"""Brain directory watcher — monitors Antigravity's brain/ for file changes.

Uses watchdog to detect file creation/modification events in the brain directory.
Emits events to an asyncio queue for the Discord bot to consume.
"""

import asyncio
import time
import logging
from pathlib import Path
from dataclasses import dataclass, field
from enum import Enum
from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler, FileSystemEvent

from config import Config

logger = logging.getLogger(__name__)


class EventType(Enum):
    """Types of brain events."""
    SESSION_START = "session_start"      # New conversation directory created
    SESSION_END = "session_end"          # Conversation directory removed (or program exit)
    FILE_CHANGED = "file_changed"        # Watched file created/modified
    FILE_CREATED = "file_created"        # Watched file first created


@dataclass
class BrainEvent:
    """An event from the brain directory."""
    event_type: EventType
    conversation_id: str
    file_name: str = ""
    file_path: Path = None
    content: str = ""
    timestamp: float = field(default_factory=time.time)


class BrainEventHandler(FileSystemEventHandler):
    """Watchdog handler that filters and debounces brain events."""

    def __init__(self, event_queue: asyncio.Queue, loop: asyncio.AbstractEventLoop):
        super().__init__()
        self.event_queue = event_queue
        self.loop = loop
        self._last_events: dict[str, float] = {}  # path -> timestamp (debounce)
        self._known_sessions: set[str] = set()
        self._initialize_known_sessions()

    def _initialize_known_sessions(self):
        """Scan existing brain directories to establish baseline."""
        brain_path = Config.BRAIN_PATH
        if brain_path.exists():
            for entry in brain_path.iterdir():
                if entry.is_dir() and self._is_conversation_id(entry.name):
                    self._known_sessions.add(entry.name)
            logger.info(f"Found {len(self._known_sessions)} existing sessions at startup")

    def _is_conversation_id(self, name: str) -> bool:
        """Check if directory name looks like a UUID conversation ID."""
        parts = name.split("-")
        return len(parts) == 5 and all(len(p) >= 4 for p in parts)

    def _get_conversation_id(self, path: Path) -> str | None:
        """Extract conversation ID from file path."""
        brain_path = Config.BRAIN_PATH
        try:
            relative = path.relative_to(brain_path)
            parts = relative.parts
            if parts and self._is_conversation_id(parts[0]):
                return parts[0]
        except ValueError:
            pass
        return None

    def _should_debounce(self, path_str: str) -> bool:
        """Check if this event should be debounced."""
        now = time.time()
        last = self._last_events.get(path_str, 0)
        if now - last < Config.DEBOUNCE_SECONDS:
            return True
        self._last_events[path_str] = now
        return False

    def _emit(self, event: BrainEvent):
        """Thread-safe emit to asyncio queue."""
        self.loop.call_soon_threadsafe(self.event_queue.put_nowait, event)

    def on_created(self, event: FileSystemEvent):
        if event.is_directory:
            self._handle_directory_created(Path(event.src_path))
        else:
            self._handle_file_event(Path(event.src_path), EventType.FILE_CREATED)

    def on_modified(self, event: FileSystemEvent):
        if not event.is_directory:
            self._handle_file_event(Path(event.src_path), EventType.FILE_CHANGED)

    def _handle_directory_created(self, path: Path):
        """Detect new session directories."""
        conv_id = self._get_conversation_id(path)
        if conv_id and conv_id not in self._known_sessions:
            # Check if this is a direct child of brain/
            if path.parent == Config.BRAIN_PATH:
                self._known_sessions.add(conv_id)
                logger.info(f"New session detected: {conv_id}")
                self._emit(BrainEvent(
                    event_type=EventType.SESSION_START,
                    conversation_id=conv_id,
                ))

    def _handle_file_event(self, path: Path, event_type: EventType):
        """Process file creation/modification events."""
        conv_id = self._get_conversation_id(path)
        if not conv_id:
            return

        file_name = path.name
        if file_name not in Config.WATCHED_FILES:
            return

        if self._should_debounce(str(path)):
            return

        # Read file content
        try:
            content = path.read_text(encoding="utf-8")
        except (OSError, UnicodeDecodeError) as e:
            logger.warning(f"Failed to read {path}: {e}")
            return

        logger.info(f"File event: {event_type.value} {conv_id}/{file_name}")
        self._emit(BrainEvent(
            event_type=event_type,
            conversation_id=conv_id,
            file_name=file_name,
            file_path=path,
            content=content,
        ))


class BrainWatcher:
    """Manages the watchdog observer for the brain directory."""

    def __init__(self, event_queue: asyncio.Queue, loop: asyncio.AbstractEventLoop):
        self.event_queue = event_queue
        self.loop = loop
        self.observer = Observer()
        self.handler = BrainEventHandler(event_queue, loop)

    def start(self):
        """Start watching the brain directory."""
        brain_path = Config.BRAIN_PATH
        if not brain_path.exists():
            logger.error(f"Brain path does not exist: {brain_path}")
            return

        self.observer.schedule(self.handler, str(brain_path), recursive=True)
        self.observer.start()
        logger.info(f"Watching brain directory: {brain_path}")

    def stop(self):
        """Stop the watcher."""
        self.observer.stop()
        self.observer.join()
        logger.info("Brain watcher stopped")

    @property
    def known_sessions(self) -> set[str]:
        return self.handler._known_sessions