Module prototype

Prototype-style chainable wrappers around RPE chart objects.

Instead of calling free functions like:

addMoveXEvent(chart, 0, 0, 0, 4, -100, 100);
addNote(chart, 0, 2, { type: 1 });
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You can use the wrapper classes for a fluent, self-documenting API:

const line = new LineBuilder(chart, 0);
line.moveX(0, 4, -100, 100).rotate(0, 4, 0, 90).addNote(2);
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All wrappers are thin value-objects — they hold a reference to the underlying chart (and target line / note) and delegate to the chart-utils functions. Nothing is copied; changes are made in place.

Entry points

• ChartBuilder.from(chart) — wrap an existing chart
• ChartBuilder.empty(bpm?, name?) — create and wrap a new chart
• new LineBuilder(chart, lineIndex) — wrap a specific line
• new NoteBuilder(chart, lineIndex, noteIndex) — wrap a specific note

Full example

import { ChartBuilder } from './prototype';

const chart = ChartBuilder.empty(140, 'Example')
  .setCharter('Me')
  .setComposer('Artist');

// Add two judge lines
const main = chart.line({ name: 'Main' });
const bg   = chart.line({ name: 'BG', texture: 'bg.png' });

// Animate the main line: slide X 0→675 over beats 0Ⅎ4
main.moveX(0, 4, 0, 675, 'cubicOut');

// Add a tap note at beat 2 and a hold from beat 4–6
main.addNote(2, { type: 1 })
    .addNote(4, { type: 2, endBeat: 6 });

// BPM change at beat 32
chart.bpm(32, 160);

// Get stats and serialize
const stats  = chart.stats();
const issues = chart.validate();
const json   = chart.serialize();
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