# app/config.py
from __future__ import annotations

import json
import os
from functools import lru_cache
from urllib.parse import quote

# pydantic v2-first import, soft-fallback to v1
try:
    from pydantic_settings import BaseSettings, SettingsConfigDict  # v2
    from pydantic import BaseModel, Field
    IS_V2 = True
except Exception:  # v1 fallback
    from pydantic import BaseSettings as _BaseSettings, BaseModel, Field
    class BaseSettings(_BaseSettings):  # shim name
        pass
    IS_V2 = False


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

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

def _env_or(raw_val: str | None, env_name: str | None):
    """
    If raw_val == ".env" -> fetch from env_name (or the obvious uppercase key).
    Otherwise return raw_val.
    """
    if raw_val != ".env":
        return raw_val
    key = env_name or ""
    if not key:
        return None
    return os.environ.get(key)

def _bool(v, default=False):
    if v is None:
        return default
    if isinstance(v, bool):
        return v
    s = str(v).strip().lower()
    if s in {"1", "true", "yes", "y", "on"}:
        return True
    if s in {"0", "false", "no", "n", "off"}:
        return False
    return default


class LocalSystemUrl(BaseModel):
    ExternalUrl: str | None = None
    IPAddress: str | None = None
    RabbitHostName: str | None = None
    RabbitPort: int | None = None
    RabbitInstanceName: str | None = None
    RabbitUserName: str | None = None
    RabbitPassword: str | None = None  # might be ".env"
    RabbitVHost: str | None = None
    UseTls: bool | None = None


class _SettingsModel(BaseModel):
    # Core (env can still override each)
    AMQP_URL: str | None = None

    # Rabbit defaults
    RABBIT_INSTANCE_NAME: str = "prod"
    RABBIT_EXCHANGE_TYPE: str = "topic"
    RABBIT_ROUTING_KEY: str = ""
    RABBIT_PREFETCH: int = 1

    # TLS controls (default to strict=False only because your broker uses custom certs)
    RABBIT_TLS_VERIFY: bool = False
    RABBIT_TLS_CHECK_HOSTNAME: bool = False
    RABBIT_TLS_CA_FILE: str | None = None

    SERVICE_ID: str = "gradllm"
    USE_TLS: bool = True

    EXCHANGE_TYPES: dict[str, str] = Field(default_factory=dict)

    # appsettings.json fields that we may use to assemble AMQP_URL
    # Rename the field to avoid clashing with the type name; keep alias for input
    LocalSystem: LocalSystemUrl | None = Field(default=None, alias="LocalSystemUrl")
    ServiceID: str | None = None
    RabbitRoutingKey: str | None = None
    RabbitExhangeType: str | None = None  # (note the spelling in your JSON)
    UseTls: bool | None = None            # top-level dup in your JSON

    # misc passthroughs if you want them later
    RedisUrl: str | None = None
    RedisSecret: str | None = None

    if IS_V2:
        model_config = SettingsConfigDict(extra="ignore", populate_by_name=True)
    else:
        class Config:
            extra = "ignore"
            allow_population_by_field_name = True


def _build_amqp_url_from_local(local: LocalSystemUrl, top_level_use_tls: bool | None):
    """
    Build amqp(s)://user:pass@host:port/vhost?heartbeat=30
    Uses LocalSystemUrl + `.env` indirections.
    """
    if not local or not local.RabbitHostName or not local.RabbitUserName:
        return None

    # determine TLS
    use_tls = local.UseTls
    if use_tls is None:
        use_tls = top_level_use_tls
    if use_tls is None:
        use_tls = True  # default secure

    scheme = "amqps" if use_tls else "amqp"

    # password indirection
    raw_pwd = local.RabbitPassword
    pwd = raw_pwd if raw_pwd and raw_pwd != ".env" else os.environ.get("RABBIT_PASSWORD")
    if not pwd:
        pwd = os.environ.get("RabbitPassword") or os.environ.get("RABBIT_PASS")

    user = local.RabbitUserName
    host = local.RabbitHostName
    port = local.RabbitPort or (5671 if scheme == "amqps" else 5672)
    vhost = local.RabbitVHost or "/"
    vhost_enc = quote(vhost, safe="")

    return f"{scheme}://{user}:{pwd}@{host}:{port}/{vhost_enc}?heartbeat=30"


def _merge_env_over_json(j: dict) -> _SettingsModel:
    """
    Precedence:
      1) Environment variables (HF Secrets)
      2) appsettings.json values
      3) built defaults
    We also synthesize AMQP_URL from LocalSystemUrl if not set via env.
    """
    # Start with JSON
    model = _SettingsModel(**j)

    # Map top-level JSON keys to our fields when used
    if model.ServiceID:
        model.SERVICE_ID = model.ServiceID
    if model.RabbitRoutingKey:
        model.RABBIT_ROUTING_KEY = model.RabbitRoutingKey
    if model.RabbitExhangeType:
        model.RABBIT_EXCHANGE_TYPE = model.RabbitExhangeType
    if model.UseTls is not None:
        model.USE_TLS = _bool(model.UseTls, model.USE_TLS)

    # If AMQP_URL not set, try to build from LocalSystem (aliased from LocalSystemUrl)
    if not model.AMQP_URL and model.LocalSystem:
        built = _build_amqp_url_from_local(model.LocalSystem, model.UseTls)
        if built:
            model.AMQP_URL = built

    # Now overlay environment variables (HF Secrets)
    env = os.environ

    # Direct env override of AMQP_URL wins
    model.AMQP_URL = env.get("AMQP_URL", model.AMQP_URL)

    # Other rabbit knobs
    model.RABBIT_INSTANCE_NAME = env.get("RABBIT_INSTANCE_NAME", model.RABBIT_INSTANCE_NAME)
    model.RABBIT_EXCHANGE_TYPE = env.get("RABBIT_EXCHANGE_TYPE", model.RABBIT_EXCHANGE_TYPE)
    model.RABBIT_ROUTING_KEY = env.get("RABBIT_ROUTING_KEY", model.RABBIT_ROUTING_KEY)
    model.RABBIT_PREFETCH = int(env.get("RABBIT_PREFETCH", model.RABBIT_PREFETCH))

    # TLS env overrides
    if "RABBIT_TLS_VERIFY" in env:
        model.RABBIT_TLS_VERIFY = _bool(env["RABBIT_TLS_VERIFY"], model.RABBIT_TLS_VERIFY)
    if "RABBIT_TLS_CHECK_HOSTNAME" in env:
        model.RABBIT_TLS_CHECK_HOSTNAME = _bool(env["RABBIT_TLS_CHECK_HOSTNAME"], model.RABBIT_TLS_CHECK_HOSTNAME)
    model.RABBIT_TLS_CA_FILE = env.get("RABBIT_TLS_CA_FILE", model.RABBIT_TLS_CA_FILE)

    # SERVICE_ID can be overridden
    model.SERVICE_ID = env.get("SERVICE_ID", model.SERVICE_ID)

    # Optional EXCHANGE_TYPES as JSON string in env
    et = env.get("EXCHANGE_TYPES")
    if et:
        try:
            model.EXCHANGE_TYPES = json.loads(et)
        except Exception:
            pass

    # Final sanity: must have AMQP_URL
    if not model.AMQP_URL:
        raise RuntimeError(
            "AMQP_URL is not configured. Set it via:\n"
            "- env secret AMQP_URL, or\n"
            "- appsettings.json LocalSystemUrl (RabbitHostName/UserName/Password/VHost/UseTls)."
        )

    return model


class Settings(BaseSettings):
    """
    Thin wrapper that exposes the merged model as attributes.
    """
    # required
    AMQP_URL: str

    # rabbit
    RABBIT_INSTANCE_NAME: str = "prod"
    RABBIT_EXCHANGE_TYPE: str = "topic"
    RABBIT_ROUTING_KEY: str = ""
    RABBIT_PREFETCH: int = 1

    # TLS
    RABBIT_TLS_VERIFY: bool = False
    RABBIT_TLS_CHECK_HOSTNAME: bool = False
    RABBIT_TLS_CA_FILE: str | None = None

    SERVICE_ID: str = "gradllm"
    USE_TLS: bool = True

    EXCHANGE_TYPES: dict[str, str] = Field(default_factory=dict)

    if IS_V2:
        model_config = SettingsConfigDict(case_sensitive=True)
    else:
        class Config:
            case_sensitive = True


@lru_cache
def get_settings() -> Settings:
    # 1) load json
    j = _load_json(APPSETTINGS_PATH)

    # 2) merge with env precedence + synthesize AMQP_URL if needed
    merged = _merge_env_over_json(j)

    # 3) project into the public Settings class
    data = merged.model_dump() if hasattr(merged, "model_dump") else merged.dict()
    return Settings(**data)


settings = get_settings()