import com.sun.management.HotSpotDiagnosticMXBean;
import java.lang.management.ManagementFactory;
import java.nio.file.*;
import java.util.concurrent.*;
import java.util.concurrent.StructuredTaskScope.Joiner;

/** The thread dump shows the scope as a container, its owner, and the threads forked in it. */
public class ThreadDump {
    public static void main(String[] args) throws Exception {
        if (args.length > 0 && args[0].equals("hold")) {      // used by run.sh: hold nested scopes open so jcmd can dump them
            try (var scope = StructuredTaskScope.open(Joiner.<String>awaitAllSuccessfulOrThrow(), cf -> cf.withName("orders"))) {
                scope.fork(() -> { Thread.sleep(6000); return "A"; });
                scope.fork(() -> {                                 // subtask B opens a child scope of its own
                    try (var child = StructuredTaskScope.open(Joiner.<String>awaitAllSuccessfulOrThrow(), cf -> cf.withName("inventory"))) {
                        child.fork(() -> { Thread.sleep(6000); return "B1"; });
                        child.join();
                    }
                    return "B";
                });
                scope.join();
            }
            return;
        }
        Path file = Files.createTempFile("dump", ".json"); Files.delete(file);
        try (var scope = StructuredTaskScope.open(Joiner.<String>awaitAllSuccessfulOrThrow(), cf -> cf.withName("orders"))) {
            for (int i = 0; i < 2; i++) {
                int n = i;
                scope.fork(() -> { Thread.sleep(1500); return "task-" + n; });
            }
            Thread.sleep(300);        // let the subtasks start and block
            ManagementFactory.getPlatformMXBean(HotSpotDiagnosticMXBean.class)
                .dumpThreads(file.toString(), HotSpotDiagnosticMXBean.ThreadDumpFormat.JSON);
            scope.join();
        }
        String json = Files.readString(file);
        int at = json.indexOf("\"container\": \"orders");
        int start = json.lastIndexOf('{', at);
        int end = json.indexOf("\"threadCount\"", at);
        String block = json.substring(start, end);
        // identity hashes, thread ids and timestamps change between runs: mask them so the transcript is stable
        block = block.replaceAll("@[0-9a-f]+", "@<hash>").replaceAll("\"tid\": \\d+", "\"tid\": <n>").replaceAll("\"owner\": \\d+", "\"owner\": <n>");
        // keep the lines that show the hierarchy: the scope, its parent and owner, and each forked thread with its own frame
        for (String line : block.split("\n")) {
            String l = line.trim();
            if (l.startsWith("\"container\"") || l.startsWith("\"parent\"") || l.startsWith("\"owner\"")
                    || l.startsWith("\"tid\"") || l.startsWith("\"virtual\"") || l.startsWith("\"state\"")
                    || l.contains("ThreadDump.lambda")) {
                System.out.println(l);
            }
        }
        Files.deleteIfExists(file);
    }
}