webamp/js/actionCreators/playlist.js

import { TRACK_HEIGHT } from "../constants";
import {
  getScrollOffset,
  getOverflowTrackCount,
  getSelectedTrackObjects
} from "../selectors";

import { clamp, sort } from "../utils";
import {
  REMOVE_TRACKS,
  REMOVE_ALL_TRACKS,
  REVERSE_LIST,
  RANDOMIZE_LIST,
  SET_TRACK_ORDER,
  SET_PLAYLIST_SCROLL_POSITION,
  DRAG_SELECTED
} from "../actionTypes";

export function cropPlaylist() {
  return (dispatch, getState) => {
    const state = getState();
    if (getSelectedTrackObjects(state).length === 0) {
      return;
    }
    const {
      playlist: { tracks }
    } = getState();
    dispatch({
      type: REMOVE_TRACKS,
      ids: Object.keys(tracks).filter(id => !tracks[id].selected)
    });
  };
}

export function removeSelectedTracks() {
  return (dispatch, getState) => {
    const {
      playlist: { tracks }
    } = getState();
    dispatch({
      type: REMOVE_TRACKS,
      ids: Object.keys(tracks).filter(id => tracks[id].selected)
    });
  };
}

export function removeAllTracks() {
  return { type: REMOVE_ALL_TRACKS };
}

export function reverseList() {
  return { type: REVERSE_LIST };
}

export function randomizeList() {
  return { type: RANDOMIZE_LIST };
}

export function sortListByTitle() {
  return (dispatch, getState) => {
    const state = getState();
    const trackOrder = sort(state.playlist.trackOrder, i =>
      `${state.playlist.tracks[i].title}`.toLowerCase()
    );
    return dispatch({ type: SET_TRACK_ORDER, trackOrder });
  };
}

export function setPlaylistScrollPosition(position) {
  return { type: SET_PLAYLIST_SCROLL_POSITION, position };
}

export function scrollNTracks(n) {
  return (dispatch, getState) => {
    const state = getState();
    const overflow = getOverflowTrackCount(state);
    const currentOffset = getScrollOffset(state);
    const position = overflow ? clamp((currentOffset + n) / overflow, 0, 1) : 0;
    return dispatch({
      type: SET_PLAYLIST_SCROLL_POSITION,
      position: position * 100
    });
  };
}

export function scrollPlaylistByDelta(e) {
  e.preventDefault();
  return (dispatch, getState) => {
    const state = getState();
    if (getOverflowTrackCount(state)) {
      e.stopPropagation();
    }
    const totalPixelHeight = state.playlist.trackOrder.length * TRACK_HEIGHT;
    const percentDelta = (e.deltaY / totalPixelHeight) * 100;
    dispatch({
      type: SET_PLAYLIST_SCROLL_POSITION,
      position: clamp(
        state.display.playlistScrollPosition + percentDelta,
        0,
        100
      )
    });
  };
}

export function scrollUpFourTracks() {
  return scrollNTracks(-4);
}

export function scrollDownFourTracks() {
  return scrollNTracks(4);
}

function findLastIndex(arr, cb) {
  for (let i = arr.length - 1; i >= 0; i--) {
    if (cb(arr[i])) {
      return i;
    }
  }
  return -1;
}

export function dragSelected(offset) {
  return (dispatch, getState) => {
    const {
      playlist: { trackOrder, tracks }
    } = getState();
    const firstSelected = trackOrder.findIndex(
      trackId => tracks[trackId] && tracks[trackId].selected
    );
    if (firstSelected === -1) {
      return;
    }
    const lastSelected = findLastIndex(
      trackOrder,
      trackId => tracks[trackId] && tracks[trackId].selected
    );
    if (lastSelected === -1) {
      throw new Error("We found a first selected, but not a last selected.");
    }
    // Ensure we don't try to drag off either end.
    const min = -firstSelected;
    const max = trackOrder.length - 1 - lastSelected;
    const normalizedOffset = clamp(offset, min, max);
    if (normalizedOffset !== 0) {
      dispatch({ type: DRAG_SELECTED, offset: normalizedOffset });
    }
  };
}