"""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 typing import TYPE_CHECKING, TypeVar, cast

import structlog

from app.utils.fail2ban_client import Fail2BanCommand, Fail2BanToken

if TYPE_CHECKING:
    from collections.abc import Awaitable, Callable

    import aiosqlite

from app.exceptions import ConfigOperationError, ConfigValidationError, JailNotFoundError
from app.models.config import (
    AddLogPathRequest,
    GlobalConfigUpdate,
    JailConfigUpdate,
    LogPreviewRequest,
    MapColorThresholdsUpdate,
    RegexTestRequest,
)
from app.models.config_domain import (
    DomainBantimeEscalation,
    DomainGlobalConfig,
    DomainJailConfig,
    DomainJailConfigList,
)
from app.services.log_service import preview_log as util_preview_log
from app.services.log_service import test_regex as util_test_regex
from app.services.settings_service import (
    get_map_color_thresholds as util_get_map_color_thresholds,
)
from app.services.settings_service import (
    set_map_color_thresholds as util_set_map_color_thresholds,
)
from app.utils.constants import FAIL2BAN_SOCKET_TIMEOUT
from app.utils.fail2ban_client import Fail2BanClient
from app.utils.fail2ban_response import (
    ensure_list,
    is_not_found_error,
    ok,
    to_dict,
)
from app.utils.path_utils import validate_log_target

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

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

# (exceptions are now defined in app.exceptions and imported above)


# ---------------------------------------------------------------------------
# Internal helpers
# ---------------------------------------------------------------------------


T = TypeVar("T")


async def _safe_get(
    client: Fail2BanClient,
    command: Fail2BanCommand,
    default: object | None = None,
) -> object | None:
    """Send a command and return *default* if it fails."""
    try:
        return ok(await client.send(command))
    except Exception:
        return default


async def _safe_get_typed[T](
    client: Fail2BanClient,
    command: Fail2BanCommand,
    default: T,
) -> T:
    """Send a command and return the result typed as ``default``'s type."""
    return cast("T", await _safe_get(client, command, default))


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) -> DomainJailConfig:
    """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_domain.DomainJailConfig`.

    Raises:
        JailNotFoundError: If *name* is not a known jail.
        ~app.utils.fail2ban_client.Fail2BanConnectionError: Socket unreachable.
    """
    client = Fail2BanClient(socket_path=socket_path, timeout=FAIL2BAN_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: int = await _safe_get_typed(client, ["get", name, "bantime"], 600)
    findtime_raw: int = await _safe_get_typed(client, ["get", name, "findtime"], 600)
    maxretry_raw: int = await _safe_get_typed(client, ["get", name, "maxretry"], 5)
    failregex_raw: list[object] = await _safe_get_typed(client, ["get", name, "failregex"], [])
    ignoreregex_raw: list[object] = await _safe_get_typed(client, ["get", name, "ignoreregex"], [])
    logpath_raw: list[object] = await _safe_get_typed(client, ["get", name, "logpath"], [])
    datepattern_raw: str | None = await _safe_get_typed(client, ["get", name, "datepattern"], None)
    logencoding_raw: str = await _safe_get_typed(client, ["get", name, "logencoding"], "UTF-8")
    backend_raw: str = await _safe_get_typed(client, ["get", name, "backend"], "polling")
    usedns_raw: str = await _safe_get_typed(client, ["get", name, "usedns"], "warn")
    prefregex_raw: str = await _safe_get_typed(client, ["get", name, "prefregex"], "")
    actions_raw: list[object] = await _safe_get_typed(client, ["get", name, "actions"], [])
    bt_increment_raw: bool = await _safe_get_typed(client, ["get", name, "bantime.increment"], False)
    bt_factor_raw: str | float | None = await _safe_get_typed(client, ["get", name, "bantime.factor"], None)
    bt_formula_raw: str | None = await _safe_get_typed(client, ["get", name, "bantime.formula"], None)
    bt_multipliers_raw: str | None = await _safe_get_typed(client, ["get", name, "bantime.multipliers"], None)
    bt_maxtime_raw: str | int | None = await _safe_get_typed(client, ["get", name, "bantime.maxtime"], None)
    bt_rndtime_raw: str | int | None = await _safe_get_typed(client, ["get", name, "bantime.rndtime"], None)
    bt_overalljails_raw: bool = await _safe_get_typed(client, ["get", name, "bantime.overalljails"], False)

    bantime_escalation = DomainBantimeEscalation(
        increment=bool(bt_increment_raw),
        factor=float(bt_factor_raw) if bt_factor_raw is not None else None,
        formula=str(bt_formula_raw) if bt_formula_raw else None,
        multipliers=str(bt_multipliers_raw) if bt_multipliers_raw else None,
        max_time=int(bt_maxtime_raw) if bt_maxtime_raw is not None else None,
        rnd_time=int(bt_rndtime_raw) if bt_rndtime_raw is not None else None,
        overall_jails=bool(bt_overalljails_raw),
    )

    jail_cfg = DomainJailConfig(
        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"),
        use_dns=str(usedns_raw or "warn"),
        prefregex=str(prefregex_raw) if prefregex_raw else "",
        actions=ensure_list(actions_raw),
        bantime_escalation=bantime_escalation,
    )

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


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

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

    Returns:
        :class:`~app.models.config_domain.DomainJailConfigList`.

    Raises:
        ~app.utils.fail2ban_client.Fail2BanConnectionError: Socket unreachable.
    """
    client = Fail2BanClient(socket_path=socket_path, timeout=FAIL2BAN_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 DomainJailConfigList(items=[], total=0)

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

    log.info("jail_configs_listed", count=len(jail_configs))
    return DomainJailConfigList(items=jail_configs, total=len(jail_configs))


# ---------------------------------------------------------------------------
# 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})")
    if update.prefregex is not None and update.prefregex:
        err = _validate_regex(update.prefregex)
        if err:
            raise ConfigValidationError(f"Invalid regex in 'prefregex': {err!r} (pattern: {update.prefregex!r})")

    client = Fail2BanClient(socket_path=socket_path, timeout=FAIL2BAN_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: Fail2BanToken) -> 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)
    # backend is managed by fail2ban and cannot be changed at runtime by API.
    # This field is therefore ignored during updates.
    if update.log_encoding is not None:
        await _set("logencoding", update.log_encoding)
    if update.prefregex is not None:
        await _set("prefregex", update.prefregex)
    if update.enabled is not None:
        await _set("idle", "off" if update.enabled else "on")

    # Ban-time escalation fields.
    if update.bantime_escalation is not None:
        esc = update.bantime_escalation
        if esc.increment is not None:
            await _set("bantime.increment", "true" if esc.increment else "false")
        if esc.factor is not None:
            await _set("bantime.factor", str(esc.factor))
        if esc.formula is not None:
            await _set("bantime.formula", esc.formula)
        if esc.multipliers is not None:
            await _set("bantime.multipliers", esc.multipliers)
        if esc.max_time is not None:
            await _set("bantime.maxtime", esc.max_time)
        if esc.rnd_time is not None:
            await _set("bantime.rndtime", esc.rnd_time)
        if esc.overall_jails is not None:
            await _set("bantime.overalljails", "true" if esc.overall_jails else "false")

    # 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: list[object] = await _safe_get_typed(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) -> DomainGlobalConfig:
    """Return fail2ban global configuration settings.

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

    Returns:
        :class:`~app.models.config_domain.DomainGlobalConfig`.

    Raises:
        ~app.utils.fail2ban_client.Fail2BanConnectionError: Socket unreachable.
    """
    client = Fail2BanClient(socket_path=socket_path, timeout=FAIL2BAN_SOCKET_TIMEOUT)

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

    return DomainGlobalConfig(
        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.
        ConfigValidationError: If log_target validation fails.
        ~app.utils.fail2ban_client.Fail2BanConnectionError: Socket unreachable.
    """
    if update.log_target is not None:
        try:
            validate_log_target(update.log_target)
        except ValueError as e:
            raise ConfigValidationError(str(e)) from e

    client = Fail2BanClient(socket_path=socket_path, timeout=FAIL2BAN_SOCKET_TIMEOUT)

    async def _set_global(key: str, value: Fail2BanToken) -> 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:
    """Proxy to log utilities for regex test without service imports."""
    return util_test_regex(request)


# ---------------------------------------------------------------------------
# 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=FAIL2BAN_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=FAIL2BAN_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,
    preview_fn: Callable[[LogPreviewRequest], Awaitable[LogPreviewResponse]] | None = None,
) -> LogPreviewResponse:
    """Proxy to an injectable log preview function."""
    if preview_fn is None:
        preview_fn = util_preview_log
    return await preview_fn(req)


# ---------------------------------------------------------------------------
# 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 util_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 util_set_map_color_thresholds(
        db,
        threshold_high=update.threshold_high,
        threshold_medium=update.threshold_medium,
        threshold_low=update.threshold_low,
    )


# ---------------------------------------------------------------------------
# fail2ban log file reader
# ---------------------------------------------------------------------------

# Log targets that are not file paths — log viewing is unavailable for these.
_NON_FILE_LOG_TARGETS: frozenset[str] = frozenset(
    {"STDOUT", "STDERR", "SYSLOG", "SYSTEMD-JOURNAL"}
)

# Only allow reading log files under these base directories (security).
_SAFE_LOG_PREFIXES: tuple[str, ...] = ("/var/log", "/config/log")