#!/usr/bin/env node
'use strict';
/**
 * build-current-era-artifact — fit ONCE, freeze, version, commit.
 *
 * Policy B (CERTIFIED_PROCEDURE_FROZEN_ARTIFACT): the walk-forward certifies the
 * PROCEDURE; the promoted artifact is then fitted on ALL eligible current-era
 * evidence through one frozen cutoff. The holdout existed to certify the
 * procedure — it is not permanently withheld from the artifact that ships.
 *
 * The output is a committed JSON file. That is the repository-native immutable
 * seam (same shape as supabase/schema/model_snapshots.columns.json): versioned
 * by git, reviewable as a diff, and impossible to mutate at runtime.
 *
 *   SUPABASE_URL=... SUPABASE_SERVICE_KEY=... node scripts/build-current-era-artifact.js
 */
require('dotenv').config({ quiet: true });
const fs = require('fs');
const path = require('path');
const crypto = require('crypto');
const { createClient } = require('@supabase/supabase-js');
const cal = require('../src/services/model/calibration');
const src = require('../src/services/model/currentEraSource');
const fitPolicy = require('../src/services/model/fitPolicy');
const { MODEL_VERSION } = require('../src/config/modelVersion');

const SPORT = 'mlb';
const STAT = 'hits';
const SUPPORT = [[0.50, 0.80]];
const MIN_FIT = 200;
const digest = (o) => crypto.createHash('sha256').update(JSON.stringify(o)).digest('hex').slice(0, 16);

/** The served function over certified support at p_win's own 3dp granularity. */
function servedCurve(map, bands) {
  const steps = []; let prev = null;
  for (const [lo, hi] of bands) {
    prev = null;
    for (let x = lo; x < hi - 1e-9; x += 0.001) {
      const raw = Math.round(x * 1000) / 1000;
      const v = cal.applyIsotonic(map, raw);
      if (v === null) continue;
      const rounded = Math.round(v * 1e6) / 1e6;
      if (rounded !== prev) { steps.push([raw, rounded]); prev = rounded; }
    }
  }
  return steps;
}

(async () => {
  const sb = createClient(process.env.SUPABASE_URL, process.env.SUPABASE_SERVICE_KEY,
    { auth: { persistSession: false } });
  const fitAsOf = process.env.FIT_AS_OF || new Date().toISOString().slice(0, 10);

  const rows = await src.loadRows(sb, { sport: SPORT, stat: STAT, modelVersion: MODEL_VERSION, before: fitAsOf });
  if (rows.length < MIN_FIT) throw new Error(`insufficient current-era rows: ${rows.length}`);
  const audit = src.eraAudit(rows, MODEL_VERSION);
  if (audit.wrong_era_rows !== 0) throw new Error(`wrong-era rows in source: ${audit.wrong_era_rows}`);

  rows.sort((a, b) => (a.date < b.date ? -1 : a.date > b.date ? 1 : (a.id < b.id ? -1 : 1)));
  const trainingCutoff = rows[rows.length - 1].date;   // NEWEST OBSERVATION ADMITTED
  const map = cal.fitIsotonic(rows, { minTotal: MIN_FIT });
  if (!map) throw new Error('fitter refused');
  const curve = servedCurve(map, SUPPORT);
  const sourceDigest = src.sourceDigest(rows);

  const artifact = {
    artifact_id: `mlb-hits-isotonic@${fitAsOf}`,
    procedure_version: fitPolicy.POLICY_V1.policy_version,
    sport: SPORT,
    stat: STAT,
    model_version: MODEL_VERSION,
    // TWO DIFFERENT FIELDS. `fit_as_of` is the eligibility bound the query used;
    // `training_cutoff` is the newest observation actually admitted. Substituting
    // one for the other would claim evidence the fit never saw.
    fit_as_of: fitAsOf,
    training_cutoff: trainingCutoff,
    fit_n: rows.length,
    withheld_from_fit: 0,          // policy B: the promoted artifact is not starved
    source_digest: sourceDigest,
    algorithm: fitPolicy.POLICY_V1.fit_algorithm,
    algorithm_version: fitPolicy.POLICY_V1.fit_algorithm_version,
    knot_count: map.length,
    knot_digest: digest(map),
    served_curve: curve,
    served_curve_digest: digest(curve),
    certified_bands: SUPPORT,
    era_audit: audit,
    // Explicit, and NOT live. Promotion to live is a separate deliberate act.
    approved_for_shadow: true,
    approved_for_live: false,
  };

  const check = fitPolicy.validate(
    { ...artifact, estimator_type: 'isotonic' },
    { era_counts: audit.era_counts },
  );
  artifact.fit_policy_valid = check.valid;
  artifact.fit_policy_violations = check.violations;
  artifact.servable = check.servable;
  if (!check.valid) throw new Error(`artifact fails its own policy: ${check.violations.join(', ')}`);

  const out = path.join(__dirname, '..', 'src', 'services', 'model', 'artifacts',
    `${artifact.artifact_id.replace(/[@:]/g, '_')}.json`);
  fs.writeFileSync(out, `${JSON.stringify(artifact, null, 2)}\n`);
  console.log(JSON.stringify({ wrote: path.relative(path.join(__dirname, '..'), out),
    artifact_id: artifact.artifact_id, fit_as_of: artifact.fit_as_of,
    training_cutoff: artifact.training_cutoff, fit_n: artifact.fit_n,
    withheld_from_fit: artifact.withheld_from_fit, era_audit: audit,
    knot_count: artifact.knot_count, knot_digest: artifact.knot_digest,
    served_curve_digest: artifact.served_curve_digest,
    source_digest: artifact.source_digest, curve_steps: curve.length,
    servable: artifact.servable, bytes: JSON.stringify(artifact).length }, null, 1));
  process.exit(0);
})().catch((e) => { console.error(e.message); process.exit(1); });