#!/usr/bin/env bash
# qemu-ram.sh — Boot Red Bear OS from RAM-disk (tmpfs)
#
# Copies the disk image into tmpfs before launching QEMU, eliminating
# all host disk I/O during OS runtime.
#
# Usage: invoked by `make qemu-ram` — not intended for direct use.
#
# Arguments:
#   $1  QEMU binary (e.g. qemu-system-x86_64)
#   $2  Disk image path (harddrive.img or live ISO)
#   $3  QEMU flags (space-separated)
#   $4  RAM directory (tmpfs mount point)

set -euo pipefail

QEMU_BIN="${1:?Usage: qemu-ram.sh <qemu-bin> <disk> <flags> <ramdir>}"
DISK="${2:?disk image path required}"
QEMU_FLAGS="${3:?QEMU flags required}"
RAMDIR="${4:?RAM directory required}"

if [ ! -f "$DISK" ]; then
    echo "ERROR: disk image not found: $DISK" >&2
    exit 1
fi

cleanup() {
    echo "Red Bear: cleaning up RAM-disk..."
    if mountpoint -q "$RAMDIR" 2>/dev/null; then
        umount "$RAMDIR" 2>/dev/null || true
    fi
    rmdir "$RAMDIR" 2>/dev/null || true
}
trap cleanup EXIT

# Size the tmpfs: image size + 512 MiB overhead, minimum 1 GiB
img_mb=$(du -m "$DISK" | cut -f1)
tmpfs_mb=$((img_mb + 512))
[ "$tmpfs_mb" -lt 1024 ] && tmpfs_mb=1024

echo "Red Bear: preparing RAM-disk boot..."
mkdir -p "$RAMDIR"

if ! mountpoint -q "$RAMDIR" 2>/dev/null; then
    mount -t tmpfs -o "size=${tmpfs_mb}m" tmpfs "$RAMDIR"
fi

echo "Red Bear: copying $DISK to RAM ($(du -h "$DISK" | cut -f1))..."
cp "$DISK" "$RAMDIR/disk.img"

ram_flags="${QEMU_FLAGS//$DISK/$RAMDIR/disk.img}"

echo "Red Bear: booting from RAM-disk..."
exec "$QEMU_BIN" $ram_flags