#!/usr/bin/env bash
# Nexus — MySQL Auto-Backup Script
# Usage: Add to crontab for daily 3AM backup
#   0 3 * * * /path/to/nexus/deploy/db_backup.sh >> /var/log/nexus_backup.log 2>&1
#
# Reads DATABASE_URL from .env for connection parameters.
# Retains backups for 30 days, auto-deletes older ones.

set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
ENV_FILE="$PROJECT_DIR/.env"
BACKUP_DIR="$PROJECT_DIR/backups"
RETENTION_DAYS=30

# ── Load .env ──
if [ ! -f "$ENV_FILE" ]; then
    echo "[$(date)] ERROR: .env not found at $ENV_FILE"
    exit 1
fi

# Parse DATABASE_URL from .env
# Format: mysql+asyncmy://user:password@host:port/dbname
DB_URL=$(grep -E '^NEXUS_DATABASE_URL=' "$ENV_FILE" | head -1 | cut -d= -f2- | tr -d '"' | tr -d "'")
if [ -z "$DB_URL" ]; then
    DB_URL=$(grep -E '^DATABASE_URL=' "$ENV_FILE" | head -1 | cut -d= -f2- | tr -d '"' | tr -d "'")
fi

if [ -z "$DB_URL" ]; then
    echo "[$(date)] ERROR: DATABASE_URL not found in .env"
    exit 1
fi

# Parse mysql URL: mysql+asyncmy://user:pass@host:port/dbname → user pass host port dbname
# Strip scheme
CONN="${DB_URL#*://}"
# Extract user:pass
USERPASS="${CONN%%@*}"
DB_USER="${USERPASS%%:*}"
DB_PASS="${USERPASS#*:}"
# Extract host:port/dbname
HOSTDB="${CONN#*@}"
DB_HOST="${HOSTDB%%:*}"
PORTDB="${HOSTDB#*:}"
DB_PORT="${PORTDB%%/*}"
DB_NAME="${PORTDB#*/}"
# Remove query params
DB_NAME="${DB_NAME%%\?*}"

if [ -z "$DB_NAME" ] || [ -z "$DB_HOST" ] || [ -z "$DB_USER" ]; then
    echo "[$(date)] ERROR: Failed to parse DATABASE_URL"
    exit 1
fi

# ── Create backup directory ──
mkdir -p "$BACKUP_DIR"

# ── Backup filename ──
TIMESTAMP=$(date +%Y%m%d_%H%M%S)
BACKUP_FILE="$BACKUP_DIR/nexus_${DB_NAME}_${TIMESTAMP}.sql.gz"

# ── Run mysqldump ──
echo "[$(date)] Starting backup: $DB_NAME @ $DB_HOST"

if [ -n "$DB_PASS" ]; then
    MYSQL_PWD="$DB_PASS" mysqldump \
        -h "$DB_HOST" \
        -P "${DB_PORT:-3306}" \
        -u "$DB_USER" \
        --single-transaction \
        --routines \
        --triggers \
        --set-gtid-purged=OFF \
        "$DB_NAME" | gzip > "$BACKUP_FILE"
else
    mysqldump \
        -h "$DB_HOST" \
        -P "${DB_PORT:-3306}" \
        -u "$DB_USER" \
        --single-transaction \
        --routines \
        --triggers \
        --set-gtid-purged=OFF \
        "$DB_NAME" | gzip > "$BACKUP_FILE"
fi

# ── Verify backup ──
if [ -f "$BACKUP_FILE" ]; then
    SIZE=$(du -h "$BACKUP_FILE" | cut -f1)
    echo "[$(date)] Backup completed: $BACKUP_FILE ($SIZE)"
else
    echo "[$(date)] ERROR: Backup file not created!"
    exit 1
fi

# ── Cleanup old backups (retain 30 days) ──
DELETED=$(find "$BACKUP_DIR" -name "nexus_*.sql.gz" -mtime +${RETENTION_DAYS} -delete -print | wc -l)
if [ "$DELETED" -gt 0 ]; then
    echo "[$(date)] Cleaned up $DELETED old backup(s) (>${RETENTION_DAYS} days)"
fi

echo "[$(date)] Backup process complete"