import { test } from "node:test";
import assert from "node:assert/strict";
import { computeLineHash } from "./hash.ts";

const ALLOWED = new Set("0123456789ABCDEFGHJKMNPQRSTVWXYZ");

test("computeLineHash is stable and uses the configured base32 length", () => {
  const a = computeLineHash(3, "code", 4);
  const b = computeLineHash(3, "code", 4);
  assert.equal(a, b);
  assert.equal(a.length, 4);
  for (const ch of a) assert.ok(ALLOWED.has(ch), `bad char ${ch}`);
  for (let i = 0; i < 2000; i++) {
    const hash = computeLineHash(i + 1, `line ${i}`, 4);
    for (const ch of hash) assert.ok(ALLOWED.has(ch), `bad char ${ch} in ${hash}`);
  }
  for (let i = 1; i <= 20; i++) {
    assert.equal(computeLineHash(i, `content ${i}`, 8).length, 8);
  }
});

test("different line number → different hash (even for identical content)", () => {
  assert.notEqual(computeLineHash(2, "", 4), computeLineHash(5, "", 4));
  assert.notEqual(computeLineHash(1, "}", 4), computeLineHash(2, "}", 4));
});

test("different content → different hash", () => {
  assert.notEqual(computeLineHash(1, "a", 4), computeLineHash(1, "b", 4));
});

test("truncated checksums can collide", () => {
  assert.equal(computeLineHash(1, "const value = 558;", 4), "TM02");
  assert.equal(computeLineHash(1, "const value = 9344;", 4), "TM02");
});

test("computeLineHash produces output identical to hashing full interpolated string", () => {
  function referenceHash(line: number, content: string, len: number): string {
    let h = 0x811c9dc5;
    const str = `${line}\n${content}`;
    for (let i = 0; i < str.length; i++) {
      h ^= str.charCodeAt(i);
      h = Math.imul(h, 0x01000193);
    }
    let s = "";
    const BASE32 = "0123456789ABCDEFGHJKMNPQRSTVWXYZ";
    let n = h >>> 0;
    for (let i = 0; i < len; i++) {
      s = BASE32[n & 31] + s;
      n = n >>> 5;
    }
    return s;
  }
  for (const line of [1, 9, 10, 99, 100, 999, 10000]) {
    for (const content of [
      "",
      "a",
      "function test() {}",
      "long line with symbols !@#$%^&*()_+-=[]{}|;:,.<>?/`~",
    ]) {
      assert.equal(computeLineHash(line, content, 4), referenceHash(line, content, 4));
      assert.equal(computeLineHash(line, content, 6), referenceHash(line, content, 6));
    }
  }
});