#!/bin/bash

# ==============================================================================
# Script Name:  systron-wp-deploy.sh
# Description:  Automated LEMP + Redis Deployer for 1GB+ WordPress Databases
# Target:       Systron Cloud SSD VPS (Ubuntu, Debian, AlmaLinux, Rocky Linux)
# ==============================================================================

# Ensure script is run as root
if [ "$EUID" -ne 0 ]; then
  echo "❌ Error: Please run this script as root or using sudo."
  exit 1
fi

# Clear screen and show banner
clear
echo "====================================================================="
echo "   🚀 Systron VPS WordPress & High-Performance DB Setup Utility 🚀  "
echo "====================================================================="
echo ""

# ------------------------------------------------------------------------------
# Step 1: Environment & Architecture Detection
# ------------------------------------------------------------------------------
echo "🔍 Detecting OS Distribution and Server Resources..."

# Detect Linux Flavor
if [ -f /etc/os-release ]; then
    . /etc/os-release
    OS_FLAVOR=$ID
    OS_VERSION=$VERSION_ID
else
    echo "❌ Error: Cannot determine operating system flavor. Exiting."
    exit 1
fi

# Detect Server RAM to calculate buffer pools dynamically
TOTAL_RAM_KB=$(grep MemTotal /proc/meminfo | awk '{print $2}')
TOTAL_RAM_MB=$((TOTAL_RAM_KB / 1024))

echo "   -> Operating System: ${OS_FLAVOR^} (Version: $OS_VERSION)"
echo "   -> Total System RAM: ${TOTAL_RAM_MB} MB"

# Dynamically calculate ideal MariaDB InnoDB Buffer Pool Size (55% of total RAM)
BUFFER_POOL_MB=$((TOTAL_RAM_MB * 55 / 100))
# Ensure buffer pool has at least 1 instance per GB
BUFFER_POOL_INSTANCES=$((BUFFER_POOL_MB / 1024))
if [ "$BUFFER_POOL_INSTANCES" -lt 1 ]; then BUFFER_POOL_INSTANCES=1; fi

echo "   -> Calculated DB Optimization Buffer Pool: ${BUFFER_POOL_MB} MB"
echo ""

# ------------------------------------------------------------------------------
# Step 2: Distribution-Specific Dependency Installation
# ------------------------------------------------------------------------------
echo "📦 Installing LEMP Stack components for ${OS_FLAVOR^}..."

case "$OS_FLAVOR" in
    ubuntu|debian)
        export DEBIAN_FRONTEND=noninteractive
        apt-get update -y
        apt-get install -y curl wget nginx mariadb-server mariadb-client redis-server php-fpm php-mysql php-redis php-curl php-gd php-mbstring php-xml php-xmlrpc php-soap php-intl php-zip unzip
        
        # Identify PHP version installed to locate correct config paths
        PHP_VER=$(php -r 'print PHP_MAJOR_VERSION.".".PHP_MINOR_VERSION;')
        PHP_INI_PATH="/etc/php/$PHP_VER/fpm/php.ini"
        PHP_FPM_POOL="/etc/php/$PHP_VER/fpm/pool.d/www.conf"
        MYSQL_CONF="/etc/mysql/mariadb.conf.d/50-server.cnf"
        [ ! -f "$MYSQL_CONF" ] && MYSQL_CONF="/etc/mysql/my.cnf"
        ;;
        
    rocky|almalinux|rhel)
        # Enable EPEL and REMI repositories for up-to-date PHP packages
        dnf install -y epel-release
        dnf install -y https://remirepo.net(echo $OS_VERSION | cut -d. -f1).rpm
        dnf module reset php -y
        dnf module enable php:remi-8.2 -y # Defaulting to stable PHP 8.2
        
        # Install packages
        dnf install -y nginx mariadb-server mariadb redis php php-fpm php-mysqlnd php-pecl-redis5 php-curl php-gd php-mbstring php-xml php-soap php-intl php-pecl-zip unzip
        
        PHP_INI_PATH="/etc/php.ini"
        PHP_FPM_POOL="/etc/php-fpm.d/www.conf"
        MYSQL_CONF="/etc/my.cnf.d/mariadb-server.cnf"
        [ ! -f "$MYSQL_CONF" ] && MYSQL_CONF="/etc/my.cnf"
        
        # Open basic firewall ports
        if systemctl is-active --quiet firewalld; then
            firewall-cmd --permanent --add-service=http
            firewall-cmd --permanent --add-service=https
            firewall-cmd --reload
        fi
        ;;
        
    *)
        echo "❌ Error: Flavor '$OS_FLAVOR' is not supported by this automation script."
        exit 1
        ;;
esac

echo "✅ Package installation complete."
echo ""

# ------------------------------------------------------------------------------
# Step 3: Injecting High-Performance Configurations
# ------------------------------------------------------------------------------
echo "⚙️ Injecting resource optimizations for 1GB+ WordPress databases..."

# 1. Optimize Database Configurations
if [ -f "$MYSQL_CONF" ]; then
    cp "$MYSQL_CONF" "${MYSQL_CONF}.bak"
    
    # Safely append configuration parameters directly under the [mysqld] block
    cat <<EOF >> "$MYSQL_CONF"

# --- Systron NVMe Database Engine Optimizations ---
[mysqld]
innodb_buffer_pool_size         = ${BUFFER_POOL_MB}M
innodb_buffer_pool_instances     = ${BUFFER_POOL_INSTANCES}
innodb_log_file_size            = 512M
innodb_log_buffer_size          = 16M
innodb_flush_log_at_trx_commit  = 2
innodb_flush_method             = O_DIRECT
innodb_file_per_table           = 1
max_connections                 = 150
tmp_table_size                  = 64M
max_heap_table_size             = 64M
join_buffer_size                = 4M
EOF
    echo "   [+] Database configurations optimized successfully."
else
    echo "   [⚠️] Warning: Could not locate MySQL/MariaDB configuration file path."
fi

# 2. Optimize PHP Engine Limits
if [ -f "$PHP_INI_PATH" ]; then
    cp "$PHP_INI_PATH" "${PHP_INI_PATH}.bak"
    sed -i "s/memory_limit =.*/memory_limit = 512M/" "$PHP_INI_PATH"
    sed -i "s/upload_max_filesize =.*/upload_max_filesize = 128M/" "$PHP_INI_PATH"
    sed -i "s/post_max_size =.*/post_max_size = 128M/" "$PHP_INI_PATH"
    sed -i "s/max_execution_time =.*/max_execution_time = 300/" "$PHP_INI_PATH"
    echo "   [+] PHP-FPM Engine limits scaled up."
fi

# 3. Configure Redis Storage Optimization
REDIS_CONF="/etc/redis/redis.conf"
[ ! -f "$REDIS_CONF" ] && REDIS_CONF="/etc/redis.conf"
if [ -f "$REDIS_CONF" ]; then
    cp "$REDIS_CONF" "${REDIS_CONF}.bak"
    # Ensure background updates don't cause performance memory warnings
    echo "maxmemory 256mb" >> "$REDIS_CONF"
    echo "maxmemory-policy allkeys-lru" >> "$REDIS_CONF"
    echo "   [+] Memory-efficient Redis configurations injected."
fi

echo ""

# ------------------------------------------------------------------------------
# Step 4: System Restart & Verification
# ------------------------------------------------------------------------------
echo "🔄 Starting and enabling application services..."

# Define service names based on architecture
NGINX_SVC="nginx"
MARIADB_SVC="mariadb"
REDIS_SVC="redis-server"
[ "$OS_FLAVOR" = "rocky" ] || [ "$OS_FLAVOR" = "almalinux" ] && REDIS_SVC="redis"

case "$OS_FLAVOR" in
    ubuntu|debian) PHP_SVC="php$PHP_VER-fpm" ;;
    rocky|almalinux|rhel) PHP_SVC="php-fpm" ;;
esac

# Enable and restart all core stack structures
for service in $NGINX_SVC $MARIADB_SVC $REDIS_SVC $PHP_SVC; do
    systemctl daemon-reload
    systemctl enable $service >/dev/null 2>&1
    systemctl restart $service
    if systemctl is-active --quiet $service; then
        echo "   [✔] Service execution confirmed: $service"
    else
        echo "   [❌] Service failure alert: $service failed to transition up."
    fi
done

echo ""
echo "====================================================================="
echo "🎉 SUCCESS: Your Systron Cloud VPS Stack is Ready for Action! 🎉"
echo "====================================================================="
echo "  • Nginx is running and ready for Virtual Host files."
echo "  • MariaDB buffer mapping dynamically scales to: ${BUFFER_POOL_MB}MB RAM."
echo "  • Redis Caching engine is listening for WordPress Object hooks."
echo "====================================================================="
echo "Next step: Point your domain to this server IP and run your WP migration!"