"""
Common exceptions that can be useful throughout the app.
"""
from flask import jsonify

from core import http_status


class APIError(Exception):
    """
    Base class for error API responses.

    Supposed to be raised in API views and handled by a handler registered in the app or in a
    blueprint.

    This class can be used directly, but more convenient is to subclass it for each type of error
    and override code, status_code and detail attributes. Using this class and its subclasses is
    preferred over abort() function, because it enforces consistent response format across all
    endpoints.

    Attributes:
        detail (str): Description that clarifies the cause of the error. It is addressed to
            developers who integrate the API with another application (e.g. web front-end), but not
            to the end user, because it can contain technical details.
        code (str): Unique identifier of an error. API consumer can use it to unambiguously identify
            the error and take appropriate actions, e.g. show human readable message to the end user
            on front-end.
        status_code (int): HTTP status code that must be used in response by error handler.
        extra: Optional arbitrary JSON-serializable structure containing data associated with the
            error. In case of validation failure it can be a mapping between field names and
            corresponding errors. In most of the cases however this attribute is None.

    """

    detail = None
    code = None
    status_code = None
    extra = None

    def __init__(self, detail=None, code=None, status_code=None, extra=None):
        if detail:
            self.detail = detail
        if code:
            self.code = code
        if status_code:
            self.status_code = status_code
        if extra:
            self.extra = extra

    def to_dict(self):
        """
        Serialize exception instance to a dictionary.

        Primary use case is to prepare exception for dumping it to JSON and adding to response body.

        Resulting dictionary always contains `code` and `detail` attributes. `extra` attribute is
        also added if it is not None.

        Returns:
            dict: Exception serialized to a dictionary.

        """
        result = {"code": self.code, "detail": self.detail}
        if self.extra:
            result["extra"] = self.extra
        return result

    def respond(self):
        """
        Generate JSON response with appropriate status code and body.

        Status code is taken from the status_code attribute of the instance. Body is generated by to_dict() method.

        Returns:
            flask.Response

        """
        response = jsonify(self.to_dict())
        response.status_code = self.status_code
        return response


class BadRequest(APIError):
    """
    HTTP 400 Bad Request.
    """

    detail = "Bad Request."
    code = "bad_request"
    status_code = http_status.HTTP_400_BAD_REQUEST


class JsonValidationError(BadRequest):
    """
    Raised if incoming JSON payload does not pass validation.
    """

    detail = "Invalid JSON payload."
    code = "validation_error.json"


class QueryParamsValidationError(BadRequest):
    """
    Raised if query string parameters validation failed.
    """

    detail = "Invalid query parameters."
    code = "validation_error.query_params"


class Unauthorized(APIError):
    """
    HTTP 401 Unauthorized.
    """

    detail = "Unauthorized."
    code = "unauthorized"
    status_code = http_status.HTTP_401_UNAUTHORIZED


class NotFound(APIError):
    """
    HTTP 404 Not Found.
    """

    detail = "Not Found."
    code = "not_found"
    status_code = http_status.HTTP_404_NOT_FOUND


class Conflict(APIError):
    """
    HTTP 409 Conflict.
    """

    detail = "Conflict."
    code = "conflict"
    status_code = http_status.HTTP_409_CONFLICT


class UnsupportedMediaType(APIError):
    """
    HTTP 415 Unsupported Media Type.
    """

    detail = "Unsupported Media Type."
    code = "unsupported_media_type"
    status_code = http_status.HTTP_415_UNSUPPORTED_MEDIA_TYPE


class TooManyRequests(APIError):
    """
    HTTP 429 Too Many Requests.
    """

    detail = "Too Many Requests."
    code = "too_many_requests"
    status_code = http_status.HTTP_429_TOO_MANY_REQUESTS


class BadGateway(APIError):
    """
    HTTP 502 Bad Gateway.

    This exception may be raised if a third party API returns invalid response.

    """

    detail = "Bad Gateway."
    code = "bad_gateway"
    status_code = http_status.HTTP_502_BAD_GATEWAY


class ServiceUnavailable(APIError):
    """
    HTTP 503 Service Unavailable.

    This exception is usually raised when a third party API we rely on is unavailable.

    """

    detail = "Service Unavailable."
    code = "service_unavailable"
    status_code = http_status.HTTP_503_SERVICE_UNAVAILABLE