"""A utility for debugging serialization issues."""
from typing import Any, Tuple, Set, Optional
import inspect
import ray.cloudpickle as cp
from contextlib import contextmanager

# Import ray first to use the bundled colorama
import ray  # noqa: F401
from ray.util.annotations import DeveloperAPI

import colorama


@contextmanager
def _indent(printer):
    printer.level += 1
    yield
    printer.level -= 1


class _Printer:
    def __init__(self):
        self.level = 0

    def indent(self):
        return _indent(self)

    def print(self, msg):
        indent = "    " * self.level
        print(indent + msg)


_printer = _Printer()


class FailureTuple:
    """Represents the serialization 'frame'.

    Attributes:
        obj: The object that fails serialization.
        name: The variable name of the object.
        parent: The object that references the `obj`.
    """

    def __init__(self, obj: Any, name: str, parent: Any):
        self.obj = obj
        self.name = name
        self.parent = parent

    def __repr__(self):
        return f"FailTuple({self.name} [obj={self.obj}, parent={self.parent}])"


def _inspect_func_serialization(base_obj, depth, parent, failure_set):
    """Adds the first-found non-serializable element to the failure_set."""
    assert inspect.isfunction(base_obj)
    closure = inspect.getclosurevars(base_obj)
    found = False
    if closure.globals:
        _printer.print(f"Detected {len(closure.globals)} global variables. "
                       "Checking serializability...")

        with _printer.indent():
            for name, obj in closure.globals.items():
                serializable, _ = inspect_serializability(
                    obj,
                    name=name,
                    depth=depth - 1,
                    _parent=parent,
                    _failure_set=failure_set)
                found = found or not serializable
                if found:
                    break

    if closure.nonlocals:
        _printer.print(
            f"Detected {len(closure.nonlocals)} nonlocal variables. "
            "Checking serializability...")
        with _printer.indent():
            for name, obj in closure.nonlocals.items():
                serializable, _ = inspect_serializability(
                    obj,
                    name=name,
                    depth=depth - 1,
                    _parent=parent,
                    _failure_set=failure_set)
                found = found or not serializable
                if found:
                    break
    if not found:
        _printer.print(
            f"WARNING: Did not find non-serializable object in {base_obj}. "
            "This may be an oversight.")
    return found


def _inspect_generic_serialization(base_obj, depth, parent, failure_set):
    """Adds the first-found non-serializable element to the failure_set."""
    assert not inspect.isfunction(base_obj)
    functions = inspect.getmembers(base_obj, predicate=inspect.isfunction)
    found = False
    with _printer.indent():
        for name, obj in functions:
            serializable, _ = inspect_serializability(
                obj,
                name=name,
                depth=depth - 1,
                _parent=parent,
                _failure_set=failure_set)
            found = found or not serializable
            if found:
                break

    with _printer.indent():
        members = inspect.getmembers(base_obj)
        for name, obj in members:
            if name.startswith("__") and name.endswith(
                    "__") or inspect.isbuiltin(obj):
                continue
            serializable, _ = inspect_serializability(
                obj,
                name=name,
                depth=depth - 1,
                _parent=parent,
                _failure_set=failure_set)
            found = found or not serializable
            if found:
                break
    if not found:
        _printer.print(
            f"WARNING: Did not find non-serializable object in {base_obj}. "
            "This may be an oversight.")
    return found


@DeveloperAPI
def inspect_serializability(
        base_obj: Any,
        name: Optional[str] = None,
        depth: int = 3,
        _parent: Optional[Any] = None,
        _failure_set: Optional[set] = None) -> Tuple[bool, Set[FailureTuple]]:
    """Identifies what objects are preventing serialization.

    Args:
        base_obj: Object to be serialized.
        name: Optional name of string.
        depth: Depth of the scope stack to walk through. Defaults to 3.

    Returns:
        bool: True if serializable.
        set[FailureTuple]: Set of unserializable objects.

    .. versionadded:: 1.1.0

    """
    colorama.init()
    top_level = False
    declaration = ""
    found = False
    if _failure_set is None:
        top_level = True
        _failure_set = set()
        declaration = f"Checking Serializability of {base_obj}"
        print("=" * min(len(declaration), 80))
        print(declaration)
        print("=" * min(len(declaration), 80))

        if name is None:
            name = str(base_obj)
    else:
        _printer.print(f"Serializing '{name}' {base_obj}...")
    try:
        cp.dumps(base_obj)
        return True, _failure_set
    except Exception as e:
        _printer.print(f"{colorama.Fore.RED}!!! FAIL{colorama.Fore.RESET} "
                       f"serialization: {e}")
        found = True
        try:
            if depth == 0:
                _failure_set.add(FailureTuple(base_obj, name, _parent))
        # Some objects may not be hashable, so we skip adding this to the set.
        except Exception:
            pass

    if depth <= 0:
        return False, _failure_set

    # TODO: we only differentiate between 'function' and 'object'
    # but we should do a better job of diving into something
    # more specific like a Type, Object, etc.
    if inspect.isfunction(base_obj):
        _inspect_func_serialization(
            base_obj, depth=depth, parent=base_obj, failure_set=_failure_set)
    else:
        _inspect_generic_serialization(
            base_obj, depth=depth, parent=base_obj, failure_set=_failure_set)

    if not _failure_set:
        _failure_set.add(FailureTuple(base_obj, name, _parent))

    if top_level:
        print("=" * min(len(declaration), 80))
        if not _failure_set:
            print("Nothing failed the inspect_serialization test, though "
                  "serialization did not succeed.")
        else:
            fail_vars = f"\n\n\t{colorama.Style.BRIGHT}" + "\n".join(
                str(k)
                for k in _failure_set) + f"{colorama.Style.RESET_ALL}\n\n"
            print(f"Variable: {fail_vars}was found to be non-serializable. "
                  "There may be multiple other undetected variables that were "
                  "non-serializable. ")
            print("Consider either removing the "
                  "instantiation/imports of these variables or moving the "
                  "instantiation into the scope of the function/class. ")
        print("If you have any suggestions on how to improve "
              "this error message, please reach out to the "
              "Ray developers on github.com/ray-project/ray/issues/")
        print("=" * min(len(declaration), 80))
    return not found, _failure_set
