using System.Text.RegularExpressions;

namespace BigRegister.Domain.Submissions;

/// <summary>
/// SERVER-OWNED submit rules (ported from the frontend submit-*.ts commands, where
/// they were hardcoded). Each method returns a rejection reason, or null when the
/// submission is accepted. The reference is generated server-side on acceptance.
/// </summary>
public static class SubmissionRules
{
  // RULE: an application reporting zero worked hours is rejected.
  public static string? RejectZeroUren(int uren) =>
      uren == 0 ? "Aanvraag afgewezen: geen gewerkte uren geregistreerd." : null;

  private static readonly Regex PhonePattern =
      new(@"^0\d{9}$", RegexOptions.Compiled);
  private static readonly Regex StrippedChars =
      new(@"[\s\-()]", RegexOptions.Compiled);
  private static readonly Regex LeadingCountryCode =
      new(@"^\+31", RegexOptions.Compiled);

  // RULE: a contact change needs a well-formed Dutch phone number (10 digits, leading
  // 0, formatting stripped). The BRP address is authoritative and cannot be changed
  // here (WP-34), so only the phone is submitted. The server re-validates format
  // authoritatively (the FE check is UX-only) — and must strip the SAME formatting the
  // FE's parseTelefoonnummer does (whitespace/dashes/parens, a leading +31 → 0; WP-75),
  // or the two sides disagree on what's a valid number.
  public static string? RejectPhoneChange(string telefoon)
  {
    var stripped = StrippedChars.Replace((telefoon ?? "").Trim(), "");
    var digits = LeadingCountryCode.Replace(stripped, "0");
    if (!PhonePattern.IsMatch(digits)) return "Voer een geldig telefoonnummer in, bijv. 0612345678.";
    return null;
  }

  public static string NewReference() =>
      // ponytail: random reference is fine for a demo; a real system reserves it transactionally.
      "BIG-2026-" + Random.Shared.Next(100_000, 1_000_000);
}