#!/usr/bin/env bash
# Generate hardware.nix for a registered host.
#
# Run this on the NEW machine (the one whose hardware you want captured),
# inside this repo.  Two contexts are auto-detected:

set -euo pipefail

NAME=""
REPO_ROOT="."

while (($#)); do
    case "$1" in
        --repo-root) REPO_ROOT="${2:?missing path}"; shift 2 ;;
        -h|--help)
            awk '/^#!/ {next} /^[^#]/ {exit} {sub(/^# ?/, ""); print}' "$0"
            exit 0 ;;
        -*) echo "[-] unknown flag: $1" >&2; exit 1 ;;
        *)
            if [[ -z "$NAME" ]]; then
                NAME="$1"; shift
            else
                echo "[-] unexpected positional arg: $1" >&2; exit 1
            fi
            ;;
    esac
done

if [[ -z "$NAME" ]]; then
    echo "[-] usage: $0 <name>" >&2
    exit 1
fi

cd "$REPO_ROOT"
target="hosts/${NAME}/hardware.nix"

if [[ ! -d "hosts/${NAME}" ]]; then
    echo "[-] hosts/${NAME} does not exist." >&2
    echo "    Run \`just register-host ${NAME}\` first." >&2
    exit 1
fi

if ! command -v nixos-generate-config >/dev/null 2>&1; then
    echo "[-] nixos-generate-config not found." >&2
    echo "    Run this on a NixOS machine (running system or installer ISO)." >&2
    exit 2
fi

# Detect installer-mounted-at-/mnt vs running-system.
extra_args=()
if mountpoint -q /mnt 2>/dev/null && [[ -d /mnt/etc ]]; then
    echo "[+] Detected mounted target at /mnt — using --root /mnt"
    extra_args+=(--root /mnt)
elif mountpoint -q /mnt 2>/dev/null; then
    echo "[!] /mnt is mounted but doesn't look like a NixOS target (no /mnt/etc)."
    echo "    Continuing as if on a running system. Edit hardware.nix afterwards"
    echo "    if disks aren't permanent."
fi

# Confirm before overwriting a non-placeholder hardware.nix.
if [[ -f "$target" ]] && ! grep -q 'PLACEHOLDER hardware.nix' "$target"; then
    echo "[!] $target already exists and doesn't look like a placeholder." >&2
    if [[ -t 0 ]]; then
        read -r -p "Overwrite? (yes/[no]) " confirm
        [[ "$confirm" == "yes" ]] || { echo "aborted."; exit 1; }
    else
        echo "[-] non-interactive; refusing to overwrite. Delete $target first." >&2
        exit 1
    fi
fi

echo "[+] Generating hardware config..."
# The redirect runs in the user's shell BEFORE sudo, so the file is owned
# by the invoking user.  sudo is needed because nixos-generate-config
# probes /proc, /sys, and may need to read mounted filesystems.
sudo nixos-generate-config --show-hardware-config "${extra_args[@]}" > "$target"
echo "[+] Wrote $target"

if command -v git >/dev/null && git rev-parse >/dev/null 2>&1; then
    echo "[+] git diff:"
    git --no-pager diff -- "$target" || true
fi