"""File I/O operations for HAProxy MCP Server."""

import fcntl
import json
import os
import tempfile
from typing import Any, Optional

from .config import (
    MAP_FILE,
    SERVERS_FILE,
    logger,
)
from .validation import domain_to_backend


def atomic_write_file(file_path: str, content: str) -> None:
    """Write content to file atomically using temp file + rename.

    Args:
        file_path: Target file path
        content: Content to write

    Raises:
        IOError: If write fails
    """
    dir_path = os.path.dirname(file_path)
    fd = None
    temp_path = None
    try:
        fd, temp_path = tempfile.mkstemp(dir=dir_path, prefix='.tmp.')
        with os.fdopen(fd, 'w', encoding='utf-8') as f:
            fd = None  # fd is now owned by the file object
            f.write(content)
        os.rename(temp_path, file_path)
        temp_path = None  # Rename succeeded
    except OSError as e:
        raise IOError(f"Failed to write {file_path}: {e}") from e
    finally:
        if fd is not None:
            try:
                os.close(fd)
            except OSError:
                pass
        if temp_path is not None:
            try:
                os.unlink(temp_path)
            except OSError:
                pass


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 save_map_file(entries: list[tuple[str, str]]) -> None:
    """Save entries to domains.map file atomically.

    Uses temp file + rename for atomic write to prevent race conditions.

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

    Raises:
        IOError: If the file cannot be written
    """
    lines = [
        "# Domain to Backend mapping\n",
        "# Format: domain backend_name\n",
        "# Wildcard: .domain.com matches *.domain.com\n\n",
    ]
    for domain, backend in entries:
        lines.append(f"{domain} {backend}\n")
    atomic_write_file(MAP_FILE, "".join(lines))


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 get_backend_and_prefix(domain: str) -> tuple[str, str]:
    """Look up backend and determine server name prefix for a domain.

    Args:
        domain: The domain name to look up

    Returns:
        Tuple of (backend_name, server_prefix)

    Raises:
        ValueError: If domain cannot be mapped to a valid backend
    """
    backend = get_domain_backend(domain)
    if not backend:
        backend = get_legacy_backend_name(domain)

    if backend.startswith("pool_"):
        server_prefix = backend
    else:
        server_prefix = domain_to_backend(domain)

    return backend, server_prefix


def load_servers_config() -> dict[str, Any]:
    """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:
                logger.debug("File locking not supported for %s", SERVERS_FILE)
            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:
        logger.warning("Corrupt config file %s: %s", SERVERS_FILE, e)
        return {}


def save_servers_config(config: dict[str, Any]) -> None:
    """Save servers configuration to JSON file atomically.

    Uses temp file + rename for atomic write to prevent race conditions.

    Args:
        config: Dictionary with server configurations
    """
    atomic_write_file(SERVERS_FILE, json.dumps(config, indent=2))


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

    Args:
        domain: Domain name
        slot: Server slot (1 to MAX_SLOTS)
        ip: Server IP address
        http_port: HTTP port
    """
    lock_path = f"{SERVERS_FILE}.lock"
    with open(lock_path, 'w') as lock_file:
        fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX)
        try:
            config = load_servers_config()
            if domain not in config:
                config[domain] = {}
            config[domain][str(slot)] = {"ip": ip, "http_port": http_port}
            save_servers_config(config)
        finally:
            fcntl.flock(lock_file.fileno(), fcntl.LOCK_UN)


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

    Args:
        domain: Domain name
        slot: Server slot to remove
    """
    lock_path = f"{SERVERS_FILE}.lock"
    with open(lock_path, 'w') as lock_file:
        fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX)
        try:
            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)
        finally:
            fcntl.flock(lock_file.fileno(), fcntl.LOCK_UN)


def remove_domain_from_config(domain: str) -> None:
    """Remove domain from persistent config with file locking.

    Args:
        domain: Domain name to remove
    """
    lock_path = f"{SERVERS_FILE}.lock"
    with open(lock_path, 'w') as lock_file:
        fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX)
        try:
            config = load_servers_config()
            if domain in config:
                del config[domain]
                save_servers_config(config)
        finally:
            fcntl.flock(lock_file.fileno(), fcntl.LOCK_UN)