import { describe, it, expect } from 'vitest';
import {
	computeRoutineState,
	computeHealthScore,
	computeHealthSeries,
	computeProjectHealthSeries,
	parseIntervalToDays,
} from './routine-metrics';
const CREATED = '2026-09-01T00:00:00.000Z';
const created = Temporal.Instant.from(CREATED);

const plusDays = (base: Temporal.Instant, days: number): Temporal.Instant =>
	base.toZonedDateTimeISO('UTC').add({ days }).toInstant();

/** ISO stamp n days after the given stamp. */
const isoPlusDays = (iso: string, days: number): string =>
	Temporal.Instant.from(iso)
		.toZonedDateTimeISO('UTC')
		.add({ days })
		.toInstant()
		.toString({ smallestUnit: 'millisecond' });

const routine = {
	id: 1,
	version: 1,
	name: 'clean kitchen',
	frequencyDays: 7,
	createdAt: CREATED,
};

describe('computeRoutineState', () => {
	it('is due immediately at creation when never done (created_at = due)', () => {
		const now = plusDays(created, 3);
		const state = computeRoutineState(routine, [], now);
		expect(state.status).toBe('due');
		expect(state.overdueDays).toBe(3);
		expect(state.health).toBe(79); // 3/7 of a period overdue
		expect(state.dueAt).toBe(CREATED);
	});

	it('uses the last completion as reference once done', () => {
		const doneAt = isoPlusDays(CREATED, 5);
		const now = plusDays(Temporal.Instant.from(doneAt), 2);
		const state = computeRoutineState(routine, [{ routineId: 1, doneAt }], now);
		expect(state.lastDoneAt).toBe(doneAt);
		expect(state.status).toBe('ok');
	});

	it('is due the calendar day after completion for a daily routine', () => {
		const daily = { ...routine, frequencyDays: 1 };
		const doneAt = '2026-09-07T20:00:00.000Z'; // yesterday evening
		const now = Temporal.Instant.from('2026-09-08T08:00:00.000Z'); // this morning, <24h later
		const state = computeRoutineState(daily, [{ routineId: 1, doneAt }], now);
		expect(state.status).toBe('due');
	});
	it('a daily done yesterday is late tomorrow, not today', () => {
		const daily = { ...routine, frequencyDays: 1 };
		const doneAt = '2026-09-07T20:00:00.000Z'; // yesterday evening
		const completions = [{ routineId: 1, doneAt }];
		const today = computeRoutineState(
			daily,
			completions,
			Temporal.Instant.from('2026-09-08T20:00:00.000Z'),
		);
		expect(today.status).toBe('due');
		const tomorrow = computeRoutineState(
			daily,
			completions,
			Temporal.Instant.from('2026-09-09T20:00:00.000Z'),
		);
		expect(tomorrow.status).toBe('late');
	});

	it('is ok later the same day it was done for a daily routine', () => {
		const daily = { ...routine, frequencyDays: 1 };
		const doneAt = '2026-09-08T08:00:00.000Z';
		const now = Temporal.Instant.from('2026-09-08T20:00:00.000Z');
		const state = computeRoutineState(daily, [{ routineId: 1, doneAt }], now);
		expect(state.status).toBe('ok');
	});
});

describe('computeHealthSeries', () => {
	it('decays from 100 at creation to 0 two periods overdue when never done', () => {
		const now = plusDays(created, 22);
		const series = computeHealthSeries(routine, [], now);
		expect(series[0].health).toBe(100);
		const at8d = series.find(
			(p) => p.at === plusDays(created, 8).epochMilliseconds,
		);
		expect(at8d?.health).toBe(43); // 8/7 of a period overdue
		const last = series[series.length - 1];
		expect(last.at).toBe(now.epochMilliseconds);
		expect(last.health).toBe(0); // more than two full periods overdue
	});

	it('resets to 100 right after a completion, then decays again (sawtooth)', () => {
		const doneAt = plusDays(created, 5);
		const now = plusDays(doneAt, 13); // 13 days after the completion
		const doneAtIso = doneAt.toString({ smallestUnit: 'millisecond' });
		const series = computeHealthSeries(
			routine,
			[{ routineId: 1, doneAt: doneAtIso }],
			now,
		);
		const rightAfter = series.find((p) => p.at >= doneAt.epochMilliseconds);
		expect(rightAfter?.health).toBe(100);
		// 8 days after the completion: 1 day into the 7-day period overdue.
		const at8d = series.find(
			(p) => p.at === plusDays(doneAt, 8).epochMilliseconds,
		);
		expect(at8d?.health).toBe(93);
	});

	it('a second completion resets the decay again', () => {
		const first = plusDays(created, 3);
		const second = plusDays(created, 10);
		const now = plusDays(created, 11);
		const stamp = (at: Temporal.Instant): string =>
			at.toString({ smallestUnit: 'millisecond' });
		const series = computeHealthSeries(
			routine,
			[
				{ routineId: 1, doneAt: stamp(first) },
				{ routineId: 1, doneAt: stamp(second) },
			],
			now,
		);
		// Just after the second completion the routine is back at full health.
		const nearEnd = series[series.length - 1];
		expect(nearEnd.health).toBe(100);
	});
});

describe('computeProjectHealthSeries', () => {
	it('is empty with no routines', () => {
		expect(computeProjectHealthSeries([], [], created)).toEqual([]);
	});

	it('averages per-routine health and ends at the current score', () => {
		const second = { ...routine, id: 2, name: 'read' };
		const doneAt = plusDays(created, 5);
		const now = plusDays(created, 8);
		const doneAtIso = doneAt.toString({ smallestUnit: 'millisecond' });
		const series = computeProjectHealthSeries(
			[routine, second],
			[{ routineId: 2, doneAt: doneAtIso }],
			now,
		);
		const states = [
			computeRoutineState(routine, [], now),
			computeRoutineState(second, [{ routineId: 2, doneAt: doneAtIso }], now),
		];
		const last = series[series.length - 1];
		expect(last.at).toBe(now.epochMilliseconds);
		expect(last.health).toBe(computeHealthScore(states));
	});

	it('only counts routines alive that day', () => {
		const late = {
			...routine,
			id: 2,
			name: 'latecomer',
			createdAt: isoPlusDays(CREATED, 10),
		};
		const now = plusDays(created, 11);
		const series = computeProjectHealthSeries([routine, late], [], now);
		const beforeLate = series.find(
			(p) => p.at === plusDays(created, 5).epochMilliseconds,
		);
		const single = computeHealthSeries(routine, [], plusDays(created, 5));
		expect(beforeLate?.health).toBe(single[single.length - 1].health);
	});
});

describe('parseIntervalToDays', () => {
	it('converts units to days', () => {
		expect(parseIntervalToDays('1d')).toBe(1);
		expect(parseIntervalToDays('2w')).toBe(14);
		expect(parseIntervalToDays('3m')).toBe(90);
		expect(parseIntervalToDays('1y')).toBe(365);
	});

	it('accepts whitespace and uppercase', () => {
		expect(parseIntervalToDays(' 2W ')).toBe(14);
	});

	it('rejects invalid input', () => {
		expect(parseIntervalToDays('2')).toBeNull();
		expect(parseIntervalToDays('w')).toBeNull();
		expect(parseIntervalToDays('2x')).toBeNull();
		expect(parseIntervalToDays('-1d')).toBeNull();
		expect(parseIntervalToDays('')).toBeNull();
	});
});

describe('computeHealthScore', () => {
	it('is 100 with no routines', () => {
		expect(computeHealthScore([])).toBe(100);
	});

	it('averages routine healths', () => {
		const now = plusDays(created, 8);
		const a = computeRoutineState(routine, [], now); // overdue 1 day
		const b = computeRoutineState(routine, [], plusDays(created, 3));
		expect(computeHealthScore([a, b])).toBe(
			Math.round((a.health + b.health) / 2),
		);
	});
});