// Three formats. Same bugs. Open/Closed Principle
// Teaching excerpts; see the explanation and boundaries on the episode page.

// One method, different output
type Report = { bugs: number };
interface Exporter {
  format(report: Report): string;
}

// Each object owns one format
class JsonExporter implements Exporter {
  format(r: Report) { return JSON.stringify(r); }
}
class CsvExporter implements Exporter {
  format(r: Report) { return `bugs\r\n${r.bugs}`; }
}

// Choose the object, then call it
const exporters = {
  json: new JsonExporter(),
  csv: new CsvExporter(),
};
type Kind = keyof typeof exporters;
const exportReport = (kind: Kind, r: Report) =>
  exporters[kind].format(r);
exportReport('csv', { bugs: 3 });

// Extend at the chosen boundary
class MarkdownExporter implements Exporter {
  format(r: Report) { return `**Bugs:** ${r.bugs}`; }
}