import logging
from typing import Dict, List, Optional
from .base import BaseVendor

logger = logging.getLogger(__name__)


class VendorRegistry:
    """
    Central registry for verification vendors.
    Manages active vendor adapters and resolves waterfall order.
    """

    def __init__(self):
        self._vendors: Dict[str, BaseVendor] = {}

    def register(self, vendor: BaseVendor, overwrite: bool = True) -> None:
        """Register a vendor instance."""
        vendor_key = vendor.name.lower()
        if vendor_key in self._vendors and not overwrite:
            logger.warning("Vendor '%s' is already registered. Skipping.", vendor_key)
            return

        self._vendors[vendor_key] = vendor
        logger.info("Registered vendor '%s' (priority=%d, active=%s)", vendor.name, vendor.priority, vendor.is_active)

    def unregister(self, vendor_name: str) -> Optional[BaseVendor]:
        """Unregister a vendor instance."""
        return self._vendors.pop(vendor_name.lower(), None)

    def get_vendor(self, vendor_name: str) -> Optional[BaseVendor]:
        """Retrieve vendor by name."""
        return self._vendors.get(vendor_name.lower())

    def get_all_vendors(self) -> List[BaseVendor]:
        """Return all registered vendors sorted by priority (lowest number = highest priority)."""
        return sorted(self._vendors.values(), key=lambda v: v.priority)

    def get_vendors_for_document(
        self,
        document_type: str,
        preferred_vendor: Optional[str] = None,
    ) -> List[BaseVendor]:
        """
        Get all active vendors that support `document_type`, sorted by priority.
        If `preferred_vendor` is specified, it is placed at the front of the chain.
        """
        doc_key = document_type.lower()
        active_candidates = [
            v for v in self._vendors.values()
            if v.is_active and v.supports(doc_key)
        ]

        # Sort by priority
        active_candidates.sort(key=lambda v: v.priority)

        # If preferred vendor is requested and available, move it to index 0
        if preferred_vendor:
            pref_key = preferred_vendor.lower()
            matching = [v for v in active_candidates if v.name.lower() == pref_key]
            if matching:
                remaining = [v for v in active_candidates if v.name.lower() != pref_key]
                return matching + remaining

        return active_candidates


# Global default registry instance
registry = VendorRegistry()