#!/usr/bin/env node
/*
 * distance.test.mjs — OSA Damerau-Levenshtein vector suite (SRCH-02).
 * -------------------------------------------------------------------
 * RED phase (plan 04-01 task 2): every case fails while
 * ../src/distance.ts does not exist (lazy import => per-case FAIL).
 *
 * The vectors are the hand-computed ones the plan pins (RESEARCH
 * §"The Damerau-Levenshtein (OSA) distance"). The 3-band row rotation
 * is the classic implementation trap — these vectors are written FIRST
 * so a wrong rotation shows up as a red suite, not a silent mis-rank.
 *
 *   D1  adjacent transposition          ab       -> ba        = 1
 *   D2  two transpositions              a cat    -> an act    = 2
 *   D3  empty vs empty                                        = 0
 *   D4  empty vs abc                                          = 3
 *   D5  abc vs empty                                          = 3
 *   D6  identical strings                                     = 0
 *   D7  KLCC transposition typo         klcc     -> kclc      = 1
 *   D8  real corpus typo                sunway   -> sunwya    = 1
 *   D9  classic Levenshtein sanity      kitten   -> sitting   = 3
 *
 * 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);
});

test("D2 two transpositions: damerau('a cat', 'an act') === 2", async () => {
  const damerau = await loadDamerau();
  assert.equal(damerau("a cat", "an act"), 2);
});

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

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

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

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

test("D7 KLCC transposition typo: damerau('klcc', 'kclc') === 1", async () => {
  const damerau = await loadDamerau();
  assert.equal(damerau("klcc", "kclc"), 1);
});

test("D8 real corpus typo: damerau('sunway', 'sunwya') === 1", async () => {
  const damerau = await loadDamerau();
  assert.equal(damerau("sunway", "sunwya"), 1);
});

test("D9 classic Levenshtein sanity: damerau('kitten', 'sitting') === 3", async () => {
  const damerau = await loadDamerau();
  assert.equal(damerau("kitten", "sitting"), 3);
});