#!/bin/bash
# Manage the microscope capture SSD mount.
#
#   microscope-ssd mount    mount the SSD (waits briefly for it to appear)
#   microscope-ssd umount   flush and unmount safely
#   microscope-ssd status   print: mounted | stale | unmounted | absent
#
# Called by the udev-triggered microscope-ssd-mount.service when the drive is
# plugged in, by fstab at boot, and by the kiosk UI (through a NOPASSWD sudoers
# entry) when the operator taps MOUNT SSD.
#
# stdout stays machine-readable (status) while everything also lands in a log
# file, because udev and systemd capture stdout in ways that are awkward to read.
set -u

MOUNT_POINT="${MICROSCOPE_MOUNT:-/mnt/microscope}"
UUID="${MICROSCOPE_UUID:-caf4320b-0fa3-4674-bfa9-f17f6165f681}"
OWNER="${MICROSCOPE_OWNER:-tyler:tyler}"
DEV="/dev/disk/by-uuid/${UUID}"
LOG_FILE="${MICROSCOPE_LOG:-/run/microscope-ssd.log}"

log() {
    local message="microscope-ssd: $*"
    echo "$message" >>"$LOG_FILE" 2>/dev/null || true
    echo "$message"
}

in_mounts() { grep -qs " ${MOUNT_POINT} " /proc/self/mounts; }

do_status() {
    # 'stale' means a mount entry survived a yank: the device node is gone.
    if in_mounts; then
        if [ -e "$DEV" ]; then echo mounted; else echo stale; fi
    elif [ -e "$DEV" ]; then
        echo unmounted
    else
        echo absent
    fi
}

do_mount() {
    mkdir -p "$MOUNT_POINT"

    if in_mounts; then
        if [ -e "$DEV" ]; then
            log "already mounted"
            return 0
        fi
        log "clearing stale mount entry"
        umount -l "$MOUNT_POINT" 2>/dev/null || true
    fi

    for _ in $(seq 1 40); do
        [ -e "$DEV" ] && break
        sleep 0.25
    done
    if [ ! -e "$DEV" ]; then
        log "SSD not present ($DEV)"
        return 1
    fi

    if mount -t ext4 -o noatime,errors=remount-ro "$DEV" "$MOUNT_POINT"; then
        chown "$OWNER" "$MOUNT_POINT" 2>/dev/null || true
        chmod 755 "$MOUNT_POINT" 2>/dev/null || true
        log "mounted $DEV at $MOUNT_POINT"
        return 0
    fi
    log "mount failed"
    return 1
}

do_umount() {
    if ! in_mounts; then
        log "not mounted"
        return 0
    fi
    sync
    if umount "$MOUNT_POINT"; then
        log "unmounted (safe to unplug)"
        return 0
    fi
    log "unmount failed - something is still using $MOUNT_POINT"
    return 1
}

ACTION="${1:-status}"
case "$ACTION" in
    mount|umount) log "--- $(date -Is) action=$ACTION euid=$(id -u) ---" ;;
esac

case "$ACTION" in
    mount)  do_mount ;;
    umount) do_umount ;;
    status) do_status ;;
    *)      echo "usage: $0 {mount|umount|status}" >&2; exit 2 ;;
esac