import { test } from "node:test";
import assert from "node:assert/strict";
import {
  createLfTextView,
  normalizeLineEndings,
  splitLines,
  detectLineEnding,
  hasFinalNewline,
} from "./lines.ts";

test("splitLines edge cases", () => {
  assert.deepEqual(splitLines(""), []);
  assert.deepEqual(splitLines("a"), ["a"]);
  assert.deepEqual(splitLines("a\nb"), ["a", "b"]);
  assert.deepEqual(splitLines("a\nb\n"), ["a", "b"]);
  assert.deepEqual(splitLines("a\n\n"), ["a", ""]);
  assert.deepEqual(splitLines("\n"), [""]);
});

test("splitLines strips CRLF \\r", () => {
  assert.deepEqual(splitLines("a\r\nb\r\n"), ["a", "b"]);
  assert.deepEqual(splitLines("a\r\nb"), ["a", "b"]);
});

test("splitLines handles mixed line endings and standalone CR correctly", () => {
  assert.deepEqual(splitLines("a\r\nb\nc\r\n"), ["a", "b", "c"]);
  assert.deepEqual(splitLines("a\rb\r\n"), ["a\rb"]);
  assert.deepEqual(splitLines("a\rb\nc"), ["a\rb", "c"]);
  assert.deepEqual(splitLines("\r\n"), [""]);
  assert.deepEqual(splitLines("\r\n\r\n"), ["", ""]);
  assert.deepEqual(splitLines("a\r\n\r\nb"), ["a", "", "b"]);
  assert.deepEqual(splitLines("a\r\n\r\n"), ["a", ""]);
});

test("hasFinalNewline", () => {
  assert.equal(hasFinalNewline("a\nb"), false);
  assert.equal(hasFinalNewline("a\nb\n"), true);
  assert.equal(hasFinalNewline("a\r\nb"), false);
  assert.equal(hasFinalNewline("a\r\nb\r\n"), true);
  assert.equal(hasFinalNewline("a"), false);
  // no lines, no terminator — rejoining [] yields "" either way
  assert.equal(hasFinalNewline(""), true);
});

test("detectLineEnding", () => {
  assert.equal(detectLineEnding("a\nb\n"), "lf");
  assert.equal(detectLineEnding("a\r\nb\r\n"), "crlf");
  assert.equal(detectLineEnding("a\nb\r\nc\n"), "crlf");
});

test("LF views map every UTF-16 boundary back to original CRLF bytes", () => {
  for (const source of ["", "a\nb", "\uFEFF😀\r\nb\nc\r\n", "\r\n\r\n", "a\rb\r\r\nc"]) {
    const view = createLfTextView(source);
    assert.equal(view.text, normalizeLineEndings(source));
    assert.equal(view.sourceOffset(view.text.length), source.length);
    for (let offset = 0; offset <= view.text.length; offset++) {
      assert.equal(
        normalizeLineEndings(source.slice(0, view.sourceOffset(offset))),
        view.text.slice(0, offset),
      );
    }
  }
});