//
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#ifndef PPCONTEXT_H
#define PPCONTEXT_H

#include <stack>
#include <unordered_map>
#include <sstream>

#include "../ParseHelper.h"
#include "PpTokens.h"

namespace QtShaderTools {
namespace glslang {

class TPpToken {
public:
    TPpToken() { clear(); }
    void clear()
    {
        space = false;
        i64val = 0;
        loc.init();
        name[0] = 0;
        fullyExpanded = false;
    }

    // Used for comparing macro definitions, so checks what is relevant for that.
    bool operator==(const TPpToken& right) const
    {
        return space == right.space &&
               ival == right.ival && dval == right.dval && i64val == right.i64val &&
               strncmp(name, right.name, MaxTokenLength) == 0;
    }
    bool operator!=(const TPpToken& right) const { return ! operator==(right); }

    TSourceLoc loc;
    // True if a space (for white space or a removed comment) should also be
    // recognized, in front of the token returned:
    bool space;

    bool fullyExpanded;
    // Numeric value of the token:
    union {
        int ival;
        double dval;
        long long i64val;
    };
    // Text string of the token:
    char name[MaxTokenLength + 1];
};

class TStringAtomMap {
//
// Implementation is in PpAtom.cpp
//
// Maintain a bi-directional mapping between relevant preprocessor strings and
// "atoms" which a unique integers (small, contiguous, not hash-like) per string.
//
public:
    TStringAtomMap();

    // Map string -> atom.
    // Return 0 if no existing string.
    int getAtom(const char* s) const
    {
        auto it = atomMap.find(s);
        return it == atomMap.end() ? 0 : it->second;
    }

    // Map a new or existing string -> atom, inventing a new atom if necessary.
    int getAddAtom(const char* s)
    {
        int atom = getAtom(s);
        if (atom == 0) {
            atom = nextAtom++;
            addAtomFixed(s, atom);
        }
        return atom;
    }

    // Map atom -> string.
    const char* getString(int atom) const { return stringMap[atom]->c_str(); }

protected:
    TStringAtomMap(TStringAtomMap&);
    TStringAtomMap& operator=(TStringAtomMap&);

    TUnorderedMap<TString, int> atomMap;
    TVector<const TString*> stringMap;    // these point into the TString in atomMap
    int nextAtom;

    // Bad source characters can lead to bad atoms, so gracefully handle those by
    // pre-filling the table with them (to avoid if tests later).
    TString badToken;

    // Add bi-directional mappings:
    //  - string -> atom
    //  - atom -> string
    void addAtomFixed(const char* s, int atom)
    {
        auto it = atomMap.insert(std::pair<TString, int>(s, atom)).first;
        if (stringMap.size() < (size_t)atom + 1)
            stringMap.resize(atom + 100, &badToken);
        stringMap[atom] = &it->first;
    }
};

class TInputScanner;

enum MacroExpandResult {
    MacroExpandNotStarted, // macro not expanded, which might not be an error
    MacroExpandError,      // a clear error occurred while expanding, no expansion
    MacroExpandStarted,    // macro expansion process has started
    MacroExpandUndef       // macro is undefined and will be expanded
};

// This class is the result of turning a huge pile of C code communicating through globals
// into a class.  This was done to allowing instancing to attain thread safety.
// Don't expect too much in terms of OO design.
class TPpContext {
public:
    TPpContext(TParseContextBase&, const std::string& rootFileName, TShader::Includer&);
    virtual ~TPpContext();

    void setPreamble(const char* preamble, size_t length);

    int tokenize(TPpToken& ppToken);
    int tokenPaste(int token, TPpToken&);

    class tInput {
    public:
        tInput(TPpContext* p) : done(false), pp(p) { }
        virtual ~tInput() { }

        virtual int scan(TPpToken*) = 0;
        virtual int getch() = 0;
        virtual void ungetch() = 0;
        virtual bool peekPasting() { return false; }             // true when about to see ##
        virtual bool peekContinuedPasting(int) { return false; } // true when non-spaced tokens can paste
        virtual bool endOfReplacementList() { return false; } // true when at the end of a macro replacement list (RHS of #define)
        virtual bool isMacroInput() { return false; }
        virtual bool isStringInput() { return false; }

        // Will be called when we start reading tokens from this instance
        virtual void notifyActivated() {}
        // Will be called when we do not read tokens from this instance anymore
        virtual void notifyDeleted() {}
    protected:
        bool done;
        TPpContext* pp;
    };

    void setInput(TInputScanner& input, bool versionWillBeError);

    void pushInput(tInput* in)
    {
        inputStack.push_back(in);
        in->notifyActivated();
    }
    void popInput()
    {
        inputStack.back()->notifyDeleted();
        delete inputStack.back();
        inputStack.pop_back();
    }

    //
    // From PpTokens.cpp
    //

    // Capture the needed parts of a token stream for macro recording/playback.
    class TokenStream {
    public:
        // Manage a stream of these 'Token', which capture the relevant parts
        // of a TPpToken, plus its atom.
        class Token {
        public:
            Token(int atom, const TPpToken& ppToken) : 
                atom(atom),
                space(ppToken.space),
                i64val(ppToken.i64val),
                name(ppToken.name) { }
            int get(TPpToken& ppToken)
            {
                ppToken.clear();
                ppToken.space = space;
                ppToken.i64val = i64val;
                snprintf(ppToken.name, sizeof(ppToken.name), "%s", name.c_str());
                return atom;
            }
            bool isAtom(int a) const { return atom == a; }
            int getAtom() const { return atom; }
            bool nonSpaced() const { return !space; }
        protected:
            Token() {}
            int atom;
            bool space;        // did a space precede the token?
            long long i64val;
            TString name;
        };

        TokenStream() : currentPos(0) { }

        void putToken(int token, TPpToken* ppToken);
        bool peekToken(int atom) { return !atEnd() && stream[currentPos].isAtom(atom); }
        bool peekContinuedPasting(int atom)
        {
            // This is basically necessary because, for example, the PP
            // tokenizer only accepts valid numeric-literals plus suffixes, so
            // separates numeric-literals plus bad suffix into two tokens, which
            // should get both pasted together as one token when token pasting.
            //
            // The following code is a bit more generalized than the above example.
            if (!atEnd() && atom == PpAtomIdentifier && stream[currentPos].nonSpaced()) {
                switch(stream[currentPos].getAtom()) {
                    case PpAtomConstInt:
                    case PpAtomConstUint:
                    case PpAtomConstInt64:
                    case PpAtomConstUint64:
                    case PpAtomConstInt16:
                    case PpAtomConstUint16:
                    case PpAtomConstFloat:
                    case PpAtomConstDouble:
                    case PpAtomConstFloat16:
                    case PpAtomConstString:
                    case PpAtomIdentifier:
                        return true;
                    default:
                        break;
                }
            }

            return false;
        }
        int getToken(TParseContextBase&, TPpToken*);
        bool atEnd() { return currentPos >= stream.size(); }
        bool peekTokenizedPasting(bool lastTokenPastes);
        void reset() { currentPos = 0; }

    protected:
        TVector<Token> stream;
        size_t currentPos;
    };

    //
    // From Pp.cpp
    //

    struct MacroSymbol {
        MacroSymbol() : functionLike(0), busy(0), undef(0) { }
        TVector<int> args;
        TokenStream body;
        unsigned functionLike : 1;  // 0 means object-like, 1 means function-like
        unsigned busy         : 1;
        unsigned undef        : 1;
    };

    typedef TMap<int, MacroSymbol> TSymbolMap;
    TSymbolMap macroDefs;  // map atoms to macro definitions
    MacroSymbol* lookupMacroDef(int atom)
    {
        auto existingMacroIt = macroDefs.find(atom);
        return (existingMacroIt == macroDefs.end()) ? nullptr : &(existingMacroIt->second);
    }
    void addMacroDef(int atom, MacroSymbol& macroDef) { macroDefs[atom] = macroDef; }

protected:
    TPpContext(TPpContext&);
    TPpContext& operator=(TPpContext&);

    TStringAtomMap atomStrings;
    char*   preamble;               // string to parse, all before line 1 of string 0, it is 0 if no preamble
    int     preambleLength;
    char**  strings;                // official strings of shader, starting a string 0 line 1
    size_t* lengths;
    int     numStrings;             // how many official strings there are
    int     currentString;          // which string we're currently parsing  (-1 for preamble)

    // Scanner data:
    int previous_token;
    TParseContextBase& parseContext;
    std::vector<int> lastLineTokens;
    std::vector<TSourceLoc> lastLineTokenLocs;
    // Get the next token from *stack* of input sources, popping input sources
    // that are out of tokens, down until an input source is found that has a token.
    // Return EndOfInput when there are no more tokens to be found by doing this.
    int scanToken(TPpToken* ppToken)
    {
        int token = EndOfInput;

        while (! inputStack.empty()) {
            token = inputStack.back()->scan(ppToken);
            if (token != EndOfInput || inputStack.empty())
                break;
            popInput();
        }
        if (!inputStack.empty() && inputStack.back()->isStringInput() && !inElseSkip) {
            if (token == '\n') {
                lastLineTokens.clear();
                lastLineTokenLocs.clear();
            } else {
                lastLineTokens.push_back(token);
                lastLineTokenLocs.push_back(ppToken->loc);
            }
        }
        return token;
    }
    int  getChar() { return inputStack.back()->getch(); }
    void ungetChar() { inputStack.back()->ungetch(); }
    bool peekPasting() { return !inputStack.empty() && inputStack.back()->peekPasting(); }
    bool peekContinuedPasting(int a)
    {
        return !inputStack.empty() && inputStack.back()->peekContinuedPasting(a);
    }
    bool endOfReplacementList() { return inputStack.empty() || inputStack.back()->endOfReplacementList(); }
    bool isMacroInput() { return inputStack.size() > 0 && inputStack.back()->isMacroInput(); }

    static const int maxIfNesting = 65;

    int ifdepth;                  // current #if-#else-#endif nesting in the cpp.c file (pre-processor)
    bool elseSeen[maxIfNesting];  // Keep a track of whether an else has been seen at a particular depth
    int elsetracker;              // #if-#else and #endif constructs...Counter.

    class tMacroInput : public tInput {
    public:
        tMacroInput(TPpContext* pp) : tInput(pp), prepaste(false), postpaste(false) { }
        virtual ~tMacroInput()
        {
            for (size_t i = 0; i < args.size(); ++i)
                delete args[i];
            for (size_t i = 0; i < expandedArgs.size(); ++i)
                delete expandedArgs[i];
        }

        virtual int scan(TPpToken*) override;
        virtual int getch() override { assert(0); return EndOfInput; }
        virtual void ungetch() override { assert(0); }
        bool peekPasting() override { return prepaste; }
        bool peekContinuedPasting(int a) override { return mac->body.peekContinuedPasting(a); }
        bool endOfReplacementList() override { return mac->body.atEnd(); }
        bool isMacroInput() override { return true; }

        MacroSymbol *mac;
        TVector<TokenStream*> args;
        TVector<TokenStream*> expandedArgs;

    protected:
        bool prepaste;         // true if we are just before ##
        bool postpaste;        // true if we are right after ##
    };

    class tMarkerInput : public tInput {
    public:
        tMarkerInput(TPpContext* pp) : tInput(pp) { }
        virtual int scan(TPpToken*) override
        {
            if (done)
                return EndOfInput;
            done = true;

            return marker;
        }
        virtual int getch() override { assert(0); return EndOfInput; }
        virtual void ungetch() override { assert(0); }
        static const int marker = -3;
    };

    class tStringifyLevelInput : public tInput {
        int what;
        tStringifyLevelInput(TPpContext* pp) : tInput(pp) { }
    public:
        static tStringifyLevelInput popMarker(TPpContext* pp)
        {
            tStringifyLevelInput sl(pp);
            sl.what = POP;
            return sl;
        }

        static tStringifyLevelInput pushMarker(TPpContext* pp)
        {
            tStringifyLevelInput sl(pp);
            sl.what = PUSH;
            return sl;
        }

        int scan(TPpToken*) override
        {
            if (done)
                return EndOfInput;
            done = true;

            return what;
        }
        virtual int getch() override { assert(0); return EndOfInput; }
        virtual void ungetch() override { assert(0); }
        static const int PUSH = -4;
        static const int POP = -5;
    };

    class tZeroInput : public tInput {
    public:
        tZeroInput(TPpContext* pp) : tInput(pp) { }
        virtual int scan(TPpToken*) override;
        virtual int getch() override { assert(0); return EndOfInput; }
        virtual void ungetch() override { assert(0); }
    };

    std::vector<tInput*> inputStack;
    bool errorOnVersion;
    bool versionSeen;

    //
    // from Pp.cpp
    //

    // Used to obtain #include content.
    TShader::Includer& includer;

    int CPPdefine(TPpToken * ppToken);
    int CPPundef(TPpToken * ppToken);
    int CPPelse(int matchelse, TPpToken * ppToken);
    int extraTokenCheck(int atom, TPpToken* ppToken, int token);
    int eval(int token, int precedence, bool shortCircuit, int& res, bool& err, TPpToken * ppToken);
    int evalToToken(int token, bool shortCircuit, int& res, bool& err, TPpToken * ppToken);
    int CPPif (TPpToken * ppToken);
    int CPPifdef(int defined, TPpToken * ppToken);
    int CPPinclude(TPpToken * ppToken);
    int CPPline(TPpToken * ppToken);
    int CPPerror(TPpToken * ppToken);
    int CPPpragma(TPpToken * ppToken);
    int CPPversion(TPpToken * ppToken);
    int CPPextension(TPpToken * ppToken);
    int readCPPline(TPpToken * ppToken);
    int scanHeaderName(TPpToken* ppToken, char delimit);
    TokenStream* PrescanMacroArg(TokenStream&, TPpToken*, bool newLineOkay);
    MacroExpandResult MacroExpand(TPpToken* ppToken, bool expandUndef, bool newLineOkay);

    //
    // From PpTokens.cpp
    //
    void pushTokenStreamInput(TokenStream&, bool pasting = false, bool expanded = false);
    void UngetToken(int token, TPpToken*);

    class tTokenInput : public tInput {
    public:
        tTokenInput(TPpContext* pp, TokenStream* t, bool prepasting, bool expanded) :
            tInput(pp),
            tokens(t),
            lastTokenPastes(prepasting),
            preExpanded(expanded) { }
        virtual int scan(TPpToken *ppToken) override {
            int token = tokens->getToken(pp->parseContext, ppToken);
            ppToken->fullyExpanded = preExpanded;
            if (tokens->atEnd() && token == PpAtomIdentifier) {
                int macroAtom = pp->atomStrings.getAtom(ppToken->name);
                MacroSymbol* macro = macroAtom == 0 ? nullptr : pp->lookupMacroDef(macroAtom);
                if (macro && macro->functionLike)
                    ppToken->fullyExpanded = false;
            }
            return token;
        }
        virtual int getch() override { assert(0); return EndOfInput; }
        virtual void ungetch() override { assert(0); }
        virtual bool peekPasting() override { return tokens->peekTokenizedPasting(lastTokenPastes); }
        bool peekContinuedPasting(int a) override { return tokens->peekContinuedPasting(a); }
    protected:
        TokenStream* tokens;
        bool lastTokenPastes; // true if the last token in the input is to be pasted, rather than consumed as a token
        bool preExpanded;
    };

    class tUngotTokenInput : public tInput {
    public:
        tUngotTokenInput(TPpContext* pp, int t, TPpToken* p) : tInput(pp), token(t), lval(*p) { }
        virtual int scan(TPpToken *) override;
        virtual int getch() override { assert(0); return EndOfInput; }
        virtual void ungetch() override { assert(0); }
    protected:
        int token;
        TPpToken lval;
    };

    //
    // From PpScanner.cpp
    //
    class tStringInput : public tInput {
    public:
        tStringInput(TPpContext* pp, TInputScanner& i) : tInput(pp), input(&i) { }
        virtual int scan(TPpToken*) override;
        bool isStringInput() override { return true; }
        // Scanner used to get source stream characters.
        //  - Escaped newlines are handled here, invisibly to the caller.
        //  - All forms of newline are handled, and turned into just a '\n'.
        int getch() override
        {
            int ch = input->get();

            if (ch == '\\') {
                // Move past escaped newlines, as many as sequentially exist
                do {
                    if (input->peek() == '\r' || input->peek() == '\n') {
                        bool allowed = pp->parseContext.lineContinuationCheck(input->getSourceLoc(), pp->inComment);
                        if (! allowed && pp->inComment)
                            return '\\';

                        // escape one newline now
                        ch = input->get();
                        int nextch = input->get();
                        if (ch == '\r' && nextch == '\n')
                            ch = input->get();
                        else
                            ch = nextch;
                    } else
                        return '\\';
                } while (ch == '\\');
            }

            // handle any non-escaped newline
            if (ch == '\r' || ch == '\n') {
                if (ch == '\r' && input->peek() == '\n')
                    input->get();
                return '\n';
            }

            return ch;
        }

        // Scanner used to backup the source stream characters.  Newlines are
        // handled here, invisibly to the caller, meaning have to undo exactly
        // what getch() above does (e.g., don't leave things in the middle of a
        // sequence of escaped newlines).
        void ungetch() override
        {
            input->unget();

            do {
                int ch = input->peek();
                if (ch == '\r' || ch == '\n') {
                    if (ch == '\n') {
                        // correct for two-character newline
                        input->unget();
                        if (input->peek() != '\r')
                            input->get();
                    }
                    // now in front of a complete newline, move past an escape character
                    input->unget();
                    if (input->peek() == '\\')
                        input->unget();
                    else {
                        input->get();
                        break;
                    }
                } else
                    break;
            } while (true);
        }

    protected:
        TInputScanner* input;
    };

    // Holds a reference to included file data, as well as a
    // prologue and an epilogue string. This can be scanned using the tInput
    // interface and acts as a single source string.
    class TokenizableIncludeFile : public tInput {
    public:
        // Copies prologue and epilogue. The includedFile must remain valid
        // until this TokenizableIncludeFile is no longer used.
        TokenizableIncludeFile(const TSourceLoc& startLoc,
                          const std::string& prologue,
                          TShader::Includer::IncludeResult* includedFile,
                          const std::string& epilogue,
                          TPpContext* pp)
            : tInput(pp),
              prologue_(prologue),
              epilogue_(epilogue),
              includedFile_(includedFile),
              scanner(3, strings, lengths, nullptr, 0, 0, true),
              prevScanner(nullptr),
              stringInput(pp, scanner)
        {
              strings[0] = prologue_.data();
              strings[1] = includedFile_->headerData;
              strings[2] = epilogue_.data();

              lengths[0] = prologue_.size();
              lengths[1] = includedFile_->headerLength;
              lengths[2] = epilogue_.size();

              scanner.setLine(startLoc.line);
              scanner.setString(startLoc.string);

              scanner.setFile(startLoc.getFilenameStr(), 0);
              scanner.setFile(startLoc.getFilenameStr(), 1);
              scanner.setFile(startLoc.getFilenameStr(), 2);
        }

        // tInput methods:
        int scan(TPpToken* t) override { return stringInput.scan(t); }
        int getch() override { return stringInput.getch(); }
        void ungetch() override { stringInput.ungetch(); }

        void notifyActivated() override
        {
            prevScanner = pp->parseContext.getScanner();
            pp->parseContext.setScanner(&scanner);
            pp->push_include(includedFile_);
        }

        void notifyDeleted() override
        {
            pp->parseContext.setScanner(prevScanner);
            pp->pop_include();
        }

    private:
        TokenizableIncludeFile& operator=(const TokenizableIncludeFile&);

        // Stores the prologue for this string.
        const std::string prologue_;

        // Stores the epilogue for this string.
        const std::string epilogue_;

        // Points to the IncludeResult that this TokenizableIncludeFile represents.
        TShader::Includer::IncludeResult* includedFile_;

        // Will point to prologue_, includedFile_->headerData and epilogue_
        // This is passed to scanner constructor.
        // These do not own the storage and it must remain valid until this
        // object has been destroyed.
        const char* strings[3];
        // Length of str_, passed to scanner constructor.
        size_t lengths[3];
        // Scans over str_.
        TInputScanner scanner;
        // The previous effective scanner before the scanner in this instance
        // has been activated.
        TInputScanner* prevScanner;
        // Delegate object implementing the tInput interface.
        tStringInput stringInput;
    };

    int ScanFromString(char* s);
    void missingEndifCheck();
    int lFloatConst(int len, int ch, TPpToken* ppToken);
    int characterLiteral(TPpToken* ppToken);

    void push_include(TShader::Includer::IncludeResult* result)
    {
        currentSourceFile = result->headerName;
        includeStack.push(result);
    }

    void pop_include()
    {
        TShader::Includer::IncludeResult* include = includeStack.top();
        includeStack.pop();
        includer.releaseInclude(include);
        if (includeStack.empty()) {
            currentSourceFile = rootFileName;
        } else {
            currentSourceFile = includeStack.top()->headerName;
        }
    }

    bool inComment;
    std::string rootFileName;
    std::stack<TShader::Includer::IncludeResult*> includeStack;
    std::string currentSourceFile;

    std::istringstream strtodStream;
    bool disableEscapeSequences;
    // True if we're skipping a section enclosed by #if/#ifdef/#elif/#else which was evaluated to
    // be inactive, e.g. #if 0
    bool inElseSkip;
};

} // end namespace glslang
} // namespace QtShaderTools

#endif  // PPCONTEXT_H
