import assert from 'node:assert/strict';
import { describe, it } from 'node:test';
import { dayLessons, dayNoteSkeleton, dayNoteTitle, lessonHeading, missingHeadings } from '../src/core/day-note.ts';
import { subjectFromHeading } from '../src/core/notes.ts';
import type { UntisLesson, UntisTimetable } from '../src/core/untis.ts';

function lesson(overrides: Partial<UntisLesson> & { periodId: number }): UntisLesson {
	return {
		lessonId: 1,
		date: '2026-09-18',
		start: '08:00',
		end: '08:45',
		statuses: ['REGULAR'],
		cancelled: false,
		changed: false,
		subjects: [{ name: 'DE', longName: 'Deutsch' }],
		teachers: [{ name: 'MEI', longName: 'Meier' }],
		rooms: [{ name: '204' }],
		classes: [],
		replaced: { subjects: [], teachers: [], rooms: [] },
		notes: {},
		homework: [],
		online: false,
		...overrides,
	};
}

function timetable(lessons: UntisLesson[]): UntisTimetable {
	return { from: '2026-09-18', to: '2026-09-18', days: [{ date: '2026-09-18', lessons, holidays: [] }] };
}

describe('dayNoteTitle', () => {
	it('is the weekday and the date, as a person would write it', () => {
		assert.equal(dayNoteTitle('2026-09-18'), 'Freitag, 18.09.2026');
	});
});

describe('lessonHeading', () => {
	it('leads with the subject, then the time, teacher and room', () => {
		assert.equal(lessonHeading(lesson({ periodId: 1 }), 0), '1. Deutsch — 08:00–08:45 · MEI · R 204');
	});

	it('marks a substitution, because the teacher is not the usual one', () => {
		assert.match(lessonHeading(lesson({ periodId: 1, changed: true }), 0), /Vertretung$/);
	});

	it('survives a period with no subject at all', () => {
		assert.match(lessonHeading(lesson({ periodId: 1, subjects: [] }), 2), /^3\. Stunde — /);
	});

	it('writes a heading subjectFromHeading reads back — the loop that makes lessons searchable', () => {
		// These two have to agree or a day's notes index under nothing: the page
		// writes the heading, the indexer reads the subject out of it again.
		for (const [index, entry] of [lesson({ periodId: 1 }), lesson({ periodId: 2, changed: true })].entries()) {
			assert.equal(subjectFromHeading(lessonHeading(entry, index)), 'Deutsch');
		}
	});
});

describe('dayLessons', () => {
	it('leaves out a cancelled period, which taught nothing', () => {
		const lessons = dayLessons(
			timetable([lesson({ periodId: 1 }), lesson({ periodId: 2, cancelled: true, start: '08:50', end: '09:35' })]),
			'2026-09-18',
		);
		assert.deepEqual(lessons.map((entry) => entry.periodId), [1]);
	});

	it('keeps a substitution, which did happen', () => {
		const lessons = dayLessons(timetable([lesson({ periodId: 1, changed: true })]), '2026-09-18');
		assert.equal(lessons[0]?.changed, true);
	});

	it('is empty for a day the timetable does not cover', () => {
		assert.deepEqual(dayLessons(timetable([lesson({ periodId: 1 })]), '2026-09-19'), []);
	});
});

describe('dayNoteSkeleton', () => {
	it('is a heading per lesson with room to write under each', () => {
		const text = dayNoteSkeleton(dayLessons(timetable([lesson({ periodId: 1 }), lesson({ periodId: 2, start: '08:50', end: '09:35' })]), '2026-09-18'));
		assert.equal(text.match(/^## /gm)?.length, 2);
		assert.match(text, /^## 1\. Deutsch/m);
	});

	it('is empty when there are no lessons, rather than a lone heading', () => {
		assert.equal(dayNoteSkeleton([]), '');
	});
});

describe('missingHeadings', () => {
	const lessons = dayLessons(
		timetable([lesson({ periodId: 1 }), lesson({ periodId: 2, start: '08:50', end: '09:35' })]),
		'2026-09-18',
	);

	it('is empty when the note already has them', () => {
		assert.deepEqual(missingHeadings(dayNoteSkeleton(lessons), lessons), []);
	});

	it('names the lesson a note started early does not have yet', () => {
		const started = '## 1. Deutsch — 08:00–08:45 · MEI · R 204\n\nErörterung.\n';
		assert.deepEqual(missingHeadings(started, lessons).map((entry) => entry.periodId), [2]);
	});

	it('recognises a heading the person shortened', () => {
		// "2. Deutsch" is still the second period; adding it again would give the
		// day two of them.
		assert.deepEqual(missingHeadings('## 1. Kurz\n## 2. Auch kurz\n', lessons), []);
	});

	it('is everything for an empty note', () => {
		assert.equal(missingHeadings('', lessons).length, 2);
	});
});