import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpHeaders;
import java.net.http.HttpRequest;
import java.net.http.HttpRequest.BodyPublishers;
import java.net.http.HttpRequest.BodyPublishers.Part;
import java.net.http.HttpResponse.BodyHandlers;
import java.nio.file.Path;
import java.util.List;
import java.util.Map;
import java.util.function.BiPredicate;

public class MultipartBodyPublisherTest {

    public static final BiPredicate<String,String> ACCEPT_ALL = (x, y) -> true;
    static final String BOUNDARY = "gc0p4Jq0M2Yt08jU534c0p";

    public static void main(String... args) throws Exception {

        // Alternative #1
        var publisher = BodyPublishers.ofMultipart(
                "the87665boundary",
                new Part(HttpHeaders.of(Map.of("Content-Type", List.of("text/plain; charset=us-ascii")),
                                        ACCEPT_ALL),
                         BodyPublishers.ofString("Hello World!"))
        );

        // Alternative #2
        var publisher2 = BodyPublishers.ofMultipart2(
                "the987654boundary",
                List.of(Map.entry(HttpHeaders.of(Map.of("Content-Type", List.of("text/plain; charset=us-ascii")),
                                                 ACCEPT_ALL),
                                  BodyPublishers.ofString("Hello World!")))
        );

        // Alternative #3
        var publisher3 = BodyPublishers.ofMultipart3(
                "the12345boundary",
                // # part 1  - no explicit headers, implicitly defaults to "text/plain" as per rfc
                BodyPublishers.ofString("Hello There"),

                // # part 2  - some text with an explicit content-type header
                BodyPublishers.multipartPart(
                        HttpHeaders.of(Map.of("Content-Type", List.of("text/plain; charset=us-ascii")),
                                       ACCEPT_ALL),
                        BodyPublishers.ofString("blah blah")),

                // # part 3  - a file
                BodyPublishers.multipartPart(
                        HttpHeaders.of(Map.of("Content-Disposition", List.of("form-data; name=\"files\"; filename=\"file1.txt\""),
                                              "Content-Type", List.of("text/plain")),
                                       ACCEPT_ALL),
                        BodyPublishers.ofFile(Path.of("/tmp/fff")))
        );

        // Alternative #3.1 ( re-stack above with locals )
        var part1 = BodyPublishers.ofString("Hello There");
        var part2 = BodyPublishers.multipartPart(
                        HttpHeaders.of(Map.of("Content-Type", List.of("text/plain; charset=us-ascii")),
                                       ACCEPT_ALL),
                        BodyPublishers.ofString("blah blah"));
        var part3 = BodyPublishers.multipartPart(
                        HttpHeaders.of(Map.of("Content-Disposition", List.of("form-data; name=\"files\"; filename=\"file1.txt\""),
                                              "Content-Type", List.of("text/plain")),
                                       ACCEPT_ALL),
                        BodyPublishers.ofFile(Path.of("/tmp/fff")));

        var publisher31 = BodyPublishers.ofMultipart3("the12345boundary",part1, part2, part3);


        // --

        var client = HttpClient.newHttpClient();
        var request = HttpRequest.newBuilder()
                .uri(URI.create("http://foo.com/"))
                // << User sets multipart + boundary explicitly! e.g.
                //  multipart/mixed : multipart/digest : multipart/mixed : multipart/alternative : etc
                .header("Content-Type", "multipart/mixed; boundary=" + BOUNDARY)
                .POST(publisher)
                .build();
        client.send(request, BodyHandlers.ofString());
    }
}