import { describe, it, expect } from 'vitest';
import { buildEventLookup, bucketLetters, hasLooseLetters } from './timelineGrouping';
import { makeEntry, makeYear, makeTimelineDTO } from './test-factories';

// Entry factories pinned to the shapes the grouping transform discriminates (#827).
const letter = (overrides = {}) => makeEntry({ kind: 'LETTER', ...overrides });

const curatedEvent = (id: string, title: string, overrides = {}) =>
	makeEntry({
		kind: 'EVENT',
		type: 'PERSONAL',
		derived: false,
		documentId: undefined,
		eventId: id,
		title,
		senderName: '',
		receiverName: '',
		...overrides
	});

describe('buildEventLookup (REQ-019)', () => {
	it('collects curated events (eventId set) from year bands and the undated bucket', () => {
		const dto = makeTimelineDTO({
			years: [makeYear(1915, [curatedEvent('e1', 'Briefe von der Front'), letter()])],
			undated: [curatedEvent('e2', 'Unbekanntes Ereignis')]
		});
		const lookup = buildEventLookup(dto);
		expect(lookup.get('e1')).toBe('Briefe von der Front');
		expect(lookup.get('e2')).toBe('Unbekanntes Ereignis');
		expect(lookup.size).toBe(2);
	});

	it('ignores letters and derived life-events (no eventId)', () => {
		const dto = makeTimelineDTO({
			years: [
				makeYear(1915, [
					letter({ linkedEventId: 'e1' }),
					makeEntry({ kind: 'EVENT', type: 'PERSONAL', derived: true, eventId: undefined })
				])
			]
		});
		expect(buildEventLookup(dto).size).toBe(0);
	});
});

describe('hasLooseLetters (REQ-018)', () => {
	it('is true when a year band or the undated bucket holds a letter', () => {
		expect(hasLooseLetters(makeTimelineDTO({ years: [makeYear(1915, [letter()])] }))).toBe(true);
		expect(hasLooseLetters(makeTimelineDTO({ undated: [letter({ documentId: 'u1' })] }))).toBe(
			true
		);
	});

	it('is false when only events remain', () => {
		const dto = makeTimelineDTO({ years: [makeYear(1915, [curatedEvent('e1', 'Ereignis')])] });
		expect(hasLooseLetters(dto)).toBe(false);
	});
});

describe('bucketLetters — Ereignis mode (REQ-003/006/019)', () => {
	const lookup = new Map([
		['e1', 'Briefe von der Front'],
		['e2', 'Weihnachten 1915']
	]);

	it('clusters letters under the curated event named by linkedEventId, with matching counts', () => {
		const letters = [
			letter({ documentId: 'a', linkedEventId: 'e1' }),
			letter({ documentId: 'b', linkedEventId: 'e1' }),
			letter({ documentId: 'c', linkedEventId: 'e2' })
		];
		const buckets = bucketLetters(letters, 'event', lookup);
		const front = buckets.find((b) => b.title === 'Briefe von der Front');
		expect(front?.kind).toBe('event');
		expect(front?.letters).toHaveLength(2);
		expect(buckets.find((b) => b.title === 'Weihnachten 1915')?.letters).toHaveLength(1);
	});

	it('drops a letter with no linkedEventId into the fallback bucket (REQ-006)', () => {
		const letters = [letter({ documentId: 'a', linkedEventId: undefined })];
		const buckets = bucketLetters(letters, 'event', lookup);
		expect(buckets).toHaveLength(1);
		expect(buckets[0].kind).toBe('fallback');
		expect(buckets[0].letters).toHaveLength(1);
	});

	it('drops a letter whose linked event is absent from the lookup into fallback (REQ-019)', () => {
		// e9 is not in the filtered view (its layer was toggled off) → no cluster.
		const letters = [letter({ documentId: 'a', linkedEventId: 'e9' })];
		const buckets = bucketLetters(letters, 'event', lookup);
		expect(buckets).toHaveLength(1);
		expect(buckets[0].kind).toBe('fallback');
	});

	it('keeps the fallback bucket last', () => {
		const letters = [
			letter({ documentId: 'a', linkedEventId: undefined }),
			letter({ documentId: 'b', linkedEventId: 'e1' })
		];
		const buckets = bucketLetters(letters, 'event', lookup);
		expect(buckets[buckets.length - 1].kind).toBe('fallback');
	});
});

describe('bucketLetters — Thema mode (REQ-004/007/008)', () => {
	const noEvents = new Map<string, string>();

	it('buckets letters under their primary root tag with name and colour', () => {
		const letters = [
			letter({ documentId: 'a', rootTagId: 't1', rootTagName: 'Krieg', rootTagColor: 'sienna' }),
			letter({ documentId: 'b', rootTagId: 't1', rootTagName: 'Krieg', rootTagColor: 'sienna' }),
			letter({
				documentId: 'c',
				rootTagId: 't2',
				rootTagName: 'Weihnachten',
				rootTagColor: 'amber'
			})
		];
		const buckets = bucketLetters(letters, 'thema', noEvents);
		const krieg = buckets.find((b) => b.title === 'Krieg');
		expect(krieg?.kind).toBe('tag');
		expect(krieg?.color).toBe('sienna');
		expect(krieg?.letters).toHaveLength(2);
		expect(buckets.find((b) => b.title === 'Weihnachten')?.color).toBe('amber');
	});

	it('drops an untagged letter into the "Ohne Thema" fallback bucket (REQ-007)', () => {
		const letters = [letter({ documentId: 'a', rootTagId: undefined })];
		const buckets = bucketLetters(letters, 'thema', noEvents);
		expect(buckets).toHaveLength(1);
		expect(buckets[0].kind).toBe('fallback');
		expect(buckets[0].color).toBeNull();
	});

	it('places a letter in exactly one bucket (REQ-008)', () => {
		const letters = [
			letter({ documentId: 'a', rootTagId: 't1', rootTagName: 'Krieg', rootTagColor: 'sienna' })
		];
		const buckets = bucketLetters(letters, 'thema', noEvents);
		const occurrences = buckets.flatMap((b) => b.letters).filter((l) => l.documentId === 'a');
		expect(occurrences).toHaveLength(1);
	});

	it('carries a null colour through for a colourless root tag', () => {
		const letters = [
			letter({
				documentId: 'a',
				rootTagId: 't3',
				rootTagName: 'Allgemein',
				rootTagColor: undefined
			})
		];
		const buckets = bucketLetters(letters, 'thema', noEvents);
		expect(buckets[0].kind).toBe('tag');
		expect(buckets[0].color).toBeNull();
	});
});