"""Discovery queries over the citation graph stored in PostgreSQL."""

from __future__ import annotations

from codex.db import get_conn


def discovery_leads(limit: int = 20) -> list[dict[str, int | str]]:
    """Return papers referenced by already-ingested papers but not yet collected.

    Returns list of dicts with keys:
        cited_id (str)   — arXiv ID, DOI, or OpenAlex W-ID of the target
        pull     (int)   — how many already-ingested papers cite this target

    Ordered by pull DESC, limited to `limit` rows.
    """
    sql = """
        SELECT cited_id, count(*) AS pull
        FROM   citations
        WHERE  cited_id NOT IN (SELECT id FROM papers)
        GROUP  BY cited_id
        ORDER  BY pull DESC
        LIMIT  %(limit)s
    """
    with get_conn() as conn:
        rows = conn.execute(sql, {"limit": limit}).fetchall()
    return [{"cited_id": row["cited_id"], "pull": row["pull"]} for row in rows]


def citing_papers(paper_id: str) -> list[str]:
    """Return IDs of all papers that cite `paper_id` (in-graph reverse citations)."""
    sql = "SELECT citing_id FROM citations WHERE cited_id = %(paper_id)s"
    with get_conn() as conn:
        rows = conn.execute(sql, {"paper_id": paper_id}).fetchall()
    return [row["citing_id"] for row in rows]


def cited_by(paper_id: str) -> list[str]:
    """Return IDs of all papers that `paper_id` cites (forward citations)."""
    sql = "SELECT cited_id FROM citations WHERE citing_id = %(paper_id)s"
    with get_conn() as conn:
        rows = conn.execute(sql, {"paper_id": paper_id}).fetchall()
    return [row["cited_id"] for row in rows]


def cocited_papers(paper_id: str, limit: int = 10) -> list[dict[str, int | str]]:
    """Return papers frequently co-cited with `paper_id`.

    A paper X is co-cited with `paper_id` if some paper cites both.
    Returns list of dicts: {paper_id: str, co_citations: int}, ordered DESC.
    """
    sql = """
        SELECT c2.cited_id AS paper_id, count(*) AS co_citations
        FROM   citations c1
        JOIN   citations c2 ON c1.citing_id = c2.citing_id
        WHERE  c1.cited_id = %(paper_id)s
          AND  c2.cited_id != %(paper_id)s
        GROUP  BY c2.cited_id
        ORDER  BY co_citations DESC
        LIMIT  %(limit)s
    """
    with get_conn() as conn:
        rows = conn.execute(sql, {"paper_id": paper_id, "limit": limit}).fetchall()
    return [{"paper_id": row["paper_id"], "co_citations": row["co_citations"]} for row in rows]