#!/usr/bin/env bash

ensure-tmp-symlink

#

Guarantees that the project's tmp/ directory exists as a symbolic link into

a project-specific subdirectory of the system tmpfs at /tmp/, so that all

ephemeral output the project produces lives in RAM rather than on disk.

#

Idempotent: safe to call repeatedly from any script that is about to write

into tmp/. The first call materialises the tmpfs target and the symlink; later

calls verify them and exit cleanly. If the path already exists as a real

directory or as a symlink pointing somewhere else, the helper fails loudly

rather than silently rewriting it — silently moving someone's data into a

tmpfs would be worse than refusing and asking a human to investigate.

#

Usage:

scripts/ensure-tmp-symlink # uses hard-coded DIR

scripts/ensure-tmp-symlink /path/to/project/root # overrides DIR

source scripts/ensure-tmp-symlink # bash callers can source

set -eu

{{{ DIR resolution

Hard-coded project root with first-argument override, per the project-wide

convention for scripts.

DIR="${1:-/mnt/mtwo/programming/ai-stuff/neocities-modernization}"

}}}

{{{ TARGET resolution

The tmpfs-backed target lives under /tmp/ with a name that uniquely

identifies this project, so multiple projects on the same host do not

collide.

TMPFS_TARGET="/tmp/neocities-modernization"
SYMLINK_PATH="${DIR}/tmp"

}}}

{{{ ensure_tmpfs_target_exists

ensure_tmpfs_target_exists() {
# If the target subdirectory of /tmp/ does not exist yet, create it. Empty
# tmpfs directories cost nothing and are wiped on reboot, so the only
# consequence of a stale target is that it might have leftover bytes from a
# previous boot — harmless, since this directory is for ephemera anyway.
if [ ! -d "${TMPFS_TARGET}" ]; then
mkdir -p "${TMPFS_TARGET}"
fi
}

}}}

{{{ ensure_symlink_correct

ensure_symlink_correct() {
# Case 1: the symlink path does not exist at all. Create the symlink.
# This is the fresh-clone case.
if [ ! -e "${SYMLINK_PATH}" ] && [ ! -L "${SYMLINK_PATH}" ]; then
ln -s "${TMPFS_TARGET}" "${SYMLINK_PATH}"
return 0
fi

# Case 2: the path is a symlink and points to the right place. Nothing to
# do. This is the steady-state happy path that most calls hit.
if [ -L "${SYMLINK_PATH}" ]; then
local current_target
current_target=$(readlink "${SYMLINK_PATH}")
if [ "${current_target}" = "${TMPFS_TARGET}" ]; then
return 0
fi
# Case 3: the path is a symlink, but points somewhere else. Fail loud.
# The user may have configured an override they care about; we will not
# silently break it.
echo "ERROR: ${SYMLINK_PATH} is a symlink to '${current_target}'," >&2
echo " expected target '${TMPFS_TARGET}'. Investigate before" >&2
echo " re-running. To accept the expected target:" >&2
echo " rm '${SYMLINK_PATH}'" >&2
echo " scripts/ensure-tmp-symlink" >&2
exit 1
fi

# Case 4: the path exists but is not a symlink. Real directory or file.
# Fail loud — this is the violation case that drove this whole issue.
# Silent migration would risk losing whatever bytes the user has placed
# there.
echo "ERROR: ${SYMLINK_PATH} exists but is not a symbolic link." >&2
echo " Move its contents elsewhere, then remove it, then re-run." >&2
echo " Suggested:" >&2
echo " mv '${SYMLINK_PATH}' '${SYMLINK_PATH}.preserved'" >&2
echo " scripts/ensure-tmp-symlink" >&2
exit 1
}

}}}

ensure_tmpfs_target_exists
ensure_symlink_correct