#!/bin/bash

# Set strict mode
set -euo pipefail

# Constants
LOG_FILE="performance_optimization.log"
CACHE_DIR="/var/cache/quantumnexus"
TEMP_DIR="/tmp/quantumnexus"
DB_NAME="quantumnexus_db"
DB_USER="quantumnexus_user"

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

# Function to clean up temporary files
cleanup_temp_files() {
    log "Cleaning up temporary files..."
    if [ -d "$TEMP_DIR" ]; then
        rm -rf "$TEMP_DIR/*"
        log "Temporary files cleaned up."
    else
        log "Temporary directory $TEMP_DIR does not exist."
    fi
}

# Function to optimize database
optimize_database() {
    log "Optimizing database..."
    if command -v mysql >/dev/null 2>&1; then
        mysqlcheck -o --all-databases -u "$DB_USER" -p
        log "Database optimization completed."
    else
        log "MySQL is not installed. Please install MySQL and try again."
        exit 1
    fi
}

# Function to clear application cache
clear_cache() {
    log "Clearing application cache..."
    if [ -d "$CACHE_DIR" ]; then
        rm -rf "$CACHE_DIR/*"
        log "Application cache cleared."
    else
        log "Cache directory $CACHE_DIR does not exist."
    fi
}

# Function to adjust system settings
adjust_system_settings() {
    log "Adjusting system settings for performance..."
    # Example: Adjusting swappiness
    echo 10 | sudo tee /proc/sys/vm/swappiness
    log "Swappiness set to 10."
    
    # Example: Adjusting file descriptor limits
    echo "* soft nofile 65536" | sudo tee -a /etc/security/limits.conf
    echo "* hard nofile 65536" | sudo tee -a /etc/security/limits.conf
    log "File descriptor limits adjusted."
}

# Main script execution
log "Starting performance optimization..."

# Create or clear the log file
: > "$LOG_FILE"

# Perform optimizations
cleanup_temp_files
optimize_database
clear_cache
adjust_system_settings

log "Performance optimization completed successfully!"
