/*
 * Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.lang.invoke;

import java.lang.reflect.Array;
import java.util.Arrays;

import static java.lang.invoke.MethodHandleStatics.*;
import static java.lang.invoke.MethodHandleNatives.Constants.*;
import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
import static java.lang.invoke.LambdaForm.*;

/**
 * Construction and caching of often-used invokers.
 * @author jrose
 */
class Invokers {
 // exact type (sans leading taget MH) for the outgoing call
 private final MethodType targetType;

 // Cached adapter information:
 private final @Stable MethodHandle[] invokers = new MethodHandle[INV_LIMIT];
 // Indexes into invokers:
 static final int
 INV_EXACT = 0, // MethodHandles.exactInvoker
 INV_GENERIC = 1, // MethodHandles.invoker (generic invocation)
 INV_BASIC = 2, // MethodHandles.basicInvoker
 INV_LIMIT = 3;

 /** Compute and cache information common to all collecting adapters
 * that implement members of the erasure-family of the given erased type.
 */
 /*non-public*/ Invokers(MethodType targetType) {
 this.targetType = targetType;
 }

 /*non-public*/ MethodHandle exactInvoker() {
 MethodHandle invoker = cachedInvoker(INV_EXACT);
 if (invoker != null) return invoker;
 invoker = makeExactOrGeneralInvoker(true);
 return setCachedInvoker(INV_EXACT, invoker);
 }

 /*non-public*/ MethodHandle genericInvoker() {
 MethodHandle invoker = cachedInvoker(INV_GENERIC);
 if (invoker != null) return invoker;
 invoker = makeExactOrGeneralInvoker(false);
 return setCachedInvoker(INV_GENERIC, invoker);
 }

 /*non-public*/ MethodHandle basicInvoker() {
 MethodHandle invoker = cachedInvoker(INV_BASIC);
 if (invoker != null) return invoker;
 MethodType basicType = targetType.basicType();
 if (basicType != targetType) {
 // double cache; not used significantly
 return setCachedInvoker(INV_BASIC, basicType.invokers().basicInvoker());
 }
 invoker = basicType.form().cachedMethodHandle(MethodTypeForm.MH_BASIC_INV);
 if (invoker == null) {
 MemberName method = invokeBasicMethod(basicType);
 invoker = DirectMethodHandle.make(method);
 assert(checkInvoker(invoker));
 invoker = basicType.form().setCachedMethodHandle(MethodTypeForm.MH_BASIC_INV, invoker);
 }
 return setCachedInvoker(INV_BASIC, invoker);
 }

 private MethodHandle cachedInvoker(int idx) {
 return invokers[idx];
 }

 private synchronized MethodHandle setCachedInvoker(int idx, final MethodHandle invoker) {
 // Simulate a CAS, to avoid racy duplication of results.
 MethodHandle prev = invokers[idx];
 if (prev != null) return prev;
 return invokers[idx] = invoker;
 }

 private MethodHandle makeExactOrGeneralInvoker(boolean isExact) {
 MethodType mtype = targetType;
 MethodType invokerType = mtype.invokerType();
 int which = (isExact ? MethodTypeForm.LF_EX_INVOKER : MethodTypeForm.LF_GEN_INVOKER);
 LambdaForm lform = invokeHandleForm(mtype, false, which);
 MethodHandle invoker = BoundMethodHandle.bindSingle(invokerType, lform, mtype);
 String whichName = (isExact ? "invokeExact" : "invoke");
 invoker = invoker.withInternalMemberName(MemberName.makeMethodHandleInvoke(whichName, mtype), false);
 assert(checkInvoker(invoker));
 maybeCompileToBytecode(invoker);
 return invoker;
 }

 /** If the target type seems to be common enough, eagerly compile the invoker to bytecodes. */
 private void maybeCompileToBytecode(MethodHandle invoker) {
 final int EAGER_COMPILE_ARITY_LIMIT = 10;
 if (targetType == targetType.erase() &&
 targetType.parameterCount() < EAGER_COMPILE_ARITY_LIMIT) {
 invoker.form.compileToBytecode();
 }
 }

 // This next one is called from LambdaForm.NamedFunction.<init>.
 /*non-public*/ static MemberName invokeBasicMethod(MethodType basicType) {
 assert(basicType == basicType.basicType());
 try {
 //Lookup.findVirtual(MethodHandle.class, name, type);
 return IMPL_LOOKUP.resolveOrFail(REF_invokeVirtual, MethodHandle.class, "invokeBasic", basicType);
 } catch (ReflectiveOperationException ex) {
 throw newInternalError("JVM cannot find invoker for "+basicType, ex);
 }
 }

 private boolean checkInvoker(MethodHandle invoker) {
 assert(targetType.invokerType().equals(invoker.type()))
 : java.util.Arrays.asList(targetType, targetType.invokerType(), invoker);
 assert(invoker.internalMemberName() == null ||
 invoker.internalMemberName().getMethodType().equals(targetType));
 assert(!invoker.isVarargsCollector());
 return true;
 }

 /**
 * Find or create an invoker which passes unchanged a given number of arguments
 * and spreads the rest from a trailing array argument.
 * The invoker target type is the post-spread type {@code (TYPEOF(uarg*), TYPEOF(sarg*))=>RT}.
 * All the {@code sarg}s must have a common type {@code C}. (If there are none, {@code Object} is assumed.}
 * @param leadingArgCount the number of unchanged (non-spread) arguments
 * @return {@code invoker.invokeExact(mh, uarg*, C[]{sarg*}) := (RT)mh.invoke(uarg*, sarg*)}
 */
 /*non-public*/ MethodHandle spreadInvoker(int leadingArgCount) {
 int spreadArgCount = targetType.parameterCount() - leadingArgCount;
 MethodType postSpreadType = targetType;
 Class<?> argArrayType = impliedRestargType(postSpreadType, leadingArgCount);
 if (postSpreadType.parameterSlotCount() <= MethodType.MAX_MH_INVOKER_ARITY) {
 return genericInvoker().asSpreader(argArrayType, spreadArgCount);
 }
 // Cannot build a generic invoker here of type ginvoker.invoke(mh, a*[254]).
 // Instead, factor sinvoker.invoke(mh, a) into ainvoker.invoke(filter(mh), a)
 // where filter(mh) == mh.asSpreader(Object[], spreadArgCount)
 MethodType preSpreadType = postSpreadType
 .replaceParameterTypes(leadingArgCount, postSpreadType.parameterCount(), argArrayType);
 MethodHandle arrayInvoker = MethodHandles.invoker(preSpreadType);
 MethodHandle makeSpreader = MethodHandles.insertArguments(Lazy.MH_asSpreader, 1, argArrayType, spreadArgCount);
 return MethodHandles.filterArgument(arrayInvoker, 0, makeSpreader);
 }

 private static Class<?> impliedRestargType(MethodType restargType, int fromPos) {
 if (restargType.isGeneric()) return Object[].class; // can be nothing else
 int maxPos = restargType.parameterCount();
 if (fromPos >= maxPos) return Object[].class; // reasonable default
 Class<?> argType = restargType.parameterType(fromPos);
 for (int i = fromPos+1; i < maxPos; i++) {
 if (argType != restargType.parameterType(i))
 throw newIllegalArgumentException("need homogeneous rest arguments", restargType);
 }
 if (argType == Object.class) return Object[].class;
 return Array.newInstance(argType, 0).getClass();
 }

 public String toString() {
 return "Invokers"+targetType;
 }

 static MemberName methodHandleInvokeLinkerMethod(String name,
 MethodType mtype,
 Object[] appendixResult) {
 int which;
 switch (name) {
 case "invokeExact": which = MethodTypeForm.LF_EX_LINKER; break;
 case "invoke": which = MethodTypeForm.LF_GEN_LINKER; break;
 default: throw new InternalError("not invoker: "+name);
 }
 LambdaForm lform;
 if (mtype.parameterSlotCount() <= MethodType.MAX_MH_ARITY - MH_LINKER_ARG_APPENDED) {
 lform = invokeHandleForm(mtype, false, which);
 appendixResult[0] = mtype;
 } else {
 lform = invokeHandleForm(mtype, true, which);
 }
 return lform.vmentry;
 }

 // argument count to account for trailing "appendix value" (typically the mtype)
 private static final int MH_LINKER_ARG_APPENDED = 1;

 /** Returns an adapter for invokeExact or generic invoke, as a MH or constant pool linker.
 * If !customized, caller is responsible for supplying, during adapter execution,
 * a copy of the exact mtype. This is because the adapter might be generalized to
 * a basic type.
 * @param mtype the caller's method type (either basic or full-custom)
 * @param customized whether to use a trailing appendix argument (to carry the mtype)
 * @param which bit-encoded 0x01 whether it is a CP adapter ("linker") or MHs.invoker value ("invoker");
 * 0x02 whether it is for invokeExact or generic invoke
 */
 private static LambdaForm invokeHandleForm(MethodType mtype, boolean customized, int which) {
 boolean isCached;
 if (!customized) {
 mtype = mtype.basicType(); // normalize Z to I, String to Object, etc.
 isCached = true;
 } else {
 isCached = false; // maybe cache if mtype == mtype.basicType()
 }
 boolean isLinker, isGeneric;
 String debugName;
 switch (which) {
 case MethodTypeForm.LF_EX_LINKER: isLinker = true; isGeneric = false; debugName = "invokeExact_MT"; break;
 case MethodTypeForm.LF_EX_INVOKER: isLinker = false; isGeneric = false; debugName = "exactInvoker"; break;
 case MethodTypeForm.LF_GEN_LINKER: isLinker = true; isGeneric = true; debugName = "invoke_MT"; break;
 case MethodTypeForm.LF_GEN_INVOKER: isLinker = false; isGeneric = true; debugName = "invoker"; break;
 default: throw new InternalError();
 }
 LambdaForm lform;
 if (isCached) {
 lform = mtype.form().cachedLambdaForm(which);
 if (lform != null) return lform;
 }
 // exactInvokerForm (Object,Object)Object
 // link with java.lang.invoke.MethodHandle.invokeBasic(MethodHandle,Object,Object)Object/invokeSpecial
 final int THIS_MH = 0;
 final int CALL_MH = THIS_MH + (isLinker ? 0 : 1);
 final int ARG_BASE = CALL_MH + 1;
 final int OUTARG_LIMIT = ARG_BASE + mtype.parameterCount();
 final int INARG_LIMIT = OUTARG_LIMIT + (isLinker && !customized ? 1 : 0);
 int nameCursor = OUTARG_LIMIT;
 final int MTYPE_ARG = customized ? -1 : nameCursor++; // might be last in-argument
 final int CHECK_TYPE = nameCursor++;
 final int CHECK_CUSTOM = (CUSTOMIZE_THRESHOLD >= 0) ? nameCursor++ : -1;
 final int LINKER_CALL = nameCursor++;
 MethodType invokerFormType = mtype.invokerType();
 if (isLinker) {
 if (!customized)
 invokerFormType = invokerFormType.appendParameterTypes(MemberName.class);
 } else {
 invokerFormType = invokerFormType.invokerType();
 }
 Name[] names = arguments(nameCursor - INARG_LIMIT, invokerFormType);
 assert(names.length == nameCursor)
 : Arrays.asList(mtype, customized, which, nameCursor, names.length);
 if (MTYPE_ARG >= INARG_LIMIT) {
 assert(names[MTYPE_ARG] == null);
 BoundMethodHandle.SpeciesData speciesData = BoundMethodHandle.speciesData_L();
 names[THIS_MH] = names[THIS_MH].withConstraint(speciesData);
 NamedFunction getter = speciesData.getterFunction(0);
 names[MTYPE_ARG] = new Name(getter, names[THIS_MH]);
 // else if isLinker, then MTYPE is passed in from the caller (e.g., the JVM)
 }

 // Make the final call. If isGeneric, then prepend the result of type checking.
 MethodType outCallType = mtype.basicType();
 Object[] outArgs = Arrays.copyOfRange(names, CALL_MH, OUTARG_LIMIT, Object[].class);
 Object mtypeArg = (customized ? mtype : names[MTYPE_ARG]);
 if (!isGeneric) {
 names[CHECK_TYPE] = new Name(NF_checkExactType, names[CALL_MH], mtypeArg);
 // mh.invokeExact(a*):R => checkExactType(mh, TYPEOF(a*:R)); mh.invokeBasic(a*)
 } else {
 names[CHECK_TYPE] = new Name(NF_checkGenericType, names[CALL_MH], mtypeArg);
 // mh.invokeGeneric(a*):R => checkGenericType(mh, TYPEOF(a*:R)).invokeBasic(a*)
 outArgs[0] = names[CHECK_TYPE];
 }
 if (CHECK_CUSTOM != -1) {
 names[CHECK_CUSTOM] = new Name(NF_checkCustomized, outArgs[0]);
 }
 names[LINKER_CALL] = new Name(outCallType, outArgs);
 lform = new LambdaForm(debugName, INARG_LIMIT, names);
 if (isLinker)
 lform.compileToBytecode(); // JVM needs a real methodOop
 if (isCached)
 lform = mtype.form().setCachedLambdaForm(which, lform);
 return lform;
 }

 /*non-public*/ static
 WrongMethodTypeException newWrongMethodTypeException(MethodType actual, MethodType expected) {
 // FIXME: merge with JVM logic for throwing WMTE
 return new WrongMethodTypeException("expected "+expected+" but found "+actual);
 }

 /** Static definition of MethodHandle.invokeExact checking code. */
 /*non-public*/ static
 @ForceInline
 void checkExactType(Object mhObj, Object expectedObj) {
 MethodHandle mh = (MethodHandle) mhObj;
 MethodType expected = (MethodType) expectedObj;
 MethodType actual = mh.type();
 if (actual != expected)
 throw newWrongMethodTypeException(expected, actual);
 }

 /** Static definition of MethodHandle.invokeGeneric checking code.
 * Directly returns the type-adjusted MH to invoke, as follows:
 * {@code (R)MH.invoke(a*) => MH.asType(TYPEOF(a*:R)).invokeBasic(a*)}
 */
 /*non-public*/ static
 @ForceInline
 Object checkGenericType(Object mhObj, Object expectedObj) {
 MethodHandle mh = (MethodHandle) mhObj;
 MethodType expected = (MethodType) expectedObj;
 return mh.asType(expected);
 /* Maybe add more paths here. Possible optimizations:
 * for (R)MH.invoke(a*),
 * let MT0 = TYPEOF(a*:R), MT1 = MH.type
 *
 * if MT0==MT1 or MT1 can be safely called by MT0
 * => MH.invokeBasic(a*)
 * if MT1 can be safely called by MT0[R := Object]
 * => MH.invokeBasic(a*) & checkcast(R)
 * if MT1 can be safely called by MT0[* := Object]
 * => checkcast(A)* & MH.invokeBasic(a*) & checkcast(R)
 * if a big adapter BA can be pulled out of (MT0,MT1)
 * => BA.invokeBasic(MT0,MH,a*)
 * if a local adapter LA can cached on static CS0 = new GICS(MT0)
 * => CS0.LA.invokeBasic(MH,a*)
 * else
 * => MH.asType(MT0).invokeBasic(A*)
 */
 }

 static MemberName linkToCallSiteMethod(MethodType mtype) {
 LambdaForm lform = callSiteForm(mtype, false);
 return lform.vmentry;
 }

 static MemberName linkToTargetMethod(MethodType mtype) {
 LambdaForm lform = callSiteForm(mtype, true);
 return lform.vmentry;
 }

 // skipCallSite is true if we are optimizing a ConstantCallSite
 private static LambdaForm callSiteForm(MethodType mtype, boolean skipCallSite) {
 mtype = mtype.basicType(); // normalize Z to I, String to Object, etc.
 final int which = (skipCallSite ? MethodTypeForm.LF_MH_LINKER : MethodTypeForm.LF_CS_LINKER);
 LambdaForm lform = mtype.form().cachedLambdaForm(which);
 if (lform != null) return lform;
 // exactInvokerForm (Object,Object)Object
 // link with java.lang.invoke.MethodHandle.invokeBasic(MethodHandle,Object,Object)Object/invokeSpecial
 final int ARG_BASE = 0;
 final int OUTARG_LIMIT = ARG_BASE + mtype.parameterCount();
 final int INARG_LIMIT = OUTARG_LIMIT + 1;
 int nameCursor = OUTARG_LIMIT;
 final int APPENDIX_ARG = nameCursor++; // the last in-argument
 final int CSITE_ARG = skipCallSite ? -1 : APPENDIX_ARG;
 final int CALL_MH = skipCallSite ? APPENDIX_ARG : nameCursor++; // result of getTarget
 final int LINKER_CALL = nameCursor++;
 MethodType invokerFormType = mtype.appendParameterTypes(skipCallSite ? MethodHandle.class : CallSite.class);
 Name[] names = arguments(nameCursor - INARG_LIMIT, invokerFormType);
 assert(names.length == nameCursor);
 assert(names[APPENDIX_ARG] != null);
 if (!skipCallSite)
 names[CALL_MH] = new Name(NF_getCallSiteTarget, names[CSITE_ARG]);
 // (site.)invokedynamic(a*):R => mh = site.getTarget(); mh.invokeBasic(a*)
 final int PREPEND_MH = 0, PREPEND_COUNT = 1;
 Object[] outArgs = Arrays.copyOfRange(names, ARG_BASE, OUTARG_LIMIT + PREPEND_COUNT, Object[].class);
 // prepend MH argument:
 System.arraycopy(outArgs, 0, outArgs, PREPEND_COUNT, outArgs.length - PREPEND_COUNT);
 outArgs[PREPEND_MH] = names[CALL_MH];
 names[LINKER_CALL] = new Name(mtype, outArgs);
 lform = new LambdaForm((skipCallSite ? "linkToTargetMethod" : "linkToCallSite"), INARG_LIMIT, names);
 lform.compileToBytecode(); // JVM needs a real methodOop
 lform = mtype.form().setCachedLambdaForm(which, lform);
 return lform;
 }

 /** Static definition of MethodHandle.invokeGeneric checking code. */
 /*non-public*/ static
 @ForceInline
 Object getCallSiteTarget(Object site) {
 return ((CallSite)site).getTarget();
 }

 /*non-public*/ static
 @ForceInline
 void checkCustomized(Object o) {
 MethodHandle mh = (MethodHandle)o;
 if (mh.form.customized == null) {
 maybeCustomize(mh);
 }
 }

 /*non-public*/ static
 @DontInline
 void maybeCustomize(MethodHandle mh) {
 byte count = mh.customizationCount;
 if (count >= CUSTOMIZE_THRESHOLD) {
 mh.customize();
 } else {
 mh.customizationCount = (byte)(count+1);
 }
 }

 // Local constant functions:
 private static final NamedFunction
 NF_checkExactType,
 NF_checkGenericType,
 NF_getCallSiteTarget,
 NF_checkCustomized;
 static {
 try {
 NamedFunction nfs[] = {
 NF_checkExactType = new NamedFunction(Invokers.class
 .getDeclaredMethod("checkExactType", Object.class, Object.class)),
 NF_checkGenericType = new NamedFunction(Invokers.class
 .getDeclaredMethod("checkGenericType", Object.class, Object.class)),
 NF_getCallSiteTarget = new NamedFunction(Invokers.class
 .getDeclaredMethod("getCallSiteTarget", Object.class)),
 NF_checkCustomized = new NamedFunction(Invokers.class
 .getDeclaredMethod("checkCustomized", Object.class))
 };
 for (NamedFunction nf : nfs) {
 // Each nf must be statically invocable or we get tied up in our bootstraps.
 assert(InvokerBytecodeGenerator.isStaticallyInvocable(nf.member)) : nf;
 nf.resolve();
 }
 } catch (ReflectiveOperationException ex) {
 throw newInternalError(ex);
 }
 }

 private static class Lazy {
 private static final MethodHandle MH_asSpreader;

 static {
 try {
 MH_asSpreader = IMPL_LOOKUP.findVirtual(MethodHandle.class, "asSpreader",
 MethodType.methodType(MethodHandle.class, Class.class, int.class));
 } catch (ReflectiveOperationException ex) {
 throw newInternalError(ex);
 }
 }
 }
}