import { describe, test, expect } from 'bun:test';
import { composeDigest } from '$lib/server/stats/digest';
import type { SnapshotPayload } from '$lib/types/stats';

const payload: SnapshotPayload = {
	asOfDate: '2026-09-14',
	activity: {
		dau: 102,
		wau: 363,
		mau: 852,
		core: 61,
		returningShare: 38,
		newPlayers: 20,
		resurrected: 4,
		churned: 25,
		netGrowth: -1,
		corePrevious: 60,
		previous: null
	},
	dailySeries: [],
	kpis: {
		d1Return: 12.2,
		return7: 18,
		overallReturnRate: 22.8,
		completionRate: null,
		shareRate: null,
		firstTryRate: 33.7,
		avgGuesses: 4.1
	},
	retention: { cohorts: [], curves: { d1: [], d7: [], d30: [] }, timeToSecondPlay: [], segmentMix: [] },
	verseMix: {
		coverage: [],
		testamentMix: [],
		entropy: [],
		repeatIntervals: [],
		firstTryByBook: [],
		retentionByBook: [],
		retentionByGuessBucket: [],
		achievability: []
	},
	habit: { streakSurvival: [], streakLengths: [], calendar: [], weekdayHour: [] },
	growth: { lifecycleFunnel: [], signups: [] },
	totals: { completions: 31775, players: 6589, yesterdayCompletions: 102, yesterdayAvgGuesses: 4.1, bestDay: null },
	signals: [
		{
			id: 'd1_return',
			severity: 'bad',
			title: 'D1 return',
			detail: 'D1 return is 12.2%, below the 20% target.',
			action: 'Test a "come back tomorrow" prompt.'
		}
	],
	meta: { hasStartedData: false, hasShareData: false, firstEventDate: null }
};

describe('composeDigest', () => {
	test('includes the core numbers in plain language', () => {
		const message = composeDigest(payload);
		expect(message).toContain('2026-09-14');
		expect(message).toContain('363');
		expect(message).toContain('12.2');
		expect(message).toContain('Top signal: D1 return');
		expect(message).toContain('/admin/stats?date=2026-09-14');
	});

	test('is at most a handful of lines', () => {
		expect(composeDigest(payload).split('\n').length).toBeLessThanOrEqual(6);
	});

	test('shows an em-dash for missing metrics', () => {
		const message = composeDigest({
			...payload,
			kpis: { ...payload.kpis, d1Return: null, return7: null }
		});
		expect(message).toContain('D1 return —%');
	});
});