"""The effective system prompts, as the process sees them.

Prompts default to code (`app/prompts/defaults.py`); an admin may override any
of them in `prompt_settings`, applied without a restart. This mirrors the LLM
settings override pattern, with two simplifications: the reset target is the
code default (prompts have no `.env` layer), and there is no bootstrap — a
missing row simply means "use the default".

`get_prompt` is called while rendering a prompt, so it reads a module-level
cache rather than awaiting a query. The cache is filled at startup and refreshed
on every admin write. Single-process by design (`--workers 1`); a multi-worker
deployment would need a notification channel.
"""

import logging

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.models import PromptSetting
from app.prompts.defaults import DEFAULTS

logger = logging.getLogger("pablan.prompts")

# Only holds the keys an admin has actually overridden.
_config: dict[str, str] = {}


async def load_config(db: AsyncSession) -> None:
    """Re-read every override row into the cache. Call at startup and after any
    admin write."""
    rows = (await db.execute(select(PromptSetting))).scalars().all()
    _config.clear()
    _config.update({row.key: row.content for row in rows if row.key in DEFAULTS})
    logger.info(
        "prompt settings loaded",
        extra={"event": "prompt_settings_loaded", "overridden": sorted(_config)},
    )


def get_prompt(key: str) -> str:
    """The effective prompt: an admin override if present, else the code default.

    `key` must be a known prompt (a `KeyError` here is a programming error, not
    user input)."""
    return _config.get(key) or DEFAULTS[key]


def is_overridden(key: str) -> bool:
    return key in _config


def clear() -> None:
    """Drop the cache — used by tests between cases."""
    _config.clear()