#!/bin/bash
# grub-mkconfig — Generate GRUB configuration file (Red Bear OS wrapper)
#
# Compatibility: Matches GNU GRUB grub-mkconfig CLI conventions.
# Generates a grub.cfg for chainloading the Redox bootloader.
#
# Usage:
#   grub-mkconfig [-o FILE]
#   grub-mkconfig --output=/boot/grub/grub.cfg

set -euo pipefail

PROG="$(basename "$0")"
OUTPUT=""
TIMEOUT=5
DEFAULT=0

usage() {
    cat <<EOF
Usage: $PROG [OPTION...]
Generate a GRUB configuration file.

  -o, --output=FILE       Write generated config to FILE [default: stdout]
      --timeout=SECS      Menu timeout in seconds [default: 5]
      --set-default=N     Default menu entry index [default: 0]
  -h, --help              Display this help and exit
  -V, --version           Print program version and exit

Examples:
  # Preview generated config
  $PROG

  # Write to standard GRUB location
  $PROG -o /boot/grub/grub.cfg

  # Write to Red Bear OS recipe directory
  $PROG -o local/recipes/core/grub/grub.cfg
EOF
    exit 0
}

version() {
    echo "$PROG (Red Bear OS) 2.12"
    echo "Compatible with GNU GRUB grub-mkconfig interface"
    exit 0
}

while [ $# -gt 0 ]; do
    case "$1" in
        -o|--output)
            OUTPUT="$2"
            shift 2
            ;;
        --output=*)
            OUTPUT="${1#--output=}"
            shift
            ;;
        --timeout=*)
            TIMEOUT="${1#--timeout=}"
            shift
            ;;
        --timeout)
            TIMEOUT="$2"
            shift 2
            ;;
        --set-default=*)
            DEFAULT="${1#--set-default=}"
            shift
            ;;
        --set-default)
            DEFAULT="$2"
            shift 2
            ;;
        -h|--help)
            usage
            ;;
        -V|--version)
            version
            ;;
        *)
            echo "$PROG: unrecognized option '$1'" >&2
            echo "Try '$PROG --help' for more information." >&2
            exit 1
            ;;
    esac
done

case "$TIMEOUT" in
    ''|*[!0-9]*) echo "$PROG: invalid timeout '$TIMEOUT' (must be a non-negative integer)" >&2; exit 1;;
esac

generate_config() {
    cat <<GRUBCFG
# Generated by $PROG — $(date -Iseconds 2>/dev/null || date)
# Red Bear OS GRUB configuration — chainloads the Redox bootloader

set timeout=$TIMEOUT
set default=$DEFAULT

menuentry "Red Bear OS" {
    chainloader /EFI/REDBEAR/redbear.efi
    boot
}

menuentry "Reboot" {
    reboot
}

menuentry "Shutdown" {
    halt
}
GRUBCFG
}

if [ -n "$OUTPUT" ]; then
    generate_config > "$OUTPUT"
else
    generate_config
fi