#!/bin/bash
# Loopback disks for exercising the multi-disk install and storage paths.
#
#   scripts/dev/lp-testdisk up [count] [size]   # default 2 disks, 30G sparse
#   scripts/dev/lp-testdisk status
#   scripts/dev/lp-testdisk down
#
# Why loopback rather than a spare partition: the code paths that matter care
# that a location sits on a DIFFERENT filesystem — appDir resolution, the
# storage registry's device numbers, `st_dev` comparisons in the installer's
# disk picker, and app-adopt's same-device mv vs cross-device copy. A loop
# device gives all of that with a real ext4 superblock, its own st_dev and its
# own free-space figures, and can be thrown away between runs.
#
# Sparse-allocated, so a 30G disk costs what is written to it, not 30G.
set -u

BACKING_DIR="${LP_TESTDISK_DIR:-/var/lib/lp-testdisks}"
MNT_PREFIX="${LP_TESTDISK_MNT:-/mnt/lptest}"

_need_root() { [[ $EUID -eq 0 ]] || { echo "lp-testdisk: run with sudo" >&2; exit 1; }; }

up() {
    _need_root
    local count="${1:-2}" size="${2:-30G}"
    mkdir -p "$BACKING_DIR"
    local i img mnt
    for (( i=1; i<=count; i++ )); do
        img="$BACKING_DIR/disk$i.img"
        mnt="${MNT_PREFIX}$i"
        if ! [[ -f "$img" ]]; then
            truncate -s "$size" "$img"
            mkfs.ext4 -q -L "lptest$i" "$img"
            echo "  created $img ($size, sparse)"
        fi
        mkdir -p "$mnt"
        if mountpoint -q "$mnt"; then
            echo "  already mounted: $mnt"
        else
            mount -o loop "$img" "$mnt" || { echo "  FAILED to mount $img" >&2; return 1; }
            # An install writes here as root and then hands ownership over, so
            # the mount point itself only needs to be traversable.
            chmod 0755 "$mnt"
            echo "  mounted $img -> $mnt"
        fi
    done
    status
}

status() {
    local mnt
    printf '  %-16s %-10s %-8s %-8s %s\n' MOUNT DEV SIZE AVAIL "st_dev"
    for mnt in "${MNT_PREFIX}"*; do
        [[ -d "$mnt" ]] || continue
        if mountpoint -q "$mnt"; then
            printf '  %-16s %-10s %-8s %-8s %s\n' "$mnt" \
                "$(findmnt -no SOURCE "$mnt" 2>/dev/null | xargs -r basename)" \
                "$(findmnt -no SIZE  "$mnt" 2>/dev/null)" \
                "$(findmnt -no AVAIL "$mnt" 2>/dev/null)" \
                "$(stat -c '%d' "$mnt" 2>/dev/null)"
        else
            printf '  %-16s %s\n' "$mnt" "(not mounted)"
        fi
    done
    printf '  %-16s %-10s %-8s %-8s %s\n' "/" \
        "$(findmnt -no SOURCE --target / | tail -1 | xargs -r basename)" \
        "$(findmnt -no SIZE --target / | tail -1)" \
        "$(findmnt -no AVAIL --target / | tail -1)" \
        "$(stat -c '%d' / 2>/dev/null)"
}

down() {
    _need_root
    local mnt
    for mnt in "${MNT_PREFIX}"*; do
        [[ -d "$mnt" ]] || continue
        if mountpoint -q "$mnt"; then
            umount "$mnt" 2>/dev/null || umount -l "$mnt" 2>/dev/null \
                || { echo "  busy, still mounted: $mnt" >&2; continue; }
            echo "  unmounted $mnt"
        fi
        rmdir "$mnt" 2>/dev/null
    done
}

destroy() {
    _need_root
    down
    [[ -d "$BACKING_DIR" ]] && { rm -rf "$BACKING_DIR"; echo "  removed $BACKING_DIR"; }
}

case "${1:-status}" in
    up)      shift; up "$@" ;;
    status)  status ;;
    down)    down ;;
    destroy) destroy ;;
    *) echo "usage: lp-testdisk {up [count] [size]|status|down|destroy}" >&2; exit 2 ;;
esac