import 'dart:convert';

import 'package:fhir/r4.dart';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

void main() {
  runApp(MaterialApp(home: const MyApp()));
}

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {

  TextEditingController controller = TextEditingController();

  String observationId = '';

  Future<Observation?> sendObs(String value) async {

    Observation observation = Observation(
      resourceType: R4ResourceType.Observation,
      status: ObservationStatus.final_,
      code: CodeableConcept(coding: [
        Coding(
          system: FhirUri('www.snomed.org'),
          display: 'Valore',
          code: Code('0000')
        )
      ]),
      subject: Reference(
        reference: "Patient/2936332", //luca rossi
      ),
      valueString: value
      );

    var response = await http.post(Uri.parse('$server/Observation'), headers: headers, body: jsonEncode(observation.toJson()));

    if(response.statusCode == 200 || response.statusCode == 201) {
      return Observation.fromJson(jsonDecode(response.body));
    } else {
      return null;
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Prova FHIR')),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
          
          children: [
            const Text('Valore Observation:'),
            TextField(
              controller: controller,
            ),
            ElevatedButton(onPressed: () async {
              Observation? obs = await sendObs(controller.text);

              setState(() {
                observationId = obs!.id.toString();
              });
            }, child: const Text('Send Observation')),
            Text(observationId),
          ],
        ),
      ),
    );
  }
}

//header chiamata
final Map<String, String> headers = {
  "Content-Type": "application/fhir+json",
};

const server = 'https://hapi.fhir.org/baseR4';