'use strict';

/**
 * A MONITORING CONTRACT WITH NO CALLSITE IS A PLAN.
 *
 * The previous tranche declared forward evaluation and shipped none. These
 * tests hold both halves: the evaluator behaves, AND production actually calls it.
 */
const fm = require('../../src/services/model/forwardMonitor');
const registry = require('../../src/services/model/artifactRegistry');

const A = registry.load('mlb', 'hits');
const AFTER = '2026-09-02';                       // strictly after training_cutoff 2026-09-01

/** Rows whose outcomes track the frozen curve, optionally shifted to force drift. */
function rows(n, shift = 0, over = {}) {
  return Array.from({ length: n }, (_, i) => {
    const raw = Math.round((0.50 + (i % 29) / 100) * 1000) / 1000;
    const served = registry.applyCurve(A, raw) ?? 0.6;
    return { p: raw, won: ((i * 2654435761) % 1000) / 1000 < served + shift ? 1 : 0,
      date: AFTER, model_version: A.model_version, ...over };
  });
}

describe('the monitor evaluates and refuses to guess', () => {
  it('says HEALTHY only on enough evidence', () => {
    const r = fm.evaluate(A, rows(1200), registry.applyCurve);
    expect(r.health).toBe(fm.HEALTH.HEALTHY);
    expect(r.healthy).toBe(true);
    expect(r.n).toBeGreaterThanOrEqual(fm.MIN_FORWARD_ROWS);
  });

  it('LOW N IS NOT HEALTHY AND NOT DRIFT — it is its own answer', () => {
    const r = fm.evaluate(A, rows(50), registry.applyCurve);
    expect(r.health).toBe(fm.HEALTH.INSUFFICIENT_SAMPLE);
    expect(r.healthy).toBeNull();                 // never false, never true
    expect(r.reason).toContain(String(fm.MIN_FORWARD_ROWS));
  });

  it('the sample floor is DERIVED from the certified tolerance, not chosen', () => {
    // SE = sqrt(0.25/n) <= TOLERANCE/2  =>  n >= 0.25 / (TOLERANCE/2)^2
    expect(fm.MIN_FORWARD_ROWS).toBe(Math.ceil(0.25 / ((fm.TOLERANCE / 2) ** 2)));
    expect(fm.TOLERANCE).toBe(0.05);              // same number certifyBands used
  });

  it('flags drift when the frozen curve stops matching outcomes', () => {
    const r = fm.evaluate(A, rows(1200, 0.20), registry.applyCurve);
    expect(r.health).toBe(fm.HEALTH.DRIFT_WARNING);
    expect(r.healthy).toBe(false);
    expect(r.drift_bands.length).toBeGreaterThan(0);
  });

  it('refuses an unservable artifact and wrong-era evidence', () => {
    expect(fm.evaluate({ ...A, servable: false }, rows(1200), registry.applyCurve).health)
      .toBe(fm.HEALTH.INVALID);
    expect(fm.evaluate(A, rows(1200, 0, { model_version: 'engine1@2026-07-20' }), registry.applyCurve).health)
      .toBe(fm.HEALTH.INVALID);
  });

  it('an unreadable read is AUDIT_UNAVAILABLE, never a health verdict', () => {
    const r = fm.evaluate(A, null, registry.applyCurve);
    expect(r.health).toBe(fm.HEALTH.AUDIT_UNAVAILABLE);
    expect(r.healthy).toBeNull();
    expect(fm.evaluate(null, rows(1200), registry.applyCurve).health).toBe(fm.HEALTH.AUDIT_UNAVAILABLE);
  });

  it('scores ONLY evidence the fit never saw', () => {
    const atCutoff = rows(1200).map((r) => ({ ...r, date: A.training_cutoff }));
    expect(fm.evaluate(A, atCutoff, registry.applyCurve).n).toBe(0);
    const before = rows(1200).map((r) => ({ ...r, date: '2026-08-01' }));
    expect(fm.evaluate(A, before, registry.applyCurve).n).toBe(0);
  });

  it('scores ONLY rows inside certified support', () => {
    const outside = rows(1200).map((r, i) => ({ ...r, p: i % 2 ? 0.9 : 0.4 }));
    expect(fm.evaluate(A, outside, registry.applyCurve).n).toBe(0);
  });
});

describe('the monitor cannot change what it watches', () => {
  it('imports no fitter and performs no write', () => {
    const src = require('fs').readFileSync(
      require('path').join(__dirname, '../../src/services/model/forwardMonitor.js'), 'utf8');
    const code = src.replace(/\/\*[\s\S]*?\*\//g, '').replace(/^\s*\/\/.*$/gm, '');
    // token-level, not substring: 'promote' also appears inside the reason
    // string 'no promoted artifact', which is a description, not a call.
    for (const forbidden of ['fitIsotonic', 'fitPlatt', 'writeFileSync', '.upsert(', '.update(',
      'promote(', 'artifactRegistry', 'PROMOTED']) {
      expect(code).not.toContain(forbidden);
    }
  });

  it('evaluating does not mutate the artifact', () => {
    const before = JSON.stringify(A);
    fm.evaluate(A, rows(1200, 0.2), registry.applyCurve);
    expect(JSON.stringify(registry.load('mlb', 'hits'))).toBe(before);
  });
});

describe('alarm discipline', () => {
  it('does not alert on HEALTHY or INSUFFICIENT_SAMPLE', () => {
    for (const h of [fm.HEALTH.HEALTHY, fm.HEALTH.INSUFFICIENT_SAMPLE]) {
      expect(fm.monitorAlarm(null, { health: h, artifact_id: 'x' }).alert).toBe(false);
    }
  });

  it('alerts once per state transition, not once per tick', () => {
    const first = fm.monitorAlarm(null, { health: fm.HEALTH.DRIFT_WARNING, artifact_id: 'x', reason: 'r' });
    expect(first.alert).toBe(true);
    expect(fm.monitorAlarm(first.key, { health: fm.HEALTH.DRIFT_WARNING, artifact_id: 'x', reason: 'r' }).alert).toBe(false);
  });

  it('says plainly that a drift alert has NOT changed the artifact', () => {
    const a = fm.monitorAlarm(null, { health: fm.HEALTH.DRIFT_WARNING, artifact_id: 'x', reason: 'r' });
    expect(a.message).toMatch(/frozen and unchanged/);
  });
});

describe('THE CALLSITE — production actually runs it', () => {
  it('the scheduler exposes and invokes the monitor on its tick', async () => {
    const src = require('fs').readFileSync(
      require('path').join(__dirname, '../../src/snapshotScheduler.js'), 'utf8');
    expect(src).toContain('await calibrationMonitorTick();');
    expect(src).toContain('calibrationMonitorTick };');
  });

  it('the tick calls evaluate with the promoted artifact and forward-only rows', async () => {
    const sched = require('../../src/snapshotScheduler');
    const calls = [];
    const fake = {
      monitorDue: () => true,
      evaluate: (artifact, rws) => { calls.push({ artifact, rws }); return { health: 'HEALTHY', healthy: true, n: 999, min_required: 400, artifact_id: artifact.artifact_id }; },
      monitorAlarm: () => ({ alert: false, key: 'k' }),
      HEALTH: fm.HEALTH,
    };
    const loaded = [];
    const prev = process.env.SNAPSHOT_CRON;
    process.env.SNAPSHOT_CRON = '1';               // the scheduler is inert unless armed
    const s = sched.startSnapshotScheduler({
      forwardMonitor: fake,
      artifactRegistry: registry,
      currentEraSource: { loadRows: async (sb, args) => { loaded.push(args); return rows(500); } },
      supabase: {},
      now: () => new Date('2026-09-03T05:00:00Z'),
      runAllSnapshots: async () => ({}),
    });
    try {
      expect(s).not.toBeNull();                    // armed, or the assertions below are vacuous
      await s.calibrationMonitorTick();
      expect(calls).toHaveLength(1);
      expect(calls[0].artifact.artifact_id).toBe(A.artifact_id);
      // forward-only: bounded strictly after the artifact's training cutoff
      expect(loaded[0].after).toBe(A.training_cutoff);
      expect(loaded[0].modelVersion).toBe(A.model_version);
    } finally {
      if (s && s.interval) clearInterval(s.interval);
      if (prev === undefined) delete process.env.SNAPSHOT_CRON; else process.env.SNAPSHOT_CRON = prev;
    }
  });
});