"""Plugin registry — manages discovered, installed, and active plugins."""

from __future__ import annotations

import importlib
import logging
from typing import Any

from fastapi import FastAPI
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncEngine, AsyncSession

from app.core.event_bus import EventBus, get_event_bus
from app.core.service_container import ServiceContainer, get_container
from app.models.plugin import Plugin as PluginModel
from app.plugins.base import BasePlugin
from app.plugins.migration_runner import MigrationRunner

logger = logging.getLogger(__name__)


class PluginRegistry:
    """Registry for managing plugin lifecycle.

    Maintains in-memory state for discovered plugins and their runtime instances,
    backed by database records for persistent status tracking.
    """

    def __init__(self) -> None:
        # name -> BasePlugin instance (discovered/loaded)
        self._plugins: dict[str, BasePlugin] = {}
        # name -> PluginModel DB record (installed status)
        self._db_status: dict[str, PluginModel] = {}
        # name -> list of actual route objects added to the FastAPI app
        # (tracked by object identity to avoid cross-plugin route removal)
        self._mounted_routes: dict[str, list[Any]] = {}
        self._engine: AsyncEngine | None = None
        self._event_bus: EventBus = get_event_bus()
        self._container: ServiceContainer = get_container()
        self._migration_runner: MigrationRunner | None = None
        self._app: FastAPI | None = None
        self._initialized = False

    def initialize(self, engine: AsyncEngine, app: FastAPI | None = None) -> None:
        """Initialize the registry with the DB engine and optional FastAPI app."""
        self._engine = engine
        self._app = app
        self._migration_runner = MigrationRunner(engine)
        self._initialized = True

    @property
    def migration_runner(self) -> MigrationRunner:
        if self._migration_runner is None:
            raise RuntimeError("Registry not initialized — call initialize() first")
        return self._migration_runner

    @property
    def engine(self) -> AsyncEngine:
        if self._engine is None:
            raise RuntimeError("Registry not initialized — call initialize() first")
        return self._engine

    # ── Discovery ──

    def discover_builtins(self) -> list[str]:
        """Discover and load built-in plugins from app.plugins.builtins.

        Scans the builtins package for modules that export a BasePlugin subclass.
        Returns list of discovered plugin names.
        """
        discovered: list[str] = []
        try:
            builtins_pkg = importlib.import_module("app.plugins.builtins")
        except ImportError:
            return discovered

        pkg_path = getattr(builtins_pkg, "__path__", None)
        if pkg_path is None:
            return discovered

        import pkgutil

        for _importer, modname, _ispkg in pkgutil.iter_modules(pkg_path):
            if modname.startswith("_"):
                continue
            try:
                full_name = f"app.plugins.builtins.{modname}"
                module = importlib.import_module(full_name)
                # Look for BasePlugin subclass in module
                for attr_name in dir(module):
                    attr = getattr(module, attr_name)
                    if (
                        isinstance(attr, type)
                        and issubclass(attr, BasePlugin)
                        and attr is not BasePlugin
                    ):
                        instance = attr()
                        if instance.name not in self._plugins:
                            self._plugins[instance.name] = instance
                            discovered.append(instance.name)
                            logger.info(f"Discovered plugin: {instance.name} v{instance.version}")
            except Exception as exc:
                logger.warning(f"Failed to load builtin plugin module {modname}: {exc}")

        return discovered

    def register_plugin(self, plugin: BasePlugin) -> None:
        """Manually register a plugin instance."""
        self._plugins[plugin.name] = plugin
        logger.info(f"Registered plugin: {plugin.name} v{plugin.version}")

    def get_plugin(self, name: str) -> BasePlugin | None:
        """Get a registered plugin instance by name."""
        return self._plugins.get(name)

    def list_discovered(self) -> list[str]:
        """List all discovered plugin names."""
        return list(self._plugins.keys())

    # ── DB Status Sync ──

    async def sync_db_status(self, db: AsyncSession) -> None:
        """Load plugin status records from the database."""
        result = await db.execute(select(PluginModel))
        self._db_status = {row.name: row for row in result.scalars().all()}

    def get_db_status(self, name: str) -> PluginModel | None:
        """Get the DB status record for a plugin."""
        return self._db_status.get(name)

    # ── Dependency Resolution ──

    async def _check_dependencies_installed(self, db: AsyncSession, name: str) -> None:
        """Verify that all declared dependencies of a plugin are installed.

        Raises ValueError listing missing dependencies.
        """
        plugin = self.get_plugin(name)
        if plugin is None:
            raise ValueError(f"Plugin '{name}' not found in registry")

        dependencies = plugin.manifest.dependencies
        if not dependencies:
            return

        missing: list[str] = []
        for dep_name in dependencies:
            dep_record = await self._get_plugin_record(db, dep_name)
            if dep_record is None or not dep_record.installed:
                missing.append(dep_name)

        if missing:
            raise ValueError(
                f"Plugin '{name}' has uninstalled dependencies: {', '.join(missing)}. "
                f"Install them first."
            )

    async def _check_dependencies_active(self, db: AsyncSession, name: str) -> None:
        """Verify that all declared dependencies of a plugin are active.

        Raises ValueError listing inactive dependencies.
        """
        plugin = self.get_plugin(name)
        if plugin is None:
            raise ValueError(f"Plugin '{name}' not found in registry")

        dependencies = plugin.manifest.dependencies
        if not dependencies:
            return

        inactive: list[str] = []
        for dep_name in dependencies:
            dep_record = await self._get_plugin_record(db, dep_name)
            if dep_record is None or not dep_record.active:
                inactive.append(dep_name)

        if inactive:
            raise ValueError(
                f"Plugin '{name}' has inactive dependencies: {', '.join(inactive)}. "
                f"Activate them first."
            )

    # ── Permission Validation (soft check) ──

    def _check_permissions(self, name: str) -> list[str]:
        """Soft-check that declared permissions exist in the system.

        Returns a list of warning messages for permissions that are not
        recognised in the available system permissions set.
        Does not raise — this is a warning-only check.
        """
        plugin = self.get_plugin(name)
        if plugin is None:
            return []

        declared = plugin.manifest.permissions
        if not declared:
            return []

        # Build a set of all known permission strings from every discovered plugin
        available: set[str] = set()
        for p in self._plugins.values():
            available.update(p.manifest.permissions)

        warnings: list[str] = []
        for perm in declared:
            if perm not in available:
                warnings.append(
                    f"Plugin '{name}' declares permission '{perm}' "
                    f"which is not found in any discovered plugin's permissions."
                )
        return warnings

    # ── Version Comparison & Update Path ──

    async def _check_and_run_version_migrations(
        self, db: AsyncSession, name: str, record: PluginModel
    ) -> bool:
        """Compare manifest version with DB version and run migrations if different.

        If the plugin's manifest version differs from the stored DB version,
        re-run all migrations to bring the schema up to date, then update
        the DB record's version field.

        Returns True if migrations were run, False otherwise.
        """
        plugin = self.get_plugin(name)
        if plugin is None:
            return False

        manifest_version = plugin.manifest.version
        db_version = record.version

        if manifest_version == db_version:
            return False

        logger.info(
            f"Plugin '{name}' version mismatch: DB={db_version}, manifest={manifest_version}. "
            f"Running migrations to update."
        )

        # Re-run migrations to apply any new migration files
        if plugin.manifest.migrations:
            await self.migration_runner.run_all_migrations(db, name, plugin.manifest.migrations)

        # Update DB version to match manifest
        record.version = manifest_version
        await db.flush()
        self._db_status[name] = record

        logger.info(f"Plugin '{name}' updated to version {manifest_version}.")
        return True

    # ── Install / Activate / Deactivate / Uninstall ──

    async def install(self, db: AsyncSession, name: str) -> PluginModel:
        """Install a plugin: run migrations and create DB record.

        Idempotent: if already installed, checks for version updates and
        returns existing record.
        Checks that all declared dependencies are installed first.
        """
        plugin = self.get_plugin(name)
        if plugin is None:
            raise ValueError(f"Plugin '{name}' not found in registry")

        # Check if already installed in DB
        existing = await self._get_plugin_record(db, name)
        if existing is not None:
            # Check for version update — run migrations if version changed
            await self._check_and_run_version_migrations(db, name, existing)
            return existing

        # Check dependencies are installed
        await self._check_dependencies_installed(db, name)

        # Run migrations
        if plugin.manifest.migrations:
            await self.migration_runner.run_all_migrations(db, name, plugin.manifest.migrations)

        # Call on_install hook
        await plugin.on_install(db, self._container)

        # Create DB record
        record = PluginModel(
            name=name,
            display_name=plugin.manifest.display_name,
            version=plugin.manifest.version,
            status="installed",
            installed=True,
            active=False,
        )
        db.add(record)
        await db.flush()
        self._db_status[name] = record

        return record

    async def activate(self, db: AsyncSession, name: str) -> PluginModel:
        """Activate a plugin: register routes, event listeners, set status=active.

        Idempotent: if already active, checks for version updates and
        returns existing record without error.
        Checks that all declared dependencies are active first.
        Performs a soft permission check and logs warnings for unknown permissions.
        """
        plugin = self.get_plugin(name)
        if plugin is None:
            raise ValueError(f"Plugin '{name}' not found in registry")

        record = await self._get_plugin_record(db, name)
        if record is None:
            raise ValueError(f"Plugin '{name}' is not installed — install first")

        # Check for version update — run migrations if version changed
        await self._check_and_run_version_migrations(db, name, record)

        # Idempotent: already active
        if record.active and record.status == "active":
            return record

        # Check dependencies are active
        await self._check_dependencies_active(db, name)

        # Soft permission check — log warnings for unknown permissions
        perm_warnings = self._check_permissions(name)
        for warning in perm_warnings:
            logger.warning(warning)

        # Call on_activate hook (registers event listeners)
        await plugin.on_activate(db, self._container, self._event_bus)

        # Register routes on FastAPI app if available
        # Track actual route objects by identity to avoid cross-plugin removal
        if self._app is not None:
            routers = plugin.get_routes()
            mounted_routes: list[Any] = []
            for router in routers:
                # Snapshot existing route object IDs before inclusion
                existing_ids = {id(r) for r in self._app.router.routes}
                self._app.include_router(router)
                # Collect newly added route objects
                for r in self._app.router.routes:
                    if id(r) not in existing_ids:
                        mounted_routes.append(r)
            self._mounted_routes[name] = mounted_routes

        # Update DB record
        record.status = "active"
        record.active = True
        await db.flush()
        self._db_status[name] = record

        return record

    async def deactivate(self, db: AsyncSession, name: str) -> PluginModel:
        """Deactivate a plugin: unregister event listeners, set status=inactive.

        Idempotent: if already inactive, returns existing record without error.
        """
        plugin = self.get_plugin(name)
        if plugin is None:
            raise ValueError(f"Plugin '{name}' not found in registry")

        record = await self._get_plugin_record(db, name)
        if record is None:
            raise ValueError(f"Plugin '{name}' is not installed")

        # Idempotent: already inactive
        if not record.active and record.status == "inactive":
            return record

        # Call on_deactivate hook (unregisters event listeners)
        await plugin.on_deactivate(db, self._container, self._event_bus)

        # Unregister only the specific route objects that belong to this plugin
        # (by object identity, not by path — prevents cross-plugin route removal)
        if self._app is not None and name in self._mounted_routes:
            mounted_routes = self._mounted_routes.pop(name, [])
            mounted_ids = {id(r) for r in mounted_routes}
            self._app.router.routes = [
                r
                for r in self._app.router.routes
                if id(r) not in mounted_ids
            ]

        # Update DB record
        record.status = "inactive"
        record.active = False
        await db.flush()
        self._db_status[name] = record

        return record

    async def uninstall(
        self, db: AsyncSession, name: str, remove_data: bool = False
    ) -> PluginModel:
        """Uninstall a plugin: deactivate, optionally drop tables, remove DB record.

        Args:
            db: Async database session.
            name: Plugin name to uninstall.
            remove_data: If True, drop all plugin-created tables.

        Returns:
            The plugin record before deletion (for response).

        Raises:
            ValueError if plugin not installed.
        """
        plugin = self.get_plugin(name)
        if plugin is None:
            raise ValueError(f"Plugin '{name}' not found in registry")

        record = await self._get_plugin_record(db, name)
        if record is None:
            raise ValueError(f"Plugin '{name}' is not installed")

        # Deactivate first if active
        if record.active:
            await self.deactivate(db, name)
            # Refetch record after deactivate
            record = await self._get_plugin_record(db, name)
            if record is None:
                raise ValueError(f"Plugin '{name}' disappeared during uninstall")

        # Call on_uninstall hook
        await plugin.on_uninstall(db, self._container)

        # Optionally drop plugin tables
        dropped_tables: list[str] = []
        if remove_data:
            dropped_tables = await self.migration_runner.drop_plugin_tables(db, name)

        # Remove DB record
        await db.delete(record)
        await db.flush()
        self._db_status.pop(name, None)

        # Return a detached copy for response
        record_dropped_tables = dropped_tables
        record.status = "uninstalled"
        record.dropped_tables = record_dropped_tables
        return record

    async def list_plugins(self, db: AsyncSession) -> list[dict[str, Any]]:
        """List all plugins with their current status.

        Merges discovered (in-memory) plugins with installed (DB) records.
        """
        result = await db.execute(select(PluginModel))
        db_records = {row.name: row for row in result.scalars().all()}

        plugins_list: list[dict[str, Any]] = []
        for name, plugin in self._plugins.items():
            record = db_records.get(name)
            if record is not None:
                plugins_list.append(
                    {
                        "name": name,
                        "display_name": record.display_name,
                        "version": record.version,
                        "status": record.status,
                        "installed": record.installed,
                        "active": record.active,
                        "description": plugin.manifest.description,
                        "dependencies": plugin.manifest.dependencies,
                        "events": plugin.manifest.events,
                        "migrations": plugin.manifest.migrations,
                        "permissions": plugin.manifest.permissions,
                    }
                )
            else:
                plugins_list.append(
                    {
                        "name": name,
                        "display_name": plugin.manifest.display_name,
                        "version": plugin.version,
                        "status": "discovered",
                        "installed": False,
                        "active": False,
                        "description": plugin.manifest.description,
                        "dependencies": plugin.manifest.dependencies,
                        "events": plugin.manifest.events,
                        "migrations": plugin.manifest.migrations,
                        "permissions": plugin.manifest.permissions,
                    }
                )

        # Also include DB-only records (plugins that were installed but no longer discovered)
        for name, record in db_records.items():
            if name not in self._plugins:
                plugins_list.append(
                    {
                        "name": name,
                        "display_name": record.display_name,
                        "version": record.version,
                        "status": record.status,
                        "installed": record.installed,
                        "active": record.active,
                        "description": "",
                        "dependencies": [],
                        "events": [],
                        "migrations": [],
                        "permissions": [],
                    }
                )

        return plugins_list

    # ── Internal Helpers ──

    async def _get_plugin_record(self, db: AsyncSession, name: str) -> PluginModel | None:
        """Fetch a plugin record from DB by name."""
        result = await db.execute(select(PluginModel).where(PluginModel.name == name))
        return result.scalar_one_or_none()


# Global registry instance
_registry: PluginRegistry | None = None


def get_registry() -> PluginRegistry:
    """Get the global plugin registry."""
    global _registry
    if _registry is None:
        _registry = PluginRegistry()
    return _registry


def reset_registry_for_testing() -> PluginRegistry:
    """Create a fresh registry for testing."""
    global _registry
    _registry = PluginRegistry()
    return _registry