#!/bin/bash

set -euo pipefail

# Configuration from environment variables
POSTGRES_HOST="${POSTGRES_HOST:-localhost}"
POSTGRES_PORT="${POSTGRES_PORT:-5432}"
POSTGRES_USER="${POSTGRES_USER:-postgres}"
POSTGRES_PASSWORD="${POSTGRES_PASSWORD:-}"
POSTGRES_DB="${POSTGRES_DB:-postgres}"
POSTGRES_DATABASES="${POSTGRES_DATABASES:-}"  # Comma-separated list of databases, if empty backs up all

S3_BUCKET="${S3_BUCKET}"
S3_PREFIX="${S3_PREFIX:-postgres-backups}"
S3_ENDPOINT="${S3_ENDPOINT}"  # Required for third-party S3 services
S3_ACCESS_KEY_ID="${S3_ACCESS_KEY_ID}"
S3_SECRET_ACCESS_KEY="${S3_SECRET_ACCESS_KEY}"
S3_REGION="${S3_REGION:-auto}"  # Default to 'auto' for S3-compatible services

BACKUP_RETENTION_DAYS="${BACKUP_RETENTION_DAYS:-7}"

# Generate timestamp
TIMESTAMP=$(date +"%Y%m%d_%H%M%S")

# Function to log messages
log() {
    echo "[$(date '+%Y-%m-%d %H:%M:%S')] $1"
}

# Function to setup rclone configuration
setup_rclone() {
    log "Setting up rclone configuration for S3-compatible storage"
    
    # Create rclone config directory
    mkdir -p ~/.config/rclone
    
    # Create rclone configuration
    cat > ~/.config/rclone/rclone.conf << EOF
[s3remote]
type = s3
provider = Other
access_key_id = ${S3_ACCESS_KEY_ID}
secret_access_key = ${S3_SECRET_ACCESS_KEY}
endpoint = ${S3_ENDPOINT}
region = ${S3_REGION}
force_path_style = true
acl = private
EOF
}

# Function to get list of databases
get_databases() {
    if [[ -n "${POSTGRES_DATABASES}" ]]; then
        echo "${POSTGRES_DATABASES}" | tr ',' '\n'
    else
        PGPASSWORD="${POSTGRES_PASSWORD}" psql -h "${POSTGRES_HOST}" -p "${POSTGRES_PORT}" -U "${POSTGRES_USER}" -d postgres -t -c "SELECT datname FROM pg_database WHERE datistemplate = false;" | grep -v '^$' | xargs
    fi
}

# Function to backup a single database
backup_database() {
    local db_name="$1"
    local backup_file="/backups/${db_name}_${TIMESTAMP}.sql.gz"
    
    log "Starting backup of database: ${db_name}"
    log "Creating compressed SQL dump"
    
    # Create database dump with gzip compression
    PGPASSWORD="${POSTGRES_PASSWORD}" pg_dump \
        -h "${POSTGRES_HOST}" \
        -p "${POSTGRES_PORT}" \
        -U "${POSTGRES_USER}" \
        -d "${db_name}" \
        --no-password \
        --format=plain \
        --clean \
        --if-exists \
        --no-privileges \
        --no-owner \
        | gzip --rsyncable > "${backup_file}"
    
    # Upload to S3 with flat structure
    local s3_key="${S3_PREFIX}/$(basename "${backup_file}")"
    log "Uploading backup to S3: s3://${S3_BUCKET}/${s3_key}"
    
    rclone copy "${backup_file}" "s3remote:${S3_BUCKET}/${S3_PREFIX}/" --progress
    
    # Verify upload
    if ! rclone ls "s3remote:${S3_BUCKET}/${s3_key}" > /dev/null; then
        log "ERROR: Failed to verify backup upload"
        return 1
    fi
    
    log "Successfully uploaded backup for ${db_name}"
    
    # Clean up local file
    rm -f "${backup_file}"
}

# Function to cleanup old backups
cleanup_old_backups() {
    local db_name="$1"
    local cutoff_date=$(date -d "${BACKUP_RETENTION_DAYS} days ago" +%Y%m%d_%H%M%S)
    
    log "Cleaning up backups older than ${BACKUP_RETENTION_DAYS} days for database: ${db_name}"
    
    # List and delete old backups using rclone with flat structure
    rclone lsf "s3remote:${S3_BUCKET}/${S3_PREFIX}/" --include "${db_name}_*.sql.gz" | while read -r backup_file; do
        # Extract timestamp from filename
        backup_date=$(echo "$backup_file" | grep -o '[0-9]\{8\}_[0-9]\{6\}' || true)
        if [[ -n "$backup_date" && "$backup_date" < "$cutoff_date" ]]; then
            log "Deleting old backup file: ${backup_file}"
            rclone delete "s3remote:${S3_BUCKET}/${S3_PREFIX}/${backup_file}" || log "Failed to delete ${backup_file}"
        fi
    done
}

# Function to send notification (placeholder for webhook/email integration)
send_notification() {
    local status="$1"
    local message="$2"
    
    if [[ -n "${WEBHOOK_URL:-}" ]]; then
        curl -X POST "${WEBHOOK_URL}" \
            -H "Content-Type: application/json" \
            -d "{\"status\": \"${status}\", \"message\": \"${message}\", \"timestamp\": \"$(date -Iseconds)\"}" \
            || log "Failed to send notification"
    fi
}

# Main execution
main() {
    log "Starting PostgreSQL backup process"
    
    # Validate required environment variables
    if [[ -z "${S3_BUCKET}" || -z "${S3_ACCESS_KEY_ID}" || -z "${S3_SECRET_ACCESS_KEY}" || -z "${S3_ENDPOINT}" ]]; then
        log "ERROR: Missing required environment variables (S3_BUCKET, S3_ACCESS_KEY_ID, S3_SECRET_ACCESS_KEY, S3_ENDPOINT)"
        exit 1
    fi
    
    # Setup rclone
    setup_rclone
    
    # Test database connection
    log "Testing database connection"
    if ! PGPASSWORD="${POSTGRES_PASSWORD}" psql -h "${POSTGRES_HOST}" -p "${POSTGRES_PORT}" -U "${POSTGRES_USER}" -d postgres -c "SELECT 1" > /dev/null 2>&1; then
        log "ERROR: Cannot connect to PostgreSQL database"
        send_notification "error" "Cannot connect to PostgreSQL database"
        exit 1
    fi
    
    # Get list of databases to backup
    databases=$(get_databases)
    log "Databases to backup: ${databases}"
    
    # Backup each database
    backup_success=true
    for db in ${databases}; do
        if backup_database "${db}"; then
            cleanup_old_backups "${db}"
        else
            log "ERROR: Failed to backup database: ${db}"
            backup_success=false
        fi
    done
    
    if [[ "${backup_success}" == "true" ]]; then
        log "All database backups completed successfully"
        send_notification "success" "All PostgreSQL database backups completed successfully"
    else
        log "Some database backups failed"
        send_notification "error" "Some PostgreSQL database backups failed"
        exit 1
    fi
}

# Execute main function
main "$@"