"""Reading and writing the settings document.

Three jobs:

* seed the document from environment variables the first time the app boots, so
  a filled-in `.env` (the same variables jira-helper uses) is a working setup;
* hand the API a copy with secrets masked, and merge an edited copy back without
  the UI ever having to know a real token;
* notify the rest of the process when something changed, so the scheduler can
  re-plan its jobs.
"""

from __future__ import annotations

import threading
from typing import Any, Callable

from sqlalchemy.orm import Session

from app.config import env_settings
from app.models import SettingsRow
from app.settings_schema import SECRET_FIELDS, SECRET_MASK, AppSettings

_SETTINGS_ID = 1
_listeners: list[Callable[[AppSettings], None]] = []
_lock = threading.Lock()


def on_change(listener: Callable[[AppSettings], None]) -> None:
    """Register a callback fired after every successful settings save."""
    _listeners.append(listener)


def _csv(value: str) -> list[str]:
    return [part.strip() for part in value.split(",") if part.strip()]


def settings_from_env() -> AppSettings:
    """Build the initial document out of the environment.

    The variable names are deliberately the ones from `~/code/jira-helper`, so
    an existing `.env` can be copied across untouched.
    """
    env = env_settings()
    settings = AppSettings(timezone=env.timezone)

    jira = settings.sources.jira
    if env.jira_base_url and env.jira_email and env.jira_api_token:
        jira.enabled = True
        jira.base_url = env.jira_base_url.rstrip("/")
        jira.email = env.jira_email
        jira.api_token = env.jira_api_token
        jira.extra_jql = env.jira_extra_jql
        jira.start_date_field = env.jira_start_date_field or jira.start_date_field

    google = settings.sources.google_tasks
    if env.google_client_id and env.google_client_secret and env.google_refresh_token:
        google.enabled = True
        google.client_id = env.google_client_id
        google.client_secret = env.google_client_secret
        google.refresh_token = env.google_refresh_token
        google.lists = _csv(env.google_tasks_lists)

    todoist = settings.sources.todoist
    if env.todoist_api_token:
        todoist.enabled = True
        todoist.api_token = env.todoist_api_token
        todoist.projects = _csv(env.todoist_projects)

    laundry = settings.sources.laundry
    if env.laundry_session:
        laundry.enabled = True
        laundry.session_cookie = env.laundry_session
        laundry.base_url = env.laundry_base_url.rstrip("/")

    telegram = settings.notifications.telegram
    if env.telegram_bot_token and env.telegram_chat_id:
        telegram.enabled = True
        telegram.bot_token = env.telegram_bot_token
        telegram.chat_id = env.telegram_chat_id

    if env.slack_webhook_url:
        settings.notifications.slack.enabled = True
        settings.notifications.slack.webhook_url = env.slack_webhook_url

    return settings


def load_settings(session: Session) -> AppSettings:
    """The current settings, creating the row from the environment if absent."""
    row = session.get(SettingsRow, _SETTINGS_ID)
    if row is None:
        settings = settings_from_env()
        row = SettingsRow(id=_SETTINGS_ID, data=settings.model_dump(mode="json"))
        session.add(row)
        session.commit()
        return settings
    try:
        return AppSettings.model_validate(row.data)
    except Exception:
        # A settings document written by an older build can be missing keys or
        # carry ones that no longer exist; defaults fill the gaps rather than
        # taking the whole app down.
        return AppSettings.model_validate(_merge(AppSettings().model_dump(mode="json"), row.data))


def save_settings(session: Session, settings: AppSettings) -> AppSettings:
    row = session.get(SettingsRow, _SETTINGS_ID)
    data = settings.model_dump(mode="json")
    if row is None:
        row = SettingsRow(id=_SETTINGS_ID, data=data)
        session.add(row)
    else:
        row.data = data
    session.commit()

    with _lock:
        listeners = list(_listeners)
    for listener in listeners:
        try:
            listener(settings)
        except Exception:  # pragma: no cover - a bad listener must not block saving
            import logging

            logging.getLogger(__name__).exception("settings listener failed")
    return settings


# --------------------------------------------------------------------------
# Secret masking
# --------------------------------------------------------------------------
def _walk(node: Any, fn: Callable[[str, Any], Any]) -> Any:
    if isinstance(node, dict):
        return {key: fn(key, _walk(value, fn)) for key, value in node.items()}
    if isinstance(node, list):
        return [_walk(item, fn) for item in node]
    return node


def mask_secrets(data: dict[str, Any]) -> dict[str, Any]:
    """Replace every configured secret that has a value with the mask."""

    def mask(key: str, value: Any) -> Any:
        if key in SECRET_FIELDS and isinstance(value, str) and value:
            return SECRET_MASK
        return value

    return _walk(data, mask)


def _merge(base: Any, incoming: Any) -> Any:
    """Deep-merge `incoming` onto `base`, keeping `base` where a key is missing."""
    if isinstance(base, dict) and isinstance(incoming, dict):
        merged = dict(base)
        for key, value in incoming.items():
            merged[key] = _merge(base.get(key), value) if key in base else value
        return merged
    return incoming


def unmask_secrets(stored: dict[str, Any], incoming: dict[str, Any]) -> dict[str, Any]:
    """Put the stored secret back wherever the client sent the mask untouched."""

    def restore(node_stored: Any, node_in: Any) -> Any:
        if isinstance(node_in, dict):
            out: dict[str, Any] = {}
            for key, value in node_in.items():
                old = node_stored.get(key) if isinstance(node_stored, dict) else None
                if key in SECRET_FIELDS and value == SECRET_MASK:
                    out[key] = old or ""
                else:
                    out[key] = restore(old, value)
            return out
        return node_in

    return restore(stored, incoming)


def apply_patch(session: Session, patch: dict[str, Any]) -> AppSettings:
    """Merge a partial settings document (as the UI sends it) and store it."""
    current = load_settings(session).model_dump(mode="json")
    patch = unmask_secrets(current, patch)
    merged = _merge(current, patch)
    return save_settings(session, AppSettings.model_validate(merged))