webamp/js/actionCreators/media.ts

import { nextTrack } from "../selectors";

import { clamp } from "../utils";
import {
  SEEK_TO_PERCENT_COMPLETE,
  SET_BALANCE,
  SET_VOLUME,
  STOP,
  TOGGLE_REPEAT,
  TOGGLE_SHUFFLE,
  PLAY,
  PAUSE,
  PLAY_TRACK
} from "../actionTypes";

import { MEDIA_STATUS } from "../constants";
import { openMediaFileDialog } from "./";
import { GetState, Dispatch, Dispatchable } from "../types";

function playRandomTrack(): Dispatchable {
  return (dispatch: Dispatch, getState: GetState) => {
    const {
      playlist: { trackOrder, currentTrack }
    } = getState();
    if (trackOrder.length === 0) {
      return;
    }
    let nextId;
    do {
      nextId = trackOrder[Math.floor(trackOrder.length * Math.random())];
    } while (nextId === currentTrack && trackOrder.length > 1);
    // TODO: Sigh... Technically, we should detect if we are looping only repeat if we are.
    // I think this would require pre-computing the "random" order of a playlist.
    dispatch({ type: PLAY_TRACK, id: nextId });
  };
}

export function play(): Dispatchable {
  return (dispatch: Dispatch, getState: GetState) => {
    const state = getState();
    if (
      state.media.status === MEDIA_STATUS.STOPPED &&
      state.playlist.currentTrack == null &&
      state.playlist.trackOrder.length === 0
    ) {
      dispatch(openMediaFileDialog());
    } else {
      dispatch({ type: PLAY });
    }
  };
}

export function pause(): Dispatchable {
  return (dispatch, getState) => {
    const { status } = getState().media;
    if (status === MEDIA_STATUS.PLAYING) {
      dispatch({ type: PAUSE });
    } else {
      dispatch({ type: PLAY });
    }
  };
}

export function stop(): Dispatchable {
  return { type: STOP };
}

export function nextN(n: number): Dispatchable {
  return (dispatch, getState) => {
    const state = getState();
    if (state.media.shuffle) {
      dispatch(playRandomTrack());
      return;
    }
    const nextTrackId = nextTrack(state, n);
    if (nextTrackId == null) {
      return;
    }
    dispatch({ type: PLAY_TRACK, id: nextTrackId });
  };
}

export function next(): Dispatchable {
  return nextN(1);
}

export function previous(): Dispatchable {
  return nextN(-1);
}

export function seekForward(seconds: number): Dispatchable {
  return function(dispatch, getState) {
    const { timeElapsed, length } = getState().media;
    if (length == null) {
      return;
    }
    const newTimeElapsed = timeElapsed + seconds;
    dispatch({
      type: SEEK_TO_PERCENT_COMPLETE,
      percent: (newTimeElapsed / length) * 100
    });
  };
}

export function seekBackward(seconds: number): Dispatchable {
  return seekForward(-seconds);
}

export function setVolume(volume: number): Dispatchable {
  return {
    type: SET_VOLUME,
    volume: clamp(volume, 0, 100)
  };
}

export function adjustVolume(volumeDiff: number): Dispatchable {
  return (dispatch, getState) => {
    const currentVolume = getState().media.volume;
    return dispatch(setVolume(currentVolume + volumeDiff));
  };
}

export function scrollVolume(
  e: React.WheelEvent<HTMLDivElement>
): Dispatchable {
  e.preventDefault();
  return (dispatch, getState) => {
    const currentVolume = getState().media.volume;
    // Using pixels as percentage difference here is a bit arbirary, but... oh well.
    return dispatch(setVolume(currentVolume + e.deltaY));
  };
}

export function setBalance(balance: number): Dispatchable {
  balance = clamp(balance, -100, 100);
  // The balance clips to the center
  if (Math.abs(balance) < 25) {
    balance = 0;
  }
  return {
    type: SET_BALANCE,
    balance
  };
}

export function toggleRepeat(): Dispatchable {
  return { type: TOGGLE_REPEAT };
}

export function toggleShuffle(): Dispatchable {
  return { type: TOGGLE_SHUFFLE };
}