import 'package:flutter/services.dart';
import 'package:intl/intl.dart';

class DateFormatter {
  DateFormatter._();

  /// Application-wide display format: DD/MM/YYYY
  static const displayDatePattern = 'dd/MM/yyyy';
  static const displayDateTimePattern = 'dd/MM/yyyy, hh:mm a';

  static final _dateFormat = DateFormat(displayDatePattern);
  static final _dateTimeFormat = DateFormat(displayDateTimePattern);
  static final _apiDateFormat = DateFormat('yyyy-MM-dd');

  static String displayDate(DateTime? date) {
    if (date == null) return '-';
    return _dateFormat.format(date.toLocal());
  }

  static String displayDateTime(DateTime? date) {
    if (date == null) return '-';
    return _dateTimeFormat.format(date.toLocal());
  }

  static String toApiDate(DateTime date) => _apiDateFormat.format(date);

  static DateTime? parseApiDate(String? value) {
    if (value == null || value.isEmpty) return null;
    return DateTime.tryParse(value);
  }

  static String formatUserLastLogin(DateTime? value) {
    if (value == null) return '—';
    final local = value.toLocal();
    final now = DateTime.now();
    final today = DateTime(now.year, now.month, now.day);
    final date = DateTime(local.year, local.month, local.day);
    final dayDiff = today.difference(date).inDays;
    final time = DateFormat('hh:mm a').format(local);

    if (dayDiff == 0) return 'Today $time';
    if (dayDiff == 1) return 'Yesterday';
    if (dayDiff < 7) return '$dayDiff days ago';
    return displayDateTime(local);
  }

  /// Multiple date formats for client-side column search.
  static String searchableDate(DateTime? date) {
    if (date == null) return '';
    final local = date.toLocal();
    return [
      displayDate(local),
      displayDateTime(local),
      formatUserLastLogin(local),
      DateFormat('yyyy-MM-dd').format(local),
      DateFormat('dd-MM-yyyy').format(local),
      DateFormat('dd/MM/yy').format(local),
      DateFormat('d/M/yyyy').format(local),
      DateFormat('d/MM/yyyy').format(local),
    ].join(' ');
  }
}

class CurrencyFormatter {
  CurrencyFormatter._();

  static const locale = 'en_IN';

  static final _formatter = NumberFormat.currency(
    locale: locale,
    symbol: '₹',
    decimalDigits: 2,
  );

  static String format(double? amount) {
    if (amount == null) return '-';
    return _formatter.format(amount);
  }

  /// Grouped amount for text fields (no currency symbol), e.g. `1,23,456.5`.
  static String formatEditable(num? amount, {int maxDecimals = 2}) {
    if (amount == null) return '';
    final value = amount.toDouble();
    if (value % 1 == 0) {
      return NumberFormat('#,##,##0', locale).format(value);
    }
    return NumberFormat(
      '#,##,##0.${'#' * maxDecimals}',
      locale,
    ).format(value);
  }

  /// Removes grouping commas so values can be parsed / sent to the API.
  static String stripGrouping(String value) => value.replaceAll(',', '').trim();

  static double? tryParse(String? value) {
    if (value == null) return null;
    final cleaned = stripGrouping(value);
    if (cleaned.isEmpty || cleaned == '.' || cleaned == '-') return null;
    return double.tryParse(cleaned);
  }

  /// Formatted + raw numeric text for client-side column search.
  static String searchable(double? amount) {
    if (amount == null) return '';
    return '${format(amount)} $amount';
  }

  /// Input formatters for cost / amount fields (Indian comma grouping).
  static List<TextInputFormatter> get amountInput => const [
        AmountThousandsSeparatorFormatter(),
      ];
}

/// Formats numeric input with Indian-style thousand separators while typing.
///
/// Example: `1234567.5` → `12,34,567.5`
class AmountThousandsSeparatorFormatter extends TextInputFormatter {
  const AmountThousandsSeparatorFormatter({this.maxDecimals = 2});

  final int maxDecimals;

  @override
  TextEditingValue formatEditUpdate(
    TextEditingValue oldValue,
    TextEditingValue newValue,
  ) {
    final raw = newValue.text;
    if (raw.isEmpty) {
      return newValue;
    }

    // Keep only digits and a single decimal point.
    final buffer = StringBuffer();
    var seenDot = false;
    var decimals = 0;
    for (final rune in raw.runes) {
      final ch = String.fromCharCode(rune);
      if (ch == ',') continue;
      if (ch == '.') {
        if (seenDot) continue;
        seenDot = true;
        buffer.write(ch);
        continue;
      }
      if (ch.compareTo('0') >= 0 && ch.compareTo('9') <= 0) {
        if (seenDot) {
          if (decimals >= maxDecimals) continue;
          decimals++;
        }
        buffer.write(ch);
      }
    }

    final cleaned = buffer.toString();
    if (cleaned.isEmpty) {
      return const TextEditingValue(
        text: '',
        selection: TextSelection.collapsed(offset: 0),
      );
    }

    final parts = cleaned.split('.');
    final intPart = parts[0];
    final hasDot = cleaned.contains('.');
    final fracPart = parts.length > 1 ? parts[1] : '';

    final formattedInt = intPart.isEmpty
        ? ''
        : NumberFormat('#,##,##0', CurrencyFormatter.locale)
            .format(int.parse(intPart));

    final formatted = hasDot ? '$formattedInt.$fracPart' : formattedInt;

    // Place caret at end; stable enough for amount entry.
    return TextEditingValue(
      text: formatted,
      selection: TextSelection.collapsed(offset: formatted.length),
    );
  }
}

/// Converts `snake_case` / `kebab-case` keys into readable Title Case labels.
String humanizeLabel(String key) {
  final cleaned = key.trim().replaceAll(RegExp(r'[_\-.]+'), ' ');
  if (cleaned.isEmpty) return key;

  const acronyms = {
    'id': 'ID',
    'amc': 'AMC',
    'gst': 'GST',
    'hsn': 'HSN',
    'uom': 'UOM',
    'po': 'PO',
    'grn': 'GRN',
    'url': 'URL',
    'api': 'API',
  };

  return cleaned
      .split(RegExp(r'\s+'))
      .where((part) => part.isNotEmpty)
      .map((part) {
        final lower = part.toLowerCase();
        if (acronyms.containsKey(lower)) return acronyms[lower]!;
        return '${lower[0].toUpperCase()}${lower.substring(1)}';
      })
      .join(' ');
}

/// Subject used in dropdown hints (`Select …` / `Search …`).
/// Strips required asterisks and title-cases each word.
String dropdownHintLabel(String label) {
  final cleaned =
      label.replaceAll('*', '').trim().replaceAll(RegExp(r'\s+'), ' ');
  if (cleaned.isEmpty) return label.trim();

  return cleaned.split(' ').map((word) {
    if (word.isEmpty) return word;
    // Keep short all-caps tokens (GST, UOM, PO…).
    if (word.length <= 4 && word == word.toUpperCase()) return word;
    final lower = word.toLowerCase();
    return '${lower[0].toUpperCase()}${lower.substring(1)}';
  }).join(' ');
}