src/chord_sheet/song.ts
import Line from './line';
import Paragraph from './paragraph';
import Key from '../key';
import ChordLyricsPair from './chord_lyrics_pair';
import Metadata from './metadata';
import ParserWarning from '../parser/parser_warning';
import MetadataAccessors from './metadata_accessors';
import Item from './item';
import { CHORUS, Modifier } from '../constants';
import Tag, {
CAPO,
CHORUS as CHORUS_TAG,
END_OF_CHORUS,
KEY,
START_OF_CHORUS,
} from './tag';
import SongBuilder from '../song_builder';
type MapItemsCallback = (_item: Item) => Item | null;
type MapLinesCallback = (_line: Line) => Line | null;
/**
* Represents a song in a chord sheet. Currently a chord sheet can only have one song.
*/
class Song extends MetadataAccessors {
/**
* The {@link Line} items of which the song consists
* @member {Line[]}
*/
lines: Line[] = [];
/**
* The song's metadata. When there is only one value for an entry, the value is a string. Else, the value is
* an array containing all unique values for the entry.
* @type {Metadata}
*/
metadata: Metadata;
_bodyLines: Line[] | null = null;
_bodyParagraphs: Paragraph[] | null = null;
warnings: ParserWarning[] = [];
/**
* Creates a new {Song} instance
* @param metadata {Object|Metadata} predefined metadata
*/
constructor(metadata = {}) {
super();
this.metadata = new Metadata(metadata);
}
/**
* Returns the song lines, skipping the leading empty lines (empty as in not rendering any content). This is useful
* if you want to skip the "header lines": the lines that only contain meta data.
* @returns {Line[]} The song body lines
*/
get bodyLines(): Line[] {
if (!this._bodyLines) {
this._bodyLines = this.selectRenderableItems(this.lines) as Line[];
}
return this._bodyLines;
}
/**
* Returns the song paragraphs, skipping the paragraphs that only contain empty lines
* (empty as in not rendering any content)
* @see {@link bodyLines}
* @returns {Paragraph[]}
*/
get bodyParagraphs(): Paragraph[] {
if (!this._bodyParagraphs) {
this._bodyParagraphs = this.selectRenderableItems(this.paragraphs) as Paragraph[];
}
return this._bodyParagraphs;
}
selectRenderableItems(items: (Line | Paragraph)[]): (Line | Paragraph)[] {
const copy = [...items];
while (copy.length && !copy[0].hasRenderableItems()) {
copy.shift();
}
return copy;
}
private expandLine(line: Line): Line[] {
const expandedLines = line.items.flatMap((item: Item) => {
if (item instanceof Tag && item.name === CHORUS_TAG) {
return this.getLastChorusBefore(line.lineNumber);
}
return [];
});
return [line, ...expandedLines];
}
private getLastChorusBefore(lineNumber: number | null): Line[] {
const lines: Line[] = [];
if (!lineNumber) {
return lines;
}
for (let i = lineNumber - 1; i >= 0; i -= 1) {
const line = this.lines[i];
if (line.type === CHORUS) {
const filteredLine = this.filterChorusStartEndDirectives(line);
if (!(line.isNotEmpty() && filteredLine.isEmpty())) {
lines.unshift(line);
}
} else if (lines.length > 0) {
break;
}
}
return lines;
}
private filterChorusStartEndDirectives(line: Line) {
return line.mapItems((item: Item) => {
if (item instanceof Tag) {
if (item.name === START_OF_CHORUS || item.name === END_OF_CHORUS) {
return null;
}
}
return item;
});
}
/**
* The {@link Paragraph} items of which the song consists
* @member {Paragraph[]}
*/
get paragraphs(): Paragraph[] {
return this.linesToParagraphs(this.lines);
}
/**
* The body paragraphs of the song, with any `{chorus}` tag expanded into the targeted chorus
* @type {Paragraph[]}
*/
get expandedBodyParagraphs(): Paragraph[] {
return this.selectRenderableItems(
this.linesToParagraphs(
this.lines.flatMap((line: Line) => this.expandLine(line)),
),
) as Paragraph[];
}
linesToParagraphs(lines: Line[]) {
let currentParagraph = new Paragraph();
const paragraphs = [currentParagraph];
lines.forEach((line, index) => {
const nextLine: Line | null = lines[index + 1] || null;
if (line.isEmpty() || (line.isSectionEnd() && nextLine && !nextLine.isEmpty())) {
currentParagraph = new Paragraph();
paragraphs.push(currentParagraph);
} else if (line.hasRenderableItems()) {
currentParagraph.addLine(line);
}
});
return paragraphs;
}
/**
* Returns a deep clone of the song
* @returns {Song} The cloned song
*/
clone(): Song {
return this.mapItems((item) => item);
}
setMetadata(name: string, value: string): void {
this.metadata.add(name, value);
}
getMetadata(name: string): string | string[] | null {
return this.metadata.getMetadata(name);
}
getSingleMetadata(name: string): string | null {
return this.metadata.getSingleMetadata(name);
}
/**
* Returns a copy of the song with the key value set to the specified key. It changes:
* - the value for `key` in the {@link metadata} set
* - any existing `key` directive
* @param {number|null} key the key. Passing `null` will:
* - remove the current key from {@link metadata}
* - remove any `key` directive
* @returns {Song} The changed song
*/
setKey(key: string | number | null): Song {
const strKey = key ? key.toString() : null;
return this.changeMetadata(KEY, strKey);
}
/**
* Returns a copy of the song with the key value set to the specified capo. It changes:
* - the value for `capo` in the {@link metadata} set
* - any existing `capo` directive
* @param {number|null} capo the capo. Passing `null` will:
* - remove the current key from {@link metadata}
* - remove any `capo` directive
* @returns {Song} The changed song
*/
setCapo(capo: number | null): Song {
const strCapo = capo ? capo.toString() : null;
return this.changeMetadata(CAPO, strCapo);
}
private setDirective(name: string, value: string | null): Song {
if (value === null) {
return this.removeItem((item: Item) => item instanceof Tag && item.name === name);
}
return this.updateItem(
(item: Item) => item instanceof Tag && item.name === name,
(item: Item) => (('set' in item) ? item.set({ value }) : item),
(song: Song) => song.insertDirective(name, value),
);
}
/**
* Transposes the song by the specified delta. It will:
* - transpose all chords, see: {@link Chord#transpose}
* - transpose the song key in {@link metadata}
* - update any existing `key` directive
* @param {number} delta The number of semitones (positive or negative) to transpose with
* @param {Object} [options={}] options
* @param {boolean} [options.normalizeChordSuffix=false] whether to normalize the chord suffixes after transposing
* @returns {Song} The transposed song
*/
transpose(delta: number, { normalizeChordSuffix = false } = {}): Song {
let transposedKey: Key | null = null;
const song = (this as Song);
return song.mapItems((item) => {
if (item instanceof Tag && item.name === KEY) {
transposedKey = Key.wrapOrFail(item.value).transpose(delta);
return item.set({ value: transposedKey.toString() });
}
if (item instanceof ChordLyricsPair) {
return item.transpose(delta, transposedKey, { normalizeChordSuffix });
}
return item;
});
}
/**
* Transposes the song up by one semitone. It will:
* - transpose all chords, see: {@link Chord#transpose}
* - transpose the song key in {@link metadata}
* - update any existing `key` directive
* @param {Object} [options={}] options
* @param {boolean} [options.normalizeChordSuffix=false] whether to normalize the chord suffixes after transposing
* @returns {Song} The transposed song
*/
transposeUp({ normalizeChordSuffix = false } = {}): Song {
return this.transpose(1, { normalizeChordSuffix });
}
/**
* Transposes the song down by one semitone. It will:
* - transpose all chords, see: {@link Chord#transpose}
* - transpose the song key in {@link metadata}
* - update any existing `key` directive
* @param {Object} [options={}] options
* @param {boolean} [options.normalizeChordSuffix=false] whether to normalize the chord suffixes after transposing
* @returns {Song} The transposed song
*/
transposeDown({ normalizeChordSuffix = false } = {}): Song {
return this.transpose(-1, { normalizeChordSuffix });
}
/**
* Returns a copy of the song with the key set to the specified key. It changes:
* - the value for `key` in the {@link metadata} set
* - any existing `key` directive
* - all chords, those are transposed according to the distance between the current and the new key
* @param {string} newKey The new key.
* @returns {Song} The changed song
*/
changeKey(newKey: string | Key): Song {
const currentKey = this.requireCurrentKey();
const targetKey = Key.wrapOrFail(newKey);
const delta = currentKey.distanceTo(targetKey);
const transposedSong = this.transpose(delta);
if (targetKey.modifier) {
return transposedSong.useModifier(targetKey.modifier);
}
return transposedSong;
}
/**
* Returns a copy of the song with all chords changed to the specified modifier.
* @param {Modifier} modifier the new modifier
* @returns {Song} the changed song
*/
useModifier(modifier: Modifier) {
return this.mapItems((item) => {
if (item instanceof ChordLyricsPair) {
return (item as ChordLyricsPair).useModifier(modifier);
}
return item;
});
}
requireCurrentKey(): Key {
const wrappedKey = Key.wrap(this.key);
if (!wrappedKey) {
throw new Error(`
Cannot change song key, the original key is unknown.
Either ensure a key directive is present in the song (when using chordpro):
\`{key: C}\`
Or set the song key before changing key:
\`song.setKey('C');\``.substring(1));
}
return wrappedKey;
}
/**
* Returns a copy of the song with the directive value set to the specified value.
* - when there is a matching directive in the song, it will update the directive
* - when there is no matching directive, it will be inserted
* If `value` is `null` it will act as a delete, any directive matching `name` will be removed.
* @param {string} name The directive name
* @param {string | null} value The value to set, or `null` to remove the directive
*/
changeMetadata(name: string, value: string | null): Song {
const updatedSong = this.setDirective(name, value);
updatedSong.metadata.set(name, value);
return updatedSong;
}
private insertDirective(name: string, value: string, { after = null } = {}): Song {
const insertIndex = this.lines.findIndex((line) => (
line.items.some((item) => (
!(item instanceof Tag) || (after && item.name === after)
))
));
const newLine = new Line();
newLine.addTag(name, value);
const clonedSong = this.clone();
const { lines } = clonedSong;
clonedSong.lines = [...lines.slice(0, insertIndex), newLine, ...lines.slice(insertIndex)];
return clonedSong;
}
addLine(line: Line) {
this.lines.push(line);
}
/**
* Change the song contents inline. Return a new {@link Item} to replace it. Return `null` to remove it.
* @example
* // transpose all chords:
* song.mapItems((item) => {
* if (item instanceof ChordLyricsPair) {
* return item.transpose(2, 'D');
* }
*
* return item;
* });
* @param {MapItemsCallback} func the callback function
* @returns {Song} the changed song
*/
mapItems(func: MapItemsCallback): Song {
const clonedSong = new Song();
const builder = new SongBuilder(clonedSong);
this.lines.forEach((line) => {
builder.addLine();
line.items.forEach((item) => {
const changedItem = func(item);
if (changedItem) {
builder.addItem(changedItem);
}
});
});
return clonedSong;
}
/**
* Change the song contents inline. Return a new {@link Line} to replace it. Return `null` to remove it.
* @example
* // remove lines with only Tags:
* song.mapLines((line) => {
* if (line.items.every(item => item instanceof Tag)) {
* return null;
* }
*
* return line;
* });
* @param {MapLinesCallback} func the callback function
* @returns {Song} the changed song
*/
mapLines(func: MapLinesCallback): Song {
const clonedSong = new Song();
const builder = new SongBuilder(clonedSong);
this.lines.forEach((line) => {
const changedLine = func(line);
if (changedLine) {
builder.addLine();
changedLine.items.forEach((item) => builder.addItem(item));
}
});
return clonedSong;
}
private updateItem(
findCallback: (_item: Item) => boolean,
updateCallback: (_item: Item) => Item,
notFoundCallback: (_song: Song) => Song,
): Song {
let found = false;
const updatedSong = this.mapItems((item) => {
if (findCallback(item)) {
found = true;
return updateCallback(item);
}
return item;
});
if (!found) {
return notFoundCallback(updatedSong);
}
return updatedSong;
}
private removeItem(callback: (_item: Item) => boolean): Song {
return this.mapLines((line) => {
const { items } = line;
const index = items.findIndex(callback);
if (index === -1) {
return line;
}
if (items.length === 1) {
return null;
}
return line.set({
items: [...items.slice(0, index), ...items.slice(index + 1)],
});
});
}
}
export default Song;