from __future__ import annotations

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 .scanner import index_file


class Handler(FileSystemEventHandler):
    def __init__(self, root: Path, db_path: Path):
        self.root = root
        self.db_path = db_path

    def _process(self, filename: str) -> None:
        path = Path(filename)
        if path.is_symlink() or path.suffix.lower() not in MUSIC_EXTENSIONS:
            return
        try:
            previous = path.stat().st_size
            stable = 0
            while stable < STABILITY_CHECKS - 1:
                time.sleep(STABILITY_INTERVAL_SECONDS)
                size = path.stat().st_size
                if size == previous:
                    stable += 1
                else:
                    previous = size
                    stable = 0
            with connect(self.db_path) as conn:
                index_file(conn, path)
        except (FileNotFoundError, PermissionError):
            return

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

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


def watch(root: Path, db_path: Path) -> None:
    observer = Observer()
    observer.schedule(Handler(root, db_path), str(root), recursive=True)
    observer.start()
    try:
        while True:
            time.sleep(1)
    finally:
        observer.stop()
        observer.join()