#!/bin/bash

# Promtail Installation and Configuration Script for Debian
# Usage: bash -c "$(curl -fsSL <your-gist-url>/install-promtail.sh)"

set -e

# Configuration
LOKI_ENDPOINT="loki.pfotenballen.de"
LOKI_PORT="3100"
PROMTAIL_VERSION="2.9.2"
PROMTAIL_USER="promtail"
PROMTAIL_DIR="/opt/promtail"
CONFIG_DIR="/etc/promtail"
LOG_DIR="/var/log/promtail"

# 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 promtail is already installed
check_promtail_installed() {
    if command -v promtail &> /dev/null || [[ -f "/usr/local/bin/promtail" ]] || [[ -f "$PROMTAIL_DIR/promtail" ]]; then
        return 0
    else
        return 1
    fi
}

# Test Loki endpoint connectivity
test_loki_connectivity() {
    log_info "Testing connectivity to Loki endpoint: $LOKI_ENDPOINT:$LOKI_PORT"
    
    if timeout 10 bash -c "</dev/tcp/$LOKI_ENDPOINT/$LOKI_PORT" 2>/dev/null; then
        log_success "Successfully connected to $LOKI_ENDPOINT:$LOKI_PORT"
        return 0
    else
        log_error "Cannot reach $LOKI_ENDPOINT:$LOKI_PORT"
        log_error "Please check your network connection and Loki server status"
        return 1
    fi
}

# Install dependencies
install_dependencies() {
    log_info "Installing dependencies..."
    apt-get update -qq
    apt-get install -y wget curl unzip systemd
    log_success "Dependencies installed"
}

# Create promtail user
create_promtail_user() {
    if ! id "$PROMTAIL_USER" &>/dev/null; then
        log_info "Creating promtail user..."
        useradd --system --no-create-home --shell /bin/false $PROMTAIL_USER
        log_success "Promtail user created"
    else
        log_info "Promtail user already exists"
    fi
}

# Download and install promtail
install_promtail() {
    log_info "Downloading Promtail v$PROMTAIL_VERSION..."
    
    # Determine architecture
    ARCH=$(uname -m)
    case $ARCH in
        x86_64)
            ARCH_SUFFIX="amd64"
            ;;
        aarch64)
            ARCH_SUFFIX="arm64"
            ;;
        armv7l)
            ARCH_SUFFIX="armv7"
            ;;
        *)
            log_error "Unsupported architecture: $ARCH"
            exit 1
            ;;
    esac
    
    # Create directories
    mkdir -p $PROMTAIL_DIR
    mkdir -p $CONFIG_DIR
    mkdir -p $LOG_DIR
    
    # Download promtail binary
    DOWNLOAD_URL="https://github.com/grafana/loki/releases/download/v$PROMTAIL_VERSION/promtail-linux-$ARCH_SUFFIX.zip"
    
    cd /tmp
    wget -q "$DOWNLOAD_URL" -O promtail.zip
    unzip -q promtail.zip
    
    # Install binary
    chmod +x promtail-linux-$ARCH_SUFFIX
    mv promtail-linux-$ARCH_SUFFIX /usr/local/bin/promtail
    
    # Set ownership
    chown root:root /usr/local/bin/promtail
    chown -R $PROMTAIL_USER:$PROMTAIL_USER $CONFIG_DIR $LOG_DIR
    
    # Cleanup
    rm -f promtail.zip
    
    log_success "Promtail installed successfully"
}

# Create promtail configuration
create_config() {
    log_info "Creating Promtail configuration..."
    
    # Get the actual hostname
    HOSTNAME=$(hostname)
    
    cat > $CONFIG_DIR/promtail.yml << EOF
server:
  http_listen_port: 9080
  grpc_listen_port: 0

positions:
  filename: /var/lib/promtail/positions.yaml

clients:
  - url: http://$LOKI_ENDPOINT:$LOKI_PORT/loki/api/v1/push

scrape_configs:
  # Direct /var/log/ files (system logs)
  - job_name: system-logs
    static_configs:
      - targets:
          - localhost
        labels:
          job: system-logs
          service: system
          host: $HOSTNAME
          __path__: /var/log/*.log

  # Service-specific logs in subdirectories
  - job_name: service-logs
    static_configs:
      - targets:
          - localhost
        labels:
          job: service-logs
          host: $HOSTNAME
          __path__: /var/log/*/*.log
    pipeline_stages:
      - regex:
          expression: '/var/log/(?P<service>[^/]+)/.*'
      - labels:
          service: '{{ .service }}'

  # Recursively capture all nested logs (deeper than one level)
  - job_name: nested-service-logs
    static_configs:
      - targets:
          - localhost
        labels:
          job: nested-service-logs
          host: $HOSTNAME
          __path__: /var/log/**/*.log
    pipeline_stages:
      - regex:
          expression: '/var/log/(?P<service>[^/]+)/.*'
      - labels:
          service: '{{ .service }}'
EOF

    # Create positions directory
    mkdir -p /var/lib/promtail
    chown $PROMTAIL_USER:$PROMTAIL_USER /var/lib/promtail
    
    # Set proper permissions
    chown $PROMTAIL_USER:$PROMTAIL_USER $CONFIG_DIR/promtail.yml
    chmod 640 $CONFIG_DIR/promtail.yml
    
    log_success "Configuration created"
}

# Create systemd service
create_systemd_service() {
    log_info "Creating systemd service..."
    
    cat > /etc/systemd/system/promtail.service << EOF
[Unit]
Description=Promtail service
Documentation=https://grafana.com/docs/loki/latest/clients/promtail/
After=network.target

[Service]
Type=simple
User=$PROMTAIL_USER
ExecStart=/usr/local/bin/promtail -config.file=$CONFIG_DIR/promtail.yml
Restart=always
RestartSec=10
StandardOutput=journal
StandardError=journal
SyslogIdentifier=promtail

[Install]
WantedBy=multi-user.target
EOF

    systemctl daemon-reload
    log_success "Systemd service created"
}

# Add promtail user to adm group for log access
configure_log_access() {
    log_info "Configuring log file access..."
    usermod -a -G adm $PROMTAIL_USER
    log_success "Log access configured"
}

# Start and enable service
start_service() {
    log_info "Starting Promtail service..."
    
    systemctl enable promtail
    systemctl start promtail
    
    # Wait a moment and check status
    sleep 2
    
    if systemctl is-active --quiet promtail; then
        log_success "Promtail service is running"
        log_info "Service status:"
        systemctl status promtail --no-pager -l
    else
        log_error "Failed to start Promtail service"
        log_error "Check logs with: journalctl -u promtail -f"
        exit 1
    fi
}

# Main installation process
main() {
    echo "=================================="
    echo "   Promtail Installation Script   "
    echo "=================================="
    echo
    
    check_root
    
    if check_promtail_installed; then
        log_warning "Promtail appears to be already installed"
        echo "Existing installation found. Do you want to continue and reconfigure? (y/N)"
        read -r response
        if [[ ! "$response" =~ ^[Yy]$ ]]; then
            log_info "Installation cancelled"
            exit 0
        fi
    fi
    
    # Test Loki connectivity first
    if ! test_loki_connectivity; then
        echo "Do you want to continue anyway? (y/N)"
        read -r response
        if [[ ! "$response" =~ ^[Yy]$ ]]; then
            log_info "Installation cancelled"
            exit 1
        fi
    fi
    
    install_dependencies
    create_promtail_user
    
    if ! check_promtail_installed; then
        install_promtail
    else
        log_info "Promtail binary already exists, skipping download"
    fi
    
    create_config
    create_systemd_service
    configure_log_access
    start_service
    
    echo
    echo "=================================="
    log_success "Promtail installation completed!"
    echo "=================================="
    echo
    echo "Configuration file: $CONFIG_DIR/promtail.yml"
    echo "Service status: systemctl status promtail"
    echo "Service logs: journalctl -u promtail -f"
    echo "Loki endpoint: http://$LOKI_ENDPOINT:$LOKI_PORT"
    echo
    echo "To check if logs are being sent to Loki:"
    echo "curl -G -s \"http://$LOKI_ENDPOINT:$LOKI_PORT/loki/api/v1/query\" --data-urlencode 'query={job=\"system-logs\"}'"
}

# Execute main function
main "$@"