import { List as ImmutableList } from "immutable";

import { debounce } from "lodash";

import api from "../api";
import { compareId } from "../compare_id";

export const MARKERS_FETCH_REQUEST = "MARKERS_FETCH_REQUEST";
export const MARKERS_FETCH_SUCCESS = "MARKERS_FETCH_SUCCESS";
export const MARKERS_FETCH_FAIL    = "MARKERS_FETCH_FAIL";
export const MARKERS_SUBMIT_SUCCESS = "MARKERS_SUBMIT_SUCCESS";

export const synchronouslySubmitMarkers = () => (dispatch, getState) => {
  const accessToken = getState().getIn(["meta", "access_token"], "");
  const params      = _buildParams(getState());

  if (Object.keys(params).length === 0 || accessToken === "") {
    return;
  }

  // The Fetch API allows us to perform requests that will be carried out
  // after the page closes. But that only works if the `keepalive` attribute
  // is supported.
  if (window.fetch && "keepalive" in new Request("")) {
    fetch("/api/v1/markers", {
      keepalive: true,
      method: "POST",
      headers: {
        "Content-Type": "application/json",
        "Authorization": `Bearer ${accessToken}`,
      },
      body: JSON.stringify(params),
    });

    return;
  } else if (navigator && navigator.sendBeacon) {
    // Failing that, we can use sendBeacon, but we have to encode the data as
    // FormData for DoorKeeper to recognize the token.
    const formData = new FormData();

    formData.append("bearer_token", accessToken);

    for (const [id, value] of Object.entries(params)) {
      formData.append(`${id}[last_read_id]`, value.last_read_id);
    }

    if (navigator.sendBeacon("/api/v1/markers", formData)) {
      return;
    }
  }

  // If neither Fetch nor sendBeacon worked, try to perform a synchronous
  // request.
  try {
    const client = new XMLHttpRequest();

    client.open("POST", "/api/v1/markers", false);
    client.setRequestHeader("Content-Type", "application/json");
    client.setRequestHeader("Authorization", `Bearer ${accessToken}`);
    client.send(JSON.stringify(params));
  } catch (e) {
    // Do not make the BeforeUnload handler error out
  }
};

const _buildParams = (state) => {
  const params = {};

  const lastHomeId         = state.getIn(["timelines", "home", "items"], ImmutableList()).find(item => item !== null);
  const lastNotificationId = state.getIn(["notifications", "lastReadId"]);

  if (lastHomeId && compareId(lastHomeId, state.getIn(["markers", "home"])) > 0) {
    params.home = {
      last_read_id: lastHomeId,
    };
  }

  if (lastNotificationId && lastNotificationId !== "0" && compareId(lastNotificationId, state.getIn(["markers", "notifications"])) > 0) {
    params.notifications = {
      last_read_id: lastNotificationId,
    };
  }

  return params;
};

const debouncedSubmitMarkers = debounce((dispatch, getState) => {
  const accessToken = getState().getIn(["meta", "access_token"], "");
  const params      = _buildParams(getState());

  if (Object.keys(params).length === 0 || accessToken === "") {
    return;
  }

  api(getState).post("/api/v1/markers", params).then(() => {
    dispatch(submitMarkersSuccess(params));
  }).catch(() => {});
}, 300000, { leading: true, trailing: true });

export function submitMarkersSuccess({ home, notifications }) {
  return {
    type: MARKERS_SUBMIT_SUCCESS,
    home: (home || {}).last_read_id,
    notifications: (notifications || {}).last_read_id,
  };
}

export function submitMarkers(params = {}) {
  const result = (dispatch, getState) => debouncedSubmitMarkers(dispatch, getState);

  if (params.immediate === true) {
    debouncedSubmitMarkers.flush();
  }

  return result;
}

export const fetchMarkers = () => (dispatch, getState) => {
  const params = { timeline: ["notifications"] };

  dispatch(fetchMarkersRequest());

  api(getState).get("/api/v1/markers", { params }).then(response => {
    dispatch(fetchMarkersSuccess(response.data));
  }).catch(error => {
    dispatch(fetchMarkersFail(error));
  });
};

export function fetchMarkersRequest() {
  return {
    type: MARKERS_FETCH_REQUEST,
    skipLoading: true,
  };
}

export function fetchMarkersSuccess(markers) {
  return {
    type: MARKERS_FETCH_SUCCESS,
    markers,
    skipLoading: true,
  };
}

export function fetchMarkersFail(error) {
  return {
    type: MARKERS_FETCH_FAIL,
    error,
    skipLoading: true,
    skipAlert: true,
  };
}