import 'dart:ui';

import 'package:font_awesome_flutter/font_awesome_flutter.dart';
import 'package:dropdown_search/dropdown_search.dart';

import 'package:inventree/api.dart';
import 'package:inventree/app_colors.dart';
import 'package:inventree/inventree/part.dart';
import 'package:inventree/inventree/stock.dart';
import 'package:inventree/widget/dialogs.dart';
import 'package:inventree/widget/fields.dart';
import 'package:inventree/l10.dart';

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:inventree/widget/snacks.dart';



/*
 * Class that represents a single "form field",
 * defined by the InvenTree API
 */
class APIFormField {

  // Constructor
  APIFormField(this.name, this.data);

  // Name of this field
  final String name;

  // JSON data which defines the field
  final dynamic data;

  dynamic initial_data;

  // Get the "api_url" associated with a related field
  String get api_url => data["api_url"] ?? "";

  // Get the "model" associated with a related field
  String get model => data["model"] ?? "";

  // Is this field hidden?
  bool get hidden => (data['hidden'] ?? false) as bool;

  // Is this field read only?
  bool get readOnly => (data['read_only'] ?? false) as bool;

  bool get multiline => (data['multiline'] ?? false) as bool;

  // Get the "value" as a string (look for "default" if not available)
  dynamic get value => (data['value'] ?? data['default']);

  // Get the "default" as a string
  dynamic get defaultValue => data['default'];

  Map<String, String> get filters {

    Map<String, String> _filters = {};

    // Start with the provided "model" filters
    if (data.containsKey("filters")) {

      dynamic f = data["filters"];

      if (f is Map) {
        f.forEach((key, value) {
          _filters[key] = value.toString();
        });
      }
    }

    // Now, look at the provided "instance_filters"
    if (data.containsKey("instance_filters")) {

      dynamic f = data["instance_filters"];

      if (f is Map) {
        f.forEach((key, value) {
          _filters[key] = value.toString();
        });
      }
    }

    return _filters;

  }

  bool hasErrors() => errorMessages().length > 0;

  // Return the error message associated with this field
  List<String> errorMessages() {
    List<dynamic> errors = data['errors'] ?? [];

    List<String> messages = [];

    for (dynamic error in errors) {
      messages.add(error.toString());
    }

    return messages;
  }

  // Is this field required?
  bool get required => (data['required'] ?? false) as bool;

  String get type => (data['type'] ?? '').toString();

  String get label => (data['label'] ?? '').toString();

  String get helpText => (data['help_text'] ?? '').toString();

  String get placeholderText => (data['placeholder'] ?? '').toString();

  List<dynamic> get choices => data["choices"] ?? [];

  Future<void> loadInitialData() async {

    // Only for "related fields"
    if (type != "related field") {
      return;
    }

    // Null value? No point!
    if (value == null) {
      return;
    }

    int? pk = int.tryParse(value.toString());

    if (pk == null) {
      return;
    }

    String url = api_url + "/" + pk.toString() + "/";

    final APIResponse response = await InvenTreeAPI().get(
      url,
      params: filters,
    );

    if (response.isValid()) {
      initial_data = response.data;
    }
  }

  // Construct a widget for this input
  Widget constructField() {
    switch (type) {
      case "string":
      case "url":
        return _constructString();
      case "boolean":
        return _constructBoolean();
      case "related field":
        return _constructRelatedField();
      case "float":
      case "decimal":
        return _constructFloatField();
      case "choice":
        return _constructChoiceField();
      default:
        return ListTile(
          title: Text(
            "Unsupported field type: '${type}'",
            style: TextStyle(
                color: COLOR_DANGER,
                fontStyle: FontStyle.italic),
          )
        );
    }
  }

  Widget _constructChoiceField() {

    dynamic _initial;

    // Check if the current value is within the allowed values
    for (var opt in choices) {
      if (opt['value'] == value) {
        _initial = opt;
        break;
      }
    }

    return DropdownSearch<dynamic>(
      mode: Mode.BOTTOM_SHEET,
      showSelectedItem: false,
      selectedItem: _initial,
      items: choices,
      label: label,
      hint: helpText,
      onChanged: null,
      autoFocusSearchBox: true,
      showClearButton: !required,
      itemAsString: (dynamic item) {
        return item['display_name'];
      },
      onSaved: (item) {
        if (item == null) {
          data['value'] = null;
        } else {
          data['value'] = item['value'];
        }
      }
    );
  }

  // Construct a floating point numerical input field
  Widget _constructFloatField() {

    return TextFormField(
      decoration: InputDecoration(
        labelText: required ? label + "*" : label,
        labelStyle: _labelStyle(),
        helperText: helpText,
        helperStyle: _helperStyle(),
        hintText: placeholderText,
      ),
      initialValue: (value ?? 0).toString(),
      keyboardType: TextInputType.numberWithOptions(signed: true, decimal: true),
      validator: (value) {

        double? quantity = double.tryParse(value.toString()) ?? null;

        if (quantity == null) {
          return L10().numberInvalid;
        }
      },
      onSaved: (val) {
        data["value"] = val;
      },
    );

  }

  // Construct an input for a related field
  Widget _constructRelatedField() {

    return DropdownSearch<dynamic>(
      mode: Mode.BOTTOM_SHEET,
      showSelectedItem: true,
      selectedItem: initial_data,
      onFind: (String filter) async {

        Map<String, String> _filters = {};

        filters.forEach((key, value) {
          _filters[key] = value;
        });

        _filters["search"] = filter;
        _filters["offset"] = "0";
        _filters["limit"] = "25";

        final APIResponse response = await InvenTreeAPI().get(
          api_url,
          params: _filters
        );

        if (response.isValid()) {

          List<dynamic> results = [];

          for (var result in response.data['results'] ?? []) {
            results.add(result);
          }

          return results;
        } else {
          return [];
        }
      },
      label: label,
      hint: helpText,
      onChanged: null,
      showClearButton: !required,
      itemAsString: (dynamic item) {
        switch (model) {
          case "part":
            return item["full_name"];
          case "partcategory":
          case "stocklocation":
            return item["pathstring"];
          default:
            return "itemAsString not implemented for '${model}'";
        }
      },
      dropdownBuilder: (context, item, itemAsString) {
        return _renderRelatedField(item, true, false);
      },
      popupItemBuilder: (context, item, isSelected) {
        return _renderRelatedField(item, isSelected, true);
      },
      onSaved: (item) {
        if (item != null) {
          data['value'] = item['pk'] ?? null;
        } else {
          data['value'] = null;
        }
      },
      isFilteredOnline: true,
      showSearchBox: true,
      autoFocusSearchBox: true,
      compareFn: (dynamic item, dynamic selectedItem) {
        // Comparison is based on the PK value

        if (item == null || selectedItem == null) {
          return false;
        }

        return item['pk'] == selectedItem['pk'];
      }
    );
  }

  Widget _renderRelatedField(dynamic item, bool selected, bool extended) {
    // Render a "related field" based on the "model" type

    if (item == null) {
      return Text(
        helpText,
        style: TextStyle(
          fontStyle: FontStyle.italic
        ),
      );
    }

    switch (model) {
      case "part":

        var part = InvenTreePart.fromJson(item);

        return ListTile(
          title: Text(
            part.fullname,
              style: TextStyle(fontWeight: selected && extended ? FontWeight.bold : FontWeight.normal)
          ),
          subtitle: extended ? Text(
            part.description,
            style: TextStyle(fontWeight: selected ? FontWeight.bold : FontWeight.normal),
          ) : null,
          leading: extended ? InvenTreeAPI().getImage(part.thumbnail, width: 32, height: 32) : null,
        );

      case "partcategory":

        var cat = InvenTreePartCategory.fromJson(item);

        return ListTile(
          title: Text(
            cat.pathstring,
            style: TextStyle(fontWeight: selected && extended ? FontWeight.bold : FontWeight.normal)
          ),
          subtitle: extended ? Text(
            cat.description,
            style: TextStyle(fontWeight: selected ? FontWeight.bold : FontWeight.normal),
          ) : null,
        );
      case "stocklocation":

        var loc = InvenTreeStockLocation.fromJson(item);

        return ListTile(
          title: Text(
            loc.pathstring,
              style: TextStyle(fontWeight: selected && extended ? FontWeight.bold : FontWeight.normal)
          ),
          subtitle: extended ? Text(
            loc.description,
            style: TextStyle(fontWeight: selected ? FontWeight.bold : FontWeight.normal),
          ) : null,
        );
      default:
        return ListTile(
          title: Text(
            "Unsupported model",
            style: TextStyle(
              fontWeight: FontWeight.bold,
              color: COLOR_DANGER
            )
          ),
          subtitle: Text("Model '${model}' rendering not supported"),
        );
    }

  }

  // Construct a string input element
  Widget _constructString() {

    return TextFormField(
      decoration: InputDecoration(
        labelText: required ? label + "*" : label,
        labelStyle: _labelStyle(),
        helperText: helpText,
        helperStyle: _helperStyle(),
        hintText: placeholderText,
      ),
      maxLines: multiline ? null : 1,
      expands: false,
      initialValue: value ?? '',
      onSaved: (val) {
        data["value"] = val;
      },
      validator: (value) {
        if (required && (value == null || value.isEmpty)) {
          // return L10().valueCannotBeEmpty;
        }
      },
    );
  }

  // Construct a boolean input element
  Widget _constructBoolean() {

    return CheckBoxField(
      label: label,
      labelStyle: _labelStyle(),
      helperText: helpText,
      helperStyle: _helperStyle(),
      initial: value,
      onSaved: (val) {
        data['value'] = val;
      },
    );
  }

  TextStyle _labelStyle() {
    return new TextStyle(
      fontWeight: FontWeight.bold,
      fontSize: 18,
      fontFamily: "arial",
      color: hasErrors() ? COLOR_DANGER : COLOR_GRAY,
      fontStyle: FontStyle.normal,
    );
  }

  TextStyle _helperStyle() {
    return new TextStyle(
      fontStyle: FontStyle.italic,
      color: hasErrors() ? COLOR_DANGER : COLOR_GRAY,
    );
  }

}


/*
 * Extract field options from a returned OPTIONS request
 */
Map<String, dynamic> extractFields(APIResponse response) {

  if (!response.isValid()) {
    return {};
  }

  if (!response.data.containsKey("actions")) {
    return {};
  }

  var actions = response.data["actions"];

  return actions["POST"] ?? actions["PUT"] ?? actions["PATCH"] ?? {};
}

/*
 * Launch an API-driven form,
 * which uses the OPTIONS metadata (at the provided URL)
 * to determine how the form elements should be rendered!
 *
 * @param title is the title text to display on the form
 * @param url is the API URl to make the OPTIONS request to
 * @param fields is a map of fields to display (with optional overrides)
 * @param modelData is the (optional) existing modelData
 * @param method is the HTTP method to use to send the form data to the server (e.g. POST / PATCH)
 */

Future<void> launchApiForm(BuildContext context, String title, String url, Map<String, dynamic> fields, {Map<String, dynamic> modelData = const {}, String method = "PATCH", Function(Map<String, dynamic>)? onSuccess, Function? onCancel}) async {

  var options = await InvenTreeAPI().options(url);

  // Invalid response from server
  if (!options.isValid()) {
    return;
  }

  var availableFields = extractFields(options);

  if (availableFields.isEmpty) {
    // User does not have permission to perform this action
    showSnackIcon(
      L10().response403,
      icon: FontAwesomeIcons.userTimes,
    );

    return;
  }

  // Construct a list of APIFormField objects
  List<APIFormField> formFields = [];

  // Iterate through the provided fields we wish to display
  for (String fieldName in fields.keys) {

    // Check that the field is actually available at the API endpoint
    if (!availableFields.containsKey(fieldName)) {
      print("Field '${fieldName}' not available at '${url}'");
      continue;
    }

    var remoteField = availableFields[fieldName] ?? {};
    var localField = fields[fieldName] ?? {};

    // Override defined field parameters, if provided
    for (String key in localField.keys) {
      // Special consideration must be taken here!
      if (key == "filters") {

        if (!remoteField.containsKey("filters")) {
          remoteField["filters"] = {};
        }

        var filters = localField["filters"];

        if (filters is Map) {
          filters.forEach((key, value) {
            remoteField["filters"][key] = value;
          });
        }

      } else {
        remoteField[key] = localField[key];
      }
    }

    // Update fields with existing model data
    for (String key in modelData.keys) {

      dynamic value = modelData[key];

      if (availableFields.containsKey(key)) {
        availableFields[key]['value'] = value;
      }
    }

    formFields.add(APIFormField(fieldName, remoteField));
  }

  // Grab existing data for each form field
  for (var field in formFields) {
    await field.loadInitialData();
  }

  // Now, launch a new widget!
  Navigator.push(
    context,
    MaterialPageRoute(builder: (context) => APIFormWidget(
        title,
        url,
        formFields,
        method,
        onSuccess: onSuccess,
    ))
  );
}


class APIFormWidget extends StatefulWidget {

  //! Form title to display
  final String title;

  //! API URL
  final String url;

  //! API method
  final String method;

  final List<APIFormField> fields;

  Function(Map<String, dynamic>)? onSuccess;

  APIFormWidget(
      this.title,
      this.url,
      this.fields,
      this.method,
      {
        Key? key,
        this.onSuccess,
      }
  ) : super(key: key);

  @override
  _APIFormWidgetState createState() => _APIFormWidgetState(title, url, fields, method, onSuccess);

}


class _APIFormWidgetState extends State<APIFormWidget> {

  final _formKey = new GlobalKey<FormState>();

  String title;

  String url;

  String method;

  List<APIFormField> fields;

  Function(Map<String, dynamic>)? onSuccess;

  _APIFormWidgetState(this.title, this.url, this.fields, this.method, this.onSuccess) : super();

  List<Widget> _buildForm() {

    List<Widget> widgets = [];

    for (var field in fields) {

      if (field.hidden) {
        continue;
      }

      widgets.add(field.constructField());

      if (field.hasErrors()) {
        for (String error in field.errorMessages()) {
          widgets.add(
            ListTile(
              title: Text(
                error,
                style: TextStyle(
                  color: COLOR_DANGER,
                  fontStyle: FontStyle.italic,
                  fontSize: 16,
                ),
              )
            )
          );
        }
      }

      // Add divider after some widgets
      switch (field.type) {
        case "related field":
        case "choice":
          widgets.add(Divider(height: 10));
          break;
        default:
          break;
      }

    }

    return widgets;
  }

  Future<APIResponse> _submit(Map<String, String> data) async {

    if (method == "POST") {
      return await InvenTreeAPI().post(
        url,
        body: data,
        expectedStatusCode: null
      );
    } else {
      return await InvenTreeAPI().patch(
        url,
        body: data,
        expectedStatusCode: null
      );
    }

  }

  Future<void> _save(BuildContext context) async {

    // Package up the form data
    Map<String, String> data = {};

    for (var field in fields) {

      dynamic value = field.value;

      if (value == null) {
        data[field.name] = "";
      } else {
        data[field.name] = value.toString();
      }
    }

    final response = await _submit(data);

    if (!response.isValid()) {
      showServerError(L10().serverError, L10().responseInvalid);
      return;
    }

    switch (response.statusCode) {
      case 200:
      case 201:
        // Form was successfully validated by the server

        // Hide this form
        Navigator.pop(context);

        // TODO: Display a snackBar

        // Run custom onSuccess function
        var successFunc = onSuccess;

        if (successFunc != null) {

          // Ensure the response is a valid JSON structure
          Map<String, dynamic> json = {};

          if (response.data != null && response.data is Map) {
            for (dynamic key in response.data.keys) {
              json[key.toString()] = response.data[key];
            }
          }

          successFunc(json);
        }
        return;
      case 400:
        // Form submission / validation error
        showSnackIcon(
          L10().error,
          success: false
        );

        // Update field errors
        for (var field in fields) {
          field.data['errors'] = response.data[field.name];
        }
        break;
      // TODO: Other status codes?
    }

    setState(() {
      // Refresh the form
    });

  }

  @override
  Widget build(BuildContext context) {

    return Scaffold(
      appBar: AppBar(
        title: Text(title),
        actions: [
          IconButton(
            icon: FaIcon(FontAwesomeIcons.save),
            onPressed: () {

              if (_formKey.currentState!.validate()) {
                _formKey.currentState!.save();

                _save(context);
              }
            },
          )
        ]
      ),
      body: Form(
        key: _formKey,
        child: SingleChildScrollView(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.start,
            mainAxisSize: MainAxisSize.min,
            crossAxisAlignment: CrossAxisAlignment.start,
            children: _buildForm(),
          ),
          padding: EdgeInsets.all(16),
        )
      )
    );

  }
}