"""Configuration loading for Meeting Room.

Provides load_config(), find_workspace_config(), and load_discussion_config()
which converts a raw YAML dict into a typed DiscussionConfig.
"""

from __future__ import annotations

import os
import re

import yaml

from meeting_room.models import DefaultsConfig, DiscussionConfig, ProviderConfig, RoleConfig

PACKAGE_DIR = os.path.dirname(os.path.abspath(__file__))


def load_config(config_path: str | None = None) -> dict:
    """Load config from file, resolve env vars, apply overrides.

    Parameters
    ----------
    config_path : str | None
        Path to the YAML config file.  When *None*, loads the package
        default config at ``meeting_room/config/config.yaml``.

    Returns
    -------
    dict
        Raw configuration dictionary (the result of ``yaml.safe_load``).
    """
    if config_path is None:
        config_path = os.path.join(PACKAGE_DIR, "config", "config.yaml")

    with open(config_path, encoding="utf-8") as f:
        raw = f.read()

    # Resolve ${ENV_VAR} placeholders
    def _env_replace(match: re.Match) -> str:
        var = match.group(1)
        return os.environ.get(var, match.group(0))

    raw = re.sub(r"\$\{(\w+)\}", _env_replace, raw)

    config = yaml.safe_load(raw)

    # Override API keys from environment if set
    for prov_name, prov_cfg in config.get("providers", {}).items():
        env_key = f"MEETING_ROOM_{prov_name.upper()}_API_KEY"
        if os.environ.get(env_key):
            prov_cfg["api_key"] = os.environ[env_key]
        env_url = f"MEETING_ROOM_{prov_name.upper()}_BASE_URL"
        if os.environ.get(env_url):
            prov_cfg["base_url"] = os.environ[env_url]

    return config


def find_workspace_config() -> str | None:
    """Search for .meeting-room/config.yaml starting from CWD upward.

    Returns
    -------
    str | None
        Absolute path to the workspace config file, or *None* if not
        found.
    """
    current = os.getcwd()
    while True:
        candidate = os.path.join(current, ".meeting-room", "config.yaml")
        if os.path.exists(candidate):
            return candidate
        parent = os.path.dirname(current)
        if parent == current:
            # Reached filesystem root
            break
        current = parent
    return None


def load_discussion_config(config_path: str | None = None) -> DiscussionConfig:
    """Load config and return a typed DiscussionConfig.

    Convenience wrapper that calls :func:`load_config` and then
    coerces the raw dict into :class:`DiscussionConfig`.

    Parameters
    ----------
    config_path : str | None
        Path to the YAML config file.  When *None*, loads the package
        default.

    Returns
    -------
    DiscussionConfig
        Typed configuration object ready for use by DiscussionEngine.
    """
    raw = load_config(config_path)

    providers = {
        name: ProviderConfig(**vals)
        for name, vals in raw.get("providers", {}).items()
    }
    roles = {
        name: RoleConfig(**vals)
        for name, vals in raw.get("roles", {}).items()
    }
    defaults = DefaultsConfig(**raw.get("defaults", {}))

    return DiscussionConfig(
        providers=providers,
        roles=roles,
        defaults=defaults,
    )