import 'Thresholds.dart';

/// Field-level validation. Returns null when valid, so it drops straight into
/// a TextFormField validator.
class Validators {
  static String? required(String? value, String field) {
    if (value == null || value.trim().isEmpty) {
      return "$field is required.";
    }
    return null;
  }

  static String? title(String? value) {
    final String? empty = required(value, "Title");
    if (empty != null) {
      return empty;
    }
    if (value!.trim().length < 3) {
      return "Give it a name you will recognise later.";
    }
    return null;
  }

  /// The excuse gate. Free text only, minimum length, no template buttons —
  /// the friction is the point.
  static String? excuse(String? value) {
    if (value == null || value.trim().isEmpty) {
      return "An excuse is required to defer.";
    }
    if (value.trim().length < Thresholds.minExcuseLength) {
      return "Write at least ${Thresholds.minExcuseLength} characters.";
    }
    return null;
  }

  static String? estimateMinutes(String? value) {
    final String? empty = required(value, "Estimate");
    if (empty != null) {
      return empty;
    }
    final int? minutes = int.tryParse(value!.trim());
    if (minutes == null || minutes <= 0) {
      return "Enter the minutes you think it will take.";
    }
    if (minutes > 720) {
      return "Nothing on a daily plan takes more than 12 hours. Split it.";
    }
    return null;
  }

  /// A window, not a date. The end must actually close after the start.
  static String? window(DateTime? start, DateTime? end) {
    if (start == null || end == null) {
      return "Set a due window, not just a day.";
    }
    if (!end.isAfter(start)) {
      return "The window has to close after it opens.";
    }
    return null;
  }

  static String? username(String? value) {
    final String? empty = required(value, "Username");
    if (empty != null) {
      return empty;
    }
    return null;
  }

  static String? password(String? value) {
    final String? empty = required(value, "Password");
    if (empty != null) {
      return empty;
    }
    if (value!.length < 8) {
      return "Passwords are at least 8 characters.";
    }
    return null;
  }
}