const DEFAULT_MAX_LENGTH = 15;
const MIN_MAX_LENGTH = 2;
const ELLIPSIS = "…";

/**
 * Maximum total length (including the leading dot) of a trailing token that
 * we are willing to treat as a file extension. 10 covers every real-world
 * extension this package routes to a recognisable icon (`.numbers`, `.fodt`,
 * `.docx`, `.xlsx`, etc.) while rejecting accidental long suffixes from
 * URL-shaped filenames. Chained pseudo-extensions like `.tar.gz` collapse
 * to the trailing portion (`.gz`), which is the common-sense user
 * expectation.
 */
const MAX_EXTENSION_LENGTH = 10;

/**
 * Truncate a filename so it fits a single line in the small file-type tile.
 *
 * Why this exists: on Android, RN's `Text` with `numberOfLines={1}` does not
 * always enforce single-line layout for URL-shaped strings with no
 * whitespace (e.g. `vertopal.com/converter`). They wrap to a second line
 * which then bleeds outside the rounded tile border. Pre-truncating in JS
 * guarantees the rendered string is short enough that single-line wrapping
 * is never required.
 *
 * The truncation preserves the trailing file extension when one is
 * detectable so the file type stays visible at a glance (examples below
 * use the default 15-character budget):
 *   `vertopal.com/converter`        → `vertopal.com/c…`
 *   `file-sample_2_dx.docx`         → `file-samp….docx`
 *   `quarterly-budget.numbers`      → `quarte….numbers`
 *   `report.pdf`                    → `report.pdf` (unchanged)
 *   `embedded\nname.txt`            → caller should pass through
 *                                     `sanitizeFileName` first
 *
 * `maxLength` is clamped to a sensible minimum of 2 so a caller passing
 * `0` or a negative value cannot violate the single-line guarantee.
 */
// eslint-disable-next-line max-statements
export function truncateFileNameForLine(
  name?: string,
  maxLength = DEFAULT_MAX_LENGTH,
): string {
  if (!name) return "";

  const budget = Math.max(MIN_MAX_LENGTH, Math.floor(maxLength));
  if (name.length <= budget) return name;

  const lastDot = name.lastIndexOf(".");
  const extensionLength = name.length - lastDot;
  const hasExtension =
    lastDot > 0 &&
    lastDot < name.length - 1 &&
    extensionLength <= MAX_EXTENSION_LENGTH;

  if (!hasExtension) {
    return name.slice(0, budget - 1) + ELLIPSIS;
  }

  const extension = name.slice(lastDot);
  const stemBudget = budget - extension.length - 1;

  if (stemBudget <= 0) {
    return name.slice(0, budget - 1) + ELLIPSIS;
  }

  return name.slice(0, stemBudget) + ELLIPSIS + extension;
}