package com.example;

import org.junit.jupiter.api.Test;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.converter.Converter;
import org.springframework.core.convert.support.GenericConversionService;
import org.springframework.core.convert.support.StringToCollectionConverter;

import java.util.List;
import java.util.Map;

import static org.assertj.core.api.Assertions.assertThat;

class GenericConversionServiceTests {

	private final GenericConversionService conversionService = new GenericConversionService();

	@Test
	@SuppressWarnings("unchecked")
	void stringToListOfString() {
		conversionService.addConverter(new StringToCollectionConverter(conversionService));
		conversionService.addConverter(new StringToListOfMapConverter());

		List<String> result = (List<String>) conversionService.convert("foo,bar",
				TypeDescriptor.valueOf(String.class),
				TypeDescriptor.collection(List.class, TypeDescriptor.valueOf(String.class))
		);

		assertThat(result.get(0)).isEqualTo("foo");
	}

	private static class StringToListOfMapConverter implements Converter<String, List<? extends Map<String, ?>>> {

		@Override
		public List<? extends Map<String, ?>> convert(String source) {
			return List.of(Map.of("bar", source));
		}
	}

	// Using this version of the converter also results in a failure
	private static class StringToListOfMapConverterWithoutWildcard implements Converter<String, List<Map<String, ?>>> {

		@Override
		public List<Map<String, ?>> convert(String source) {
			return List.of(Map.of("bar", source));
		}
	}
}