"""Application configuration from environment + runtime overrides."""

from functools import lru_cache
from pathlib import Path

from pydantic_settings import BaseSettings


class Settings(BaseSettings):
    """App settings loaded from env."""

    app_name: str = "Fund Tracer API"
    debug: bool = False

    # Database
    database_url: str = "sqlite+aiosqlite:///./fund_tracer.db"

    # Uploads
    upload_dir: Path = Path("./uploads")
    max_upload_size_mb: int = 20
    allowed_extensions: set[str] = {"png", "jpg", "jpeg", "webp"}

    # --- OCR (vision) model ---
    ocr_provider: str = "openai"  # openai | anthropic | deepseek | custom_openai
    ocr_model: str | None = None  # if None, falls back to provider default

    # --- Inference (reasoning) model ---
    inference_provider: str = "openai"
    inference_model: str | None = None

    # --- Provider credentials (shared between OCR and inference) ---
    openai_api_key: str | None = None
    anthropic_api_key: str | None = None
    deepseek_api_key: str | None = None
    custom_openai_api_key: str | None = None
    custom_openai_base_url: str | None = None

    # Provider default model names (used when ocr_model / inference_model is None)
    openai_model: str = "gpt-4o"
    anthropic_model: str = "claude-3-5-sonnet-20241022"
    deepseek_model: str = "deepseek-chat"
    custom_openai_model: str = "gpt-4o-mini"

    # Legacy compat: llm_provider maps to ocr_provider on load
    llm_provider: str | None = None

    class Config:
        env_file = ".env"
        env_file_encoding = "utf-8"
        extra = "ignore"


_runtime_overrides: dict[str, str | None] = {}

_ALLOWED_RUNTIME_KEYS = {
    "ocr_provider",
    "ocr_model",
    "inference_provider",
    "inference_model",
    "openai_api_key",
    "anthropic_api_key",
    "deepseek_api_key",
    "custom_openai_api_key",
    "custom_openai_base_url",
    "custom_openai_model",
}


def _apply_overrides(settings: Settings) -> Settings:
    # Legacy: if llm_provider is set but ocr_provider is default, use it
    if settings.llm_provider and settings.ocr_provider == "openai":
        settings.ocr_provider = settings.llm_provider
    for key, value in _runtime_overrides.items():
        if hasattr(settings, key):
            setattr(settings, key, value)
    return settings


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


def _resolve_model(provider: str, explicit_model: str | None, settings: Settings) -> str:
    """Return the model name to use for a given provider."""
    if explicit_model:
        return explicit_model
    defaults = {
        "openai": settings.openai_model,
        "anthropic": settings.anthropic_model,
        "deepseek": settings.deepseek_model,
        "custom_openai": settings.custom_openai_model,
    }
    return defaults.get(provider, settings.openai_model)


def get_ocr_model() -> str:
    s = get_settings()
    return _resolve_model(s.ocr_provider, s.ocr_model, s)


def get_inference_model() -> str:
    s = get_settings()
    return _resolve_model(s.inference_provider, s.inference_model, s)


def update_runtime_settings(payload: dict[str, str | None]) -> Settings:
    for key, value in payload.items():
        if key in _ALLOWED_RUNTIME_KEYS:
            _runtime_overrides[key] = value
    get_settings.cache_clear()
    return get_settings()


def public_settings() -> dict:
    s = get_settings()
    return {
        "ocr_provider": s.ocr_provider,
        "ocr_model": get_ocr_model(),
        "inference_provider": s.inference_provider,
        "inference_model": get_inference_model(),
        "providers": ["openai", "anthropic", "deepseek", "custom_openai"],
        "provider_defaults": {
            "openai": s.openai_model,
            "anthropic": s.anthropic_model,
            "deepseek": s.deepseek_model,
            "custom_openai": s.custom_openai_model,
        },
        "base_urls": {
            "custom_openai": s.custom_openai_base_url or "",
        },
        "has_keys": {
            "openai": bool(s.openai_api_key),
            "anthropic": bool(s.anthropic_api_key),
            "deepseek": bool(s.deepseek_api_key),
            "custom_openai": bool(s.custom_openai_api_key),
        },
    }