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 *     derived from this software without specific prior written permission.
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/**
 * @file
 *   This file implements methods for Network Diagnostics helper types and classes.
 */

#include "net_diag_types.hpp"

#include "instance/instance.hpp"

namespace ot {
namespace NetDiag {

AnswerBuilder::AnswerBuilder(Instance &aInstance)
    : InstanceLocator(aInstance)
    , mAnswer(nullptr)
    , mAnswerIndex(0)
    , mQueryId(0)
    , mHasQueryId(false)
    , mPriority(Message::kPriorityNormal)
{
}

AnswerBuilder::~AnswerBuilder(void) { mAnswers.DequeueAndFreeAll(); }

Error AnswerBuilder::Start(const Coap::Message &aRequest)
{
    mAnswerIndex = 0;
    mHasQueryId  = (Tlv::Find<QueryIdTlv>(aRequest, mQueryId) == kErrorNone);
    mPriority    = aRequest.GetPriority();

    return Allocate();
}

Error AnswerBuilder::Finish(void) { return AppendAnswerTlv(AnswerTlvValue::kIsLast); }

Error AnswerBuilder::Allocate(void)
{
    Error error = kErrorNone;

    mAnswer = Get<Tmf::Agent>().AllocateAndInitConfirmablePostMessage(kUriDiagnosticGetAnswer);
    VerifyOrExit(mAnswer != nullptr, error = kErrorNoBufs);

    IgnoreError(mAnswer->SetPriority(mPriority));

    mAnswers.Enqueue(*mAnswer);

    if (mHasQueryId)
    {
        SuccessOrExit(error = Tlv::Append<QueryIdTlv>(*mAnswer, mQueryId));
    }

exit:
    return error;
}

Error AnswerBuilder::AppendAnswerTlv(AnswerTlvValue::IsLastFlag aFlag)
{
    AnswerTlvValue value;

    value.Init(mAnswerIndex++, aFlag);

    return Tlv::Append<AnswerTlv>(*mAnswer, value);
}

Error AnswerBuilder::CheckAnswerLength(void)
{
    Error error = kErrorNone;

    VerifyOrExit(mAnswer->GetLength() >= kAnswerMessageLengthThreshold);

    SuccessOrExit(error = AppendAnswerTlv(AnswerTlvValue::kMoreToFollow));

    error = Allocate();

exit:
    return error;
}

} // namespace NetDiag
} // namespace ot
