JIMRI/java/graalvm/jmri/script/jsr223graalpython/GraalJSBindings.java

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package jmri.script.jsr223graalpython;

import java.util.AbstractMap;
import java.util.Collections;
import java.util.Map;
import java.util.Objects;
import java.util.Set;

import javax.script.Bindings;
import javax.script.ScriptContext;

import org.graalvm.polyglot.Context;
import org.graalvm.polyglot.TypeLiteral;
import org.graalvm.polyglot.Value;
import org.graalvm.polyglot.proxy.ProxyObject;

import jmri.script.jsr223graalpython.GraalJSScriptEngine.MagicBindingsOptionSetter;

final class GraalJSBindings extends AbstractMap<String, Object> implements Bindings, AutoCloseable {
    private static final String SCRIPT_CONTEXT_GLOBAL_BINDINGS_IMPORT_FUNCTION_NAME = "importScriptEngineGlobalBindings";

    private static final TypeLiteral<Map<String, Object>> STRING_MAP = new TypeLiteral<>() {
    };

    private Context context;
    private Map<String, Object> global;
    private Value deleteProperty;
    private Value clear;
    private Context.Builder contextBuilder;
    // ScriptContext of the ScriptEngine where these bindings form ENGINE_SCOPE bindings
    private ScriptContext engineScriptContext;

    GraalJSBindings(Context.Builder contextBuilder, ScriptContext scriptContext) {
        log.trace("ctor(C.B, S) invoked");
        this.contextBuilder = contextBuilder;
        this.engineScriptContext = scriptContext;
    }

    GraalJSBindings(Context context, ScriptContext scriptContext) {
        log.trace("ctor(C, S) invoked");
        this.context = context;
        initGlobal();
        this.engineScriptContext = scriptContext;
    }

    private void requireContext() {
        if (context == null) {
            initContext();
        }
    }

    private void initContext() {
        log.trace("initContext");
        context = GraalJSScriptEngine.createDefaultContext(contextBuilder);
        log.trace("  initContext created context {}", context);
        initGlobal();
    }

    private void initGlobal() {
        log.trace("initGlobal with \"{}\"", context);
        var temp = GraalJSScriptEngine.evalInternal(context, "locals()");  // this line combined with next
        log.trace("    temp: "+temp);
        this.global = temp.as(STRING_MAP); // was "this"
        log.trace("    defines  "+this.global);
    }

    private Value deletePropertyFunction() {
        if (this.deleteProperty == null) {
            this.deleteProperty = GraalJSScriptEngine.evalInternal(context, "(function(obj, prop) {delete obj[prop]})");
        }
        return this.deleteProperty;
    }

    private Value clearFunction() {
        if (this.clear == null) {
            this.clear = GraalJSScriptEngine.evalInternal(context, "(function(obj) {for (var prop in obj) {delete obj[prop]}})");
        }
        return this.clear;
    }

    @Override
    public Object put(String name, Object v) {
        checkKey(name);
        if (name.startsWith(GraalJSScriptEngine.MAGIC_OPTION_PREFIX)) {
            if (context == null) {
                MagicBindingsOptionSetter optionSetter = GraalJSScriptEngine.MAGIC_BINDINGS_OPTION_MAP.get(name);
                if (optionSetter == null) {
                    throw new IllegalArgumentException("unkown graal-js option \"" + name + "\"");
                } else {
                    contextBuilder = optionSetter.setOption(contextBuilder, v);
                    return true;
                }
            } else {
                throw magicOptionContextInitializedError(name);
            }
        }
        requireContext();
        return global.put(name, v);
    }

    @Override
    public void clear() {
        if (context != null) {
            clearFunction().execute(global);
        }
    }

    @Override
    public Object get(Object key) {
        checkKey((String) key);
        requireContext();
        if (engineScriptContext != null) {
            importGlobalBindings(engineScriptContext);
        }
        return global.get(key);
    }

    private static void checkKey(String key) {
        Objects.requireNonNull(key, "key can not be null");
        if (key.isEmpty()) {
            throw new IllegalArgumentException("key can not be empty");
        }
    }

    @Override
    public Object remove(Object key) {
        requireContext();
        Object prev = get(key);
        deletePropertyFunction().execute(global, key);
        return prev;
    }

    public Context getContext() {
        requireContext();
        return context;
    }

    @Override
    public Set<Entry<String, Object>> entrySet() {
        requireContext();
        return global.entrySet();
    }

    @Override
    public void close() {
        if (context != null) {
            context.close();
        }
    }

    private static IllegalStateException magicOptionContextInitializedError(String name) {
        return new IllegalStateException(String.format("failed to set graal-js option \"%s\": js context is already initialized", name));
    }

    void importGlobalBindings(ScriptContext scriptContext) {
        // was originally there, NPE at end
//         Bindings globalBindings = scriptContext.getBindings(ScriptContext.GLOBAL_SCOPE);
//         if (globalBindings != null && !globalBindings.isEmpty() && this != globalBindings) {
//             ProxyObject bindingsProxy = ProxyObject.fromMap(Collections.unmodifiableMap(globalBindings));
//             log.trace("getBindings(python) {} type {}", getContext().getBindings("python"),  getContext().getBindings("python").getClass());
//             getContext()
//                 .getBindings("python")
//                     .getMember(SCRIPT_CONTEXT_GLOBAL_BINDINGS_IMPORT_FUNCTION_NAME)
//                         .execute(bindingsProxy);
//         }
     }

    void updateEngineScriptContext(ScriptContext scriptContext) {
        engineScriptContext = scriptContext;
    }

    private final static org.slf4j.Logger log = org.slf4j.LoggerFactory.getLogger(GraalJSBindings.class);
}