"""JSON utility functions."""
from collections import deque
import json
import logging
import os
import tempfile
from typing import Any, Dict, List, Optional, Type, Union

import orjson

from homeassistant.exceptions import HomeAssistantError

_LOGGER = logging.getLogger(__name__)


class SerializationError(HomeAssistantError):
    """Error serializing the data to JSON."""


class WriteError(HomeAssistantError):
    """Error writing the data."""


def load_json(
    filename: str, default: Union[List, Dict, None] = None
) -> Union[List, Dict]:
    """Load JSON data from a file and return as dict or list.

    Defaults to returning empty dict if file is not found.
    """
    try:
        with open(filename, encoding="utf-8") as fdesc:
            return orjson.loads(fdesc.read())  # type: ignore
    except FileNotFoundError:
        # This is not a fatal error
        _LOGGER.debug("JSON file not found: %s", filename)
    except ValueError as error:
        _LOGGER.exception("Could not parse JSON content: %s", filename)
        raise HomeAssistantError(error)
    except OSError as error:
        _LOGGER.exception("JSON file reading failed: %s", filename)
        raise HomeAssistantError(error)
    return {} if default is None else default


def save_json(
    filename: str,
    data: Union[List, Dict],
    private: bool = False,
    *,
    encoder: Optional[Type[json.JSONEncoder]] = None,
) -> None:
    """Save JSON data to a file.

    Returns True on success.
    """
    try:
        json_data = json.dumps(data, sort_keys=True, indent=4, cls=encoder)
    except TypeError:
        # pylint: disable=no-member
        msg = f"Failed to serialize to JSON: {filename}. Bad data found at {', '.join(find_paths_unserializable_data(data))}"
        _LOGGER.error(msg)
        raise SerializationError(msg)

    tmp_filename = ""
    tmp_path = os.path.split(filename)[0]
    try:
        # Modern versions of Python tempfile create this file with mode 0o600
        with tempfile.NamedTemporaryFile(
            mode="w", encoding="utf-8", dir=tmp_path, delete=False
        ) as fdesc:
            fdesc.write(json_data)
            tmp_filename = fdesc.name
        if not private:
            os.chmod(tmp_filename, 0o644)
        os.replace(tmp_filename, filename)
    except OSError as error:
        _LOGGER.exception("Saving JSON file failed: %s", filename)
        raise WriteError(error)
    finally:
        if os.path.exists(tmp_filename):
            try:
                os.remove(tmp_filename)
            except OSError as err:
                # If we are cleaning up then something else went wrong, so
                # we should suppress likely follow-on errors in the cleanup
                _LOGGER.error("JSON replacement cleanup failed: %s", err)


def find_paths_unserializable_data(bad_data: Any) -> List[str]:
    """Find the paths to unserializable data.

    This method is slow! Only use for error handling.
    """
    to_process = deque([(bad_data, "$")])
    invalid = []

    while to_process:
        obj, obj_path = to_process.popleft()

        try:
            orjson.dumps(obj)
            continue
        except TypeError:
            pass

        if isinstance(obj, dict):
            for key, value in obj.items():
                try:
                    # Is key valid?
                    orjson.dumps({key: None})
                except TypeError:
                    invalid.append(f"{obj_path}<key: {key}>")
                else:
                    # Process value
                    to_process.append((value, f"{obj_path}.{key}"))
        elif isinstance(obj, list):
            for idx, value in enumerate(obj):
                to_process.append((value, f"{obj_path}[{idx}]"))
        else:
            invalid.append(obj_path)

    return invalid