v lfs "${LFS}"/{usr{,/*},lib,var,etc,bin,lib64,sbin,tools,sources} 2>/dev/null || true

# --- Write lfs user's shell profile -------------------------------------------
echo ">>> Writing lfs shell profile..."
cat > /home/lfs/.bash_profile << 'PROFILE_EOF'
exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash
PROFILE_EOF

cat > /home/lfs/.bashrc << BASHRC_EOF
set +h
umask 022
LFS=${LFS}
LC_ALL=POSIX
LFS_TGT=${LFS_TGT}
PATH=${LFS}/tools/bin:/usr/bin
if [ ! -L /bin ]; then PATH=/bin:\$PATH; fi
export LFS LC_ALL LFS_TGT PATH
export MAKEFLAGS="${DF_MAKEFLAGS}"
BASHRC_EOF

chown lfs:lfs /home/lfs/.bash_profile /home/lfs/.bashrc

# --- Write persistent environment config for other scripts --------------------
cat > "${LFS}/sources/darkforge-env.sh" << ENV_EOF
# DarkForge build environment — sourced by all toolchain scripts
export LFS="${LFS}"
export LFS_TGT="${LFS_TGT}"
export LC_ALL=POSIX
export PATH="${LFS}/tools/bin:/usr/bin"
if [ ! -L /bin ]; then export PATH="/bin:\${PATH}"; fi
export MAKEFLAGS="${DF_MAKEFLAGS}"

# Hardware-specific flags (only for native compilation, NOT cross-compile)
export DF_CFLAGS="${DF_CFLAGS}"
export DF_CXXFLAGS="${DF_CXXFLAGS}"
export DF_LDFLAGS="${DF_LDFLAGS}"
ENV_EOF

echo "=== Environment setup complete ==="
echo ""
echo "Next steps:"
echo "  1. Download source tarballs to ${LFS}/sources/"
echo "  2. Switch to lfs user:  su - lfs"
echo "  3. Run toolchain build scripts in order (001, 002, ...)"