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using System;

using System.Collections.Concurrent;

using System.Collections.Generic;

using System.Diagnostics;

using Python.Runtime.StateSerialization;

namespace Python.Runtime

{

/// <summary>

/// Implements the "import hook" used to integrate Python with the CLR.

/// </summary>

internal static class ImportHook

{

#pragma warning disable CS8618 // Non-nullable field must contain a non-null value when exiting constructor. Consider declaring as nullable.

// set in Initialize

private static PyObject root;

private static CLRModule clrModule;

private static PyModule py_clr_module;

#pragma warning restore CS8618 // Non-nullable field must contain a non-null value when exiting constructor. Consider declaring as nullable.

internal static BorrowedReference ClrModuleReference => py_clr_module.Reference;

private const string LoaderCode = @"

import importlib.abc

import sys

class DotNetLoader(importlib.abc.Loader):

@classmethod

def exec_module(klass, mod):

# This method needs to exist.

pass

@classmethod

def create_module(klass, spec):

import clr

return clr._load_clr_module(spec)

class DotNetFinder(importlib.abc.MetaPathFinder):

@classmethod

def find_spec(klass, fullname, paths=None, target=None):

# Don't import, we might call ourselves recursively!

if 'clr' not in sys.modules:

return None

clr = sys.modules['clr']

clr._add_pending_namespaces()

if clr._available_namespaces and fullname in clr._available_namespaces:

return importlib.machinery.ModuleSpec(fullname, DotNetLoader(), is_package=True)

return None

const string _available_namespaces = "_available_namespaces";

/// <summary>

/// Initialization performed on startup of the Python runtime.

/// </summary>

internal static unsafe void Initialize()

{

// Initialize the clr module and tell Python about it.

root = CLRModule.Create(out clrModule).MoveToPyObject();

// create a python module with the same methods as the clr module-like object

py_clr_module = new PyModule(Runtime.PyModule_New("clr").StealOrThrow());

// both dicts are borrowed references

BorrowedReference mod_dict = Runtime.PyModule_GetDict(ClrModuleReference);

using var clr_dict = Runtime.PyObject_GenericGetDict(root);

Runtime.PyDict_Update(mod_dict, clr_dict.BorrowOrThrow());

BorrowedReference dict = Runtime.PyImport_GetModuleDict();

Runtime.PyDict_SetItemString(dict, "CLR", ClrModuleReference);

Runtime.PyDict_SetItemString(dict, "clr", ClrModuleReference);

SetupNamespaceTracking();

SetupImportHook();

}

/// <summary>

/// Cleanup resources upon shutdown of the Python runtime.

/// </summary>

internal static void Shutdown()

{

if (Runtime.Py_IsInitialized() == 0)

{

return;

}

TeardownNameSpaceTracking();

clrModule.ResetModuleMembers();

Runtime.Py_CLEAR(ref py_clr_module!);

root.Dispose();

root = null!;

}

private static Dictionary<PyString, PyObject> GetDotNetModules()

{

BorrowedReference pyModules = Runtime.PyImport_GetModuleDict();

using var items = Runtime.PyDict_Items(pyModules);

nint length = Runtime.PyList_Size(items.BorrowOrThrow());

Debug.Assert(length >= 0);

var modules = new Dictionary<PyString, PyObject>();

for (nint i = 0; i < length; i++)

{

BorrowedReference item = Runtime.PyList_GetItem(items.Borrow(), i);

BorrowedReference name = Runtime.PyTuple_GetItem(item, 0);

BorrowedReference module = Runtime.PyTuple_GetItem(item, 1);

if (ManagedType.IsInstanceOfManagedType(module))

{

modules.Add(new PyString(name), new PyObject(module));

}

return modules;

}

internal static ImportHookState SaveRuntimeData()

{

return new()

{

PyCLRModule = py_clr_module,

Root = new PyObject(root),

Modules = GetDotNetModules(),

};

}

private static void RestoreDotNetModules(Dictionary<PyString, PyObject> modules)

{

var pyMoudles = Runtime.PyImport_GetModuleDict();

foreach (var item in modules)

{

var moduleName = item.Key;

var module = item.Value;

int res = Runtime.PyDict_SetItem(pyMoudles, moduleName, module);

PythonException.ThrowIfIsNotZero(res);

item.Key.Dispose();

item.Value.Dispose();

}

modules.Clear();

}

internal static void RestoreRuntimeData(ImportHookState storage)

{

py_clr_module = storage.PyCLRModule;

var rootHandle = storage.Root;

root = new PyObject(rootHandle);

clrModule = (CLRModule)ManagedType.GetManagedObject(rootHandle)!;

BorrowedReference dict = Runtime.PyImport_GetModuleDict();

Runtime.PyDict_SetItemString(dict, "clr", ClrModuleReference);

SetupNamespaceTracking();

RestoreDotNetModules(storage.Modules);

}

static void SetupImportHook()

{

// Create the import hook module

using var import_hook_module = Runtime.PyModule_New("clr.loader");

BorrowedReference mod_dict = Runtime.PyModule_GetDict(import_hook_module.BorrowOrThrow());

Debug.Assert(mod_dict != null);

// Run the python code to create the module's classes.

var builtins = Runtime.PyEval_GetBuiltins();

var exec = Runtime.PyDict_GetItemString(builtins, "exec");

using var args = Runtime.PyTuple_New(2);

PythonException.ThrowIfIsNull(args);

using var codeStr = Runtime.PyString_FromString(LoaderCode);

Runtime.PyTuple_SetItem(args.Borrow(), 0, codeStr.StealOrThrow());

// reference not stolen due to overload incref'ing for us.

Runtime.PyTuple_SetItem(args.Borrow(), 1, mod_dict);

Runtime.PyObject_Call(exec, args.Borrow(), default).Dispose();

// Set as a sub-module of clr.

if(Runtime.PyModule_AddObject(ClrModuleReference, "loader", import_hook_module.Steal()) != 0)

{

throw PythonException.ThrowLastAsClrException();

}

// Finally, add the hook to the meta path

var findercls = Runtime.PyDict_GetItemString(mod_dict, "DotNetFinder");

using var finderCtorArgs = Runtime.PyTuple_New(0);

using var finder_inst = Runtime.PyObject_CallObject(findercls, finderCtorArgs.Borrow());

var metapath = Runtime.PySys_GetObject("meta_path");

PythonException.ThrowIfIsNotZero(Runtime.PyList_Append(metapath, finder_inst.BorrowOrThrow()));

}

/// <summary>

/// Sets up the tracking of loaded namespaces. This makes available to

/// Python, as a Python object, the loaded namespaces. The set of loaded

/// namespaces is used during the import to verify if we can import a

/// CLR assembly as a module or not. The set is stored on the clr module.

/// </summary>

static void SetupNamespaceTracking()

{

using var newset = Runtime.PySet_New(default);

foreach (var ns in AssemblyManager.GetNamespaces())

{

using var pyNs = Runtime.PyString_FromString(ns);

if (Runtime.PySet_Add(newset.Borrow(), pyNs.BorrowOrThrow()) != 0)

{

throw PythonException.ThrowLastAsClrException();

}

if (Runtime.PyDict_SetItemString(clrModule.dict, _available_namespaces, newset.Borrow()) != 0)

{

throw PythonException.ThrowLastAsClrException();

}

/// <summary>

/// Removes the set of available namespaces from the clr module.

/// </summary>

static void TeardownNameSpaceTracking()

{

// If the C# runtime isn't loaded, then there are no namespaces available

Runtime.PyDict_SetItemString(clrModule.dict, _available_namespaces, Runtime.PyNone);

}

static readonly ConcurrentQueue<string> addPending = new();

public static void AddNamespace(string name) => addPending.Enqueue(name);

internal static int AddPendingNamespaces()

{

int added = 0;

while (addPending.TryDequeue(out string ns))

{

AddNamespaceWithGIL(ns);

added++;

}

return added;

}

internal static void AddNamespaceWithGIL(string name)

{

using var pyNs = Runtime.PyString_FromString(name);

var nsSet = Runtime.PyDict_GetItemString(clrModule.dict, _available_namespaces);

if (!(nsSet.IsNull || nsSet == Runtime.PyNone))

{

if (Runtime.PySet_Add(nsSet, pyNs.BorrowOrThrow()) != 0)

{

throw PythonException.ThrowLastAsClrException();

}

/// <summary>

/// Because we use a proxy module for the clr module, we somtimes need

/// to force the py_clr_module to sync with the actual clr module's dict.

/// </summary>

internal static void UpdateCLRModuleDict()

{

clrModule.InitializePreload();

// update the module dictionary with the contents of the root dictionary

clrModule.LoadNames();

BorrowedReference py_mod_dict = Runtime.PyModule_GetDict(ClrModuleReference);

using var clr_dict = Runtime.PyObject_GenericGetDict(root);

Runtime.PyDict_Update(py_mod_dict, clr_dict.BorrowOrThrow());

}

/// <summary>

/// Return the clr python module (new reference)

/// </summary>

public static unsafe NewReference GetCLRModule()

{

UpdateCLRModuleDict();

return new NewReference(py_clr_module);

}

/// <summary>

/// The hook to import a CLR module into Python. Returns a new reference

/// to the module.

/// </summary>

public static PyObject Import(string modname)

{

// Traverse the qualified module name to get the named module.

// Note that if

// we are running in interactive mode we pre-load the names in

// each module, which is often useful for introspection. If we

// are not interactive, we stick to just-in-time creation of

// objects at lookup time, which is much more efficient.

// NEW: The clr got a new module variable preload. You can

// enable preloading in a non-interactive python processing by

// setting clr.preload = True

ModuleObject? head = null;

ModuleObject tail = clrModule;

clrModule.InitializePreload();

string[] names = modname.Split('.');

foreach (string name in names)

{

using var nested = tail.GetAttribute(name, true);

if (nested.IsNull() || ManagedType.GetManagedObject(nested.Borrow()) is not ModuleObject module)

{

Exceptions.SetError(Exceptions.ImportError, $"'{name}' Is not a ModuleObject.");

throw PythonException.ThrowLastAsClrException();

}

if (head == null)

{

head = module;

}

tail = module;

if (CLRModule.preload)

{

tail.LoadNames();

}

return tail.Alloc().MoveToPyObject();

}