from __future__ import annotations

import json
import threading
import time
from pathlib import Path

from watchdog.events import FileSystemEventHandler
from watchdog.observers import Observer

from .constants import MUSIC_EXTENSIONS, STABILITY_CHECKS, STABILITY_INTERVAL_SECONDS
from .db import connect
from .exact import exact_dedupe
from .l2 import acoustic_dedupe
from .scanner import index_file, scan


class Handler(FileSystemEventHandler):
    def __init__(self, root: Path, db_path: Path, l2: bool = False):
        self.root = root.resolve()
        self.db_path = db_path
        self.l2 = l2
        self._lock = threading.Lock()
        self._timers: dict[str, threading.Timer] = {}
        self._timers_lock = threading.Lock()

    def _record_job(self, kind: str, status: str, job_id: int, result=None, error=None):
        with connect(self.db_path) as conn:
            conn.execute("UPDATE jobs SET status=?,finished_at=CURRENT_TIMESTAMP,result=?,error=? WHERE id=?",
                         (status, json.dumps(result, ensure_ascii=False) if result is not None else None, error, job_id))

    def _new_job(self, kind: str) -> int:
        with connect(self.db_path) as conn:
            return conn.execute("INSERT INTO jobs(kind,status) VALUES(?,?)", (kind, "running")).lastrowid

    def _process(self, filename: str) -> None:
        path = Path(filename)
        if path.is_symlink() or path.suffix.lower() not in MUSIC_EXTENSIONS:
            return
        try:
            path.relative_to(self.root)
        except ValueError:
            return
        if ".dedupe" in path.parts or path.name.startswith("."):
            return

        with self._lock:
            job_id = self._new_job("auto-exact")
            try:
                previous = path.stat()
                stable = 0
                while stable < STABILITY_CHECKS - 1:
                    time.sleep(STABILITY_INTERVAL_SECONDS)
                    current = path.stat()
                    if (current.st_size, current.st_mtime_ns) == (previous.st_size, previous.st_mtime_ns):
                        stable += 1
                    else:
                        previous = current
                        stable = 0
                with connect(self.db_path) as conn:
                    index_file(conn, path)
                actions = exact_dedupe(self.db_path, self.root)
                result = {"indexed": 1, "exact_hardlinked": len(actions), "path": str(path)}
                if self.l2:
                    result["acoustic"] = acoustic_dedupe(self.db_path, self.root)
                self._record_job("auto-exact", "success", job_id, result=result)
            except (FileNotFoundError, PermissionError, OSError) as exc:
                self._record_job("auto-exact", "skipped", job_id, error=str(exc))
            except Exception as exc:
                self._record_job("auto-exact", "failed", job_id, error=str(exc))

    def _schedule(self, filename: str) -> None:
        with self._timers_lock:
            old = self._timers.pop(filename, None)
            if old:
                old.cancel()
            timer = threading.Timer(1.0, self._run_scheduled, args=(filename,))
            timer.daemon = True
            self._timers[filename] = timer
            timer.start()

    def _run_scheduled(self, filename: str) -> None:
        with self._timers_lock:
            self._timers.pop(filename, None)
        self._process(filename)

    def on_created(self, event):
        if not event.is_directory:
            self._schedule(event.src_path)

    def on_modified(self, event):
        if not event.is_directory:
            self._schedule(event.src_path)

    def on_moved(self, event):
        if not event.is_directory:
            self._schedule(event.dest_path)


def _initial_reconcile(root: Path, db_path: Path, l2: bool) -> None:
    with connect(db_path) as conn:
        job_id = conn.execute("INSERT INTO jobs(kind,status) VALUES(?,?)", ("startup-reconcile", "running")).lastrowid
    try:
        indexed = scan(root, db_path)
        actions = exact_dedupe(db_path, root)
        result = {"indexed": indexed, "exact_hardlinked": len(actions)}
        if l2:
            result["acoustic"] = acoustic_dedupe(db_path, root)
        with connect(db_path) as conn:
            conn.execute("UPDATE jobs SET status='success',finished_at=CURRENT_TIMESTAMP,result=? WHERE id=?",
                         (json.dumps(result, ensure_ascii=False), job_id))
    except Exception as exc:
        with connect(db_path) as conn:
            conn.execute("UPDATE jobs SET status='failed',finished_at=CURRENT_TIMESTAMP,error=? WHERE id=?", (str(exc), job_id))
        raise


def watch(root: Path, db_path: Path, l2: bool = False) -> None:
    root = root.resolve()
    if not root.is_dir():
        raise ValueError(f"music root does not exist or is not a directory: {root}")
    db_path.parent.mkdir(parents=True, exist_ok=True)
    _initial_reconcile(root, db_path, l2)
    observer = Observer()
    observer.schedule(Handler(root, db_path, l2=l2), str(root), recursive=True)
    observer.start()
    print(f"AM Deduper watcher active: {root}", flush=True)
    try:
        while True:
            time.sleep(1)
    finally:
        observer.stop()
        observer.join()