#!/usr/bin/env bash
# =============================================================================
# tools/boot-image.sh — Create a bootable disk image from the ESP directory
#
# Produces a raw disk image (bootable via UEFI) for dd-ing to a USB stick
# or attaching to QEMU as a hard disk.
#
# Usage:
#   ./tools/boot-image.sh [output.img]
#
# Default output: raisernics.img
# =============================================================================
set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "$0")/.." && pwd)"
cd "$SCRIPT_DIR"

OUTPUT="${1:-raisernics.img}"
ESP_DIR="${ESP_DIR:-esp}"
MBR_SZ=1 # 1 MB reserved at start for GPT/pmbr
SECTOR_SZ=512

# Rebuild ESP if stale
make all

if [ ! -d "$ESP_DIR" ]; then
	echo "ERROR: ESP directory '$ESP_DIR' not found. Run 'make all' first."
	exit 1
fi

# Calculate required size: ESP contents + MBR gap + some slack
ESP_SIZE_MB=$(du -sm "$ESP_DIR" 2>/dev/null | cut -f1 || echo 1)
TOTAL_MB=$((ESP_SIZE_MB + MBR_SZ + 1)) # +1 MB slack

echo "Creating ${TOTAL_MB} MB disk image: ${OUTPUT}"

# Create empty image with MBR gap
dd if=/dev/zero of="$OUTPUT" bs=1M count="$TOTAL_MB" status=none 2>/dev/null

# Partition table: single GPT partition, type EFI System (C12A7328-F81F-11D2-BA4B-00A0C93EC93B)
sgdisk --clear \
	--new=1:${MBR_SZ}M:0 \
	--typecode=1:C12A7328-F81F-11D2-BA4B-00A0C93EC93B \
	--change-name=1:"raisernics" \
	"$OUTPUT" >/dev/null

# Find partition offset
PART_START=$(sgdisk --info=1 "$OUTPUT" 2>/dev/null | grep "Partition start sector" | awk '{print $NF}')
if [ -z "$PART_START" ]; then
	PART_START=$((MBR_SZ * 1024 * 1024 / SECTOR_SZ))
fi

# Format as FAT32
mformat -i "$OUTPUT"@$((PART_START * SECTOR_SZ)) -h 32 -s 32 -t "$((TOTAL_MB * 2))" >/dev/null 2>&1 || true

# Copy the ESP contents onto the partition
mcopy -i "$OUTPUT"@$((PART_START * SECTOR_SZ)) -s "$ESP_DIR"/* ::/ 2>/dev/null

echo "  -> ${OUTPUT}  ($(ls -lh "$OUTPUT" | awk '{print $5}'))"
echo ""
echo "To write to USB:     sudo dd if=${OUTPUT} of=/dev/sdX bs=4M status=progress"
echo "To test with QEMU:   qemu-system-x86_64 -bios <OVMF> -drive file=${OUTPUT},format=raw"