"""Source adapters that load structured data into the kiosk catalog."""

from __future__ import annotations

import csv
from abc import ABC, abstractmethod
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any, Callable, Dict, Iterable, List, Optional

from .utils import canonicalize_name


@dataclass
class EntityDefinition:
    """Specification for registering an entity in the data catalog."""

    name: str
    records: List[Dict[str, Any]]
    key_field: Optional[str] = None
    origin: Optional[str] = None
    normalizer: Optional[Callable[[str], str]] = None


@dataclass
class SourceResult:
    """Payload returned by a data source."""

    entities: List[EntityDefinition] = field(default_factory=list)
    metadata: Dict[str, Any] = field(default_factory=dict)


class DataSource(ABC):
    """Interface for ingesting structured data into the catalog."""

    def __init__(self, name: str) -> None:
        self.name = name

    @abstractmethod
    def load(self) -> SourceResult:
        raise NotImplementedError


class CSVSource(DataSource):
    """Loads a CSV file into an entity definition."""

    def __init__(
        self,
        name: str,
        path: Path,
        entity_name: str,
        *,
        key_field: Optional[str] = None,
        normalizer: Optional[Callable[[str], str]] = None,
    ) -> None:
        super().__init__(name)
        self.path = path
        self.entity_name = entity_name
        self.key_field = key_field
        self.normalizer = normalizer

    def load(self) -> SourceResult:
        if not self.path.exists():
            return SourceResult()
        records = self._read_csv(self.path)
        entity = EntityDefinition(
            name=self.entity_name,
            records=records,
            key_field=self.key_field,
            origin=str(self.path),
            normalizer=self.normalizer,
        )
        return SourceResult(entities=[entity])

    @staticmethod
    def _read_csv(path: Path) -> List[Dict[str, Any]]:
        with path.open(newline="", encoding="utf-8-sig") as handle:
            reader = csv.DictReader(handle)
            return [dict(row) for row in reader]


class FeedListSource(DataSource):
    """Loads newline-delimited feed URLs into catalog metadata."""

    def __init__(self, name: str, path: Path, metadata_key: str) -> None:
        super().__init__(name)
        self.path = path
        self.metadata_key = metadata_key

    def load(self) -> SourceResult:
        if not self.path.exists():
            return SourceResult()
        urls = [
            line.strip()
            for line in self.path.read_text(encoding="utf-8").splitlines()
            if line.strip()
        ]
        return SourceResult(metadata={self.metadata_key: {"urls": urls}})


def default_sources(base_dir: Path, *, name_normalizer: Optional[Callable[[str], str]] = None) -> List[DataSource]:
    """
    Produce the default set of data sources used by the backend.

    Additional sources (e.g., TA office hours) can be appended to this list
    without modifying the rest of the pipeline.
    """

    base_dir = base_dir.resolve()
    normalizer = name_normalizer or canonicalize_name
    sources: List[DataSource] = [
        CSVSource(
            name="faculty_roster",
            path=base_dir / "faculty_2.csv",
            entity_name="faculty",
            key_field="Name",
            normalizer=normalizer,
        ),
        CSVSource(
            name="faculty_offices",
            path=base_dir / "Faculty.csv",
            entity_name="faculty_offices",
            key_field="Assignee Name",
            normalizer=normalizer,
        ),
        CSVSource(
            name="staff_roster",
            path=base_dir / "staff.csv",
            entity_name="staff",
            key_field="Name",
            normalizer=normalizer,
        ),
        CSVSource(
            name="students_roster",
            path=base_dir / "students.csv",
            entity_name="students",
            key_field="Name",
            normalizer=normalizer,
        ),
        CSVSource(
            name="office_hours",
            path=base_dir / "CS Office Hours Room Reservations.csv",
            entity_name="office_hours",
            key_field="Course Name",
            normalizer=normalizer,
        ),
        CSVSource(
            name="centers_catalog",
            path=base_dir / "centers.csv",
            entity_name="centers",
            key_field="Name",
            normalizer=normalizer,
        ),
        CSVSource(
            name="mudd_seating",
            path=base_dir / "Mudd Seating Sample.csv",
            entity_name="mudd_seating",
            key_field="Student/Visitor",
            normalizer=normalizer,
        ),
        FeedListSource(
            name="event_feeds",
            path=base_dir / "feed.txt",
            metadata_key="event_feeds",
        ),
    ]
    return sources