#!/bin/bash
# =============================================================================
# SAP HANA Monitoring Scripts Installer
# Downloads and installs HANA monitoring scripts to /root/hana-scripts/
# Preserves existing configuration if hana.conf already exists
# =============================================================================

set -e

# Configuration
INSTALL_DIR="/root/hana-scripts"
REPO_URL="https://git.technopunk.space/tomi/hana-scripts/raw/branch/main"
BACKUP_DIR="/root/hana-scripts-backup-$(date +%Y%m%d_%H%M%S)"

# List of files to install
FILES=(
    "hana.conf"
    "hana_lib.sh"
    "hana_disk.sh"
    "hana_backup.sh"
    "hana_log_segments.sh"
    "hana_processes.sh"
    "hana_queue.sh"
    "sld_watchdog.sh"
)

# Colors for output
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
BLUE='\033[0;34m'
NC='\033[0m' # No Color

# Logging functions
log_info() {
    echo -e "${BLUE}[INFO]${NC} $1"
}

log_success() {
    echo -e "${GREEN}[SUCCESS]${NC} $1"
}

log_warning() {
    echo -e "${YELLOW}[WARNING]${NC} $1"
}

log_error() {
    echo -e "${RED}[ERROR]${NC} $1"
}

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

# Check if curl is available
check_curl() {
    if ! command -v curl &> /dev/null; then
        log_error "curl is required but not installed. Please install curl first."
        exit 1
    fi
    log_info "curl is available"
}

# Create backup of existing installation
backup_existing() {
    if [ -d "$INSTALL_DIR" ]; then
        log_info "Existing installation found at $INSTALL_DIR"
        log_info "Creating backup at $BACKUP_DIR..."
        
        mkdir -p "$BACKUP_DIR"
        cp -r "$INSTALL_DIR"/* "$BACKUP_DIR"/ 2>/dev/null || true
        
        # Save the existing hana.conf separately for easy access
        if [ -f "$INSTALL_DIR/hana.conf" ]; then
            cp "$INSTALL_DIR/hana.conf" "$BACKUP_DIR/hana.conf.preserved"
            log_success "Existing hana.conf backed up to $BACKUP_DIR/hana.conf.preserved"
        fi
        
        log_success "Backup completed"
    fi
}

# Create installation directory
create_install_dir() {
    log_info "Creating installation directory: $INSTALL_DIR"
    mkdir -p "$INSTALL_DIR"
}

# Download a file from the repository
download_file() {
    local filename="$1"
    local url="${REPO_URL}/${filename}"
    local dest="${INSTALL_DIR}/${filename}"
    
    log_info "Downloading ${filename}..."
    
    if curl -sSf -o "$dest" "$url"; then
        log_success "Downloaded ${filename}"
        return 0
    else
        log_error "Failed to download ${filename}"
        return 1
    fi
}

# Restore preserved configuration
restore_config() {
    local preserved_config="$BACKUP_DIR/hana.conf.preserved"
    
    if [ -f "$preserved_config" ]; then
        log_info "Preserving existing hana.conf..."
        
        # Download the new config to a temp location
        local temp_config="${INSTALL_DIR}/hana.conf.new"
        if curl -sSf -o "$temp_config" "${REPO_URL}/hana.conf"; then
            # Compare configs to check for new settings
            if ! diff -q "$preserved_config" "$temp_config" > /dev/null 2>&1; then
                log_warning "Configuration file has updates. Merging changes..."
                
                # Keep the old config but add any new settings from the new config
                # First, copy the preserved config
                cp "$preserved_config" "$dest"
                
                # Extract new settings from the new config (settings not in old config)
                # This is a simple merge - new variables are appended if not present
                while IFS= read -r line; do
                    # Skip comments and empty lines
                    if [[ "$line" =~ ^[[:space:]]*# ]] || [[ -z "${line// }" ]]; then
                        continue
                    fi
                    
                    # Extract variable name
                    var_name="${line%%=*}"
                    var_name="${var_name// /}"
                    
                    # Check if variable exists in preserved config
                    if ! grep -q "^${var_name}=" "$preserved_config" 2>/dev/null; then
                        log_info "Adding new configuration: ${var_name}"
                        echo "" >> "$dest"
                        echo "$line" >> "$dest"
                    fi
                done < "$temp_config"
                
                log_success "Configuration merged successfully"
            else
                log_info "No configuration changes detected, keeping existing config"
                cp "$preserved_config" "$dest"
            fi
            
            # Clean up temp file
            rm -f "$temp_config"
        else
            log_warning "Could not download new hana.conf, keeping existing config"
            cp "$preserved_config" "$dest"
        fi
        
        return 0
    fi
    
    return 1
}

# Set executable permissions
set_permissions() {
    log_info "Setting executable permissions..."
    chmod +x "${INSTALL_DIR}"/*.sh 2>/dev/null || true
    log_success "Permissions set"
}

# Verify installation
verify_installation() {
    log_info "Verifying installation..."
    
    local errors=0
    
    for file in "${FILES[@]}"; do
        if [ ! -f "${INSTALL_DIR}/${file}" ]; then
            log_error "Missing file: ${file}"
            errors=$((errors + 1))
        fi
    done
    
    if [ $errors -eq 0 ]; then
        log_success "Installation verified successfully"
        return 0
    else
        log_error "Verification failed with ${errors} errors"
        return 1
    fi
}

# Print summary
print_summary() {
    echo ""
    echo "=============================================="
    echo "  Installation Complete!"
    echo "=============================================="
    echo ""
    echo "Installation directory: ${INSTALL_DIR}"
    echo ""
    
    if [ -d "$BACKUP_DIR" ]; then
        echo "Backup location: ${BACKUP_DIR}"
        echo ""
    fi
    
    echo "Next steps:"
    echo "  1. Review and update ${INSTALL_DIR}/hana.conf with your settings"
    echo "  2. Make scripts executable: chmod +x ${INSTALL_DIR}/*.sh"
    echo "  3. Test individual scripts manually"
    echo "  4. Set up cron jobs for automated monitoring"
    echo ""
    echo "Example cron entries (run crontab -e):"
    echo "  */5 * * * *     ${INSTALL_DIR}/hana_disk.sh"
    echo "  */5 * * * *     ${INSTALL_DIR}/hana_processes.sh"
    echo "  */10 * * * *    ${INSTALL_DIR}/hana_backup.sh"
    echo "  */5 * * * *     ${INSTALL_DIR}/hana_queue.sh"
    echo "  */5 * * * *     ${INSTALL_DIR}/hana_log_segments.sh"
    echo "  */5 * * * *     ${INSTALL_DIR}/sld_watchdog.sh"
    echo ""
}

# Main installation function
main() {
    echo ""
    echo "=============================================="
    echo "  SAP HANA Monitoring Scripts Installer"
    echo "=============================================="
    echo ""
    
    # Pre-flight checks
    check_root
    check_curl
    
    # Backup existing installation
    backup_existing
    
    # Create installation directory
    create_install_dir
    
    # Download all files
    local download_errors=0
    for file in "${FILES[@]}"; do
        if [ "$file" == "hana.conf" ]; then
            # Handle config file specially
            if ! restore_config; then
                # No existing config, download fresh
                download_file "$file" || download_errors=$((download_errors + 1))
            fi
        else
            download_file "$file" || download_errors=$((download_errors + 1))
        fi
    done
    
    if [ $download_errors -gt 0 ]; then
        log_error "Failed to download ${download_errors} files"
        exit 1
    fi
    
    # Set permissions
    set_permissions
    
    # Verify installation
    if ! verify_installation; then
        exit 1
    fi
    
    # Print summary
    print_summary
}

# Run main function
main "$@"