scarpet corountines idea

src/main/java/carpet/script/CarpetScriptHost.java

@@ -866,7 +866,7 @@ public class CarpetScriptHost extends ScriptHost
             assertAppIntegrity(function.getModule());
             Context context = new CarpetContext(this, source);
             return function.getExpression().evalValue(
-                    () -> function.execute(context, Context.VOID, function.getExpression(), function.getToken(), argv),
+                    () -> function.execute(context, Context.VOID, function.getExpression(), function.getToken(), argv, null),
                     context,
                     Context.VOID
             );
@@ -903,7 +903,7 @@ public class CarpetScriptHost extends ScriptHost
             assertAppIntegrity(fun.getModule());
             Context context = new CarpetContext(this, source, origin);
             return fun.getExpression().evalValue(
-                    () -> fun.execute(context, Context.VOID, fun.getExpression(), fun.getToken(), argv),
+                    () -> fun.execute(context, Context.VOID, fun.getExpression(), fun.getToken(), argv, null),
                     context,
                     Context.VOID);
         }
@@ -1215,4 +1215,10 @@ public class CarpetScriptHost extends ScriptHost
         }
         return false;
     }
+
+    @Override
+    public boolean canSynchronouslyExecute()
+    {
+        return !scriptServer().server.isSameThread();
+    }
 }

src/main/java/carpet/script/Context.java

@@ -1,6 +1,7 @@
 package carpet.script;
 
 import carpet.script.exception.InternalExpressionException;
+import carpet.script.value.ThreadValue;
 import carpet.script.value.Value;
 
 import java.util.HashMap;
@@ -30,6 +31,8 @@ public class Context
 
     public final ScriptHost host;
 
+    private ThreadValue threadContext = null;
+
     public Context(ScriptHost host)
     {
         this.host = host;
@@ -69,10 +72,21 @@ public class Context
     public Context recreate()
     {
         Context ctx = duplicate();
+        ctx.threadContext = threadContext;
         ctx.initialize();
         return ctx;
     }
 
+    public void setThreadContext(ThreadValue callingThread)
+    {
+        this.threadContext = callingThread;
+    }
+
+    public ThreadValue getThreadContext()
+    {
+        return threadContext;
+    }
+
     protected void initialize()
     {
         //special variables for second order functions so we don't need to check them all the time

src/main/java/carpet/script/ScriptHost.java

@@ -58,6 +58,11 @@ public abstract class ScriptHost
         return scriptServer.resolveResource(suffix);
     }
 
+    public boolean canSynchronouslyExecute()
+    {
+        return true;
+    }
+
     public static class ModuleData
     {
         Module parent;

src/main/java/carpet/script/language/Loops.java

@@ -143,6 +143,9 @@ public class Loops
             for (int i = 0; iterator.hasNext(); i++)
             {
                 Value next = iterator.next();
+                if(next == Value.EOL) {
+                    continue;
+                }
                 String variable = next.boundVariable;
                 next.bindTo("_");
                 int doYouReally = i;
@@ -197,6 +200,9 @@ public class Loops
             for (int i = 0; iterator.hasNext(); i++)
             {
                 Value next = iterator.next();
+                if(next == Value.EOL) {
+                    continue;
+                }
                 String veriable = next.boundVariable;
                 next.bindTo("_");
                 int seriously = i;
@@ -254,6 +260,9 @@ public class Loops
             for (int i = 0; iterator.hasNext(); i++)
             {
                 Value next = iterator.next();
+                if(next == Value.EOL) {
+                    continue;
+                }
                 String variable = next.boundVariable;
                 next.bindTo("_");
                 int seriously = i;
@@ -311,6 +320,9 @@ public class Loops
             for (int i = 0; iterator.hasNext(); i++)
             {
                 Value next = iterator.next();
+                if(next == Value.EOL) {
+                    continue;
+                }
                 String variable = next.boundVariable;
                 next.bindTo("_");
                 int seriously = i;
@@ -381,6 +393,9 @@ public class Loops
             for (int i = 0; iterator.hasNext(); i++)
             {
                 Value next = iterator.next();
+                if(next == Value.EOL) {
+                    continue;
+                }
                 String variable = next.boundVariable;
                 next.bindTo("_");
                 int seriously = i;
@@ -452,6 +467,9 @@ public class Loops
             for (int i = 0; iterator.hasNext(); i++)
             {
                 Value next = iterator.next();
+                if(next == Value.EOL) {
+                    continue;
+                }
                 String variable = next.boundVariable;
                 next.bindTo("_");
                 Value promiseWontChangeYou = acc;

src/main/java/carpet/script/language/Threading.java

@@ -1,5 +1,6 @@
 package carpet.script.language;
 
+import carpet.script.Context;
 import carpet.script.Expression;
 import carpet.script.argument.FunctionArgument;
 import carpet.script.exception.ExitStatement;
@@ -128,5 +129,63 @@ public class Threading
             }
             return (cc, tt) -> new NumericValue(time); // pass through for variables
         });
+
+        expression.addLazyFunction("yield", (c, t, lv) ->
+        {
+            if (c.getThreadContext() == null)
+            {
+                throw new InternalExpressionException("'yield' can only be used in a task");
+            }
+            if (lv.isEmpty())
+            {
+                throw new InternalExpressionException("'yield' requires at least one argument");
+            }
+            boolean lock = lv.size() > 1 && lv.get(1).evalValue(c, Context.BOOLEAN).getBoolean();
+            Value value = lv.get(0).evalValue(c);
+            Value ret = c.getThreadContext().ping(value, lock);
+            return (cc, tt) -> ret;
+        });
+
+        expression.addLazyFunction("task_send", 2, (c, t, lv) ->
+        {
+            Value threadValue = lv.get(0).evalValue(c);
+            if (!(threadValue instanceof ThreadValue thread))
+            {
+                throw new InternalExpressionException("'task_next' requires a task value");
+            }
+            if (!thread.isCoroutine)
+            {
+                throw new InternalExpressionException("'task_next' requires a coroutine task value");
+            }
+            Value ret = lv.get(1).evalValue(c);
+            thread.send(ret);
+            return (cc, tt) -> Value.NULL;
+        });
+
+        expression.addLazyFunction("task_await", 1, (c, t, lv) ->
+        {
+            Value threadValue = lv.get(0).evalValue(c);
+            if (!(threadValue instanceof ThreadValue thread))
+            {
+                throw new InternalExpressionException("'task_await' requires a task value");
+            }
+            if (!thread.isCoroutine)
+            {
+                throw new InternalExpressionException("'task_await' requires a coroutine task value");
+            }
+            Value ret = thread.next();
+            return ret == Value.EOL ? ((cc, tt) -> Value.NULL) : ((cc, tt) -> ret);
+        });
+
+        expression.addLazyFunction("task_ready", 1, (c, t, lv) ->
+        {
+            Value threadValue = lv.get(0).evalValue(c);
+            if (!(threadValue instanceof ThreadValue thread))
+            {
+                throw new InternalExpressionException("'task_ready' requires a task value");
+            }
+            boolean ret = thread.isCoroutine && thread.hasNext();
+            return (cc, tt) -> BooleanValue.of(ret);
+        });
     }
 }

src/main/java/carpet/script/value/AbstractListValue.java

@@ -3,13 +3,21 @@ package carpet.script.value;
 import carpet.script.exception.InternalExpressionException;
 import com.google.common.collect.Lists;
 
+import java.util.ArrayList;
 import java.util.List;
 
 public abstract class AbstractListValue extends Value implements Iterable<Value>
 {
     public List<Value> unpack()
     {
-        List<Value> retVal = Lists.newArrayList(iterator());
+        ArrayList<Value> retVal = Lists.newArrayList();
+        for (Value value : this)
+        {
+            if (value != Value.EOL)
+            {
+                retVal.add(value);
+            }
+        }
         fatality();
         return retVal;
     }

src/main/java/carpet/script/value/FunctionValue.java

@@ -22,6 +22,8 @@ import java.util.function.Consumer;
 import net.minecraft.nbt.StringTag;
 import net.minecraft.nbt.Tag;
 
+import javax.annotation.Nullable;
+
 public class FunctionValue extends Value implements Fluff.ILazyFunction
 {
     private final Expression expression;
@@ -158,7 +160,7 @@ public class FunctionValue extends Value implements Fluff.ILazyFunction
     {
         try
         {
-            return execute(c, type, expression, token, params);
+            return execute(c, type, expression, token, params, null);
         }
         catch (ExpressionException exc)
         {
@@ -214,10 +216,10 @@ public class FunctionValue extends Value implements Fluff.ILazyFunction
     public LazyValue lazyEval(Context c, Context.Type type, Expression e, Tokenizer.Token t, List<LazyValue> lazyParams)
     {
         List<Value> resolvedParams = unpackArgs(lazyParams, c);
-        return execute(c, type, e, t, resolvedParams);
+        return execute(c, type, e, t, resolvedParams, null);
     }
 
-    public LazyValue execute(Context c, Context.Type type, Expression e, Tokenizer.Token t, List<Value> params)
+    public LazyValue execute(Context c, Context.Type type, Expression e, Tokenizer.Token t, List<Value> params, @Nullable ThreadValue freshNewCallingThread)
     {
         assertArgsOk(params, fixedArgs -> {
             if (fixedArgs)  // wrong number of args for fixed args
@@ -237,6 +239,10 @@ public class FunctionValue extends Value implements Fluff.ILazyFunction
             );
         });
         Context newFrame = c.recreate();
+        if (freshNewCallingThread != null)
+        {
+            newFrame.setThreadContext(freshNewCallingThread);
+        }
 
         if (outerState != null)
         {

src/main/java/carpet/script/value/LazyListValue.java

@@ -137,7 +137,12 @@ public abstract class LazyListValue extends AbstractListValue implements Iterato
     public List<Value> unroll()
     {
         List<Value> result = new ArrayList<>();
-        this.forEachRemaining(result::add);
+        this.forEachRemaining(v -> {
+            if (v != Value.EOL)
+            {
+                result.add(v);
+            }
+        });
         fatality();
         return result;
     }

src/main/java/carpet/script/value/ThreadValue.java

@@ -7,34 +7,39 @@ import carpet.script.exception.ExitStatement;
 import carpet.script.exception.ExpressionException;
 import carpet.script.exception.InternalExpressionException;
 
+import java.util.ArrayDeque;
+import java.util.Deque;
+import java.util.Iterator;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
+import java.util.concurrent.atomic.AtomicReference;
 
 import net.minecraft.nbt.Tag;
 
-public class ThreadValue extends Value
+public class ThreadValue extends LazyListValue
 {
     private final CompletableFuture<Value> taskFuture;
     private final long id;
     private static long sequence = 0L;
-
+    private final Deque<Value> coState = new ArrayDeque<>();
-    public ThreadValue(CompletableFuture<Value> taskFuture)
+    private final AtomicReference<Value> coLock = new AtomicReference<>(Value.EOL);
-    {
+    public final boolean isCoroutine;
-        this.taskFuture = taskFuture;
-        this.id = sequence++;
-    }
 
     public ThreadValue(Value pool, FunctionValue function, Expression expr, Tokenizer.Token token, Context ctx, List<Value> args)
     {
-        this(getCompletableFutureFromFunction(pool, function, expr, token, ctx, args));
+        this.id = sequence++;
+        this.isCoroutine = ctx.host.canSynchronouslyExecute();
+        this.taskFuture = getCompletableFutureFromFunction(pool, function, expr, token, ctx, args);
+
         Thread.yield();
     }
 
-    public static CompletableFuture<Value> getCompletableFutureFromFunction(Value pool, FunctionValue function, Expression expr, Tokenizer.Token token, Context ctx, List<Value> args)
+    public CompletableFuture<Value> getCompletableFutureFromFunction(Value pool, FunctionValue function, Expression expr, Tokenizer.Token token, Context ctx, List<Value> args)
     {
         ExecutorService executor = ctx.host.getExecutor(pool);
+        ThreadValue callingThread = isCoroutine ? this : null;
         if (executor == null)
         {
             // app is shutting down - no more threads can be spawned.
@@ -45,7 +50,7 @@ public class ThreadValue extends Value
             return CompletableFuture.supplyAsync(() -> {
                 try
                 {
-                    return function.execute(ctx, Context.NONE, expr, token, args).evalValue(ctx);
+                    return function.execute(ctx, Context.NONE, expr, token, args, callingThread).evalValue(ctx);
                 }
                 catch (ExitStatement exit)
                 {
@@ -137,4 +142,143 @@ public class ThreadValue extends Value
     {
         return "task";
     }
+
+    @Override
+    public void fatality()
+    {
+        // we signal that won't be interested in the co-thread anymore
+        // but threads run client code, so we can't just kill them
+    }
+
+    @Override
+    public void reset()
+    {
+        //throw new InternalExpressionException("Illegal operation on a task");
+    }
+
+
+    @Override
+    public Iterator<Value> iterator()
+    {
+        if (!isCoroutine)
+        {
+            throw new InternalExpressionException("Cannot iterate over this task");
+        }
+        return this;
+    }
+
+    @Override
+    public boolean hasNext()
+    {
+        return !(coState.isEmpty() && taskFuture.isDone());
+    }
+
+    @Override
+    public Value next()
+    {
+        Value popped = null;
+        synchronized (coState)
+        {
+            while (true)
+            {
+                if (!coState.isEmpty())
+                {
+                    popped = coState.pop();
+                }
+                else if (taskFuture.isDone())
+                {
+                    popped = Value.EOL;
+                }
+                if (popped != null)
+                {
+                    break;
+                }
+                try
+                {
+                    coState.wait(1);
+                }
+                catch (InterruptedException ignored)
+                {
+                }
+            }
+            coState.notifyAll();
+        }
+        return popped;
+    }
+
+    public void send(Value value)
+    {
+        synchronized (coLock)
+        {
+            coLock.set(value);
+            coLock.notifyAll();
+        }
+    }
+
+    public Value ping(Value value, boolean lock)
+    {
+        synchronized (coState)
+        {
+            try
+            {
+                if (!lock)
+                {
+                    coState.add(value);
+                    return Value.NULL;
+                }
+                while (true)
+                {
+                    if (coState.isEmpty())
+                    {
+                        coState.add(value);
+                        break;
+                    }
+                    try
+                    {
+                        coState.wait(1);
+                    }
+
+                    catch (InterruptedException ignored)
+                    {
+                    }
+                }
+            }
+            finally
+            {
+                coState.notifyAll();
+            }
+        }
+
+        // locked mode
+
+        synchronized (coLock)
+        {
+            Value ret;
+            try
+            {
+                while (true)
+                {
+                    Value current = coLock.get();
+                    if (current != Value.EOL)
+                    {
+                        ret = current;
+                        coLock.set(Value.EOL);
+                        break;
+                    }
+                    try
+                    {
+                        coLock.wait(1);
+                    }
+                    catch (InterruptedException ignored)
+                    {
+                    }
+                }
+            }
+            finally
+            {
+                coLock.notifyAll();
+            }
+            return ret;
+        }
+    }
 }

src/main/java/carpet/script/value/UndefValue.java

@@ -7,6 +7,7 @@ import net.minecraft.nbt.Tag;
 public class UndefValue extends NullValue
 {
     public static final UndefValue UNDEF = new UndefValue();
+    public static final UndefValue EOL = new UndefValue();
 
     private RuntimeException getError()
     {

src/main/java/carpet/script/value/Value.java

@@ -25,6 +25,7 @@ public abstract class Value implements Comparable<Value>, Cloneable
 
     public static final NullValue NULL = NullValue.NULL;
     public static final UndefValue UNDEF = UndefValue.UNDEF;
+    public static final UndefValue EOL = UndefValue.EOL;
 
     public String boundVariable;