#!/usr/bin/env bash
# backup.sh — snapshot the fleet-manager durable state to timestamped tarballs.
#
# Two docker named volumes hold everything that isn't reproducible from the image:
#   - fleet-data  : inventory.json + admins.json + enroll.key  (CRITICAL — losing
#                   admins.json/enroll.key locks every admin out of the UI)
#   - influx-data : the metrics time-series (history; regenerates going forward)
#
# Runs a throwaway alpine container to tar each volume read-only into $DEST. Safe
# to run live. Schedule it (systemd timer / cron); copy $DEST offsite.
#
# Usage:
#   ./backup.sh [dest-dir]                 # default dest: ./backups
#   COMPOSE_PROJECT_NAME=foo ./backup.sh   # if you run compose under another project
#
# Restore (manager stopped):
#   docker run --rm -v <project>_fleet-data:/dest -v "$PWD/backups":/src alpine \
#     sh -c 'rm -rf /dest/* && tar xzf /src/fleet-data-YYYYmmdd-HHMMSS.tar.gz -C /dest'
set -euo pipefail

DEST=${1:-./backups}
PROJECT=${COMPOSE_PROJECT_NAME:-fleet-manager}   # compose derives volume names as <project>_<key>
STAMP=$(date -u +%Y%m%d-%H%M%S)
VOLUMES=${BACKUP_VOLUMES:-"fleet-data influx-data"}

mkdir -p "$DEST"
DEST_ABS=$(cd "$DEST" && pwd)

for key in $VOLUMES; do
    vol="${PROJECT}_${key}"
    if ! docker volume inspect "$vol" >/dev/null 2>&1; then
        echo "backup: SKIP $vol (no such volume — wrong COMPOSE_PROJECT_NAME?)"
        continue
    fi
    out="${key}-${STAMP}.tar.gz"
    echo "backup: $vol -> $DEST_ABS/$out"
    docker run --rm \
        -v "${vol}:/src:ro" \
        -v "${DEST_ABS}:/backup" \
        alpine tar czf "/backup/${out}" -C /src .
done

# Retention: keep the newest $KEEP of each volume's tarballs (0 = keep all).
KEEP=${BACKUP_KEEP:-14}
if [ "$KEEP" -gt 0 ]; then
    for key in $VOLUMES; do
        # ls -t for mtime order; our filenames are safe (key + UTC timestamp).
        # shellcheck disable=SC2012
        ls -1t "$DEST_ABS/${key}-"*.tar.gz 2>/dev/null | tail -n +"$((KEEP + 1))" | while read -r old; do
            echo "backup: prune $old"
            rm -f "$old"
        done
    done
fi

echo "backup: done ($STAMP) — copy $DEST_ABS offsite."