#!/usr/bin/env bash
# ---------------------------------------------------------------------------
# scripts/backup.sh — local SQLite + media snapshot
#
# Produces two artifacts under data/backups/:
#   app-<ts>.db          : SQLite .backup of the live database (safe while
#                          the app is running; sqlite3 .backup coordinates
#                          with WAL).
#   media-<ts>.tar.gz    : tar archive of the media upload directory.
#
# Retention: keep the 14 newest of each artifact; prune the rest.
#
# The script is intended to be invoked by cron on the Debian VM. Example
# crontab line (daily at 03:15 UTC):
#     15 3 * * * cd /srv/chicken_babies_site && ./scripts/backup.sh \
#         >> /var/log/chicken_babies/backup.log 2>&1
#
# Exit codes:
#   0 on success. Any failing step aborts via `set -e` with a non-zero
#   status so cron emails / log scrapers can flag it.
# ---------------------------------------------------------------------------

set -euo pipefail

# UTC timestamp: sortable, compact, unambiguous. Matches the ISO-8601
# "basic" form with a literal Z suffix.
TS="$(date -u +%Y%m%dT%H%M%SZ)"

BACKUP_DIR="data/backups"
DB_SRC="data/app.db"
MEDIA_SRC="data/media"

# Ensure the output directory exists. `mkdir -p` is idempotent and never
# fails if the directory already exists, which is exactly what we want.
mkdir -p "${BACKUP_DIR}"

# --- SQLite snapshot ------------------------------------------------------
# Use sqlite3's .backup command rather than `cp` so we get a consistent
# copy even if the database is actively being written to. sqlite3 serialises
# with the WAL and produces a file that's safe to open elsewhere.
DB_DEST="${BACKUP_DIR}/app-${TS}.db"
sqlite3 "${DB_SRC}" ".backup ${DB_DEST}"

# --- Media archive --------------------------------------------------------
# tar the whole media tree. gzip compression keeps the archive small for
# typical image payloads; restore is just `tar -xzf`.
MEDIA_DEST="${BACKUP_DIR}/media-${TS}.tar.gz"
tar -czf "${MEDIA_DEST}" "${MEDIA_SRC}"

# --- Retention prune -------------------------------------------------------
# Keep the 14 newest of each type; delete the rest. ls -t sorts newest-
# first; tail -n +15 drops the first 14 lines (the survivors). We guard
# each rm with `|| true` so a cold start with fewer than 14 artifacts
# doesn't cause the script to exit non-zero via `set -e`.
keep_newest_14() {
    local pattern="$1"
    # shellcheck disable=SC2012  # `ls -t` is the simplest way to sort by mtime
    ls -1t ${pattern} 2>/dev/null | tail -n +15 | xargs -r rm -f
}

keep_newest_14 "${BACKUP_DIR}/app-*.db"
keep_newest_14 "${BACKUP_DIR}/media-*.tar.gz"

echo "backup complete: ${DB_DEST}, ${MEDIA_DEST}"