#!/bin/bash
# backup-sqlite.sh — Safe hot backup of the XAMXAM SQLite database.
#
# Uses sqlite3's .backup command (WAL-safe) then gzip-compresses.
# Prunes backups older than RETENTION_DAYS.
#
# Usage:
#   /usr/local/bin/backup-sqlite.sh                      # default: 30 days
#   RETENTION_DAYS=90 /usr/local/bin/backup-sqlite.sh     # 90 days
#
# Expected to be run from cron:
#   0 * * * * /usr/local/bin/backup-sqlite.sh >> /var/log/xamxam-backup-$(date +%Y-%m-%d).log 2>&1
#   0 2 * * * RETENTION_DAYS=90 /usr/local/bin/backup-sqlite.sh >> /var/log/xamxam-backup-$(date +%Y-%m-%d).log 2>&1

set -euo pipefail

DB_PATH="${DB_PATH:-/var/www/xamxam/storage/xamxam.db}"
BACKUP_DIR="${BACKUP_DIR:-/var/backups/xamxam}"
RETENTION_DAYS="${RETENTION_DAYS:-30}"

TIMESTAMP=$(date +"%Y-%m-%dT%H-%M-%S")
BACKUP_FILE="$BACKUP_DIR/db-$TIMESTAMP.db.gz"
TMP_SNAPSHOT="/tmp/xamxam-snapshot-$$.db"

mkdir -p "$BACKUP_DIR" 2>/dev/null || {
    echo "ERROR: Cannot create backup directory '$BACKUP_DIR'. Run: just deploy-backup-cron" >&2
    exit 1
}

# Safe hot backup using SQLite's online backup API
sqlite3 "$DB_PATH" ".backup $TMP_SNAPSHOT"
gzip -c "$TMP_SNAPSHOT" > "$BACKUP_FILE"
rm -f "$TMP_SNAPSHOT"

# Prune old backups.
# Use filename timestamps (deterministic) rather than -mtime, which has
# day-rounding ambiguity (-mtime +N means N+1 days). Files are named
# db-YYYY-MM-DDTHH-MM-SS.db.gz, so we delete anything whose date is more
# than RETENTION_DAYS in the past.
RETENTION_SECONDS=$((RETENTION_DAYS * 86400))
NOW_EPOCH=$(date +%s)
for f in "$BACKUP_DIR"/db-*.db.gz; do
    [ -e "$f" ] || continue
    base=$(basename "$f" .db.gz)          # db-YYYY-MM-DDTHH-MM-SS
    stamp=${base#db-}                        # YYYY-MM-DDTHH-MM-SS
    # Reformat YYYY-MM-DDTHH-MM-SS → YYYY-MM-DD HH:MM:SS for date(1).
    named=$(echo "$stamp" | sed 's/T/ /; s/-/:/3g') || continue
    ts=$(date -d "$named" +%s 2>/dev/null) || continue
    if [ $((NOW_EPOCH - ts)) -gt $RETENTION_SECONDS ]; then
        rm -f "$f"
    fi
done

echo "[$(date '+%Y-%m-%d %H:%M:%S')] Backup written: $BACKUP_FILE ($(du -h "$BACKUP_FILE" | cut -f1))"