/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef frontend_ForOfEmitter_h
#define frontend_ForOfEmitter_h

#include "mozilla/Attributes.h"
#include "mozilla/Maybe.h"

#include <stdint.h>

#include "frontend/ForOfLoopControl.h"
#include "frontend/JumpList.h"
#include "frontend/TDZCheckCache.h"
#include "vm/Iteration.h"

namespace js {
namespace frontend {

struct BytecodeEmitter;
class EmitterScope;

// Class for emitting bytecode for for-of loop.
//
// Usage: (check for the return value is omitted for simplicity)
//
//   `for (init of iterated) body`
//     // headLexicalEmitterScope: lexical scope for init
//     ForOfEmitter forOf(this, headLexicalEmitterScope);
//     forOf.emitIterated();
//     emit(iterated);
//     forOf.emitInitialize(Some(offset_of_for));
//     emit(init);
//     forOf.emitBody();
//     emit(body);
//     forOf.emitEnd(Some(offset_of_iterated));
//
class MOZ_STACK_CLASS ForOfEmitter
{
    BytecodeEmitter* bce_;

    // The source note index for SRC_FOR_OF.
    unsigned noteIndex_ = 0;

#ifdef DEBUG
    // The stack depth before emitting IteratorNext code inside loop.
    int32_t loopDepth_ = 0;
#endif

    bool allowSelfHostedIter_;
    IteratorKind iterKind_;

    // Jump from into JSOP_LOOPENTRY.
    JumpList initialJump_;

    mozilla::Maybe<ForOfLoopControl> loopInfo_;

    // The lexical scope to be freshened for each iteration.
    // See the comment in `emitBody` for more details.
    const EmitterScope* headLexicalEmitterScope_;

    // Cache for the iterated value.
    // (The cache for the iteration body is inside `loopInfo_`)
    mozilla::Maybe<TDZCheckCache> tdzCacheForIteratedValue_;

#ifdef DEBUG
    // The state of this emitter.
    //
    // +-------+ emitIterated +----------+ emitInitialize +------------+
    // | Start |------------->| Iterated |--------------->| Initialize |-+
    // +-------+              +----------+                +------------+ |
    //                                                                   |
    //                                +----------------------------------+
    //                                |
    //                                | emitBody +------+ emitEnd  +-----+
    //                                +----------| Body |--------->| End |
    //                                           +------+          +-----+
    enum class State {
        // The initial state.
        Start,

        // After calling emitIterated.
        Iterated,

        // After calling emitInitialize.
        Initialize,

        // After calling emitBody.
        Body,

        // After calling emitEnd.
        End
    };
    State state_ = State::Start;
#endif

  public:
    ForOfEmitter(BytecodeEmitter* bce, const EmitterScope* headLexicalEmitterScope,
                 bool allowSelfHostedIter, IteratorKind iterKind);

    // The offset in the source code for each character below:
    //
    //   for ( var x of obj ) { ... }
    //   ^              ^
    //   |              |
    //   |              iteratedPos
    //   |
    //   forPos
    //
    // Can be Nothing() if not available.
    MOZ_MUST_USE bool emitIterated();
    MOZ_MUST_USE bool emitInitialize(const mozilla::Maybe<uint32_t>& forPos);
    MOZ_MUST_USE bool emitBody();
    MOZ_MUST_USE bool emitEnd(const mozilla::Maybe<uint32_t>& iteratedPos);
};

} /* namespace frontend */
} /* namespace js */

#endif /* frontend_ForOfEmitter_h */
