"""
Configuration loader for xonotic_exporter.

TOML format:
    [exporter]
    host = "0.0.0.0"
    port = 9260

    [[servers]]
    name       = "vehicles"
    host       = "localhost"
    port       = 26010
    rcon_password = ""
    rcon_mode  = 2      # 0=nonsecure, 1=secure-time, 2=secure-challenge (MD4)
"""

from __future__ import annotations

import tomllib
import os
from dataclasses import dataclass, field
from typing import Optional


# ── RCON mode constants ────────────────────────────────────────────────────────

RCON_MODE_NONSECURE        = 0
RCON_MODE_SECURE_TIME      = 1
RCON_MODE_SECURE_CHALLENGE = 2   # MD4 HMAC challenge/response

RCON_MODE_NAMES = {
    RCON_MODE_NONSECURE:        "nonsecure",
    RCON_MODE_SECURE_TIME:      "secure-time",
    RCON_MODE_SECURE_CHALLENGE: "secure-challenge (MD4)",
}

VALID_RCON_MODES = set(RCON_MODE_NAMES)


# ── Data classes ───────────────────────────────────────────────────────────────

@dataclass
class ServerConfig:
    name: str
    host: str
    port: int
    rcon_password: str
    rcon_mode: int

    def __post_init__(self) -> None:
        if not self.name:
            raise ConfigError("server 'name' must not be empty")
        if not self.host:
            raise ConfigError(f"[{self.name}] 'host' must not be empty")
        if not (1 <= self.port <= 65535):
            raise ConfigError(f"[{self.name}] 'port' must be 1-65535, got {self.port}")
        if self.rcon_mode not in VALID_RCON_MODES:
            raise ConfigError(
                f"[{self.name}] 'rcon_mode' must be one of {sorted(VALID_RCON_MODES)}, "
                f"got {self.rcon_mode}"
            )


@dataclass
class ExporterConfig:
    host: str = "0.0.0.0"
    port: int = 9260
    servers: list[ServerConfig] = field(default_factory=list)

    # derived index for O(1) lookup by name
    _index: dict[str, ServerConfig] = field(default_factory=dict, init=False, repr=False)

    def __post_init__(self) -> None:
        self._build_index()

    def _build_index(self) -> None:
        self._index = {s.name: s for s in self.servers}

    def get_server(self, name: str) -> Optional[ServerConfig]:
        return self._index.get(name)

    def server_names(self) -> list[str]:
        return list(self._index)


# ── Exceptions ─────────────────────────────────────────────────────────────────

class ConfigError(ValueError):
    """Raised for any configuration problem."""


# ── Loader ─────────────────────────────────────────────────────────────────────

_EXPORTER_DEFAULTS: dict = {
    "host": "0.0.0.0",
    "port": 9260,
}

_SERVER_DEFAULTS: dict = {
    "port":      26000,
    "rcon_mode": RCON_MODE_SECURE_CHALLENGE,
}


def load_config(path: str) -> ExporterConfig:
    """Parse and validate *path* (a TOML file). Returns :class:`ExporterConfig`."""
    try:
        with open(path, "rb") as fh:
            raw = tomllib.load(fh)
    except FileNotFoundError:
        raise ConfigError(f"config file not found: {path}")
    except tomllib.TOMLDecodeError as exc:
        raise ConfigError(f"TOML parse error: {exc}") from exc

    return _parse_raw(raw)


def load_config_from_string(text: str) -> ExporterConfig:
    """Parse TOML from *text* (used in tests / --validate)."""
    try:
        raw = tomllib.loads(text)
    except tomllib.TOMLDecodeError as exc:
        raise ConfigError(f"TOML parse error: {exc}") from exc
    return _parse_raw(raw)


def _parse_raw(raw: dict) -> ExporterConfig:
    exp_raw = raw.get("exporter", {})
    exp_host = exp_raw.get("host", _EXPORTER_DEFAULTS["host"])
    exp_port = exp_raw.get("port", _EXPORTER_DEFAULTS["port"])

    if not isinstance(exp_port, int) or not (1 <= exp_port <= 65535):
        raise ConfigError(f"[exporter] 'port' must be 1-65535, got {exp_port!r}")

    servers_raw = raw.get("servers", [])
    if not isinstance(servers_raw, list):
        raise ConfigError("'servers' must be an array of tables ([[servers]])")
    if not servers_raw:
        raise ConfigError("at least one [[servers]] entry is required")

    servers: list[ServerConfig] = []
    seen_names: set[str] = set()

    for idx, entry in enumerate(servers_raw, start=1):
        if not isinstance(entry, dict):
            raise ConfigError(f"servers[{idx}] must be a table")

        name = entry.get("name", "")
        if not isinstance(name, str) or not name:
            raise ConfigError(f"servers[{idx}] missing or empty 'name'")
        if name in seen_names:
            raise ConfigError(f"duplicate server name: {name!r}")
        seen_names.add(name)

        host = entry.get("host", "")
        if not isinstance(host, str):
            raise ConfigError(f"[{name}] 'host' must be a string")

        port = entry.get("port", _SERVER_DEFAULTS["port"])
        if not isinstance(port, int):
            raise ConfigError(f"[{name}] 'port' must be an integer")

        rcon_password = entry.get("rcon_password", "")
        if not isinstance(rcon_password, str):
            raise ConfigError(f"[{name}] 'rcon_password' must be a string")

        rcon_mode = entry.get("rcon_mode", _SERVER_DEFAULTS["rcon_mode"])
        if not isinstance(rcon_mode, int):
            raise ConfigError(f"[{name}] 'rcon_mode' must be an integer (0, 1, or 2)")

        servers.append(ServerConfig(
            name=name,
            host=host,
            port=port,
            rcon_password=rcon_password,
            rcon_mode=rcon_mode,
        ))

    return ExporterConfig(host=exp_host, port=exp_port, servers=servers)