"""Configuration inspection and editing service.

Provides methods to read and update fail2ban jail configuration and global
server settings via the Unix domain socket.  Regex validation is performed
locally with Python's :mod:`re` module before any write is sent to the daemon
so that invalid patterns are rejected early.

Architecture note: this module is a pure service — it contains **no**
HTTP/FastAPI concerns.  All results are returned as Pydantic models so
routers can serialise them directly.
"""

from __future__ import annotations

import asyncio
import contextlib
import re
from pathlib import Path
from typing import TYPE_CHECKING, Any

import structlog

if TYPE_CHECKING:
    import aiosqlite

from app.models.config import (
    AddLogPathRequest,
    GlobalConfigResponse,
    GlobalConfigUpdate,
    JailConfig,
    JailConfigListResponse,
    JailConfigResponse,
    JailConfigUpdate,
    LogPreviewLine,
    LogPreviewRequest,
    LogPreviewResponse,
    MapColorThresholdsResponse,
    MapColorThresholdsUpdate,
    RegexTestRequest,
    RegexTestResponse,
)
from app.services import setup_service
from app.utils.fail2ban_client import Fail2BanClient

log: structlog.stdlib.BoundLogger = structlog.get_logger()

_SOCKET_TIMEOUT: float = 10.0

# ---------------------------------------------------------------------------
# Custom exceptions
# ---------------------------------------------------------------------------


class JailNotFoundError(Exception):
    """Raised when a requested jail name does not exist in fail2ban."""

    def __init__(self, name: str) -> None:
        """Initialise with the jail name that was not found.

        Args:
            name: The jail name that could not be located.
        """
        self.name: str = name
        super().__init__(f"Jail not found: {name!r}")


class ConfigValidationError(Exception):
    """Raised when a configuration value fails validation before writing."""


class ConfigOperationError(Exception):
    """Raised when a configuration write command fails."""


# ---------------------------------------------------------------------------
# Internal helpers (mirrored from jail_service for isolation)
# ---------------------------------------------------------------------------


def _ok(response: Any) -> Any:
    """Extract payload from a fail2ban ``(return_code, data)`` response.

    Args:
        response: Raw value returned by :meth:`~Fail2BanClient.send`.

    Returns:
        The payload ``data`` portion of the response.

    Raises:
        ValueError: If the return code indicates an error.
    """
    try:
        code, data = response
    except (TypeError, ValueError) as exc:
        raise ValueError(f"Unexpected fail2ban response shape: {response!r}") from exc
    if code != 0:
        raise ValueError(f"fail2ban returned error code {code}: {data!r}")
    return data


def _to_dict(pairs: Any) -> dict[str, Any]:
    """Convert a list of ``(key, value)`` pairs to a plain dict."""
    if not isinstance(pairs, (list, tuple)):
        return {}
    result: dict[str, Any] = {}
    for item in pairs:
        try:
            k, v = item
            result[str(k)] = v
        except (TypeError, ValueError):
            pass
    return result


def _ensure_list(value: Any) -> list[str]:
    """Coerce a fail2ban ``get`` result to a list of strings."""
    if value is None:
        return []
    if isinstance(value, str):
        return [value] if value.strip() else []
    if isinstance(value, (list, tuple)):
        return [str(v) for v in value if v is not None]
    return [str(value)]


async def _safe_get(
    client: Fail2BanClient,
    command: list[Any],
    default: Any = None,
) -> Any:
    """Send a command and return *default* if it fails."""
    try:
        return _ok(await client.send(command))
    except Exception:
        return default


def _is_not_found_error(exc: Exception) -> bool:
    """Return ``True`` if *exc* signals an unknown jail."""
    msg = str(exc).lower()
    return any(
        phrase in msg
        for phrase in ("unknown jail", "no jail", "does not exist", "not found")
    )


def _validate_regex(pattern: str) -> str | None:
    """Try to compile *pattern* and return an error message if invalid.

    Args:
        pattern: A regex pattern string to validate.

    Returns:
        ``None`` if valid, or an error message string if the pattern is broken.
    """
    try:
        re.compile(pattern)
        return None
    except re.error as exc:
        return str(exc)


# ---------------------------------------------------------------------------
# Public API — read jail configuration
# ---------------------------------------------------------------------------


async def get_jail_config(socket_path: str, name: str) -> JailConfigResponse:
    """Return the editable configuration for a single jail.

    Args:
        socket_path: Path to the fail2ban Unix domain socket.
        name: Jail name.

    Returns:
        :class:`~app.models.config.JailConfigResponse`.

    Raises:
        JailNotFoundError: If *name* is not a known jail.
        ~app.utils.fail2ban_client.Fail2BanConnectionError: Socket unreachable.
    """
    client = Fail2BanClient(socket_path=socket_path, timeout=_SOCKET_TIMEOUT)

    # Verify existence.
    try:
        _ok(await client.send(["status", name, "short"]))
    except ValueError as exc:
        if _is_not_found_error(exc):
            raise JailNotFoundError(name) from exc
        raise

    (
        bantime_raw,
        findtime_raw,
        maxretry_raw,
        failregex_raw,
        ignoreregex_raw,
        logpath_raw,
        datepattern_raw,
        logencoding_raw,
        backend_raw,
        actions_raw,
    ) = await asyncio.gather(
        _safe_get(client, ["get", name, "bantime"], 600),
        _safe_get(client, ["get", name, "findtime"], 600),
        _safe_get(client, ["get", name, "maxretry"], 5),
        _safe_get(client, ["get", name, "failregex"], []),
        _safe_get(client, ["get", name, "ignoreregex"], []),
        _safe_get(client, ["get", name, "logpath"], []),
        _safe_get(client, ["get", name, "datepattern"], None),
        _safe_get(client, ["get", name, "logencoding"], "UTF-8"),
        _safe_get(client, ["get", name, "backend"], "polling"),
        _safe_get(client, ["get", name, "actions"], []),
    )

    jail_cfg = JailConfig(
        name=name,
        ban_time=int(bantime_raw or 600),
        find_time=int(findtime_raw or 600),
        max_retry=int(maxretry_raw or 5),
        fail_regex=_ensure_list(failregex_raw),
        ignore_regex=_ensure_list(ignoreregex_raw),
        log_paths=_ensure_list(logpath_raw),
        date_pattern=str(datepattern_raw) if datepattern_raw else None,
        log_encoding=str(logencoding_raw or "UTF-8"),
        backend=str(backend_raw or "polling"),
        actions=_ensure_list(actions_raw),
    )

    log.info("jail_config_fetched", jail=name)
    return JailConfigResponse(jail=jail_cfg)


async def list_jail_configs(socket_path: str) -> JailConfigListResponse:
    """Return configuration for all active jails.

    Args:
        socket_path: Path to the fail2ban Unix domain socket.

    Returns:
        :class:`~app.models.config.JailConfigListResponse`.

    Raises:
        ~app.utils.fail2ban_client.Fail2BanConnectionError: Socket unreachable.
    """
    client = Fail2BanClient(socket_path=socket_path, timeout=_SOCKET_TIMEOUT)

    global_status = _to_dict(_ok(await client.send(["status"])))
    jail_list_raw: str = str(global_status.get("Jail list", "") or "").strip()
    jail_names: list[str] = (
        [j.strip() for j in jail_list_raw.split(",") if j.strip()]
        if jail_list_raw
        else []
    )

    if not jail_names:
        return JailConfigListResponse(jails=[], total=0)

    responses: list[JailConfigResponse] = await asyncio.gather(
        *[get_jail_config(socket_path, name) for name in jail_names],
        return_exceptions=False,
    )

    jails = [r.jail for r in responses]
    log.info("jail_configs_listed", count=len(jails))
    return JailConfigListResponse(jails=jails, total=len(jails))


# ---------------------------------------------------------------------------
# Public API — write jail configuration
# ---------------------------------------------------------------------------


async def update_jail_config(
    socket_path: str,
    name: str,
    update: JailConfigUpdate,
) -> None:
    """Apply *update* to the configuration of a running jail.

    Each non-None field in *update* is sent as a separate ``set`` command.
    Regex patterns are validated locally before any write is sent.

    Args:
        socket_path: Path to the fail2ban Unix domain socket.
        name: Jail name.
        update: Partial update payload.

    Raises:
        JailNotFoundError: If *name* is not a known jail.
        ConfigValidationError: If a regex pattern fails to compile.
        ConfigOperationError: If a ``set`` command is rejected by fail2ban.
        ~app.utils.fail2ban_client.Fail2BanConnectionError: Socket unreachable.
    """
    # Validate all regex patterns before touching the daemon.
    for pattern_list, field in [
        (update.fail_regex, "fail_regex"),
        (update.ignore_regex, "ignore_regex"),
    ]:
        if pattern_list is None:
            continue
        for pattern in pattern_list:
            err = _validate_regex(pattern)
            if err:
                raise ConfigValidationError(f"Invalid regex in {field!r}: {err!r} (pattern: {pattern!r})")

    client = Fail2BanClient(socket_path=socket_path, timeout=_SOCKET_TIMEOUT)

    # Verify existence.
    try:
        _ok(await client.send(["status", name, "short"]))
    except ValueError as exc:
        if _is_not_found_error(exc):
            raise JailNotFoundError(name) from exc
        raise

    async def _set(key: str, value: Any) -> None:
        try:
            _ok(await client.send(["set", name, key, value]))
        except ValueError as exc:
            raise ConfigOperationError(f"Failed to set {key!r} = {value!r}: {exc}") from exc

    if update.ban_time is not None:
        await _set("bantime", update.ban_time)
    if update.find_time is not None:
        await _set("findtime", update.find_time)
    if update.max_retry is not None:
        await _set("maxretry", update.max_retry)
    if update.date_pattern is not None:
        await _set("datepattern", update.date_pattern)
    if update.dns_mode is not None:
        await _set("usedns", update.dns_mode)
    if update.enabled is not None:
        await _set("idle", "off" if update.enabled else "on")

    # Replacing regex lists requires deleting old entries then adding new ones.
    if update.fail_regex is not None:
        await _replace_regex_list(client, name, "failregex", update.fail_regex)
    if update.ignore_regex is not None:
        await _replace_regex_list(client, name, "ignoreregex", update.ignore_regex)

    log.info("jail_config_updated", jail=name)


async def _replace_regex_list(
    client: Fail2BanClient,
    jail: str,
    field: str,
    new_patterns: list[str],
) -> None:
    """Replace the full regex list for *field* in *jail*.

    Deletes all existing entries (highest index first to preserve ordering)
    then inserts all *new_patterns* in order.

    Args:
        client: Shared :class:`~app.utils.fail2ban_client.Fail2BanClient`.
        jail: Jail name.
        field: Either ``"failregex"`` or ``"ignoreregex"``.
        new_patterns: Replacement list (may be empty to clear).
    """
    # Determine current count.
    current_raw = await _safe_get(client, ["get", jail, field], [])
    current: list[str] = _ensure_list(current_raw)

    del_cmd = f"del{field}"
    add_cmd = f"add{field}"

    # Delete in reverse order so indices stay stable.
    for idx in range(len(current) - 1, -1, -1):
        with contextlib.suppress(ValueError):
            _ok(await client.send(["set", jail, del_cmd, idx]))

    # Add new patterns.
    for pattern in new_patterns:
        err = _validate_regex(pattern)
        if err:
            raise ConfigValidationError(f"Invalid regex: {err!r} (pattern: {pattern!r})")
        try:
            _ok(await client.send(["set", jail, add_cmd, pattern]))
        except ValueError as exc:
            raise ConfigOperationError(f"Failed to add {field} pattern: {exc}") from exc


# ---------------------------------------------------------------------------
# Public API — global configuration
# ---------------------------------------------------------------------------


async def get_global_config(socket_path: str) -> GlobalConfigResponse:
    """Return fail2ban global configuration settings.

    Args:
        socket_path: Path to the fail2ban Unix domain socket.

    Returns:
        :class:`~app.models.config.GlobalConfigResponse`.

    Raises:
        ~app.utils.fail2ban_client.Fail2BanConnectionError: Socket unreachable.
    """
    client = Fail2BanClient(socket_path=socket_path, timeout=_SOCKET_TIMEOUT)

    (
        log_level_raw,
        log_target_raw,
        db_purge_age_raw,
        db_max_matches_raw,
    ) = await asyncio.gather(
        _safe_get(client, ["get", "loglevel"], "INFO"),
        _safe_get(client, ["get", "logtarget"], "STDOUT"),
        _safe_get(client, ["get", "dbpurgeage"], 86400),
        _safe_get(client, ["get", "dbmaxmatches"], 10),
    )

    return GlobalConfigResponse(
        log_level=str(log_level_raw or "INFO").upper(),
        log_target=str(log_target_raw or "STDOUT"),
        db_purge_age=int(db_purge_age_raw or 86400),
        db_max_matches=int(db_max_matches_raw or 10),
    )


async def update_global_config(socket_path: str, update: GlobalConfigUpdate) -> None:
    """Apply *update* to fail2ban global settings.

    Args:
        socket_path: Path to the fail2ban Unix domain socket.
        update: Partial update payload.

    Raises:
        ConfigOperationError: If a ``set`` command is rejected.
        ~app.utils.fail2ban_client.Fail2BanConnectionError: Socket unreachable.
    """
    client = Fail2BanClient(socket_path=socket_path, timeout=_SOCKET_TIMEOUT)

    async def _set_global(key: str, value: Any) -> None:
        try:
            _ok(await client.send(["set", key, value]))
        except ValueError as exc:
            raise ConfigOperationError(f"Failed to set global {key!r} = {value!r}: {exc}") from exc

    if update.log_level is not None:
        await _set_global("loglevel", update.log_level.upper())
    if update.log_target is not None:
        await _set_global("logtarget", update.log_target)
    if update.db_purge_age is not None:
        await _set_global("dbpurgeage", update.db_purge_age)
    if update.db_max_matches is not None:
        await _set_global("dbmaxmatches", update.db_max_matches)

    log.info("global_config_updated")


# ---------------------------------------------------------------------------
# Public API — regex tester (stateless, no socket)
# ---------------------------------------------------------------------------


def test_regex(request: RegexTestRequest) -> RegexTestResponse:
    """Test a regex pattern against a sample log line.

    This is a pure in-process operation — no socket communication occurs.

    Args:
        request: The :class:`~app.models.config.RegexTestRequest` payload.

    Returns:
        :class:`~app.models.config.RegexTestResponse` with match result.
    """
    try:
        compiled = re.compile(request.fail_regex)
    except re.error as exc:
        return RegexTestResponse(matched=False, groups=[], error=str(exc))

    match = compiled.search(request.log_line)
    if match is None:
        return RegexTestResponse(matched=False)

    groups: list[str] = list(match.groups() or [])
    return RegexTestResponse(matched=True, groups=[str(g) for g in groups if g is not None])


# ---------------------------------------------------------------------------
# Public API — log observation
# ---------------------------------------------------------------------------


async def add_log_path(
    socket_path: str,
    jail: str,
    req: AddLogPathRequest,
) -> None:
    """Add a log path to an existing jail.

    Args:
        socket_path: Path to the fail2ban Unix domain socket.
        jail: Jail name to which the log path should be added.
        req: :class:`~app.models.config.AddLogPathRequest` with the path to add.

    Raises:
        JailNotFoundError: If *jail* is not a known jail.
        ConfigOperationError: If the command is rejected by fail2ban.
        ~app.utils.fail2ban_client.Fail2BanConnectionError: Socket unreachable.
    """
    client = Fail2BanClient(socket_path=socket_path, timeout=_SOCKET_TIMEOUT)

    try:
        _ok(await client.send(["status", jail, "short"]))
    except ValueError as exc:
        if _is_not_found_error(exc):
            raise JailNotFoundError(jail) from exc
        raise

    tail_flag = "tail" if req.tail else "head"
    try:
        _ok(await client.send(["set", jail, "addlogpath", req.log_path, tail_flag]))
        log.info("log_path_added", jail=jail, path=req.log_path)
    except ValueError as exc:
        raise ConfigOperationError(f"Failed to add log path {req.log_path!r}: {exc}") from exc


async def delete_log_path(
    socket_path: str,
    jail: str,
    log_path: str,
) -> None:
    """Remove a monitored log path from an existing jail.

    Uses ``set <jail> dellogpath <path>`` to remove the path at runtime
    without requiring a daemon restart.

    Args:
        socket_path: Path to the fail2ban Unix domain socket.
        jail: Jail name from which the log path should be removed.
        log_path: Absolute path of the log file to stop monitoring.

    Raises:
        JailNotFoundError: If *jail* is not a known jail.
        ConfigOperationError: If the command is rejected by fail2ban.
        ~app.utils.fail2ban_client.Fail2BanConnectionError: Socket unreachable.
    """
    client = Fail2BanClient(socket_path=socket_path, timeout=_SOCKET_TIMEOUT)

    try:
        _ok(await client.send(["status", jail, "short"]))
    except ValueError as exc:
        if _is_not_found_error(exc):
            raise JailNotFoundError(jail) from exc
        raise

    try:
        _ok(await client.send(["set", jail, "dellogpath", log_path]))
        log.info("log_path_deleted", jail=jail, path=log_path)
    except ValueError as exc:
        raise ConfigOperationError(f"Failed to delete log path {log_path!r}: {exc}") from exc


async def preview_log(req: LogPreviewRequest) -> LogPreviewResponse:
    """Read the last *num_lines* of a log file and test *fail_regex* against each.

    This operation reads from the local filesystem — no socket is used.

    Args:
        req: :class:`~app.models.config.LogPreviewRequest`.

    Returns:
        :class:`~app.models.config.LogPreviewResponse` with line-by-line results.
    """
    # Validate the regex first.
    try:
        compiled = re.compile(req.fail_regex)
    except re.error as exc:
        return LogPreviewResponse(
            lines=[],
            total_lines=0,
            matched_count=0,
            regex_error=str(exc),
        )

    path = Path(req.log_path)
    if not path.is_file():
        return LogPreviewResponse(
            lines=[],
            total_lines=0,
            matched_count=0,
            regex_error=f"File not found: {req.log_path!r}",
        )

    # Read the last num_lines lines efficiently.
    try:
        raw_lines = await asyncio.get_event_loop().run_in_executor(
            None,
            _read_tail_lines,
            str(path),
            req.num_lines,
        )
    except OSError as exc:
        return LogPreviewResponse(
            lines=[],
            total_lines=0,
            matched_count=0,
            regex_error=f"Cannot read file: {exc}",
        )

    result_lines: list[LogPreviewLine] = []
    matched_count = 0
    for line in raw_lines:
        m = compiled.search(line)
        groups = [str(g) for g in (m.groups() or []) if g is not None] if m else []
        result_lines.append(LogPreviewLine(line=line, matched=(m is not None), groups=groups))
        if m:
            matched_count += 1

    return LogPreviewResponse(
        lines=result_lines,
        total_lines=len(result_lines),
        matched_count=matched_count,
    )


def _read_tail_lines(file_path: str, num_lines: int) -> list[str]:
    """Read the last *num_lines* from *file_path* synchronously.

    Uses a memory-efficient approach that seeks from the end of the file.

    Args:
        file_path: Absolute path to the log file.
        num_lines: Number of lines to return.

    Returns:
        A list of stripped line strings.
    """
    chunk_size = 8192
    raw_lines: list[bytes] = []
    with open(file_path, "rb") as fh:
        fh.seek(0, 2)  # seek to end
        end_pos = fh.tell()
        if end_pos == 0:
            return []
        buf = b""
        pos = end_pos
        while len(raw_lines) <= num_lines and pos > 0:
            read_size = min(chunk_size, pos)
            pos -= read_size
            fh.seek(pos)
            chunk = fh.read(read_size)
            buf = chunk + buf
            raw_lines = buf.split(b"\n")
        # Strip incomplete leading line unless we've read the whole file.
        if pos > 0 and len(raw_lines) > 1:
            raw_lines = raw_lines[1:]
    return [ln.decode("utf-8", errors="replace").rstrip() for ln in raw_lines[-num_lines:] if ln.strip()]


# ---------------------------------------------------------------------------
# Map color thresholds
# ---------------------------------------------------------------------------


async def get_map_color_thresholds(db: aiosqlite.Connection) -> MapColorThresholdsResponse:
    """Retrieve the current map color threshold configuration.

    Args:
        db: Active aiosqlite connection to the application database.

    Returns:
        A :class:`MapColorThresholdsResponse` containing the three threshold values.
    """
    high, medium, low = await setup_service.get_map_color_thresholds(db)
    return MapColorThresholdsResponse(
        threshold_high=high,
        threshold_medium=medium,
        threshold_low=low,
    )


async def update_map_color_thresholds(
    db: aiosqlite.Connection,
    update: MapColorThresholdsUpdate,
) -> None:
    """Update the map color threshold configuration.

    Args:
        db: Active aiosqlite connection to the application database.
        update: The new threshold values.

    Raises:
        ValueError: If validation fails (thresholds must satisfy high > medium > low).
    """
    await setup_service.set_map_color_thresholds(
        db,
        threshold_high=update.threshold_high,
        threshold_medium=update.threshold_medium,
        threshold_low=update.threshold_low,
    )