# app/config.py
import json
import os
import re
from functools import lru_cache
from urllib.parse import quote

APPSETTINGS_PATH = os.environ.get("APPSETTINGS_JSON", "appsettings.json")


class Settings:
    """Simple settings object loaded from appsettings.json + env vars."""
    def __init__(self, data: dict):
        for k, v in data.items():
            setattr(self, k, v)


def _to_upper_snake(name: str) -> str:
    """Convert CamelCase or mixedCase to UPPER_SNAKE_CASE."""
    s1 = re.sub("(.)([A-Z][a-z]+)", r"\1_\2", name)
    s2 = re.sub("([a-z0-9])([A-Z])", r"\1_\2", s1)
    return s2.upper()


def _load_json(path):
    if not os.path.exists(path):
        return {}
    with open(path, "r", encoding="utf-8") as f:
        return json.load(f)


def _replace_env_vars(d, parent_key=None):
    if isinstance(d, dict):
        return {k: _replace_env_vars(v, k) for k, v in d.items()}
    elif isinstance(d, str) and d.strip() == ".env":
        env_key = _to_upper_snake(parent_key or "")
        return os.environ.get(env_key)
    else:
        return d


def _normalize_keys(d):
    """Recursively normalize dict keys to UPPER_SNAKE_CASE."""
    if isinstance(d, dict):
        return {_to_upper_snake(k): _normalize_keys(v) for k, v in d.items()}
    elif isinstance(d, list):
        return [_normalize_keys(i) for i in d]
    else:
        return d


def build_amqp_url(cfg: dict):
    local = cfg.get("LOCAL_SYSTEM_URL")
    if not local:
        return None
    scheme = "amqps" if local.get("USE_TLS", True) else "amqp"
    host = local.get("RABBIT_HOST_NAME")
    port = local.get("RABBIT_PORT") or (5671 if scheme == "amqps" else 5672)
    user = local.get("RABBIT_USER_NAME")
    pwd = local.get("RABBIT_PASSWORD") or os.environ.get("RABBIT_PASSWORD")
    vhost = local.get("RABBIT_V_HOST") or "/"
    vhost_enc = quote(vhost, safe="")
    if not (host and user and pwd):
        return None
    return f"{scheme}://{user}:{pwd}@{host}:{port}/{vhost_enc}?heartbeat=30"


@lru_cache
def get_settings() -> Settings:
    cfg = _load_json(APPSETTINGS_PATH)
    cfg = _replace_env_vars(cfg)
    cfg = _normalize_keys(cfg)  # normalize AFTER env replacement
    if not cfg.get("AMQP_URL"):
        amqp_url = build_amqp_url(cfg)
        if amqp_url:
            cfg["AMQP_URL"] = amqp_url
    return Settings(cfg)


settings = get_settings()