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

Most data access is now delegated to db.py (SQLite).
This module retains atomic file writes, map file I/O for HAProxy,
and provides backward-compatible function signatures.
"""

import fcntl
import os
import tempfile
from contextlib import contextmanager
from typing import Any, Generator, Optional

from .config import (
    MAP_FILE,
    WILDCARDS_MAP_FILE,
    REMOTE_MODE,
    logger,
)
from .validation import domain_to_backend


@contextmanager
def file_lock(lock_path: str) -> Generator[None, None, None]:
    """Acquire exclusive file lock for atomic operations.

    In REMOTE_MODE, locking is skipped (single-writer assumption
    with atomic writes on the remote host).

    Args:
        lock_path: Path to the lock file (typically config_file.lock)

    Yields:
        None - the lock is held for the duration of the context
    """
    if REMOTE_MODE:
        yield
        return

    with open(lock_path, 'w') as lock_file:
        fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX)
        try:
            yield
        finally:
            fcntl.flock(lock_file.fileno(), fcntl.LOCK_UN)


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
    """
    if REMOTE_MODE:
        from .ssh_ops import remote_write_file
        remote_write_file(file_path, content)
        return

    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 _read_map_file(file_path: str) -> list[tuple[str, str]]:
    """Read a single map file and return list of (domain, backend) tuples.

    Args:
        file_path: Path to the map file

    Returns:
        List of (domain, backend) tuples from the map file
    """
    entries = []
    try:
        content = _read_file(file_path)
        for line in content.splitlines():
            line = line.strip()
            if not line or line.startswith("#"):
                continue
            parts = line.split()
            if len(parts) >= 2:
                entries.append((parts[0], parts[1]))
    except FileNotFoundError:
        logger.debug("Map file not found: %s", file_path)
    return entries


def _read_file(file_path: str) -> str:
    """Read a file locally or remotely based on REMOTE_MODE.

    Args:
        file_path: Path to the file

    Returns:
        File contents as string

    Raises:
        FileNotFoundError: If file doesn't exist
    """
    if REMOTE_MODE:
        from .ssh_ops import remote_read_file
        return remote_read_file(file_path)

    with open(file_path, "r", encoding="utf-8") as f:
        try:
            fcntl.flock(f.fileno(), fcntl.LOCK_SH)
        except OSError as e:
            logger.debug("File locking not supported for %s: %s", file_path, e)
        try:
            return f.read()
        finally:
            try:
                fcntl.flock(f.fileno(), fcntl.LOCK_UN)
            except OSError:
                pass


def get_map_contents() -> list[tuple[str, str]]:
    """Get all domain-to-backend mappings from SQLite.

    Returns:
        List of (domain, backend) tuples including wildcards.
    """
    from .db import db_get_map_contents
    return db_get_map_contents()


def split_domain_entries(entries: list[tuple[str, str]]) -> tuple[list[tuple[str, str]], list[tuple[str, str]]]:
    """Split entries into exact domains and wildcards.

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

    Returns:
        Tuple of (exact_entries, wildcard_entries)
    """
    exact = []
    wildcards = []
    for domain, backend in entries:
        if domain.startswith("."):
            wildcards.append((domain, backend))
        else:
            exact.append((domain, backend))
    return exact, wildcards


def save_map_file(entries: list[tuple[str, str]]) -> None:
    """Sync map files from the database.

    Regenerates domains.map and wildcards.map from the current
    database state. The entries parameter is ignored (kept for
    backward compatibility during transition).

    Raises:
        IOError: If map files cannot be written.
    """
    from .db import sync_map_files
    sync_map_files()


def get_domain_backend(domain: str) -> Optional[str]:
    """Look up the backend for a domain from SQLite (O(1)).

    Args:
        domain: The domain to look up

    Returns:
        Backend name if found, None otherwise
    """
    from .db import db_get_domain_backend
    return db_get_domain_backend(domain)


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

    Pool backends: pool_1, pool_2, ..., pool_100 (dynamic, zero-reload)
    Legacy backends: {domain}_backend (static, requires reload)

    Args:
        backend: Backend name to check.

    Returns:
        True if legacy backend, False if pool backend.
    """
    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 SQLite.

    Returns:
        Dictionary with server configurations (legacy format compatible).
    """
    from .db import db_load_servers_config
    return db_load_servers_config()


def add_server_to_config(domain: str, slot: int, ip: str, http_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
    """
    from .db import db_add_server, sync_servers_json
    db_add_server(domain, slot, ip, http_port)
    sync_servers_json()


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
    """
    from .db import db_remove_server, sync_servers_json
    db_remove_server(domain, slot)
    sync_servers_json()


def remove_domain_from_config(domain: str) -> None:
    """Remove domain from persistent config (servers + domain entry).

    Args:
        domain: Domain name to remove
    """
    from .db import db_remove_domain_servers, sync_servers_json
    db_remove_domain_servers(domain)
    sync_servers_json()


def get_shared_domain(domain: str) -> Optional[str]:
    """Get the parent domain that this domain shares a pool with.

    Args:
        domain: Domain name to check

    Returns:
        Parent domain name if sharing, None otherwise
    """
    from .db import db_get_shared_domain
    return db_get_shared_domain(domain)


def add_shared_domain_to_config(domain: str, shares_with: str) -> None:
    """Add a domain that shares a pool with another domain.

    Args:
        domain: New domain name
        shares_with: Existing domain to share pool with
    """
    from .db import db_add_shared_domain, sync_servers_json
    db_add_shared_domain(domain, shares_with)
    sync_servers_json()


def get_domains_sharing_pool(pool: str) -> list[str]:
    """Get all domains that use a specific pool.

    Args:
        pool: Pool name (e.g., 'pool_5')

    Returns:
        List of domain names using this pool
    """
    from .db import db_get_domains_sharing_pool
    return db_get_domains_sharing_pool(pool)


def is_shared_domain(domain: str) -> bool:
    """Check if a domain is sharing another domain's pool.

    Args:
        domain: Domain name to check

    Returns:
        True if domain has _shares reference, False otherwise
    """
    from .db import db_is_shared_domain
    return db_is_shared_domain(domain)


# Certificate configuration functions

def load_certs_config() -> list[str]:
    """Load certificate domain list from SQLite.

    Returns:
        Sorted list of domain names.
    """
    from .db import db_load_certs
    return db_load_certs()


def add_cert_to_config(domain: str) -> None:
    """Add a domain to the certificate config.

    Args:
        domain: Domain name to add
    """
    from .db import db_add_cert, sync_certs_json
    db_add_cert(domain)
    sync_certs_json()


def remove_cert_from_config(domain: str) -> None:
    """Remove a domain from the certificate config.

    Args:
        domain: Domain name to remove
    """
    from .db import db_remove_cert, sync_certs_json
    db_remove_cert(domain)
    sync_certs_json()


# Domain map helper functions (used by domains.py)

def add_domain_to_map(domain: str, backend: str, is_wildcard: bool = False,
                      shares_with: Optional[str] = None) -> None:
    """Add a domain to SQLite and sync map files.

    Args:
        domain: Domain name (e.g., "example.com").
        backend: Backend pool name (e.g., "pool_5").
        is_wildcard: Whether this is a wildcard entry.
        shares_with: Parent domain if sharing a pool.
    """
    from .db import db_add_domain, sync_map_files
    db_add_domain(domain, backend, is_wildcard, shares_with)
    sync_map_files()


def remove_domain_from_map(domain: str) -> None:
    """Remove a domain (exact + wildcard) from SQLite and sync map files.

    Args:
        domain: Base domain name (without leading dot).
    """
    from .db import db_remove_domain, sync_map_files
    db_remove_domain(domain)
    sync_map_files()


def find_available_pool() -> Optional[str]:
    """Find the first available pool not assigned to any domain.

    Uses SQLite query for O(1) lookup vs previous O(n) list scan.

    Returns:
        Pool name (e.g., "pool_5") or None if all pools are in use.
    """
    from .db import db_find_available_pool
    return db_find_available_pool()