import { test } from "node:test";
import assert from "node:assert/strict";
import { readFileSync } from "node:fs";

export function loadCorpus(path) {
  return JSON.parse(readFileSync(path, "utf8"));
}

export function defineParityTests({ name = "applier", applier, corpusPath, records, expectedCount }) {
  const applyTags = typeof applier === "function" ? applier : applier && applier.applyTags;
  if (typeof applyTags !== "function") {
    throw new Error("applier must be a function or a module exporting applyTags");
  }
  const list = records ?? loadCorpus(corpusPath);
  if (expectedCount != null) {
    test(`${name}: parity corpus has the full record set`, () => {
      assert.equal(list.length, expectedCount);
    });
  }
  test(`${name}: reconstructs every parity record exactly`, () => {
    assert.ok(list.length > 0, "parity corpus is empty");
    for (const [index, record] of list.entries()) {
      const { text, spans } = applyTags(record.tokens, record.tags);
      assert.equal(text, record.expected_text, `record ${index}: text mismatch`);
      if (record.expected_spans) {
        assert.deepEqual(spans, record.expected_spans, `record ${index}: span mismatch`);
      }
    }
  });
}