//
// Copyright (c) 2002-2015 The ANGLE Project Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//

#include "compiler/translator/ValidateSwitch.h"

#include "compiler/translator/ParseContext.h"

bool ValidateSwitch::validate(TBasicType switchType, TParseContext *context,
    TIntermAggregate *statementList, const TSourceLoc &loc)
{
    ValidateSwitch validate(switchType, context);
    ASSERT(statementList);
    statementList->traverse(&validate);
    return validate.validateInternal(loc);
}

ValidateSwitch::ValidateSwitch(TBasicType switchType, TParseContext *context)
    : TIntermTraverser(true, false, true),
      mSwitchType(switchType),
      mContext(context),
      mCaseTypeMismatch(false),
      mFirstCaseFound(false),
      mStatementBeforeCase(false),
      mLastStatementWasCase(false),
      mControlFlowDepth(0),
      mCaseInsideControlFlow(false),
      mDefaultCount(0),
      mDuplicateCases(false)
{}

void ValidateSwitch::visitSymbol(TIntermSymbol *)
{
    if (!mFirstCaseFound)
        mStatementBeforeCase = true;
    mLastStatementWasCase = false;
}

void ValidateSwitch::visitConstantUnion(TIntermConstantUnion *)
{
    // Conditions of case labels are not traversed, so this is some other constant
    // Could be just a statement like "0;"
    if (!mFirstCaseFound)
        mStatementBeforeCase = true;
    mLastStatementWasCase = false;
}

bool ValidateSwitch::visitBinary(Visit, TIntermBinary *)
{
    if (!mFirstCaseFound)
        mStatementBeforeCase = true;
    mLastStatementWasCase = false;
    return true;
}

bool ValidateSwitch::visitUnary(Visit, TIntermUnary *)
{
    if (!mFirstCaseFound)
        mStatementBeforeCase = true;
    mLastStatementWasCase = false;
    return true;
}

bool ValidateSwitch::visitSelection(Visit visit, TIntermSelection *)
{
    if (visit == PreVisit)
        ++mControlFlowDepth;
    if (visit == PostVisit)
        --mControlFlowDepth;
    if (!mFirstCaseFound)
        mStatementBeforeCase = true;
    mLastStatementWasCase = false;
    return true;
}

bool ValidateSwitch::visitSwitch(Visit, TIntermSwitch *)
{
    if (!mFirstCaseFound)
        mStatementBeforeCase = true;
    mLastStatementWasCase = false;
    // Don't go into nested switch statements
    return false;
}

bool ValidateSwitch::visitCase(Visit, TIntermCase *node)
{
    const char *nodeStr = node->hasCondition() ? "case" : "default";
    if (mControlFlowDepth > 0)
    {
        mContext->error(node->getLine(), "label statement nested inside control flow", nodeStr);
        mCaseInsideControlFlow = true;
    }
    mFirstCaseFound = true;
    mLastStatementWasCase = true;
    if (!node->hasCondition())
    {
        ++mDefaultCount;
        if (mDefaultCount > 1)
        {
            mContext->error(node->getLine(), "duplicate default label", nodeStr);
        }
    }
    else
    {
        TIntermConstantUnion *condition = node->getCondition()->getAsConstantUnion();
        if (condition == nullptr)
        {
            // This can happen in error cases.
            return false;
        }
        TBasicType conditionType = condition->getBasicType();
        if (conditionType != mSwitchType)
        {
            mContext->error(condition->getLine(),
                "case label type does not match switch init-expression type", nodeStr);
            mCaseTypeMismatch = true;
        }

        if (conditionType == EbtInt)
        {
            int iConst = condition->getIConst(0);
            if (mCasesSigned.find(iConst) != mCasesSigned.end())
            {
                mContext->error(condition->getLine(), "duplicate case label", nodeStr);
                mDuplicateCases = true;
            }
            else
            {
                mCasesSigned.insert(iConst);
            }
        }
        else if (conditionType == EbtUInt)
        {
            unsigned int uConst = condition->getUConst(0);
            if (mCasesUnsigned.find(uConst) != mCasesUnsigned.end())
            {
                mContext->error(condition->getLine(), "duplicate case label", nodeStr);
                mDuplicateCases = true;
            }
            else
            {
                mCasesUnsigned.insert(uConst);
            }
        }
        // Other types are possible only in error cases, where the error has already been generated
        // when parsing the case statement.
    }
    // Don't traverse the condition of the case statement
    return false;
}

bool ValidateSwitch::visitAggregate(Visit visit, TIntermAggregate *)
{
    if (getParentNode() != nullptr)
    {
        // This is not the statementList node, but some other node.
        if (!mFirstCaseFound)
            mStatementBeforeCase = true;
        mLastStatementWasCase = false;
    }
    return true;
}

bool ValidateSwitch::visitLoop(Visit visit, TIntermLoop *)
{
    if (visit == PreVisit)
        ++mControlFlowDepth;
    if (visit == PostVisit)
        --mControlFlowDepth;
    if (!mFirstCaseFound)
        mStatementBeforeCase = true;
    mLastStatementWasCase = false;
    return true;
}

bool ValidateSwitch::visitBranch(Visit, TIntermBranch *)
{
    if (!mFirstCaseFound)
        mStatementBeforeCase = true;
    mLastStatementWasCase = false;
    return true;
}

bool ValidateSwitch::validateInternal(const TSourceLoc &loc)
{
    if (mStatementBeforeCase)
    {
        mContext->error(loc,
            "statement before the first label", "switch");
    }
    if (mLastStatementWasCase)
    {
        mContext->error(loc,
            "no statement between the last label and the end of the switch statement", "switch");
    }
    return !mStatementBeforeCase && !mLastStatementWasCase && !mCaseInsideControlFlow &&
        !mCaseTypeMismatch && mDefaultCount <= 1 && !mDuplicateCases;
}