import inspect
import json
import re
import datetime

import six
from django.db import connection, transaction
from django.http import HttpResponse, HttpResponseNotAllowed
from django.http.response import HttpResponseBadRequest
from django.shortcuts import render
from django.utils.decorators import method_decorator
from django.views.generic import View
from django.views.decorators.csrf import ensure_csrf_cookie

from graphql import get_default_backend
from graphql.error import format_error as format_graphql_error
from graphql.error import GraphQLError
from graphql.execution import ExecutionResult
from graphql.type.schema import GraphQLSchema
from graphql.execution.middleware import MiddlewareManager

from graphene_django.constants import MUTATION_ERRORS_FLAG
from graphene_django.utils.utils import set_rollback

from .settings import graphene_settings


class HttpError(Exception):
    def __init__(self, response, message=None, *args, **kwargs):
        self.response = response
        self.message = message = message or response.content.decode()
        super(HttpError, self).__init__(message, *args, **kwargs)


def get_accepted_content_types(request):
    def qualify(x):
        parts = x.split(";", 1)
        if len(parts) == 2:
            match = re.match(r"(^|;)q=(0(\.\d{,3})?|1(\.0{,3})?)(;|$)", parts[1])
            if match:
                return parts[0].strip(), float(match.group(2))
        return parts[0].strip(), 1

    raw_content_types = request.META.get("HTTP_ACCEPT", "*/*").split(",")
    qualified_content_types = map(qualify, raw_content_types)
    return list(
        x[0] for x in sorted(qualified_content_types, key=lambda x: x[1], reverse=True)
    )


def instantiate_middleware(middlewares):
    for middleware in middlewares:
        if inspect.isclass(middleware):
            yield middleware()
            continue
        yield middleware


def stringify_datetime(value):
    if isinstance(value, datetime.datetime):
        return value.__str__()


class GraphQLView(View):
    graphiql_template = "graphene/graphiql.html"

    # Polyfill for window.fetch.
    whatwg_fetch_version = "3.6.2"
    whatwg_fetch_sri = "sha256-+pQdxwAcHJdQ3e/9S4RK6g8ZkwdMgFQuHvLuN5uyk5c="

    # React and ReactDOM.
    react_version = "17.0.2"
    react_sri = "sha256-Ipu/TQ50iCCVZBUsZyNJfxrDk0E2yhaEIz0vqI+kFG8="
    react_dom_sri = "sha256-nbMykgB6tsOFJ7OdVmPpdqMFVk4ZsqWocT6issAPUF0="

    # The GraphiQL React app.
    graphiql_version = "1.4.1"
    graphiql_sri = "sha256-JUMkXBQWZMfJ7fGEsTXalxVA10lzKOS9loXdLjwZKi4="
    graphiql_css_sri = "sha256-Md3vdR7PDzWyo/aGfsFVF4tvS5/eAUWuIsg9QHUusCY="

    # The websocket transport library for subscriptions.
    subscriptions_transport_ws_version = "0.9.18"
    subscriptions_transport_ws_sri = (
        "sha256-i0hAXd4PdJ/cHX3/8tIy/Q/qKiWr5WSTxMFuL9tACkw="
    )

    schema = None
    graphiql = False
    executor = None
    backend = None
    middleware = None
    root_value = None
    pretty = False
    batch = False
    subscription_path = None

    def __init__(
        self,
        schema=None,
        executor=None,
        middleware=None,
        root_value=None,
        graphiql=False,
        pretty=False,
        batch=False,
        backend=None,
        subscription_path=None,
    ):
        if not schema:
            schema = graphene_settings.SCHEMA

        if backend is None:
            backend = get_default_backend()

        if middleware is None:
            middleware = graphene_settings.MIDDLEWARE

        self.schema = self.schema or schema
        if middleware is not None:
            if isinstance(middleware, MiddlewareManager):
                self.middleware = middleware
            else:
                self.middleware = list(instantiate_middleware(middleware))
        self.executor = executor
        self.root_value = root_value
        self.pretty = self.pretty or pretty
        self.graphiql = self.graphiql or graphiql
        self.batch = self.batch or batch
        self.backend = backend
        if subscription_path is None:
            self.subscription_path = graphene_settings.SUBSCRIPTION_PATH

        assert isinstance(
            self.schema, GraphQLSchema
        ), "A Schema is required to be provided to GraphQLView."
        assert not all((graphiql, batch)), "Use either graphiql or batch processing"

    # noinspection PyUnusedLocal
    def get_root_value(self, request):
        return self.root_value

    def get_middleware(self, request):
        return self.middleware

    def get_context(self, request):
        return request

    def get_backend(self, request):
        return self.backend

    @method_decorator(ensure_csrf_cookie)
    def dispatch(self, request, *args, **kwargs):
        try:
            if request.method.lower() not in ("get", "post"):
                raise HttpError(
                    HttpResponseNotAllowed(
                        ["GET", "POST"], "GraphQL only supports GET and POST requests."
                    )
                )

            data = self.parse_body(request)
            show_graphiql = self.graphiql and self.can_display_graphiql(request, data)

            if show_graphiql:
                return self.render_graphiql(
                    request,
                    # Dependency parameters.
                    whatwg_fetch_version=self.whatwg_fetch_version,
                    whatwg_fetch_sri=self.whatwg_fetch_sri,
                    react_version=self.react_version,
                    react_sri=self.react_sri,
                    react_dom_sri=self.react_dom_sri,
                    graphiql_version=self.graphiql_version,
                    graphiql_sri=self.graphiql_sri,
                    graphiql_css_sri=self.graphiql_css_sri,
                    subscriptions_transport_ws_version=self.subscriptions_transport_ws_version,
                    subscriptions_transport_ws_sri=self.subscriptions_transport_ws_sri,
                    # The SUBSCRIPTION_PATH setting.
                    subscription_path=self.subscription_path,
                    # GraphiQL headers tab,
                    graphiql_header_editor_enabled=graphene_settings.GRAPHIQL_HEADER_EDITOR_ENABLED,
                )

            if self.batch:
                responses = [self.get_response(request, entry) for entry in data]
                result = "[{}]".format(
                    ",".join([response[0] for response in responses])
                )
                status_code = (
                    responses
                    and max(responses, key=lambda response: response[1])[1]
                    or 200
                )
            else:
                result, status_code = self.get_response(request, data, show_graphiql)

            return HttpResponse(
                status=status_code, content=result, content_type="application/json"
            )

        except HttpError as e:
            response = e.response
            response["Content-Type"] = "application/json"
            response.content = self.json_encode(
                request, {"errors": [self.format_error(e)]}
            )
            return response

    def get_response(self, request, data, show_graphiql=False):
        query, variables, operation_name, id = self.get_graphql_params(request, data)

        execution_result = self.execute_graphql_request(
            request, data, query, variables, operation_name, show_graphiql
        )

        if getattr(request, MUTATION_ERRORS_FLAG, False) is True:
            set_rollback()

        status_code = 200
        if execution_result:
            response = {}

            if execution_result.errors:
                set_rollback()
                response["errors"] = [
                    self.format_error(e) for e in execution_result.errors
                ]

            if execution_result.invalid:
                status_code = 400
            else:
                response["data"] = execution_result.data

            if self.batch:
                response["id"] = id
                response["status"] = status_code

            result = self.json_encode(request, response, pretty=show_graphiql)
        else:
            result = None

        return result, status_code

    def render_graphiql(self, request, **data):
        return render(request, self.graphiql_template, data)

    def json_encode(self, request, d, pretty=False):
        if not (self.pretty or pretty) and not request.GET.get("pretty"):
            return json.dumps(d, separators=(",", ":"), default=stringify_datetime)

        return json.dumps(
            d,
            sort_keys=True,
            indent=2,
            separators=(",", ": "),
            default=stringify_datetime,
        )

    def parse_body(self, request):
        content_type = self.get_content_type(request)

        if content_type == "application/graphql":
            return {"query": request.body.decode()}

        elif content_type == "application/json":
            # noinspection PyBroadException
            try:
                body = request.body.decode("utf-8")
            except Exception as e:
                raise HttpError(HttpResponseBadRequest(str(e)))

            try:
                request_json = json.loads(body)
                if self.batch:
                    assert isinstance(request_json, list), (
                        "Batch requests should receive a list, but received {}."
                    ).format(repr(request_json))
                    assert (
                        len(request_json) > 0
                    ), "Received an empty list in the batch request."
                else:
                    assert isinstance(
                        request_json, dict
                    ), "The received data is not a valid JSON query."
                return request_json
            except AssertionError as e:
                raise HttpError(HttpResponseBadRequest(str(e)))
            except (TypeError, ValueError):
                raise HttpError(HttpResponseBadRequest("POST body sent invalid JSON."))

        elif content_type in [
            "application/x-www-form-urlencoded",
            "multipart/form-data",
        ]:
            return request.POST

        return {}

    def execute_graphql_request(
        self, request, data, query, variables, operation_name, show_graphiql=False
    ):
        if not query:
            if show_graphiql:
                return None
            raise HttpError(HttpResponseBadRequest("Must provide query string."))

        try:
            backend = self.get_backend(request)
            document = backend.document_from_string(self.schema, query)
        except Exception as e:
            return ExecutionResult(errors=[e], invalid=True)

        if request.method.lower() == "get":
            operation_type = document.get_operation_type(operation_name)
            if operation_type and operation_type != "query":
                if show_graphiql:
                    return None

                raise HttpError(
                    HttpResponseNotAllowed(
                        ["POST"],
                        "Can only perform a {} operation from a POST request.".format(
                            operation_type
                        ),
                    )
                )

        try:
            extra_options = {}
            if self.executor:
                # We only include it optionally since
                # executor is not a valid argument in all backends
                extra_options["executor"] = self.executor

            options = {
                "root_value": self.get_root_value(request),
                "variable_values": variables,
                "operation_name": operation_name,
                "context_value": self.get_context(request),
                "middleware": self.get_middleware(request),
            }
            options.update(extra_options)

            operation_type = document.get_operation_type(operation_name)
            if operation_type == "mutation" and (
                graphene_settings.ATOMIC_MUTATIONS is True
                or connection.settings_dict.get("ATOMIC_MUTATIONS", False) is True
            ):
                with transaction.atomic():
                    result = document.execute(**options)
                    if getattr(request, MUTATION_ERRORS_FLAG, False) is True:
                        transaction.set_rollback(True)
                return result

            return document.execute(**options)
        except Exception as e:
            return ExecutionResult(errors=[e], invalid=True)

    @classmethod
    def can_display_graphiql(cls, request, data):
        raw = "raw" in request.GET or "raw" in data
        return not raw and cls.request_wants_html(request)

    @classmethod
    def request_wants_html(cls, request):
        accepted = get_accepted_content_types(request)
        accepted_length = len(accepted)
        # the list will be ordered in preferred first - so we have to make
        # sure the most preferred gets the highest number
        html_priority = (
            accepted_length - accepted.index("text/html")
            if "text/html" in accepted
            else 0
        )
        json_priority = (
            accepted_length - accepted.index("application/json")
            if "application/json" in accepted
            else 0
        )

        return html_priority > json_priority

    @staticmethod
    def get_graphql_params(request, data):
        query = request.GET.get("query") or data.get("query")
        variables = request.GET.get("variables") or data.get("variables")
        id = request.GET.get("id") or data.get("id")

        if variables and isinstance(variables, six.text_type):
            try:
                variables = json.loads(variables)
            except Exception:
                raise HttpError(HttpResponseBadRequest("Variables are invalid JSON."))

        operation_name = request.GET.get("operationName") or data.get("operationName")
        if operation_name == "null":
            operation_name = None

        return query, variables, operation_name, id

    @staticmethod
    def format_error(error):
        if isinstance(error, GraphQLError):
            return format_graphql_error(error)

        return {"message": six.text_type(error)}

    @staticmethod
    def get_content_type(request):
        meta = request.META
        content_type = meta.get("CONTENT_TYPE", meta.get("HTTP_CONTENT_TYPE", ""))
        return content_type.split(";", 1)[0].lower()