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

import '../../core/theme/design_tokens.dart';

typedef CodeValueChanged = void Function(String value);

class FixedLengthCodeInput extends StatefulWidget {
  final TextEditingController controller;
  final int length;
  final CodeValueChanged? onChanged;
  final TextInputType keyboardType;
  final Iterable<String>? allowedCharacters;
  final bool uppercase;
  final String semanticLabel;

  const FixedLengthCodeInput({
    required this.controller,
    required this.length,
    required this.semanticLabel,
    super.key,
    this.onChanged,
    this.keyboardType = TextInputType.text,
    this.allowedCharacters,
    this.uppercase = false,
  });

  @override
  State<FixedLengthCodeInput> createState() => _FixedLengthCodeInputState();
}

class _FixedLengthCodeInputState extends State<FixedLengthCodeInput> {
  late final FocusNode _focusNode;
  bool _isFocused = false;

  @override
  void initState() {
    super.initState();
    _focusNode = FocusNode();
    _focusNode.addListener(_onFocusChanged);
    widget.controller.addListener(_onControllerChanged);
  }

  @override
  void didUpdateWidget(covariant FixedLengthCodeInput oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.controller != widget.controller) {
      oldWidget.controller.removeListener(_onControllerChanged);
      widget.controller.addListener(_onControllerChanged);
    }
  }

  @override
  void dispose() {
    widget.controller.removeListener(_onControllerChanged);
    _focusNode.removeListener(_onFocusChanged);
    _focusNode.dispose();
    super.dispose();
  }

  void _onFocusChanged() {
    if (_isFocused != _focusNode.hasFocus) {
      _isFocused = _focusNode.hasFocus;
    }
  }

  void _onControllerChanged() {
    if (mounted) {
      setState(() {});
    }
  }

  void _handleRawChanged(String rawValue) {
    final normalized = _normalize(rawValue);
    if (normalized != widget.controller.text) {
      widget.controller.value = TextEditingValue(
        text: normalized,
        selection: TextSelection.collapsed(offset: normalized.length),
      );
    }
    widget.onChanged?.call(normalized);
  }

  String _normalize(String value) {
    var output = widget.uppercase ? value.toUpperCase() : value;

    if (widget.allowedCharacters != null) {
      final allow = widget.allowedCharacters!.toSet();
      output = output.split('').where(allow.contains).join();
    }

    if (output.length > widget.length) {
      output = output.substring(0, widget.length);
    }
    return output;
  }

  @override
  Widget build(BuildContext context) {
    final chars = widget.controller.text.split('');
    final slotHeight = AppSpacing.xl * 2;
    final slotSpacing = AppSpacing.sm;

    return Semantics(
      label: widget.semanticLabel,
      child: GestureDetector(
        onTap: () => _focusNode.requestFocus(),
        behavior: HitTestBehavior.opaque,
        child: SizedBox(
          height: slotHeight,
          child: Stack(
            alignment: Alignment.center,
            children: [
              Opacity(
                opacity: 0,
                child: SizedBox(
                  width: double.infinity,
                  height: slotHeight,
                  child: TextField(
                    controller: widget.controller,
                    focusNode: _focusNode,
                    keyboardType: widget.keyboardType,
                    inputFormatters: [
                      LengthLimitingTextInputFormatter(widget.length),
                    ],
                    onChanged: _handleRawChanged,
                    autofillHints: const [AutofillHints.oneTimeCode],
                  ),
                ),
              ),
              IgnorePointer(
                child: Row(
                  mainAxisSize: MainAxisSize.max,
                  crossAxisAlignment: CrossAxisAlignment.center,
                  children: [
                    for (var index = 0; index < widget.length; index++) ...[
                      Expanded(
                        child: _buildCodeCell(
                          index: index,
                          chars: chars,
                          slotHeight: slotHeight,
                        ),
                      ),
                      if (index != widget.length - 1)
                        SizedBox(width: slotSpacing),
                    ],
                  ],
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }

  Widget _buildCodeCell({
    required int index,
    required List<String> chars,
    required double slotHeight,
  }) {
    final hasChar = index < chars.length;
    final isActive =
        (chars.length == index && _isFocused) ||
        (chars.length >= widget.length && index == widget.length - 1);

    return Container(
      height: slotHeight,
      alignment: Alignment.center,
      decoration: BoxDecoration(
        color: AppColors.white,
        borderRadius: BorderRadius.circular(AppRadius.sm),
        border: Border.all(
          color: isActive ? AppColors.primary : AppColors.slate300,
        ),
      ),
      child: Text(
        hasChar ? chars[index] : '',
        style: const TextStyle(
          fontSize: AppSpacing.xl,
          fontWeight: FontWeight.w600,
          color: AppColors.slate900,
        ),
      ),
    );
  }
}