from __future__ import annotations

import os
from pathlib import Path
from .db import connect
from .hashing import sha256


def confirm_sha256(conn, row) -> str | None:
    path = Path(row["file_path"])
    try: st = path.stat()
    except FileNotFoundError: return None
    if st.st_size != row["file_size"]: return None
    digest = sha256(path)
    try:
        st2 = path.stat()
    except FileNotFoundError: return None
    if st2.st_size != st.st_size or st2.st_mtime_ns != st.st_mtime_ns: return None
    conn.execute("UPDATE audio_tracks SET sha256=?,updated_at=CURRENT_TIMESTAMP WHERE id=?", (digest,row["id"]))
    return digest


def hardlink_duplicate(loser: Path, winner: Path) -> None:
    tmp = loser.with_name(loser.name + ".dedupe-linking")
    try:
        if tmp.exists(): tmp.unlink()
        os.link(winner, tmp)
        os.replace(tmp, loser)
    finally:
        if tmp.exists():
            try: tmp.unlink()
            except OSError: pass


def choose_winner(rows):
    def key(r):
        p=str(r["file_path"]); admin="/admin/" in p or p.endswith("/admin")
        return (0 if admin else 1, r["created_at"], p)
    return min(rows,key=key)


def exact_dedupe(db_path: Path, root: Path) -> list[tuple[str,str]]:
    actions=[]
    with connect(db_path) as conn:
        rows=conn.execute("SELECT * FROM audio_tracks WHERE status IN ('active','hardlinked')").fetchall()
        groups={}
        for r in rows: groups.setdefault((r["file_size"],r["fast_hash"]),[]).append(r)
        for candidates in groups.values():
            if len(candidates)<2: continue
            for r in candidates:
                if not r["sha256"]: confirm_sha256(conn,r)
            ids=[r["id"] for r in candidates]
            refreshed=conn.execute("SELECT * FROM audio_tracks WHERE id IN (%s)"%','.join('?'*len(ids)),ids).fetchall()
            by={}
            for r in refreshed:
                if r["sha256"]: by.setdefault(r["sha256"],[]).append(r)
            for same in by.values():
                if len(same)<2: continue
                winner=choose_winner(same); wp=Path(winner["file_path"])
                if not wp.exists(): continue
                for r in same:
                    if r["id"]==winner["id"]: continue
                    lp=Path(r["file_path"])
                    if not lp.exists(): continue
                    if lp.stat().st_ino != wp.stat().st_ino: hardlink_duplicate(lp,wp)
                    conn.execute("UPDATE audio_tracks SET status='hardlinked',updated_at=CURRENT_TIMESTAMP WHERE id=?",(r["id"],))
                    actions.append((str(lp),str(wp)))
    return actions