"""Switch-preset contract.

A preset tells the portal:
  * what human-readable label to show in the dropdown
  * which credential fields to render
  * what CDR format adapter to hook the output through
  * what cron cadence is appropriate by default

And provides two methods to the cdr_puller worker:
  * validate(profile) → (ok, detail)  — "test connection" button
  * fetch(profile, since) → Iterator[(remote_path, bytes)]  — pull new files

Credentials on ``profile`` are loaded at the puller layer from the
ERPNext Sensitive ID record linked by ``profile.pull_sensitive_id``.
"""

from __future__ import annotations

import logging
from dataclasses import dataclass
from datetime import datetime
from typing import Iterable, Optional

logger = logging.getLogger(__name__)


@dataclass
class CredentialField:
    """One field the portal should render in the preset credential form."""
    key: str                  # JSON key stored under profile.preset_config / Sensitive ID
    label: str                # shown on the form
    kind: str                 # 'text' | 'password' | 'ssh_key' | 'select' | 'number'
    required: bool = True
    sensitive: bool = False   # if True, stored encrypted in Sensitive ID not profile_config
    help: str = ""
    options: Optional[list[str]] = None  # for kind='select'


@dataclass
class FetchedFile:
    remote_path: str
    mtime: datetime
    content: bytes
    size_bytes: int


class BasePreset:
    """Abstract preset. Subclasses set class attributes + implement methods."""

    PRESET_SLUG: str = ""               # matches cdr_ingestion_profiles.switch_preset
    LABEL: str = ""                     # shown in the portal dropdown
    CDR_FORMAT: str = "generic_csv"     # matches cdr_ingestion_profiles.format
    TRANSPORT_METHOD: str = ""          # 'api' | 'scrape' | 'sftp' | 'ftps'
    DEFAULT_CRON: str = "0 2 * * *"
    CREDENTIAL_FIELDS: tuple[CredentialField, ...] = ()

    def validate(self, profile_config: dict, secrets: dict) -> tuple[bool, str]:
        """Test-connection hook for the portal. Returns (ok, detail)."""
        raise NotImplementedError

    def fetch(
        self,
        profile_config: dict,
        secrets: dict,
        since: Optional[datetime],
    ) -> Iterable[FetchedFile]:
        """Yield new CDR files since `since`. Puller streams them to MinIO."""
        raise NotImplementedError