"""Environment-based application configuration.

All runtime configuration flows through this module. Nothing else in the
codebase should read `os.environ` directly, so that configuration stays
auditable and testable in one place.
"""

from __future__ import annotations

from functools import lru_cache

from pydantic import Field, field_validator
from pydantic_settings import BaseSettings, SettingsConfigDict


class Settings(BaseSettings):
    model_config = SettingsConfigDict(
        env_file=".env",
        env_file_encoding="utf-8",
        case_sensitive=False,
        extra="ignore",
    )

    # --- Runtime ---
    AURORA_ENV: str = Field(default="development")
    AURORA_LOG_LEVEL: str = Field(default="INFO")
    AURORA_API_DOCS_ENABLED: bool = Field(default=True)

    # --- Database ---
    DATABASE_URL: str = Field(
        default="postgresql+asyncpg://aurora:aurora@localhost:5432/aurora_core"
    )
    DATABASE_URL_SYNC: str = Field(
        default="postgresql+psycopg2://aurora:aurora@localhost:5432/aurora_core"
    )
    DATABASE_POOL_SIZE: int = Field(default=10)
    DATABASE_MAX_OVERFLOW: int = Field(default=20)
    # Set true when DATABASE_URL points at PgBouncer in transaction pooling
    # mode (docker-compose.prod.yml): asyncpg's server-side prepared
    # statements don't survive connections being handed to different clients
    # between transactions, so they must be disabled.
    DATABASE_BEHIND_TRANSACTION_POOLER: bool = Field(default=False)

    # --- Redis ---
    REDIS_URL: str = Field(default="redis://localhost:6379/0")
    REDIS_REQUIRED: bool = Field(default=False)

    # --- Security ---
    AURORA_SECRET_KEY: str = Field(default="changeme-generate-a-real-secret")
    AURORA_ADMIN_API_KEYS: str = Field(default="")

    # --- CORS ---
    CORS_ORIGINS: str = Field(default="http://localhost:3000")

    # --- Providers ---
    TMDB_API_KEY: str = Field(default="")

    # --- Workers ---
    WORKER_CONCURRENCY: int = Field(default=4)

    # --- Caching ---
    CACHE_DEFAULT_TTL: int = Field(default=300)

    # --- Rate limiting ---
    RATE_LIMIT_ENABLED: bool = Field(default=True)
    RATE_LIMIT_PER_MINUTE: int = Field(default=120)

    @field_validator("AURORA_ENV")
    @classmethod
    def _validate_env(cls, v: str) -> str:
        allowed = {"development", "test", "staging", "production"}
        if v not in allowed:
            raise ValueError(f"AURORA_ENV must be one of {allowed}, got {v!r}")
        return v

    @property
    def cors_origins_list(self) -> list[str]:
        return [origin.strip() for origin in self.CORS_ORIGINS.split(",") if origin.strip()]

    @property
    def admin_api_keys_set(self) -> set[str]:
        return {key.strip() for key in self.AURORA_ADMIN_API_KEYS.split(",") if key.strip()}

    @property
    def is_production(self) -> bool:
        return self.AURORA_ENV == "production"

    @property
    def docs_url(self) -> str | None:
        if not self.AURORA_API_DOCS_ENABLED:
            return None
        return "/docs"

    @property
    def openapi_url(self) -> str | None:
        if not self.AURORA_API_DOCS_ENABLED:
            return None
        return "/openapi.json"


@lru_cache
def get_settings() -> Settings:
    return Settings()