"""Lightweight in-memory catalog for loading CSV data into named tables."""

from __future__ import annotations

from dataclasses import dataclass, field
from pathlib import Path
from typing import Any, Callable, Dict, Iterable, List, Optional
import logging

from .sources import DataSource, default_sources
from .utils import (
    canonicalize_name,
    centers_for_faculty,
    extract_leadership_names,
    extract_advisor_names,
    generate_name_variants,
    tokenize_name,
)


@dataclass
class EntityRecords:
    """Container for a structured dataset plus helpful indices."""

    name: str
    records: List[Dict[str, Any]]
    key_field: Optional[str] = None
    origin: Optional[str] = None
    _index: Dict[str, Dict[str, Any]] = field(default_factory=dict, init=False, repr=False)

    def build_index(self, normalizer: Optional[Callable[[str], str]] = None) -> None:
        if self.key_field is None:
            return
        normalizer = normalizer or canonicalize_name
        for row in self.records:
            key = row.get(self.key_field)
            if not key:
                continue
            self._index[normalizer(str(key))] = row

    def get_by_key(self, value: str, normalizer: Optional[Callable[[str], str]] = None) -> Optional[Dict[str, Any]]:
        if not value or self.key_field is None:
            return None
        normalizer = normalizer or canonicalize_name
        return self._index.get(normalizer(value))


class DataCatalog:
    """
    Registry that mirrors Satyrn's Ring layer.

    Each entity (faculty, staff, events...) is stored with metadata so
    analysis blueprints can retrieve and join information deterministically.
    """

    def __init__(self) -> None:
        self.entities: Dict[str, EntityRecords] = {}
        self.metadata: Dict[str, Dict[str, Any]] = {}
        self.relationships: Dict[str, RelationshipDefinition] = {}

    def register_entity(
        self,
        name: str,
        records: Iterable[Dict[str, Any]],
        *,
        key_field: Optional[str] = None,
        origin: Optional[str] = None,
        normalizer: Optional[Callable[[str], str]] = None,
    ) -> None:
        dataset = EntityRecords(
            name=name,
            records=list(records),
            key_field=key_field,
            origin=origin,
        )
        dataset.build_index(normalizer)
        self.entities[name] = dataset

    def get(self, name: str) -> EntityRecords:
        if name not in self.entities:
            raise KeyError(f"Unknown entity '{name}'")
        return self.entities[name]

    def try_get(self, name: str) -> Optional[EntityRecords]:
        return self.entities.get(name)

    # Relationship handling -------------------------------------------------
    def register_relationship(self, relationship: RelationshipDefinition) -> None:
        self.relationships[relationship.name] = relationship

    def resolve_relationship(self, name: str, source_row: Dict[str, Any]) -> List[Dict[str, Any]]:
        relationship = self.relationships.get(name)
        if not relationship:
            raise KeyError(f"Relationship '{name}' not registered.")

        source_value = source_row.get(relationship.from_field)
        if not source_value:
            return []

        target_entity = self.try_get(relationship.to_entity)
        if not target_entity:
            return []

        candidates = relationship.variant_generator(source_value) if relationship.variant_generator else [source_value]
        matches: List[Dict[str, Any]] = []
        for candidate in candidates:
            target_row = target_entity.get_by_key(candidate, relationship.normalizer)
            if target_row:
                matches.append(target_row)

        if matches:
            return matches

        if relationship.allow_token_subset:
            source_tokens = tokenize_name(source_value)
            if source_tokens:
                for row in target_entity.records:
                    dest_tokens = tokenize_name(row.get(relationship.to_field, ""))
                    if source_tokens.issubset(dest_tokens):
                        matches.append(row)
            if matches:
                return matches

        if relationship.fallback_matcher:
            extra = relationship.fallback_matcher(source_row, target_entity.records)
            if extra:
                matches.extend(extra)

        return matches


@dataclass
class RelationshipDefinition:
    name: str
    from_entity: str
    to_entity: str
    from_field: str
    to_field: str
    normalizer: Callable[[str], str] = canonicalize_name
    variant_generator: Optional[Callable[[str], Iterable[str]]] = lambda value: generate_name_variants(value)
    allow_token_subset: bool = False
    fallback_matcher: Optional[Callable[[Dict[str, Any], List[Dict[str, Any]]], List[Dict[str, Any]]]] = None


def load_default_catalog(
    base_dir: Path | str = "Archive",
    *,
    sources: Optional[Iterable[DataSource]] = None,
) -> DataCatalog:
    """
    Load the project CSVs into a catalog with sensible defaults.

    This mirrors the datasets referenced in the exploratory notebook,
    giving downstream code a single call to bootstrap the backend.

    A custom ``sources`` iterable can be supplied to extend or override
    the default data sources (e.g., to add TA office hours).
    """

    base_path = Path(base_dir)
    catalog = DataCatalog()
    logger = logging.getLogger(__name__)

    source_list = list(sources) if sources is not None else default_sources(base_path, name_normalizer=canonicalize_name)

    for source in source_list:
        result = source.load()
        for entity in result.entities:
            if not entity.records:
                continue
            catalog.register_entity(
                entity.name,
                entity.records,
                key_field=entity.key_field,
                origin=entity.origin,
                normalizer=entity.normalizer,
            )
            # Log which file provided this entity so we can trace provenance
            try:
                origin_txt = entity.origin or "(unknown)"
            except Exception:
                origin_txt = "(unknown)"
            logger.info("Loaded entity '%s' with %d records from %s", entity.name, len(entity.records), origin_txt)
        for key, value in result.metadata.items():
            existing = catalog.metadata.get(key)
            if isinstance(existing, dict) and isinstance(value, dict):
                existing.update(value)
            else:
                catalog.metadata[key] = value

    # Register common relationships between entities to mirror Satyrn's Ring metadata.
    if catalog.try_get("faculty") and catalog.try_get("faculty_offices"):
        catalog.register_relationship(
            RelationshipDefinition(
                name="faculty_to_office",
                from_entity="faculty",
                to_entity="faculty_offices",
                from_field="Name",
                to_field="Assignee Name",
                allow_token_subset=True,
            )
        )

    if catalog.try_get("centers") and catalog.try_get("faculty"):
        catalog.register_relationship(
            RelationshipDefinition(
                name="center_to_faculty_leads",
                from_entity="centers",
                to_entity="faculty",
                from_field="Leadership",
                to_field="Name",
                normalizer=canonicalize_name,
                variant_generator=lambda value: extract_leadership_names(value),
                allow_token_subset=False,
            )
        )
        catalog.register_relationship(
            RelationshipDefinition(
                name="faculty_to_centers",
                from_entity="faculty",
                to_entity="centers",
                from_field="Name",
                to_field="Leadership",
                normalizer=canonicalize_name,
                variant_generator=None,
                allow_token_subset=False,
                fallback_matcher=centers_for_faculty,
            )
        )

    if catalog.try_get("students") and catalog.try_get("mudd_seating"):
        catalog.register_relationship(
            RelationshipDefinition(
                name="student_to_mudd_seat",
                from_entity="students",
                to_entity="mudd_seating",
                from_field="Name",
                to_field="Student/Visitor",
                allow_token_subset=True,
            )
        )

    if catalog.try_get("students") and catalog.try_get("faculty"):
        catalog.register_relationship(
            RelationshipDefinition(
                name="student_to_advisors",
                from_entity="students",
                to_entity="faculty",
                from_field="Advisor(s)",
                to_field="Name",
                normalizer=canonicalize_name,
                variant_generator=lambda value: extract_advisor_names(value),
                allow_token_subset=False,
            )
        )
        catalog.register_relationship(
            RelationshipDefinition(
                name="faculty_to_advisees",
                from_entity="faculty",
                to_entity="students",
                from_field="Name",
                to_field="Advisor(s)",
                normalizer=canonicalize_name,
                variant_generator=None,
                allow_token_subset=False,
                fallback_matcher=lambda source, students: [
                    row for row in students if canonicalize_name(source.get("Name", "")) in {
                        canonicalize_name(name) for name in extract_advisor_names(row.get("Advisor(s)"))
                    }
                ],
            )
        )

    return catalog