import abc
import json
import os
import posixpath
from typing import Any, Dict, Optional  # noqa: F401
from urllib.parse import urlencode

from uaclient import config, http, system, util, version


class UAServiceClient(metaclass=abc.ABCMeta):

    url_timeout = 30  # type: Optional[int]
    # Cached serviceclient_url_responses if provided in uaclient.conf
    # via features: {serviceclient_url_responses: /some/file.json}
    _response_overlay = None  # type: Dict[str, Any]

    @property
    @abc.abstractmethod
    def cfg_url_base_attr(self) -> str:
        """String in subclasses, the UAConfig attribute containing base url"""
        pass

    def __init__(self, cfg: Optional[config.UAConfig] = None) -> None:
        if not cfg:
            self.cfg = config.UAConfig()
        else:
            self.cfg = cfg

    def headers(self):
        return {
            "user-agent": "UA-Client/{}".format(version.get_version()),
            "accept": "application/json",
            "content-type": "application/json",
        }

    def request_url(
        self,
        path,
        data=None,
        headers=None,
        method=None,
        query_params=None,
        log_response_body: bool = True,
        timeout: Optional[int] = None,
    ) -> http.HTTPResponse:
        path = path.lstrip("/")
        if not headers:
            headers = self.headers()
        if headers.get("content-type") == "application/json" and data:
            data = json.dumps(data, cls=util.DatetimeAwareJSONEncoder).encode(
                "utf-8"
            )
        url = posixpath.join(getattr(self.cfg, self.cfg_url_base_attr), path)

        fake_response = self._get_fake_responses(url)
        if fake_response:
            return fake_response  # URL faked by uaclient.conf

        if query_params:
            # filter out None values
            filtered_params = {
                k: v for k, v in sorted(query_params.items()) if v is not None
            }
            url += "?" + urlencode(filtered_params)
        timeout_to_use = timeout if timeout is not None else self.url_timeout

        return http.readurl(
            url=url,
            data=data,
            headers=headers,
            method=method,
            timeout=timeout_to_use,
            log_response_body=log_response_body,
        )

    def _get_response_overlay(self, url: str):
        """Return a list of fake response dicts for a given URL.

        serviceclient_url_responses in uaclient.conf should be a path
        to a json file which contains a dictionary keyed by full URL path.
        Each value will be a list of dicts representing each faked response
        for the given URL.

            The response dict item will have a code: <HTTP_STATUS_CODE> and
               response: "some string of content".
            The JSON string below fakes the available_resources URL on the
            contract server:
            '{"https://contracts.canonical.com/v1/resources": \
               [{"code": 200, "response": {"key": "val1", "key2": "val2"}}]}'

        :return: List of dicts for each faked response matching the url, or
           and empty list when no matching url found.
        """
        if self._response_overlay is not None:
            # Cache it so we don't re-read config every readurl call
            return self._response_overlay.get(url, [])
        response_overlay_path = self.cfg.features.get(
            "serviceclient_url_responses"
        )
        if not response_overlay_path:
            self._response_overlay = {}
        elif not os.path.exists(response_overlay_path):
            self._response_overlay = {}
        else:
            self._response_overlay = json.loads(
                system.load_file(response_overlay_path)
            )
        return self._response_overlay.get(url, [])

    def _get_fake_responses(self, url: str) -> Optional[http.HTTPResponse]:
        """Return response if faked for this URL in uaclient.conf."""
        responses = self._get_response_overlay(url)
        if not responses:
            return None

        if len(responses) == 1:
            # When only one response is defined, repeat it for all calls
            response = responses[0]
        else:
            # When multiple responses defined pop the first one off the list.
            response = responses.pop(0)

        json_dict = {}
        json_list = []
        resp = response["response"]
        if isinstance(resp, dict):
            json_dict = resp
        elif isinstance(resp, list):
            json_list = resp

        return http.HTTPResponse(
            code=response["code"],
            headers=response.get("headers", {}),
            body=json.dumps(response["response"], sort_keys=True),
            json_dict=json_dict,
            json_list=json_list,
        )