haproxy-mcp/mcp/server.py

#!/usr/bin/env python3
"""HAProxy MCP Server - Direct Runtime API Integration

This module provides an MCP (Model Context Protocol) server for managing HAProxy
configuration and runtime state. It supports dynamic domain/server management
with HTTP, HTTPS, and HTTP/3 (QUIC) protocols.
"""

import socket
import subprocess
import re
import json
import sys
import time
import fcntl
from typing import Dict, Generator, List, Optional, Set, Tuple
from mcp.server.fastmcp import FastMCP

mcp = FastMCP("haproxy", host="0.0.0.0", port=8000)

# Constants
HAPROXY_SOCKET: Tuple[str, int] = ("localhost", 9999)
STATE_FILE: str = "/opt/haproxy/data/servers.state"
MAP_FILE: str = "/opt/haproxy/conf/domains.map"
MAP_FILE_CONTAINER: str = "/usr/local/etc/haproxy/domains.map"
SERVERS_FILE: str = "/opt/haproxy/conf/servers.json"
POOL_COUNT: int = 100
MAX_SLOTS: int = 10

# Validation patterns - compiled once for performance
DOMAIN_PATTERN = re.compile(
    r'^[a-zA-Z0-9]([a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?'
    r'(\.[a-zA-Z0-9]([a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?)*$'
)
IP_PATTERN = re.compile(r'^(\d{1,3}\.){3}\d{1,3}$')
# Backend/server names: alphanumeric, underscore, hyphen only
BACKEND_NAME_PATTERN = re.compile(r'^[a-zA-Z0-9_-]+$')
# Pattern for converting domain to backend name
NON_ALNUM_PATTERN = re.compile(r'[^a-zA-Z0-9]')

# Limits
MAX_RESPONSE_SIZE = 10 * 1024 * 1024  # 10 MB max response from HAProxy
SUBPROCESS_TIMEOUT = 30  # seconds
STARTUP_RETRY_COUNT = 10  # HAProxy ready check retries
STATE_MIN_COLUMNS = 19  # Minimum columns in HAProxy server state output
SOCKET_TIMEOUT = 5  # seconds for HAProxy socket connection


class HaproxyError(Exception):
    """HAProxy operation error"""
    pass


# CSV field indices for HAProxy stats (show stat command)
class StatField:
    """HAProxy CSV stat field indices."""
    PXNAME = 0      # Proxy name (frontend/backend)
    SVNAME = 1      # Server name (or FRONTEND/BACKEND)
    SCUR = 4        # Current sessions
    SMAX = 6        # Max sessions
    STATUS = 17     # Status (UP/DOWN/MAINT/etc)
    WEIGHT = 18     # Server weight
    CHECK_STATUS = 36  # Check status


def haproxy_cmd(command: str) -> str:
    """Send command to HAProxy Runtime API.

    Args:
        command: The HAProxy runtime API command to execute

    Returns:
        The response from HAProxy

    Raises:
        HaproxyError: If connection fails or response exceeds size limit
    """
    try:
        with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
            s.settimeout(SOCKET_TIMEOUT)
            s.connect(HAPROXY_SOCKET)
            s.sendall(f"{command}\n".encode())
            s.shutdown(socket.SHUT_WR)
            response = b""
            while True:
                data = s.recv(8192)
                if not data:
                    break
                response += data
                if len(response) > MAX_RESPONSE_SIZE:
                    raise HaproxyError(f"Response exceeded {MAX_RESPONSE_SIZE} bytes limit")
            return response.decode().strip()
    except socket.timeout:
        raise HaproxyError("Connection timeout")
    except ConnectionRefusedError:
        raise HaproxyError("Connection refused - HAProxy not running?")
    except UnicodeDecodeError:
        raise HaproxyError("Invalid UTF-8 in response")
    except HaproxyError:
        raise
    except Exception as e:
        raise HaproxyError(str(e))


def reload_haproxy() -> Tuple[bool, str]:
    """Validate and reload HAProxy configuration.

    Returns:
        Tuple of (success, message)
    """
    try:
        validate = subprocess.run(
            ["podman", "exec", "haproxy", "haproxy", "-c", "-f", "/usr/local/etc/haproxy/haproxy.cfg"],
            capture_output=True, text=True, timeout=SUBPROCESS_TIMEOUT
        )
        if validate.returncode != 0:
            return False, f"Config validation failed:\n{validate.stderr}"

        result = subprocess.run(
            ["podman", "kill", "--signal", "USR2", "haproxy"],
            capture_output=True, text=True, timeout=SUBPROCESS_TIMEOUT
        )
        if result.returncode != 0:
            return False, f"Reload failed: {result.stderr}"
        return True, "OK"
    except subprocess.TimeoutExpired:
        return False, f"Command timed out after {SUBPROCESS_TIMEOUT} seconds"
    except FileNotFoundError:
        return False, "podman command not found"
    except OSError as e:
        return False, f"OS error: {e}"


def validate_domain(domain: str) -> bool:
    """Validate domain format.

    Args:
        domain: The domain name to validate

    Returns:
        True if domain is valid, False otherwise
    """
    if not domain or len(domain) > 253:
        return False
    return bool(DOMAIN_PATTERN.match(domain))


def validate_ip(ip: str, allow_empty: bool = False) -> bool:
    """Validate IPv4 address format.

    Args:
        ip: The IP address to validate
        allow_empty: If True, empty string is considered valid

    Returns:
        True if IP is valid, False otherwise
    """
    if not ip:
        return allow_empty
    if not IP_PATTERN.match(ip):
        return False
    return all(0 <= int(octet) <= 255 for octet in ip.split('.'))


def validate_backend_name(name: str) -> bool:
    """Validate backend or server name to prevent command injection.

    Args:
        name: The backend or server name to validate

    Returns:
        True if name contains only safe characters
    """
    if not name or len(name) > 255:
        return False
    return bool(BACKEND_NAME_PATTERN.match(name))


def domain_to_backend(domain: str) -> str:
    """Convert domain to backend name (alphanumeric + underscore only).

    Args:
        domain: The domain name to convert

    Returns:
        Backend name with non-alphanumeric characters replaced by underscores

    Raises:
        ValueError: If resulting name is invalid
    """
    result = NON_ALNUM_PATTERN.sub('_', domain)
    if not validate_backend_name(result):
        raise ValueError(f"Invalid backend name after conversion: {result}")
    return result


def parse_stat_csv(stat_output: str) -> Generator[Dict[str, str], None, None]:
    """Parse HAProxy stat CSV output into structured data.

    Args:
        stat_output: Raw output from 'show stat' command

    Yields:
        Dictionaries with parsed stat fields for each row
    """
    for line in stat_output.split("\n"):
        if not line or line.startswith("#"):
            continue
        parts = line.split(",")
        if len(parts) > StatField.STATUS:
            yield {
                "pxname": parts[StatField.PXNAME],
                "svname": parts[StatField.SVNAME],
                "scur": parts[StatField.SCUR] if len(parts) > StatField.SCUR else "0",
                "smax": parts[StatField.SMAX] if len(parts) > StatField.SMAX else "0",
                "status": parts[StatField.STATUS],
                "weight": parts[StatField.WEIGHT] if len(parts) > StatField.WEIGHT else "0",
                "check_status": parts[StatField.CHECK_STATUS] if len(parts) > StatField.CHECK_STATUS else "",
            }


def validate_port(port: str) -> bool:
    """Validate port number is in valid range.

    Args:
        port: Port number as string

    Returns:
        True if port is valid (1-65535), False otherwise
    """
    if not port or not port.isdigit():
        return False
    port_num = int(port)
    return 1 <= port_num <= 65535


def get_map_contents() -> List[Tuple[str, str]]:
    """Read domains.map file and return list of (domain, backend) tuples.

    Returns:
        List of (domain, backend) tuples from the map file
    """
    entries = []
    try:
        with open(MAP_FILE, "r", encoding="utf-8") as f:
            try:
                fcntl.flock(f.fileno(), fcntl.LOCK_SH)
            except OSError:
                pass  # Continue without lock if not supported
            try:
                for line in f:
                    line = line.strip()
                    if not line or line.startswith("#"):
                        continue
                    parts = line.split()
                    if len(parts) >= 2:
                        entries.append((parts[0], parts[1]))
            finally:
                try:
                    fcntl.flock(f.fileno(), fcntl.LOCK_UN)
                except OSError:
                    pass
    except FileNotFoundError:
        pass
    return entries


def find_available_pool() -> Optional[str]:
    """Find first unused pool from pool_1 to pool_{POOL_COUNT}.

    Returns:
        Pool name (e.g., 'pool_1') if available, None if all pools are used
    """
    used_pools: Set[str] = set()
    for domain, backend in get_map_contents():
        if backend.startswith("pool_"):
            used_pools.add(backend)

    for i in range(1, POOL_COUNT + 1):
        pool_name = f"pool_{i}"
        if pool_name not in used_pools:
            return pool_name
    return None


def get_domain_backend(domain: str) -> Optional[str]:
    """Look up the backend for a domain from domains.map.

    Args:
        domain: The domain to look up

    Returns:
        Backend name if found, None otherwise
    """
    for map_domain, backend in get_map_contents():
        if map_domain == domain:
            return backend
    return None


def is_legacy_backend(backend: str) -> bool:
    """Check if backend is a legacy static backend (not a pool).

    Args:
        backend: Backend name to check

    Returns:
        True if this is a legacy backend, False if it's a pool
    """
    return not backend.startswith("pool_")


def get_legacy_backend_name(domain: str) -> str:
    """Convert domain to legacy backend name format.

    Args:
        domain: Domain name

    Returns:
        Legacy backend name (e.g., 'api_example_com_backend')
    """
    return f"{domain_to_backend(domain)}_backend"


def save_map_file(entries: List[Tuple[str, str]]) -> None:
    """Save entries to domains.map file with file locking.

    Args:
        entries: List of (domain, backend) tuples to write

    Raises:
        IOError: If the file cannot be written
    """
    with open(MAP_FILE, "w", encoding="utf-8") as f:
        try:
            fcntl.flock(f.fileno(), fcntl.LOCK_EX)
        except OSError:
            pass  # Continue without lock if not supported
        try:
            f.write("# Domain to Backend mapping\n")
            f.write("# Format: domain backend_name\n")
            f.write("# Wildcard: .domain.com matches *.domain.com\n\n")
            for domain, backend in entries:
                f.write(f"{domain} {backend}\n")
        finally:
            try:
                fcntl.flock(f.fileno(), fcntl.LOCK_UN)
            except OSError:
                pass


def load_servers_config() -> Dict:
    """Load servers configuration from JSON file with file locking.

    Returns:
        Dictionary with server configurations
    """
    try:
        with open(SERVERS_FILE, "r", encoding="utf-8") as f:
            try:
                fcntl.flock(f.fileno(), fcntl.LOCK_SH)
            except OSError:
                pass  # Continue without lock if not supported
            try:
                return json.load(f)
            finally:
                try:
                    fcntl.flock(f.fileno(), fcntl.LOCK_UN)
                except OSError:
                    pass
    except FileNotFoundError:
        return {}
    except json.JSONDecodeError as e:
        print(f"Warning: Corrupt config file {SERVERS_FILE}: {e}", file=sys.stderr)
        return {}


def save_servers_config(config: Dict) -> None:
    """Save servers configuration to JSON file with file locking.

    Args:
        config: Dictionary with server configurations
    """
    with open(SERVERS_FILE, "w", encoding="utf-8") as f:
        try:
            fcntl.flock(f.fileno(), fcntl.LOCK_EX)
        except OSError:
            pass  # Continue without lock if not supported
        try:
            json.dump(config, f, indent=2)
        finally:
            try:
                fcntl.flock(f.fileno(), fcntl.LOCK_UN)
            except OSError:
                pass


def add_server_to_config(domain: str, slot: int, ip: str, http_port: int, https_port: int) -> None:
    """Add server configuration to persistent storage.

    Args:
        domain: Domain name
        slot: Server slot (1 to MAX_SLOTS)
        ip: Server IP address
        http_port: HTTP port
        https_port: HTTPS port
    """
    config = load_servers_config()
    if domain not in config:
        config[domain] = {}
    config[domain][str(slot)] = {
        "ip": ip,
        "http_port": http_port,
        "https_port": https_port
    }
    save_servers_config(config)


def remove_server_from_config(domain: str, slot: int) -> None:
    """Remove server configuration from persistent storage.

    Args:
        domain: Domain name
        slot: Server slot to remove
    """
    config = load_servers_config()
    if domain in config and str(slot) in config[domain]:
        del config[domain][str(slot)]
        if not config[domain]:
            del config[domain]
        save_servers_config(config)


def remove_domain_from_config(domain: str) -> None:
    """Remove all server configurations for a domain.

    Args:
        domain: Domain name to remove
    """
    config = load_servers_config()
    if domain in config:
        del config[domain]
        save_servers_config(config)


def get_server_suffixes(http_port: int, https_port: int) -> List[Tuple[str, int]]:
    """Get server suffixes and ports based on port configuration.

    Args:
        http_port: HTTP port
        https_port: HTTPS port

    Returns:
        List of (suffix, port) tuples
    """
    if http_port == 80 and https_port == 443:
        # Default ports: HTTP + HTTPS + HTTP/3
        return [("", 80), ("_ssl", 443), ("_h3", 443)]
    else:
        # Custom port: HTTP only
        return [("", http_port)]


def restore_servers_from_config() -> int:
    """Restore all servers from configuration file.

    Returns:
        Number of servers restored
    """
    config = load_servers_config()
    restored = 0

    for domain, slots in config.items():
        backend = get_domain_backend(domain)
        if not backend:
            continue

        try:
            if backend.startswith("pool_"):
                server_prefix = backend
            else:
                server_prefix = domain_to_backend(domain)
        except ValueError as e:
            print(f"Warning: Invalid domain '{domain}': {e}", file=sys.stderr)
            continue

        for slot_str, server_info in slots.items():
            try:
                slot = int(slot_str)
            except ValueError:
                print(f"Warning: Invalid slot '{slot_str}' for {domain}, skipping", file=sys.stderr)
                continue

            ip = server_info.get("ip", "")
            if not ip:
                continue

            try:
                http_port = int(server_info.get("http_port", 80))
                https_port = int(server_info.get("https_port", 443))
            except (ValueError, TypeError):
                print(f"Warning: Invalid port for {domain} slot {slot}, skipping", file=sys.stderr)
                continue

            try:
                for suffix, port in get_server_suffixes(http_port, https_port):
                    server = f"{server_prefix}{suffix}_{slot}"
                    haproxy_cmd(f"set server {backend}/{server} addr {ip} port {port}")
                    haproxy_cmd(f"set server {backend}/{server} state ready")
                restored += 1
            except HaproxyError as e:
                print(f"Warning: Failed to restore {domain} slot {slot}: {e}", file=sys.stderr)

    return restored


@mcp.tool()
def haproxy_list_domains() -> str:
    """List all configured domains with their backend servers.

    Returns:
        List of domains with their associated backend servers
    """
    try:
        domains = []
        state = haproxy_cmd("show servers state")

        # Build server map from HAProxy state
        server_map: Dict[str, list] = {}
        for line in state.split("\n"):
            parts = line.split()
            if len(parts) >= STATE_MIN_COLUMNS and parts[4] != "0.0.0.0":
                backend = parts[1]
                if backend not in server_map:
                    server_map[backend] = []
                server_map[backend].append(f"{parts[3]}={parts[4]}:{parts[18]}")

        # Read from domains.map (skip wildcard entries starting with .)
        seen_domains: Set[str] = set()
        for domain, backend in get_map_contents():
            if domain.startswith("."):
                continue
            if domain in seen_domains:
                continue
            seen_domains.add(domain)
            servers = server_map.get(backend, ["(none)"])
            backend_type = "pool" if backend.startswith("pool_") else "static"
            domains.append(f"• {domain} -> {backend} ({backend_type}): {', '.join(servers)}")

        return "\n".join(domains) if domains else "No domains configured"
    except HaproxyError as e:
        return f"Error: {e}"


@mcp.tool()
def haproxy_add_domain(domain: str, ip: str = "", http_port: int = 80, https_port: int = 443) -> str:
    """Add a new domain to HAProxy using map-based routing (no reload required).

    Args:
        domain: The domain name to add (e.g., api.example.com)
        ip: Optional IP address for initial server; if provided, adds to slot 1
        http_port: HTTP port for the backend server (default: 80)
        https_port: HTTPS port for the backend server (default: 443)

    Returns:
        Success message or error description
    """
    # Validate inputs
    if not validate_domain(domain):
        return "Error: Invalid domain format"
    if not validate_ip(ip, allow_empty=True):
        return "Error: Invalid IP address format"
    if not (1 <= http_port <= 65535) or not (1 <= https_port <= 65535):
        return "Error: Port must be between 1 and 65535"

    # Check if domain already exists
    existing_backend = get_domain_backend(domain)
    if existing_backend:
        return f"Error: Domain {domain} already exists (mapped to {existing_backend})"

    # Find available pool
    pool = find_available_pool()
    if not pool:
        return f"Error: No available pools (all {POOL_COUNT} pools are in use)"

    try:
        # Update HAProxy map via Runtime API first (immediate effect)
        haproxy_cmd(f"add map {MAP_FILE_CONTAINER} {domain} {pool}")
        haproxy_cmd(f"add map {MAP_FILE_CONTAINER} .{domain} {pool}")

        # Read current map entries and save to file (persistence)
        entries = get_map_contents()
        entries.append((domain, pool))
        entries.append((f".{domain}", pool))
        save_map_file(entries)

        # If IP provided, add server to slot 1
        if ip:
            suffixes = get_server_suffixes(http_port, https_port)
            for suffix, port in suffixes:
                server = f"{pool}{suffix}_1"
                haproxy_cmd(f"set server {pool}/{server} addr {ip} port {port}")
                haproxy_cmd(f"set server {pool}/{server} state ready")

            # Save to persistent config
            add_server_to_config(domain, 1, ip, http_port, https_port)

            if len(suffixes) == 1:
                return f"Domain {domain} added to {pool} with server {ip}:{http_port} (HTTP only)"
            return f"Domain {domain} added to {pool} with server {ip}:{http_port}/{https_port}"

        return f"Domain {domain} added to {pool} (no servers configured)"

    except HaproxyError as e:
        return f"Error: {e}"
    except IOError as e:
        return f"Error: Failed to update map file: {e}"


@mcp.tool()
def haproxy_remove_domain(domain: str) -> str:
    """Remove a domain from HAProxy (no reload required for pool-based domains).

    Args:
        domain: The domain name to remove

    Returns:
        Success message or error description
    """
    if not validate_domain(domain):
        return "Error: Invalid domain format"

    # Look up the domain in the map
    backend = get_domain_backend(domain)
    if not backend:
        return f"Error: Domain {domain} not found"

    # Check if this is a legacy backend (not a pool)
    if is_legacy_backend(backend):
        return f"Error: Cannot remove legacy domain {domain} (uses static backend {backend})"

    try:
        # Clear map entries via Runtime API first (immediate effect)
        haproxy_cmd(f"del map {MAP_FILE_CONTAINER} {domain}")
        haproxy_cmd(f"del map {MAP_FILE_CONTAINER} .{domain}")

        # Remove entries from map file (persistence)
        entries = get_map_contents()
        new_entries = [(d, b) for d, b in entries if d != domain and d != f".{domain}"]
        save_map_file(new_entries)

        # Disable all servers in the pool (reset to 0.0.0.0:0)
        for slot in range(1, MAX_SLOTS + 1):
            for suffix in ["", "_ssl", "_h3"]:
                server = f"{backend}{suffix}_{slot}"
                try:
                    haproxy_cmd(f"set server {backend}/{server} state maint")
                    haproxy_cmd(f"set server {backend}/{server} addr 0.0.0.0 port 0")
                except HaproxyError:
                    pass  # Ignore errors for individual servers

        # Remove from persistent config
        remove_domain_from_config(domain)

        return f"Domain {domain} removed from {backend}"

    except HaproxyError as e:
        return f"Error: {e}"
    except IOError as e:
        return f"Error: Failed to update map file: {e}"


@mcp.tool()
def haproxy_list_servers(domain: str) -> str:
    """List all servers for a specific domain.

    Args:
        domain: The domain name to list servers for

    Returns:
        List of servers with their addresses and status
    """
    if not validate_domain(domain):
        return "Error: Invalid domain format"

    try:
        # Look up backend from map
        backend = get_domain_backend(domain)
        if not backend:
            # Fall back to legacy naming convention
            backend = get_legacy_backend_name(domain)

        servers = []
        state = haproxy_cmd("show servers state")

        for line in state.split("\n"):
            parts = line.split()
            if len(parts) >= STATE_MIN_COLUMNS and parts[1] == backend:
                status = "active" if parts[4] != "0.0.0.0" else "disabled"
                servers.append(f"• {parts[3]}: {parts[4]}:{parts[18]} ({status})")

        if not servers:
            return f"Backend {backend} not found"

        return f"Servers for {domain} ({backend}):\n" + "\n".join(servers)
    except (HaproxyError, ValueError) as e:
        return f"Error: {e}"


@mcp.tool()
def haproxy_add_server(domain: str, slot: int, ip: str, http_port: int = 80, https_port: int = 443) -> str:
    """Add a server to a domain's backend at specified slot.

    Args:
        domain: The domain name to add the server to
        slot: Server slot number (1 to MAX_SLOTS)
        ip: IP address of the server (required)
        http_port: HTTP port (default: 80)
        https_port: HTTPS port (default: 443)

    Returns:
        Success message or error description
    """
    if not validate_domain(domain):
        return "Error: Invalid domain format"
    if not ip:
        return "Error: IP address is required"
    if not validate_ip(ip):
        return "Error: Invalid IP address format"
    if not (1 <= slot <= MAX_SLOTS):
        return f"Error: Slot must be between 1 and {MAX_SLOTS}"
    if not (1 <= http_port <= 65535) or not (1 <= https_port <= 65535):
        return "Error: Port must be between 1 and 65535"

    try:
        # Look up backend from map
        backend = get_domain_backend(domain)
        if not backend:
            # Fall back to legacy naming convention
            backend = get_legacy_backend_name(domain)

        # Determine server name prefix based on backend type
        if backend.startswith("pool_"):
            # Pool backends use pool_N_slot naming
            server_prefix = backend
        else:
            # Legacy backends use domain-based naming
            server_prefix = domain_to_backend(domain)

        results = []
        for suffix, port in get_server_suffixes(http_port, https_port):
            server = f"{server_prefix}{suffix}_{slot}"
            haproxy_cmd(f"set server {backend}/{server} addr {ip} port {port}")
            haproxy_cmd(f"set server {backend}/{server} state ready")
            results.append(f"{server} → {ip}:{port}")

        # Save to persistent config
        add_server_to_config(domain, slot, ip, http_port, https_port)

        return f"Added to {domain} ({backend}) slot {slot}:\n" + "\n".join(results)
    except (HaproxyError, ValueError) as e:
        return f"Error: {e}"


@mcp.tool()
def haproxy_remove_server(domain: str, slot: int) -> str:
    """Remove a server from a domain's backend at specified slot.

    Args:
        domain: The domain name to remove the server from
        slot: Server slot number (1 to MAX_SLOTS) to remove

    Returns:
        Success message or error description
    """
    if not validate_domain(domain):
        return "Error: Invalid domain format"
    if not (1 <= slot <= MAX_SLOTS):
        return f"Error: Slot must be between 1 and {MAX_SLOTS}"

    try:
        # Look up backend from map
        backend = get_domain_backend(domain)
        if not backend:
            # Fall back to legacy naming convention
            backend = get_legacy_backend_name(domain)

        # Determine server name prefix based on backend type
        if backend.startswith("pool_"):
            # Pool backends use pool_N_slot naming
            server_prefix = backend
        else:
            # Legacy backends use domain-based naming
            server_prefix = domain_to_backend(domain)

        # Get server config to determine which suffixes to remove
        config = load_servers_config()
        suffixes = ["", "_ssl", "_h3"]  # Default: remove all
        if domain in config and str(slot) in config[domain]:
            server_info = config[domain][str(slot)]
            try:
                http_port = int(server_info.get("http_port", 80))
                https_port = int(server_info.get("https_port", 443))
                suffixes = [s for s, _ in get_server_suffixes(http_port, https_port)]
            except (ValueError, TypeError):
                pass  # Use default suffixes

        for suffix in suffixes:
            server = f"{server_prefix}{suffix}_{slot}"
            haproxy_cmd(f"set server {backend}/{server} state maint")
            haproxy_cmd(f"set server {backend}/{server} addr 0.0.0.0 port 0")

        # Remove from persistent config
        remove_server_from_config(domain, slot)

        return f"Removed server at slot {slot} from {domain} ({backend})"
    except (HaproxyError, ValueError) as e:
        return f"Error: {e}"


@mcp.tool()
def haproxy_stats() -> str:
    """Get HAProxy status and statistics.

    Returns:
        Key HAProxy metrics (name, version, uptime, connections, etc.)
    """
    try:
        result = haproxy_cmd("show info")
        stats = {}
        for line in result.split("\n"):
            if ":" in line:
                key, value = line.split(":", 1)
                stats[key.strip()] = value.strip()

        important = ["Name", "Version", "Uptime_sec", "CurrConns", "MaxConn", "Run_queue", "Tasks"]
        output = []
        for key in important:
            if key in stats:
                output.append(f"• {key}: {stats[key]}")

        return "\n".join(output) if output else result
    except HaproxyError as e:
        return f"Error: {e}"


@mcp.tool()
def haproxy_backends() -> str:
    """List all HAProxy backends.

    Returns:
        List of all configured backend names
    """
    try:
        result = haproxy_cmd("show backend")
        backends = [line for line in result.split("\n") if line and not line.startswith("#")]
        return "Backends:\n" + "\n".join(f"• {b}" for b in backends)
    except HaproxyError as e:
        return f"Error: {e}"


@mcp.tool()
def haproxy_list_frontends() -> str:
    """List all HAProxy frontends with their status.

    Returns:
        List of frontends with status and session counts
    """
    try:
        result = haproxy_cmd("show stat")
        frontends = []
        for stat in parse_stat_csv(result):
            if stat["svname"] == "FRONTEND":
                frontends.append(
                    f"• {stat['pxname']}: {stat['status']} (sessions: {stat['scur']})"
                )
        if not frontends:
            return "No frontends found"
        return "Frontends:\n" + "\n".join(frontends)
    except HaproxyError as e:
        return f"Error: {e}"


@mcp.tool()
def haproxy_set_server_state(backend: str, server: str, state: str) -> str:
    """Set server state. States: ready (enable), drain (graceful shutdown), maint (maintenance/disable)

    Args:
        backend: Backend name (alphanumeric, underscore, hyphen only)
        server: Server name within the backend
        state: Target state - ready, drain, or maint

    Returns:
        Success message or error description
    """
    if not validate_backend_name(backend):
        return "Error: Invalid backend name (use alphanumeric, underscore, hyphen only)"
    if not validate_backend_name(server):
        return "Error: Invalid server name (use alphanumeric, underscore, hyphen only)"
    if state not in ["ready", "drain", "maint"]:
        return "Error: state must be 'ready', 'drain', or 'maint'"
    try:
        result = haproxy_cmd(f"set server {backend}/{server} state {state}")
        return result if result else f"Server {backend}/{server} set to {state}"
    except HaproxyError as e:
        return f"Error: {e}"


@mcp.tool()
def haproxy_get_server_health(backend: str = "") -> str:
    """Get health status of all servers or servers in a specific backend.

    Args:
        backend: Optional backend name to filter results

    Returns:
        Server health status or error description
    """
    if backend and not validate_backend_name(backend):
        return "Error: Invalid backend name (use alphanumeric, underscore, hyphen only)"
    try:
        result = haproxy_cmd("show stat")
        servers = []
        for stat in parse_stat_csv(result):
            if stat["svname"] not in ["FRONTEND", "BACKEND", ""]:
                if backend and stat["pxname"] != backend:
                    continue
                servers.append(
                    f"• {stat['pxname']}/{stat['svname']}: {stat['status']} "
                    f"(weight: {stat['weight']}, check: {stat['check_status']})"
                )
        return "\n".join(servers) if servers else "No servers found"
    except HaproxyError as e:
        return f"Error: {e}"


@mcp.tool()
def haproxy_set_server_weight(backend: str, server: str, weight: int) -> str:
    """Set server weight (0-256). Weight 0 disables the server for new connections.

    Args:
        backend: Backend name (alphanumeric, underscore, hyphen only)
        server: Server name within the backend
        weight: Server weight from 0 to 256

    Returns:
        Success message or error description
    """
    if not validate_backend_name(backend):
        return "Error: Invalid backend name (use alphanumeric, underscore, hyphen only)"
    if not validate_backend_name(server):
        return "Error: Invalid server name (use alphanumeric, underscore, hyphen only)"
    if not (0 <= weight <= 256):
        return "Error: weight must be between 0 and 256"
    try:
        result = haproxy_cmd(f"set server {backend}/{server} weight {weight}")
        return result if result else f"Server {backend}/{server} weight set to {weight}"
    except HaproxyError as e:
        return f"Error: {e}"


@mcp.tool()
def haproxy_get_connections(backend: str = "") -> str:
    """Get active connections per server.

    Args:
        backend: Optional backend name to filter results

    Returns:
        Connection statistics or error description
    """
    if backend and not validate_backend_name(backend):
        return "Error: Invalid backend name (use alphanumeric, underscore, hyphen only)"
    try:
        result = haproxy_cmd("show stat")
        connections = []
        for stat in parse_stat_csv(result):
            if backend and stat["pxname"] != backend:
                continue
            if stat["svname"] in ["FRONTEND", "BACKEND"]:
                connections.append(
                    f"• {stat['pxname']} ({stat['svname']}): {stat['scur']} current, {stat['smax']} max"
                )
            elif stat["svname"]:
                connections.append(f"  - {stat['svname']}: {stat['scur']} connections")
        return "\n".join(connections) if connections else "No connection data"
    except HaproxyError as e:
        return f"Error: {e}"


@mcp.tool()
def haproxy_reload() -> str:
    """Reload HAProxy configuration (validates config first).

    Returns:
        Success message or error details if validation/reload failed
    """
    success, msg = reload_haproxy()
    if not success:
        return msg
    return "HAProxy configuration reloaded successfully"


@mcp.tool()
def haproxy_check_config() -> str:
    """Validate HAProxy configuration file syntax.

    Returns:
        Validation result or error details
    """
    try:
        result = subprocess.run(
            ["podman", "exec", "haproxy", "haproxy", "-c", "-f", "/usr/local/etc/haproxy/haproxy.cfg"],
            capture_output=True, text=True, timeout=SUBPROCESS_TIMEOUT
        )
        if result.returncode == 0:
            return "Configuration is valid"
        return f"Configuration errors:\n{result.stderr}"
    except subprocess.TimeoutExpired:
        return f"Error: Command timed out after {SUBPROCESS_TIMEOUT} seconds"
    except FileNotFoundError:
        return "Error: podman command not found"
    except OSError as e:
        return f"Error: OS error: {e}"


@mcp.tool()
def haproxy_save_state() -> str:
    """Save current server state to disk.

    Returns:
        Success message or error description
    """
    try:
        state = haproxy_cmd("show servers state")
        with open(STATE_FILE, "w", encoding="utf-8") as f:
            try:
                fcntl.flock(f.fileno(), fcntl.LOCK_EX)
            except OSError:
                pass  # Continue without lock if not supported
            try:
                f.write(state)
            finally:
                try:
                    fcntl.flock(f.fileno(), fcntl.LOCK_UN)
                except OSError:
                    pass
        return "Server state saved"
    except HaproxyError as e:
        return f"Error: {e}"
    except IOError as e:
        return f"Error: Failed to save state: {e}"


@mcp.tool()
def haproxy_restore_state() -> str:
    """Restore server state from disk.

    Returns:
        Summary of restored servers or error description
    """
    try:
        with open(STATE_FILE, "r", encoding="utf-8") as f:
            try:
                fcntl.flock(f.fileno(), fcntl.LOCK_SH)
            except OSError:
                pass  # Continue without lock if not supported
            try:
                state = f.read()
            finally:
                try:
                    fcntl.flock(f.fileno(), fcntl.LOCK_UN)
                except OSError:
                    pass

        restored = 0
        skipped = 0
        for line in state.split("\n"):
            parts = line.split()
            if len(parts) >= STATE_MIN_COLUMNS and not line.startswith("#"):
                backend = parts[1]
                server = parts[3]
                addr = parts[4]
                port = parts[18]

                # Skip disabled servers
                if addr == "0.0.0.0":
                    continue

                # Validate names from state file to prevent injection
                if not validate_backend_name(backend) or not validate_backend_name(server):
                    skipped += 1
                    continue

                # Validate IP and port
                if not validate_ip(addr) or not validate_port(port):
                    skipped += 1
                    continue

                haproxy_cmd(f"set server {backend}/{server} addr {addr} port {port}")
                haproxy_cmd(f"enable server {backend}/{server}")
                restored += 1

        result = f"Server state restored ({restored} servers)"
        if skipped:
            result += f", {skipped} entries skipped due to validation"
        return result
    except FileNotFoundError:
        return "Error: No saved state found"
    except HaproxyError as e:
        return f"Error: {e}"


def startup_restore() -> None:
    """Restore servers from config file on startup."""
    # Wait for HAProxy to be ready
    for _ in range(STARTUP_RETRY_COUNT):
        try:
            haproxy_cmd("show info")
            break
        except HaproxyError:
            time.sleep(1)
    else:
        print("Warning: HAProxy not ready, skipping restore", file=sys.stderr)
        return

    try:
        count = restore_servers_from_config()
        if count > 0:
            print(f"Restored {count} servers from config", file=sys.stderr)
    except (HaproxyError, OSError, ValueError, json.JSONDecodeError) as e:
        print(f"Warning: Failed to restore servers: {e}", file=sys.stderr)


if __name__ == "__main__":
    startup_restore()
    mcp.run(transport="streamable-http")