// dart
import 'package:flutter/material.dart';
import 'package:flutter_markdown_plus_latex/flutter_markdown_plus_latex.dart';
import 'package:flutter_markdown_plus/flutter_markdown_plus.dart';
import 'package:markdown/markdown.dart' as markdown;
import '../formula_models.dart';
import '../formula_evaluator.dart';
import '../corpus.dart';
import '../error_handler.dart';
import 'd4rt_editing_controller.dart';
import 'unit_dropdown.dart';
import 'formula_editor.dart';

class FormulaScreen extends StatefulWidget {
  Formula formula;
  final Corpus corpus;

  FormulaScreen({super.key, required this.formula, required this.corpus});

  @override
  State<FormulaScreen> createState() => _FormulaScreenState();
}


class _FormulaScreenState extends State<FormulaScreen> {
  final _formKey = GlobalKey<FormState>();
  final Map<String, D4rtEditingController> _inputControllers = {};
  final Map<String, String?> _selectedUnits = {};
  final Map<String, String?> _selectedValues = {}; // for string dropdowns
  String? _result;
  String? _selectedOutputUnit;
  bool _isDescriptionExpanded = false; // Track description expansion state
  String? _errorMessage; // Track error message for expansion tile
  bool _isErrorExpanded = false; // Track error expansion state

  @override
  void initState() {
    super.initState();
    // Initialize controllers and units with listeners
    for (final input in widget.formula.input) {
      _selectedUnits[input.name] = input.unit;
      if (input.values != null && input.values!.isNotEmpty) {
        // string/categorical variable -> use dropdown
        _selectedValues[input.name] = input.values!.first;
      } else {
        // numeric variable -> use D4rtEditingController
        _inputControllers[input.name] = D4rtEditingController(isString: input.unit == "string");
        _inputControllers[input.name]!.addListener(_evaluateFormula);
      }
    }
    _selectedOutputUnit = widget.formula.output.unit;
  }

  @override
  void dispose() {
    // Clean up controllers and listeners
    for (final controller in _inputControllers.values) {
      controller.removeListener(_evaluateFormula);
      controller.dispose();
    }
    super.dispose();
  }

  void _evaluateFormula() {
    try {
      final inputValues = <String, dynamic>{};
      for (final input in widget.formula.input) {
        // string/categorical variable
        if (input.values != null && input.values!.isNotEmpty) {
          final selected = _selectedValues[input.name];
          if (selected == null) {
            _result = "";
            return;
          }
          inputValues[input.name] = selected;
          continue;
        }

        // numeric variable - must have controller
        final controller = _inputControllers[input.name]!;
        final val = controller.d4rtValue;
        if (val == null) {
          _result = "";
          return;
        }

        dynamic convertedValue;
        if (val is NumberResult) {
          if (input.unit != null) {
            convertedValue = widget.corpus.convert(
              val.value,
              _selectedUnits[input.name]!,
              input.unit as String,
            );
          } else {
            convertedValue = val.value;
          }
        } else if (val is StringResult) {
          convertedValue = val.value;
        } else {
          throw FormulaEvaluationException(
            "Field ${input.name} has unsupported type ${val.runtimeType}",
          );
        }

        inputValues[input.name] = convertedValue;
      }

      final evaluator = FormulaEvaluator();
      final result = evaluator.evaluate(widget.formula, inputValues);

      // Convert output to selected unit if needed
      String? unit = widget.formula.output.unit;
      if (unit != null && result is Number) {
        final converted = widget.corpus.convert(result, unit, _selectedOutputUnit!);
        if (converted is num) {
          _result = converted.toStringAsFixed(2);
        } else {
          _result = converted.toString();
        }
      } else {
        _result = result?.toString();
      }

      setState(() {
        _errorMessage = null; // Clear error on successful evaluation
      });
    } catch (e, stack) {
      errorHandler.notify(e, stack);
      setState(() {
        _errorMessage = e.toString();
        _isErrorExpanded = true; // Auto-expand on error
        _result = null;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.formula.name),
        actions: [
          IconButton(
            icon: const Icon(Icons.edit),
            onPressed: () {
              Navigator.push(
                context,
                MaterialPageRoute(
                  builder: (context) => FormulaEditor(
                    formula: widget.formula,
                    corpus: widget.corpus,
                    onSave: (updatedFormula) {
                      // Refresh the screen after saving
                      setState(() {
                        // The corpus has been updated, refresh the displayed formula
                        widget.formula = updatedFormula;
                      });
                    },
                  ),
                ),
              );
            },
            tooltip: 'Edit Formula',
          ),
        ],
      ),
      body: Form(
        key: _formKey,
        child: Padding(
          padding: const EdgeInsets.all(16.0),
          child: ListView(
            children: [
              _buildDescriptionSection(),
              _buildErrorSection(),
              _buildInputSection(),
              const SizedBox(height: 24),
              _buildOutputSection(),
            ],
          ),
        ),
      ),
    );
  }

  Widget _buildDescriptionSection() {
    if (widget.formula.description == null ||
        widget.formula.description!.isEmpty) {
      return const SizedBox.shrink();
    }

    return Card(
      margin: const EdgeInsets.only(bottom: 16),
      child: ExpansionTile(
        title: Text(
          'Description',
          style: Theme.of(context).textTheme.titleMedium?.copyWith(
            fontWeight: FontWeight.bold,
          ),
        ),
        initiallyExpanded: _isDescriptionExpanded,
        onExpansionChanged: (bool expanded) {
          setState(() {
            _isDescriptionExpanded = expanded;
          });
        },
        children: [
          Padding(
            padding: const EdgeInsets.all(16.0),
            child: Container(
              padding: const EdgeInsets.all(8),
              decoration: BoxDecoration(
                color: Theme.of(context).colorScheme.surfaceVariant,
                borderRadius: BorderRadius.circular(8),
              ),
              child: Markdown(
                data: widget.formula.description!,
                shrinkWrap: true,
                builders: {
                  'latex': LatexElementBuilder(),
                },
                extensionSet: markdown.ExtensionSet(
                  [LatexBlockSyntax()],
                  [LatexInlineSyntax()],
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildErrorSection() {
    if (_errorMessage == null) {
      return const SizedBox.shrink();
    }

    return Card(
      margin: const EdgeInsets.only(bottom: 16),
      color: Theme.of(context).colorScheme.errorContainer,
      child: ExpansionTile(
        title: Text(
          '⚠️ There were an error. Show details...',
          style: Theme.of(context).textTheme.titleMedium?.copyWith(
            fontWeight: FontWeight.bold,
            color: Theme.of(context).colorScheme.onErrorContainer,
          ),
        ),
        initiallyExpanded: _isErrorExpanded,
        onExpansionChanged: (bool expanded) {
          setState(() {
            _isErrorExpanded = expanded;
          });
        },
        children: [
          Padding(
            padding: const EdgeInsets.all(16.0),
            child: Container(
              padding: const EdgeInsets.all(8),
              decoration: BoxDecoration(
                color: Theme.of(context).colorScheme.surfaceVariant,
                borderRadius: BorderRadius.circular(8),
              ),
              child: SelectableText(
                _errorMessage!,
                style: TextStyle(
                  color: Theme.of(context).colorScheme.onErrorContainer,
                  fontFamily: 'monospace',
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildInputSection() {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Text(
          'Input Variables',
          style: Theme.of(
            context,
          ).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.bold),
        ),
        const SizedBox(height: 8),
        ...widget.formula.input.map((variable) => _buildVariableRow(variable)),
      ],
    );
  }

  Widget _buildOutputSection() {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Text(
          'Result',
          style: Theme.of(
            context,
          ).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.bold),
        ),
        const SizedBox(height: 8),
        Row(
          children: [
            // Fixed width for field name
            SizedBox(
              width: 150,
              child: Text(
                widget.formula.output.name,
                overflow: TextOverflow.ellipsis,
              ),
            ),
            const SizedBox(width: 8), // Add some spacing
            // Flexible space for result field
            Expanded(
              child: TextFormField(
                readOnly: true,
                enabled: false,
                controller: TextEditingController(text: _result),
                decoration: const InputDecoration(
                  border: UnderlineInputBorder(),
                  filled: true,
                ),
              ),
            ),
            const SizedBox(width: 8),
            UnitDropdown(
              corpus: widget.corpus,
              variable: widget.formula.output,
              selectedUnit: _selectedOutputUnit,
              onUnitChanged: (unit) {
                _selectedOutputUnit = unit;
                _evaluateFormula();
                print( "En output unit changed to $unit: $_result");
                setState(() {
                });
              },
            ),
          ],
        ),
      ],
    );
  }

  Widget _buildVariableRow(VariableSpec variable) {
    final isCategorical = variable.values != null && variable.values!.isNotEmpty;

    return Padding(
      padding: const EdgeInsets.symmetric(vertical: 8.0),
      child: Row(
        children: [
          // Fixed width for field name
          SizedBox(
            width: 150,
            child: Text(
              variable.name,
              overflow: TextOverflow.ellipsis,
            ),
          ),
          const SizedBox(width: 8), // Add some spacing
          // Flexible space for input field
          Expanded(
            child: isCategorical 
              ? DropdownButtonFormField<String>(
                  value: _selectedValues[variable.name],
                  items: variable.values!
                      .map((v) => DropdownMenuItem<String>(value: v, child: Text(v)))
                      .toList(),
                  onChanged: (v) {
                    _selectedValues[variable.name] = v;
                    _evaluateFormula();
                    setState(() {
                    });
                  },
                  decoration: const InputDecoration(
                    border: UnderlineInputBorder(),
                  ),
                  validator: (value) {
                    if (value == null || value.isEmpty) return 'Required';
                    return null;
                  },
                )
              : TextFormField(
                  controller: _inputControllers[variable.name],
                  keyboardType: TextInputType.number,
                  inputFormatters: [
                    //FilteringTextInputFormatter.allow(RegExp(r'[0-9\.\-]')),
                  ],
                  decoration: const InputDecoration(
                    border: UnderlineInputBorder(),
                  ),
                  autovalidateMode: AutovalidateMode.always,
                  validator: (value) {
                    if (value == null || value.isEmpty) {
                      return 'Required';
                    }
                    return _inputControllers[variable.name]!.lastError;
                  },
                ),
          ),
          const SizedBox(width: 8),
          if (variable.unit != null)
            UnitDropdown(
              corpus: widget.corpus,
              variable: variable,
              selectedUnit: _selectedUnits[variable.name],
              onUnitChanged: (unit) {
                setState(() {
                  _selectedUnits[variable.name] = unit;
                });
                _evaluateFormula();
              },
            ),
        ],
      ),
    );
  }
}