import { describe, expect, it } from 'bun:test';
import {
  type BumpType,
  type ModuleVersionPlan,
  applyBump,
  maxBump,
  parseChangeset,
  planModuleVersion,
  renderChangelogSection,
} from './changeset-version';

describe('parseChangeset', () => {
  it('parses quoted id + bump and the summary body', () => {
    const r = parseChangeset('---\n"lunacycle": minor\n---\n\nAdded a thing.\n');
    expect(r.bumps).toEqual({ lunacycle: 'minor' });
    expect(r.summary).toBe('Added a thing.');
  });

  it('parses unquoted ids and multiple modules', () => {
    const r = parseChangeset('---\nlunacycle: patch\nnigredo: major\n---\nfix\n');
    expect(r.bumps).toEqual({ lunacycle: 'patch', nigredo: 'major' });
  });

  it('throws on a missing frontmatter fence', () => {
    expect(() => parseChangeset('just a summary, no frontmatter')).toThrow(/frontmatter/);
  });

  it('throws on an invalid bump keyword', () => {
    expect(() => parseChangeset('---\nlunacycle: huge\n---\n')).toThrow(/major\|minor\|patch/);
  });

  it('throws on a frontmatter line without a colon', () => {
    expect(() => parseChangeset('---\nlunacycle minor\n---\n')).toThrow(/not "id: bump"/);
  });
});

describe('maxBump', () => {
  it('ranks major > minor > patch', () => {
    expect(maxBump(['patch', 'major', 'minor'])).toBe('major');
    expect(maxBump(['patch', 'minor'])).toBe('minor');
    expect(maxBump(['patch'])).toBe('patch');
  });
  it('returns null for an empty list', () => {
    expect(maxBump([])).toBeNull();
  });
});

describe('applyBump', () => {
  it('bumps each level and zeroes lower segments', () => {
    expect(applyBump('1.2.3', 'major')).toBe('2.0.0');
    expect(applyBump('1.2.3', 'minor')).toBe('1.3.0');
    expect(applyBump('1.2.3', 'patch')).toBe('1.2.4');
  });
  it('throws on a non x.y.z version', () => {
    expect(() => applyBump('1.2', 'patch')).toThrow(/x\.y\.z/);
    expect(() => applyBump('1.0.0+4', 'patch')).toThrow(/x\.y\.z/);
  });
});

describe('planModuleVersion', () => {
  const cs = (id: string, bump: BumpType, summary = '') =>
    parseChangeset(`---\n"${id}": ${bump}\n---\n${summary}\n`);

  it('returns null when no changeset targets the module', () => {
    expect(planModuleVersion('1.0.0', 'lunacycle', [])).toBeNull();
    expect(planModuleVersion('1.0.0', 'lunacycle', [cs('nigredo', 'minor')])).toBeNull();
  });

  it('takes the max bump across relevant changesets', () => {
    const plan = planModuleVersion('1.2.3', 'lunacycle', [
      cs('lunacycle', 'patch', 'a'),
      cs('lunacycle', 'minor', 'b'),
      cs('nigredo', 'major', 'unrelated'),
    ]);
    expect(plan).not.toBeNull();
    expect(plan?.bump).toBe('minor');
    expect(plan?.next).toBe('1.3.0');
    expect(plan?.entries).toEqual(['a', 'b']);
  });

  it('omits empty summaries from entries', () => {
    const plan = planModuleVersion('1.0.0', 'lunacycle', [
      cs('lunacycle', 'patch', ''),
      cs('lunacycle', 'patch', 'real'),
    ]);
    expect(plan?.entries).toEqual(['real']);
  });
});

describe('renderChangelogSection', () => {
  it('renders a newest-on-top section with the bump heading', () => {
    const plan = planModuleVersion('1.0.0', 'lunacycle', [
      parseChangeset('---\nlunacycle: minor\n---\nAdded tasks view.\n'),
    ]);
    expect(plan).not.toBeNull();
    const md = renderChangelogSection(plan as ModuleVersionPlan);
    expect(md).toContain('## 1.1.0');
    expect(md).toContain('### Minor Changes');
    expect(md).toContain('- Added tasks view.');
  });

  it('falls back to a generic bullet when there are no summaries', () => {
    const plan = planModuleVersion('1.0.0', 'lunacycle', [
      parseChangeset('---\nlunacycle: patch\n---\n'),
    ]);
    expect(renderChangelogSection(plan as ModuleVersionPlan)).toContain('- Version bump.');
  });
});