/*

 * Copyright 2021 Google LLC

 *

 * Use of this source code is governed by a BSD-style license that can be

 * found in the LICENSE file.

 */

#include "src/sksl/ir/SkSLConstructorArrayCast.h"

#include "src/sksl/SkSLConstantFolder.h"

#include "src/sksl/ir/SkSLConstructorArray.h"

#include "src/sksl/ir/SkSLConstructorCompoundCast.h"

#include "src/sksl/ir/SkSLConstructorScalarCast.h"

namespace SkSL {

static std::unique_ptr<Expression> cast_constant_array(const Context& context,

                                                       const Type& destType,

                                                       std::unique_ptr<Expression> constCtor) {

    const Type& scalarType = destType.componentType();

    // Create a ConstructorArray(...) which typecasts each argument inside.

    auto inputArgs = constCtor->as<ConstructorArray>().argumentSpan();

    ExpressionArray typecastArgs;

    typecastArgs.reserve_back(inputArgs.size());

    for (std::unique_ptr<Expression>& arg : inputArgs) {

        int offset = arg->fOffset;

        if (arg->type().isScalar()) {

            typecastArgs.push_back(ConstructorScalarCast::Make(context, offset, scalarType,

                                                               std::move(arg)));

        } else {

            typecastArgs.push_back(ConstructorCompoundCast::Make(context, offset, scalarType,

                                                                 std::move(arg)));

        }

    }

    return ConstructorArray::Make(context, constCtor->fOffset, destType, std::move(typecastArgs));

}

std::unique_ptr<Expression> ConstructorArrayCast::Make(const Context& context,

                                                       int offset,

                                                       const Type& type,

                                                       std::unique_ptr<Expression> arg) {

    // Only arrays of the same size are allowed.

    SkASSERT(type.isArray());

    SkASSERT(arg->type().isArray());

    SkASSERT(type.columns() == arg->type().columns());

    // If this is a no-op cast, return the expression as-is.

    if (type == arg->type()) {

        return arg;

    }

    // When optimization is on, look up the value of constant variables. This allows expressions

    // like `myArray` to be replaced with the compile-time constant `int[2](0, 1)`.

    if (context.fConfig->fSettings.fOptimize) {

        arg = ConstantFolder::MakeConstantValueForVariable(std::move(arg));

    }

    // We can cast a vector of compile-time constants at compile-time.

    if (arg->isCompileTimeConstant()) {

        return cast_constant_array(context, type, std::move(arg));

    }

    return std::make_unique<ConstructorArrayCast>(offset, type, std::move(arg));

}

}  // namespace SkSL