"""Federated paper sources.

Concrete sources implement `PaperSource` and are registered explicitly
below. `federated_search`, `_VALID_SOURCES` in the MCP server, and the
`list_sources` tool all read from `REGISTRY`. Adding a new source means
adding one module, one class, and one `register_source(...)` call here.

The original `sources.py` module-level helper names (`_http`,
`_ARXIV_BASE_URL`, `fetch_arxiv`, `fetch_pubmed`, `fetch_semantic_scholar`,
the `fetch_s2_*` helpers, and `federated_search`) are re-exported so
callers in `core.py` and existing tests keep working unchanged.
"""

from ._http import _http
from .arxiv import (
    ArxivSource,
    _ARXIV_BASE_URL,
    _ARXIV_CATEGORY_TOPICS,
    fetch_arxiv,
    fetch_arxiv_by_id,
    fetch_arxiv_multi,
)
from .base import (
    Capability,
    PaperSource,
    RateLimitHint,
    REGISTRY,
    _paper_dict,
    paper_dict,
    register_source,
    unregister_source,
)
from .federated import federated_search
from .openalex import (
    OpenAlexSource,
    fetch_openalex,
    fetch_openalex_by_id,
    fetch_openalex_cross_refs,
)
from .pubmed import PubmedSource, fetch_pubmed, fetch_pubmed_by_id
from .semantic_scholar import (
    SemanticScholarSource,
    fetch_s2_by_id,
    fetch_s2_citations,
    fetch_s2_recommendations,
    fetch_s2_references,
    fetch_semantic_scholar,
)


# Explicit registration. No metaclass magic, no plugin discovery.
register_source(ArxivSource())
register_source(PubmedSource())
register_source(SemanticScholarSource())
register_source(OpenAlexSource())


__all__ = [
    "Capability",
    "PaperSource",
    "RateLimitHint",
    "REGISTRY",
    "register_source",
    "unregister_source",
    "paper_dict",
    "ArxivSource",
    "OpenAlexSource",
    "PubmedSource",
    "SemanticScholarSource",
    "fetch_arxiv",
    "fetch_arxiv_by_id",
    "fetch_arxiv_multi",
    "fetch_openalex",
    "fetch_openalex_by_id",
    "fetch_openalex_cross_refs",
    "fetch_pubmed",
    "fetch_pubmed_by_id",
    "fetch_semantic_scholar",
    "fetch_s2_by_id",
    "fetch_s2_citations",
    "fetch_s2_recommendations",
    "fetch_s2_references",
    "federated_search",
]