import { mkdir, readFile, writeFile } from "node:fs/promises";

import {
  evaluateFieldBudget,
  percentile75,
} from "../src/application/policies/performance-budgets.js";
import { validateFieldEvidenceInput } from "./lib/field-vitals-evidence.mjs";

const inputPath =
  process.env.FIELD_WEB_VITALS_INPUT ||
  "config/performance/field-input.example.json";
const rawInput = JSON.parse(await readFile(inputPath, "utf8"));
const now = new Date();
const validation = validateFieldEvidenceInput(
  rawInput,
  process.env.MIN_ELIGIBLE_SAMPLES,
  now,
);
const input = validation.data;
const configured =
  /** @type {{
   *   p75LcpMs: number,
   *   p75Cls: number,
   *   p75InpMs: number,
   *   minimumEligibleSamples: number | null
   * }} */ (
    JSON.parse(await readFile("config/performance/budgets.json", "utf8")).field
  );
const minimumEligibleSamples = validation.minimumEligibleSamples;
const fallbackEnd = now;
const fallbackStart = new Date(fallbackEnd);
fallbackStart.setUTCDate(fallbackStart.getUTCDate() - 28);
const start = input ? new Date(input.window.start) : fallbackStart;
const end = input ? new Date(input.window.end) : fallbackEnd;
const eligible = (input?.samples ?? []).filter((sample) => {
  const timestamp = new Date(sample.timestamp);
  return (
    sample.consent === true &&
    sample.releaseId === input?.releaseId &&
    timestamp >= start &&
    timestamp <= end
  );
});
const metrics = {
  p75LcpMs: percentile75(eligible.map((sample) => sample.lcpMs)),
  p75Cls: percentile75(eligible.map((sample) => sample.cls)),
  p75InpMs: percentile75(eligible.map((sample) => sample.inpMs)),
};
const thresholds = { ...configured, minimumEligibleSamples };
const result = evaluateFieldBudget(
  { metrics, eligibleSamples: eligible.length },
  thresholds,
);
const passed = validation.passed && result.passed;
const status = validation.passed ? result.status : "FAIL_UNVERIFIED";
const routeSamples = Object.fromEntries(
  Object.entries(
    eligible.reduce(
      (counts, sample) => {
        counts[sample.routeId] = (counts[sample.routeId] ?? 0) + 1;
        return counts;
      },
      /** @type {Record<string, number>} */ ({}),
    ),
  ).sort(([left], [right]) => left.localeCompare(right)),
);
const report = {
  schemaVersion: 1,
  generatedAt: now.toISOString(),
  window: { days: 28, start: start.toISOString(), end: end.toISOString() },
  context: {
    source: inputPath,
    sourceSystem: input?.source.system ?? null,
    exportId: input?.source.exportId ?? null,
    network: "production-real-user",
    routeAggregation: "route-id-only",
    releaseId: input?.releaseId ?? null,
    privacyApprovalRef: input?.privacy.approvalRef ?? null,
    thresholdDecisionRef: input?.thresholdDecision.evidenceRef ?? null,
    validationFailures: validation.failures,
  },
  metrics,
  thresholds,
  eligibility: {
    consentRequired: true,
    totalSamples: input?.samples.length ?? 0,
    eligibleSamples: eligible.length,
    minimumEligibleSamples,
    routeSamples,
  },
  status,
  passed,
};

await mkdir("artifacts/performance", { recursive: true });
await writeFile(
  "artifacts/performance/field-web-vitals.json",
  `${JSON.stringify(report, null, 2)}\n`,
);
if (!passed) {
  process.stderr.write(
    `Field Web Vitals: ${status} (approved threshold decision and valid 28-day production evidence are required)\n`,
  );
  process.exit(1);
}
process.stdout.write("Field Web Vitals: PASS\n");