tonality/packages/library-song-utils/src/index.ts

import {Note, parseNote, PITCH_CLASSES} from "./note";
import {toRawDuration} from './duration';

export interface Playable {
	key?: number,
	start: number,
	end: number,
	startIndex: number,
	endIndex: number,
}

export interface SongData<T = Playable> {
	playables: T[],
	duration: number,
	index: number,
}

export * from './note'
export * from './duration'

export const toPlayable = (n: Note, tempo: number) => {
	const rawDurationBase = toRawDuration(n.duration, tempo)
	const duration = n.dotted ? rawDurationBase * 1.5 : rawDurationBase
	const pitchClassIndex = PITCH_CLASSES.indexOf(n.pitchClass!)
	if (!isNaN(pitchClassIndex) && 0 <= pitchClassIndex && pitchClassIndex <= 11 && !isNaN(n.octave!)) {
		return {
			duration,
			key: pitchClassIndex + (12 * (n.octave! + 1))
		}
	}
	return {
		duration,
	}
}

export const parseSong = <T>(s: string, tempo: number) => {
	return s.split(' ').reduce(
		(state, n, i, nn) => {
			let note
			try {
				note = parseNote(n)
			} catch {
				return state
			}
			const playable = toPlayable(note, tempo)
			return {
				...state,
				playables: [
					...state.playables,
					{
						key: playable.key,
						start: state.duration,
						end: state.duration + playable.duration,
						startIndex: state.index,
						endIndex: state.index + n.length
					}
				],
				duration: (
					i < nn.length - 1
						? state.duration + playable.duration
						: state.duration + playable.duration + 100
				),
				index: state.index + n.length + 1
			} as SongData<T>
		},
		{
			playables: [] as T[],
			duration: 100,
			index: 0,
		}
	)
}