#!/bin/bash

# Advanced backup script with logging and error handling
set -euo pipefail  # Exit on error, undefined vars, pipe failures

# Configuration
readonly SCRIPT_NAME="${0##*/}"
readonly BACKUP_DIR="/backup"
readonly LOG_FILE="/var/log/backup.log"
readonly MAX_BACKUPS=7
readonly TIMESTAMP=$(date +"%Y%m%d_%H%M%S")

# Color codes for output
readonly RED='\033[0;31m'
readonly GREEN='\033[0;32m'
readonly YELLOW='\033[1;33m'
readonly NC='\033[0m' # No Color

# Logging function
log() {
    local level="$1"
    shift
    local message="$*"
    local timestamp=$(date '+%Y-%m-%d %H:%M:%S')

    echo -e "${timestamp} [${level}] ${message}" | tee -a "${LOG_FILE}"
}

log_info() { log "INFO" "$@"; }
log_warn() { log "WARN" "$@"; }
log_error() { log "ERROR" "$@"; }

# Error handling
cleanup() {
    local exit_code=$?
    if [[ $exit_code -ne 0 ]]; then
        log_error "Script failed with exit code $exit_code"
    fi
    exit $exit_code
}

trap cleanup EXIT

# Check if running as root
check_root() {
    if [[ $EUID -ne 0 ]]; then
        log_error "This script must be run as root"
        exit 1
    fi
}

# Create backup directory structure
setup_backup_dir() {
    local backup_path="${BACKUP_DIR}/${TIMESTAMP}"

    if ! mkdir -p "$backup_path"; then
        log_error "Failed to create backup directory: $backup_path"
        return 1
    fi

    echo "$backup_path"
}

# Database backup function
backup_database() {
    local db_name="$1"
    local backup_path="$2"
    local db_file="${backup_path}/${db_name}_${TIMESTAMP}.sql"

    log_info "Starting database backup for: $db_name"

    if command -v mysqldump >/dev/null 2>&1; then
        if mysqldump --single-transaction --routines --triggers \
           --user="${DB_USER:-root}" --password="${DB_PASS}" \
           "$db_name" > "$db_file"; then
            log_info "Database backup completed: $db_file"
            gzip "$db_file"
            return 0
        else
            log_error "Database backup failed for: $db_name"
            return 1
        fi
    else
        log_warn "mysqldump not found, skipping database backup"
        return 1
    fi
}

# File system backup
backup_files() {
    local source_dir="$1"
    local backup_path="$2"
    local archive_name="${backup_path}/files_${TIMESTAMP}.tar.gz"

    log_info "Starting file backup from: $source_dir"

    # Exclude common unnecessary files
    local exclude_patterns=(
        "*.log"
        "*.tmp"
        "*cache*"
        "node_modules"
        ".git"
    )

    local tar_excludes=""
    for pattern in "${exclude_patterns[@]}"; do
        tar_excludes+="--exclude=${pattern} "
    done

    if tar czf "$archive_name" $tar_excludes -C "$(dirname "$source_dir")" \
       "$(basename "$source_dir")"; then
        log_info "File backup completed: $archive_name"
        return 0
    else
        log_error "File backup failed for: $source_dir"
        return 1
    fi
}

# Cleanup old backups
cleanup_old_backups() {
    log_info "Cleaning up old backups (keeping $MAX_BACKUPS)"

    # Find and remove old backup directories
    find "$BACKUP_DIR" -maxdepth 1 -type d -name "[0-9]*_[0-9]*" \
         -printf '%T@ %p\n' | sort -nr | tail -n +$((MAX_BACKUPS + 1)) | \
         cut -d' ' -f2- | while read -r old_backup; do
        log_info "Removing old backup: $old_backup"
        rm -rf "$old_backup"
    done
}

# Main backup function
main() {
    log_info "Starting backup process"

    check_root

    local backup_path
    backup_path=$(setup_backup_dir)

    # Backup databases
    while IFS= read -r database; do
        [[ -n "$database" ]] && backup_database "$database" "$backup_path"
    done <<< "${DATABASES:-}"

    # Backup file systems
    local directories=("/etc" "/home" "/var/www")
    for dir in "${directories[@]}"; do
        [[ -d "$dir" ]] && backup_files "$dir" "$backup_path"
    done

    cleanup_old_backups

    log_info "Backup process completed successfully"
    echo -e "${GREEN}✓ Backup completed: $backup_path${NC}"
}

# Script usage
usage() {
    cat << EOF
Usage: $SCRIPT_NAME [OPTIONS]

A comprehensive backup script for databases and file systems.

OPTIONS:
    -h, --help      Show this help message
    -d, --database  Database name to backup
    -v, --verbose   Enable verbose output

EXAMPLES:
    $SCRIPT_NAME
    $SCRIPT_NAME -d myapp_production

ENVIRONMENT VARIABLES:
    DB_USER         Database username (default: root)
    DB_PASS         Database password
    DATABASES       Newline-separated list of databases to backup

EOF
}

# Parse command line arguments
while [[ $# -gt 0 ]]; do
    case $1 in
        -h|--help)
            usage
            exit 0
            ;;
        -d|--database)
            DATABASES="${DATABASES:-}${2}\n"
            shift 2
            ;;
        -v|--verbose)
            set -x
            shift
            ;;
        *)
            log_error "Unknown option: $1"
            usage
            exit 1
            ;;
    esac
done

# Run main function
main "$@"