#!/usr/bin/env node
/*
 * distance.test.mjs — hand-computed Damerau-Levenshtein (OSA) vectors (SRCH-02).
 * ---------------------------------------------------------------------------
 * RED phase (plan 04-01): every case fails while ../src/distance.ts does not
 * exist — the import happens lazily inside each case, so D1–D9 report one
 * FAIL per vector instead of a lost suite load.
 *
 * The row-rotation in a 3-band OSA is easy to get wrong — these vectors are
 * written FIRST and made to pass second (the repo RED->GREEN convention).
 *
 * Run:  npm run search:test     (exit 0 = all green)
 */
import { strict as assert } from "node:assert";
import { test } from "./harness.mjs";

// Lazy distance load — missing module => per-case ERR_MODULE_NOT_FOUND (the RED state).
let distancePromise = null;
function loadDamerau() {
  if (!distancePromise) {
    distancePromise = import("../src/distance.ts").then((m) => m.damerau);
  }
  return distancePromise;
}

test("D1 adjacent transposition — damerau('ab','ba') === 1", async () => {
  const damerau = await loadDamerau();
  assert.equal(damerau("ab", "ba"), 1, "a swap of adjacent chars is ONE edit in OSA");
});

test("D2 two transpositions — damerau('a cat','an act') === 2", async () => {
  const damerau = await loadDamerau();
  assert.equal(damerau("a cat", "an act"), 2, "insert n, then transpose 'ca' -> 'ac'");
});

test("D3 empty/empty — damerau('','') === 0", async () => {
  const damerau = await loadDamerau();
  assert.equal(damerau("", ""), 0);
});

test("D4 empty target — damerau('','abc') === 3", async () => {
  const damerau = await loadDamerau();
  assert.equal(damerau("", "abc"), 3, "three insertions");
});

test("D5 empty source — damerau('abc','') === 3", async () => {
  const damerau = await loadDamerau();
  assert.equal(damerau("abc", ""), 3, "three deletions");
});

test("D6 identity — damerau('same','same') === 0", async () => {
  const damerau = await loadDamerau();
  assert.equal(damerau("same", "same"), 0);
});

test("D7 corpus typo transposition — damerau('klcc','kclc') === 1", async () => {
  const damerau = await loadDamerau();
  assert.equal(damerau("klcc", "kclc"), 1, "KCLC must reach KLCC as ONE edit (D-13 typo bucket)");
});

test("D8 corpus typo transposition — damerau('sunway','sunwya') === 1", async () => {
  const damerau = await loadDamerau();
  assert.equal(damerau("sunway", "sunwya"), 1, "SUNWYA must reach SUNWAY as ONE edit");
});

test("D9 classic Levenshtein sanity — damerau('kitten','sitting') === 3", async () => {
  const damerau = await loadDamerau();
  assert.equal(damerau("kitten", "sitting"), 3, "sub k->s, sub e->i, append g");
});