// Pure queue logic for the Queued Pastes tool. Kept free of DOM and
// clipboard APIs so it can be unit tested under Node (see queue.test.mjs).

// Returns the range of the first line, excluding its trailing newline.
export function firstLineRange(text) {
  const newline = text.indexOf('\n');
  return { start: 0, end: newline === -1 ? text.length : newline };
}

// Returns the first line of text, without its trailing newline.
export function currentLine(text) {
  const { start, end } = firstLineRange(text);
  return text.slice(start, end);
}

// Returns the text with the first line (and its trailing newline) removed.
export function advance(text) {
  const newline = text.indexOf('\n');
  return newline === -1 ? '' : text.slice(newline + 1);
}

// Returns the text to copy for the first line, honoring the
// include-new-line setting.
export function copyText(text, includeNewline) {
  const line = currentLine(text);
  return includeNewline ? line + '\n' : line;
}

// Returns the clipboard contents adjusted for a toggled include-new-line
// setting, or null if the clipboard does not currently hold the given line
// (in which case it must be left untouched).
export function adjustCopiedLine(clipboardText, line, includeNewline) {
  const stripped = clipboardText.endsWith('\n') ? clipboardText.slice(0, -1) : clipboardText;
  if (stripped !== line) {
    return null;
  }
  return includeNewline ? line + '\n' : line;
}

// Removes trailing whitespace (spaces, tabs, newlines) from the end of the
// text, so enabling the queue does not leave phantom trailing lines.
export function trimTrailing(text) {
  return text.replace(/\s+$/, '');
}