import { describe, expect, it } from 'vitest';
import { scalingSettings, type ScalingMember, type ScalingPolicy, type ScalingSnapshot } from '../../src/lib/autoscaling.js';
import { emptyObservation, planScaling } from '../../src/lib/server/autoscaling/planner.js';
import { mapIdentity } from '../../src/lib/server/autoscaling/snapshot.js';

const now = 2_000_000;
const policy: ScalingPolicy = { ...scalingSettings({ game: 't6', mapSlug: 'town', maximum: 4, mode: 'dry-run' }), id: 'policy', revision: 1, nextActionAt: 0, pausedReason: null, updatedAt: '' };
const name = (n: number) => `t6_zombie_town_${n}`;
const member = (n: number, state: ScalingMember['state'] = 'empty'): ScalingMember => ({ name: name(n), identity: `instance:${n}`, state, players: state === 'occupied' ? 1 : state === 'empty' ? 0 : null, observedAt: now, source: 'rcon', emptySince: 1, blocker: null, operationId: null });
const snapshot = (...members: ScalingMember[]): ScalingSnapshot => ({ members, reservedNames: members.map(m => m.name), keyedNames: [1, 2, 3, 4].map(name), blockers: [] });

describe('autoscaling policy planning', () => {
    it('requires explicit bounded maximum and valid variant', () => {
        for (const input of [{}, { game: 't6', mapSlug: 'town' }, { game: 't5', mapSlug: 'town', maximum: 4 }, { game: 't6', mapSlug: 'town', maximum: 21 }, { ...policy, minimum: 5 }, { ...policy, spares: 0 }, { ...policy, emptyMinutes: 1.5 }]) expect(() => scalingSettings(input)).toThrow();
        expect(scalingSettings({ game: 't6', mapSlug: 'town', maximum: 4 }).mode).toBe('off');
    });
    it('creates a spare even with free player slots and bootstraps an empty map', () => {
        expect(planScaling(policy, snapshot(member(1, 'occupied')), now)).toMatchObject({ action: 'create', server: name(2), desired: 2 });
        expect(planScaling(policy, snapshot(), now)).toMatchObject({ action: 'create', desired: 1 });
        expect(planScaling(policy, snapshot(member(1, 'occupied'), member(2)), now).action).toBe('wait');
    });
    it('uses nonconsecutive keyed identities without moving keys', () => {
        expect(planScaling(policy, { ...snapshot(), keyedNames: [name(8), name(3)] }, now).server).toBe(name(3));
        expect(planScaling(policy, { ...snapshot(), keyedNames: [] }, now).reason).toContain('saved key');
    });
    it('holds for pending creation, unknown, stopped, or protected members', () => {
        for (const state of ['creating', 'removing', 'unknown', 'stopped', 'protected'] as const) expect(planScaling(policy, snapshot(member(1, state)), now).action).toBe('wait');
        expect(planScaling(policy, { ...snapshot(), blockers: ['Unresolved instance'] }, now).action).toBe('wait');
    });
    it('holds for stale and future samples, cooldown, and disabled policies', () => {
        for (const stamp of [null, now - 90_001, now + 1]) expect(planScaling(policy, snapshot({ ...member(1, 'occupied'), observedAt: stamp }), now).action).toBe('wait');
        expect(planScaling({ ...policy, nextActionAt: now + 1 }, snapshot(), now).action).toBe('wait');
        expect(planScaling({ ...policy, mode: 'off' }, snapshot(), now).action).toBe('wait');
    });
    it('never sacrifices occupied lobbies or minimum/spare capacity to a maximum', () => {
        expect(planScaling(policy, snapshot(...[1, 2, 3, 4].map(n => member(n, 'occupied'))), now)).toMatchObject({ action: 'wait', desired: 4 });
        expect(planScaling({ ...policy, maximum: 1 }, snapshot(member(1, 'occupied'), member(2)), now).action).toBe('wait');
        expect(planScaling({ ...policy, minimum: 3 }, snapshot(member(1), member(2), member(3)), now).action).toBe('wait');
    });
    it('trims one longest-empty lobby and requires a full observed interval', () => {
        expect(planScaling(policy, snapshot(member(1, 'occupied'), member(2), member(3), member(4)), now)).toMatchObject({ action: 'destroy', server: name(2), desired: 2 });
        expect(planScaling(policy, snapshot({ ...member(1), emptySince: now }, { ...member(2), emptySince: now }), now).action).toBe('wait');
    });
    it('preserves map variants and refuses ambiguous engine maps', () => {
        expect(mapIdentity({ name: 'legacy', game: 't6', map: 'zm_transit' })).toBeNull();
        expect(mapIdentity({ name: name(1), map: 'zm_transit' })?.mapSlug).toBe('town');
        expect(mapIdentity({ name: 'legacy', game: 't6', map_slug: 'farm', map: 'zm_transit' })?.mapSlug).toBe('farm');
    });
});

describe('continuous empty evidence', () => {
    it('does not turn rereads into new evidence', () => {
        const previous = emptyObservation(member(1), undefined, now);
        const reread = emptyObservation(member(1), previous, now + 60_000);
        expect(reread).toMatchObject({ observedAt: now, emptySince: now });
        expect(emptyObservation({ ...member(1), observedAt: now + 60_000 }, previous, now + 60_000).emptySince).toBe(now);
    });
    it('resets on unknown, players, lifecycle replacement, and observation gaps', () => {
        const previous = emptyObservation(member(1), undefined, now);
        expect(emptyObservation(member(1, 'occupied'), previous, now).emptySince).toBeNull();
        expect(emptyObservation(member(1, 'unknown'), previous, now).emptySince).toBeNull();
        expect(emptyObservation({ ...member(1), identity: 'replacement', observedAt: now + 1 }, previous, now + 1).emptySince).toBe(now + 1);
        expect(emptyObservation({ ...member(1), observedAt: now + 120_000 }, previous, now + 120_000).emptySince).toBe(now + 120_000);
        expect(emptyObservation({ ...member(1), emptyStartedAt: now + 10_000, observedAt: now + 15_000 }, previous, now + 15_000).emptySince).toBe(now + 15_000);
    });
});