"""
Session Manager

Handles all session CRUD operations with HF persistent storage.
Manages user isolation, alias resolution, and concurrent access.
"""

import uuid
from pathlib import Path
from typing import List, Optional, Dict, Any
from datetime import datetime

from hf_storage import (
    write_json_safe,
    read_json_safe,
    get_user_dir,
    get_session_dir,
    list_user_session_dirs,
    delete_session_dir,
    ensure_session_dir,
)

from session_models import (
    SessionMetadata,
    SessionState,
    AliasIndex,
    AliasIndexEntry,
    JobReference,
)


class SessionManager:
    """
    Manages session lifecycle and persistence for multi-user environment.
    Ensures user isolation and safe concurrent access.
    """
    
    def __init__(self, user_id: str):
        """
        Initialize session manager for a specific user.
        
        Args:
            user_id: Unique identifier for the user
        """
        self.user_id = user_id
        self.user_dir = get_user_dir(user_id)
        ensure_session_dir()
        self._alias_index = self._load_alias_index()
    
    def _load_alias_index(self) -> AliasIndex:
        """Load or create the alias index for this user."""
        index_path = self.user_dir / "aliases_index.json"
        data = read_json_safe(index_path, {})
        return AliasIndex.from_dict(data) if data else AliasIndex()
    
    def _save_alias_index(self) -> bool:
        """Save the alias index to disk."""
        index_path = self.user_dir / "aliases_index.json"
        return write_json_safe(index_path, self._alias_index.to_dict())
    
    def create_session(
        self,
        alias: str,
        app_type: str,
        description: str = ""
    ) -> tuple[str, SessionMetadata]:
        """
        Create a new session.
        
        Args:
            alias: User-friendly name for the session
            app_type: Type of app ("EM" or "QLBM")
            description: Optional description
            
        Returns:
            Tuple of (session_id, metadata)
        """
        session_id = str(uuid.uuid4())
        
        # Create metadata
        metadata = SessionMetadata(
            session_id=session_id,
            user_id=self.user_id,
            alias=alias,
            app_type=app_type,
            description=description,
        )
        
        # Create empty state
        state = SessionState(
            session_id=session_id,
            app_type=app_type,
        )
        
        # Save to disk
        session_dir = get_session_dir(self.user_id, session_id)
        metadata_path = session_dir / "metadata.json"
        state_path = session_dir / "state.json"
        
        write_json_safe(metadata_path, metadata.to_dict())
        write_json_safe(state_path, state.to_dict())
        
        # Update alias index
        entry = AliasIndexEntry(
            alias=alias,
            session_id=session_id,
            created_at=metadata.created_at,
            last_modified=metadata.last_modified,
        )
        self._alias_index.add(alias, entry)
        self._save_alias_index()
        
        return session_id, metadata
    
    def load_session(self, session_id: str) -> tuple[SessionMetadata, SessionState]:
        """
        Load a session by ID.
        
        Args:
            session_id: Session to load
            
        Returns:
            Tuple of (metadata, state)
            
        Raises:
            FileNotFoundError: If session doesn't exist
        """
        session_dir = get_session_dir(self.user_id, session_id)
        metadata_path = session_dir / "metadata.json"
        state_path = session_dir / "state.json"
        
        if not metadata_path.exists():
            raise FileNotFoundError(f"Session {session_id} not found")
        
        metadata_data = read_json_safe(metadata_path)
        state_data = read_json_safe(state_path)
        
        metadata = SessionMetadata.from_dict(metadata_data)
        state = SessionState.from_dict(state_data) if state_data else SessionState(
            session_id=session_id,
            app_type=metadata.app_type,
        )
        
        # Update access timestamp
        metadata.last_accessed = datetime.utcnow().isoformat()
        
        return metadata, state
    
    def save_session(self, metadata: SessionMetadata, state: SessionState) -> bool:
        """
        Save a session's state and metadata.
        
        Args:
            metadata: Session metadata
            state: Session state
            
        Returns:
            True if successful
        """
        session_dir = get_session_dir(self.user_id, metadata.session_id)
        metadata_path = session_dir / "metadata.json"
        state_path = session_dir / "state.json"
        
        # Update timestamps
        metadata.update_timestamp()
        state.update_timestamp()
        
        success = True
        success &= write_json_safe(metadata_path, metadata.to_dict())
        success &= write_json_safe(state_path, state.to_dict())
        
        if success:
            # Update alias index
            entry = AliasIndexEntry(
                alias=metadata.alias,
                session_id=metadata.session_id,
                created_at=metadata.created_at,
                last_modified=metadata.last_modified,
            )
            self._alias_index.add(metadata.alias, entry)
            self._save_alias_index()
        
        return success
    
    def get_by_alias(self, alias: str) -> List[tuple[SessionMetadata, str]]:
        """
        Get all sessions matching an alias (sorted by recency).
        
        Args:
            alias: Session alias to search for
            
        Returns:
            List of (metadata, session_id) tuples, newest first
        """
        entries = self._alias_index.get_by_alias(alias)
        results = []
        
        for entry in entries:
            try:
                metadata, _ = self.load_session(entry.session_id)
                results.append((metadata, entry.session_id))
            except FileNotFoundError:
                # Session file was deleted, skip
                pass
        
        return results
    
    def get_most_recent_by_alias(self, alias: str) -> Optional[tuple[SessionMetadata, str]]:
        """
        Get the most recent session matching an alias.
        
        Args:
            alias: Session alias to search for
            
        Returns:
            (metadata, session_id) tuple or None if not found
        """
        results = self.get_by_alias(alias)
        return results[0] if results else None
    
    def list_all_sessions(self) -> List[SessionMetadata]:
        """
        List all sessions for this user (unsorted).
        
        Returns:
            List of metadata for all user's sessions
        """
        session_ids = list_user_session_dirs(self.user_id)
        sessions = []
        
        for session_id in session_ids:
            try:
                metadata, _ = self.load_session(session_id)
                sessions.append(metadata)
            except FileNotFoundError:
                pass
        
        return sessions
    
    def list_sessions_by_app(self, app_type: str) -> List[SessionMetadata]:
        """
        List all sessions for a specific app type.
        
        Args:
            app_type: "EM" or "QLBM"
            
        Returns:
            List of metadata for sessions of this app type
        """
        return [s for s in self.list_all_sessions() if s.app_type == app_type]
    
    def list_sessions_sorted_recent(self, limit: Optional[int] = None) -> List[SessionMetadata]:
        """
        List sessions sorted by last accessed time (most recent first).
        
        Args:
            limit: Maximum number of sessions to return
            
        Returns:
            Sorted list of session metadata
        """
        sessions = self.list_all_sessions()
        sessions.sort(key=lambda s: s.last_accessed, reverse=True)
        return sessions[:limit] if limit else sessions
    
    def delete_session(self, session_id: str) -> bool:
        """
        Delete a session.
        
        Args:
            session_id: Session to delete
            
        Returns:
            True if successful
        """
        try:
            # Load metadata to get alias
            metadata, _ = self.load_session(session_id)
            
            # Remove from alias index
            self._alias_index.remove(metadata.alias, session_id)
            self._save_alias_index()
            
            # Delete directory
            return delete_session_dir(self.user_id, session_id)
        except FileNotFoundError:
            return False
    
    def rename_session(self, session_id: str, new_alias: str) -> bool:
        """
        Rename a session.
        
        Args:
            session_id: Session to rename
            new_alias: New alias
            
        Returns:
            True if successful
        """
        try:
            metadata, state = self.load_session(session_id)
            
            # Update alias index
            old_alias = metadata.alias
            self._alias_index.remove(old_alias, session_id)
            
            # Update metadata
            metadata.alias = new_alias
            
            # Save
            return self.save_session(metadata, state)
        except FileNotFoundError:
            return False
    
    def add_job_to_session(
        self,
        session_id: str,
        job_id: str,
        service_type: str
    ) -> bool:
        """
        Add a job reference to a session.
        
        Args:
            session_id: Session ID
            job_id: Cloud service job ID
            service_type: Service type (e.g., "qiskit_ibm", "ionq")
            
        Returns:
            True if successful
        """
        try:
            metadata, state = self.load_session(session_id)
            job = JobReference(
                job_id=job_id,
                service_type=service_type,
            )
            state.add_job(job)
            return self.save_session(metadata, state)
        except FileNotFoundError:
            return False
    
    def update_job_status(
        self,
        session_id: str,
        job_id: str,
        status: str,
        result: Optional[Dict[str, Any]] = None
    ) -> bool:
        """
        Update a job's status in a session.
        
        Args:
            session_id: Session ID
            job_id: Job ID
            status: New status
            result: Optional result data
            
        Returns:
            True if job was found and updated
        """
        try:
            metadata, state = self.load_session(session_id)
            found = state.update_job_status(job_id, status, result)
            if found:
                self.save_session(metadata, state)
            return found
        except FileNotFoundError:
            return False