import copy
import importlib.util
import json
import os
import re
import threading
from collections import OrderedDict
from functools import lru_cache
from typing import Any, Dict

from .text_utils import is_made_of_sub_strings


class Singleton(type):
    _instances = {}

    def __call__(cls, *args, **kwargs):
        if cls not in cls._instances:
            cls._instances[cls] = super().__call__(*args, **kwargs)
        return cls._instances[cls]


class LRUCache:
    """An LRU (Least Recently Used) cache that stores a limited number of items.

    This cache automatically removes the least recently used item when it
    exceeds its max size. It behaves similarly to a dictionary, allowing
    items to be added and accessed using `[]` syntax.

    This implementation is thread-safe, using a lock to ensure that only one
    thread can modify or access the cache at any time.

    Attributes:
        max_size (int): The maximum number of items to store in the cache.
            Items exceeding this limit are automatically removed based on least
            recent usage.
    """

    def __init__(self, max_size=10):
        self._max_size = max_size
        self._cache = OrderedDict()
        self._lock = threading.Lock()  # Lock to ensure thread safety

    @property
    def max_size(self):
        with self._lock:
            return self._max_size

    @max_size.setter
    def max_size(self, size):
        with self._lock:
            self._max_size = size
            # Adjust the cache if the new size is smaller than the current number of items
            while len(self._cache) > self._max_size:
                self._cache.popitem(last=False)

    def __setitem__(self, key, value):
        with self._lock:
            # If the key already exists, remove it first to refresh its order
            if key in self._cache:
                self._cache.pop(key)

            # Add the new item to the cache (most recently used)
            self._cache[key] = value

            # If the cache exceeds the specified size, remove the least recently used item
            while len(self._cache) > self._max_size:
                self._cache.popitem(last=False)

    def __getitem__(self, key):
        with self._lock:
            if key in self._cache:
                # Move the accessed item to the end (mark as most recently used)
                value = self._cache.pop(key)
                self._cache[key] = value
                return value
            raise KeyError(f"{key} not found in cache")

    def set(self, key, value):
        """Sets a key-value pair in the cache."""
        with self._lock:
            if key in self._cache:
                self._cache.pop(key)
            self._cache[key] = value
            while len(self._cache) > self._max_size:
                self._cache.popitem(last=False)

    def get(self, key, default=None):
        """Gets a value from the cache by key, returning `default` if the key is not found."""
        with self._lock:
            if key in self._cache:
                value = self._cache.pop(key)
                self._cache[key] = value  # Move item to end to mark as recently used
                return value
            return default

    def __contains__(self, key):
        with self._lock:
            return key in self._cache

    def __len__(self):
        with self._lock:
            return len(self._cache)

    def __repr__(self):
        with self._lock:
            return f"LRUCache(max_size={self._max_size}, items={list(self._cache.items())})"


def flatten_dict(
    d: Dict[str, Any], parent_key: str = "", sep: str = "_"
) -> Dict[str, Any]:
    items = []
    for k, v in d.items():
        new_key = parent_key + sep + k if parent_key else k
        if isinstance(v, dict):
            items.extend(flatten_dict(v, new_key, sep=sep).items())
        else:
            items.append((new_key, v))

    return dict(items)


@lru_cache(maxsize=None)
def artifacts_json_cache(artifact_path):
    return load_json(artifact_path)


def load_json(path):
    with open(path) as f:
        try:
            return json.load(f)
        except json.decoder.JSONDecodeError as e:
            with open(path) as f:
                file_content = "\n".join(f.readlines())
            raise RuntimeError(
                f"Failed to decode json file at '{path}' with file content:\n{file_content}"
            ) from e


def save_to_file(path, data):
    with open(path, "w") as f:
        f.write(data)
        f.write("\n")


def json_dump(data):
    return json.dumps(data, indent=4, ensure_ascii=False)


def is_package_installed(package_name):
    """Check if a package is installed.

    Parameters:
    - package_name (str): The name of the package to check.

    Returns:
    - bool: True if the package is installed, False otherwise.
    """
    unitxt_pkg = importlib.util.find_spec(package_name)
    return unitxt_pkg is not None


def is_module_available(module_name):
    """Check if a module is available in the current Python environment.

    Parameters:
    - module_name (str): The name of the module to check.

    Returns:
    - bool: True if the module is available, False otherwise.
    """
    try:
        __import__(module_name)
        return True
    except ImportError:
        return False


def remove_numerics_and_quoted_texts(input_str):
    # Remove floats first to avoid leaving stray periods
    input_str = re.sub(r"\d+\.\d+", "", input_str)

    # Remove integers
    input_str = re.sub(r"\d+", "", input_str)

    # Remove strings in single quotes
    input_str = re.sub(r"'.*?'", "", input_str)

    # Remove strings in double quotes
    input_str = re.sub(r'".*?"', "", input_str)

    # Remove strings in triple quotes
    return re.sub(r'""".*?"""', "", input_str, flags=re.DOTALL)


def safe_eval(expression: str, context: dict, allowed_tokens: list) -> any:
    """Evaluates a given expression in a restricted environment, allowing only specified tokens and context variables.

    Args:
        expression (str): The expression to evaluate.
        context (dict): A dictionary mapping variable names to their values, which
                        can be used in the expression.
        allowed_tokens (list): A list of strings representing allowed tokens (such as
                               operators, function names, etc.) that can be used in the expression.

    Returns:
        any: The result of evaluating the expression.

    Raises:
        ValueError: If the expression contains tokens not in the allowed list or context keys.

    Note:
        This function should be used carefully, as it employs `eval`, which can
        execute arbitrary code. The function attempts to mitigate security risks
        by restricting the available tokens and not exposing built-in functions.
    """
    allowed_sub_strings = list(context.keys()) + allowed_tokens
    if is_made_of_sub_strings(
        remove_numerics_and_quoted_texts(expression), allowed_sub_strings
    ):
        return eval(expression, {"__builtins__": {}}, context)
    raise ValueError(
        f"The expression '{expression}' can not be evaluated because it contains tokens outside the allowed list of {allowed_sub_strings}."
    )


def import_module_from_file(file_path):
    # Get the module name (file name without extension)
    module_name = os.path.splitext(os.path.basename(file_path))[0]
    # Create a module specification
    spec = importlib.util.spec_from_file_location(module_name, file_path)
    # Create a new module based on the specification
    module = importlib.util.module_from_spec(spec)
    # Load the module
    spec.loader.exec_module(module)
    return module


def deep_copy(obj):
    """Creates a deep copy of the given object.

    Args:
        obj: The object to be deep copied.

    Returns:
        A deep copy of the original object.
    """
    return copy.deepcopy(obj)


def shallow_copy(obj):
    """Creates a shallow copy of the given object.

    Args:
        obj: The object to be shallow copied.

    Returns:
        A shallow copy of the original object.
    """
    return copy.copy(obj)


def recursive_copy(obj, internal_copy=None):
    """Recursively copies an object with a selective copy method.

    For `list`, `dict`, and `tuple` types, it recursively copies their contents.
    For other types, it uses the provided `internal_copy` function if available.
    Objects without a `copy` method are returned as is.

    Args:
        obj: The object to be copied.
        internal_copy (callable, optional): The copy function to use for non-container objects.
            If `None`, objects without a `copy` method are returned as is.

    Returns:
        The recursively copied object.
    """
    # Handle dictionaries
    if isinstance(obj, dict):
        return type(obj)(
            {key: recursive_copy(value, internal_copy) for key, value in obj.items()}
        )

    # Handle named tuples
    if isinstance(obj, tuple) and hasattr(obj, "_fields"):
        return type(obj)(*(recursive_copy(item, internal_copy) for item in obj))

    # Handle tuples and lists
    if isinstance(obj, (tuple, list)):
        return type(obj)(recursive_copy(item, internal_copy) for item in obj)

    if internal_copy is None:
        return obj

    return internal_copy(obj)


def recursive_deep_copy(obj):
    """Performs a recursive deep copy of the given object.

    This function uses `deep_copy` as the internal copy method for non-container objects.

    Args:
        obj: The object to be deep copied.

    Returns:
        A recursively deep-copied version of the original object.
    """
    return recursive_copy(obj, deep_copy)


def recursive_shallow_copy(obj):
    """Performs a recursive shallow copy of the given object.

    This function uses `shallow_copy` as the internal copy method for non-container objects.

    Args:
        obj: The object to be shallow copied.

    Returns:
        A recursively shallow-copied version of the original object.
    """
    return recursive_copy(obj, shallow_copy)


class LongString(str):
    def __new__(cls, value, *, repr_str=None):
        obj = super().__new__(cls, value)
        obj._repr_str = repr_str
        return obj

    def __repr__(self):
        if self._repr_str is not None:
            return self._repr_str
        return super().__repr__()