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package org.jruby;

import org.jruby.anno.JRubyClass;
import org.jruby.anno.JRubyMethod;
import org.jruby.runtime.Block;
import org.jruby.runtime.BlockCallback;
import org.jruby.runtime.CallBlock19;
import org.jruby.runtime.ClassIndex;
import org.jruby.runtime.Signature;
import org.jruby.runtime.ThreadContext;

import static org.jruby.api.Error.argumentError;
import static org.jruby.runtime.Visibility.*;
import org.jruby.runtime.builtin.IRubyObject;

@JRubyClass(name = "Enumerator::Yielder")
public class RubyYielder extends RubyObject {
    private Block block;

    public static RubyClass createYielderClass(ThreadContext context, RubyClass Object, RubyClass Enumerator) {
        return Enumerator.defineClassUnder(context, "Yielder", Object, RubyYielder::new).
                kindOf(new RubyModule.JavaClassKindOf(RubyYielder.class)).
                classIndex(ClassIndex.YIELDER).
                defineMethods(context, RubyYielder.class);
    }

    public RubyYielder(Ruby runtime, RubyClass klass) {
        super(runtime, klass);
    }

    public RubyYielder(Ruby runtime) {
        super(runtime, runtime.getYielder());
    }

    public static RubyYielder newYielder(ThreadContext context, final Block block) {
        Ruby runtime = context.runtime;
        RubyYielder yielder = new RubyYielder(runtime, runtime.getYielder());

        if (!block.isGiven()) {
            throw context.runtime.newLocalJumpError(RubyLocalJumpError.Reason.NOREASON, context.nil, "no block given");
        }

        yielder.initialize(context, CallBlock19.newCallClosure(
                yielder,
                yielder.metaClass,
                Signature.NO_ARGUMENTS,
                new BlockCallbackImpl(RubyProc.newProc(context.runtime, block, block.type == Block.Type.NORMAL ? Block.Type.PROC : block.type)),
                context));

        return yielder;
    }

    private static class BlockCallbackImpl implements BlockCallback {

        private final RubyProc proc;

        BlockCallbackImpl(RubyProc proc) {
            this.proc = proc;
        }

        public IRubyObject call(ThreadContext context, IRubyObject[] args, Block inner) {
            return proc.call(context, args, inner);
        }

        @Override
        public IRubyObject call(ThreadContext context, IRubyObject arg, Block inner) {
            return proc.call(context, arg, inner);
        }

    }

    @JRubyMethod(visibility = PRIVATE)
    public IRubyObject initialize(ThreadContext context, Block block) {
        Ruby runtime = context.runtime;
        if (!block.isGiven()) throw runtime.newLocalJumpErrorNoBlock();
        this.block = block;
        return this;
    }

    @JRubyMethod(rest = true, keywords = true)
    public IRubyObject yield(ThreadContext context, IRubyObject[] args) {
        if (block == null) throw argumentError(context, "uninitialized yielder");
        return block.yieldValues(context, args);
    }

    @JRubyMethod(name = "<<", rest = true)
    public IRubyObject op_lshift(ThreadContext context, IRubyObject[] args) {
        this.yield(context, args);
        return this;
    }

    @JRubyMethod(name = "to_proc")
    public IRubyObject to_proc(ThreadContext context) {
        return RubyProc.newProc(context.runtime, CallBlock19.newCallClosure(this, this.getMetaClass(), Signature.OPTIONAL, new BlockCallback() {
            @Override
            public IRubyObject call(ThreadContext context, IRubyObject[] args, Block block) {
                return RubyYielder.this.yield(context, args);
            }
        }, context), Block.Type.PROC);
    }
}
