﻿/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

#pragma once

#include "Recognizer.h"
#include "TokenSource.h"
#include "CharStream.h"
#include "Token.h"

namespace antlr4 {

  /// A lexer is recognizer that draws input symbols from a character stream.
  /// lexer grammars result in a subclass of this object. A Lexer object
  /// uses simplified match() and error recovery mechanisms in the interest
  /// of speed.
  class ANTLR4CPP_PUBLIC Lexer : public Recognizer, public TokenSource {
  public:
    static const size_t DEFAULT_MODE = 0;
    static const size_t MORE = static_cast<size_t>(-2);
    static const size_t SKIP = static_cast<size_t>(-3);

    static const size_t DEFAULT_TOKEN_CHANNEL = Token::DEFAULT_CHANNEL;
    static const size_t HIDDEN = Token::HIDDEN_CHANNEL;
    static const size_t MIN_CHAR_VALUE = 0;
    static const size_t MAX_CHAR_VALUE = 0x10FFFF;

    CharStream *_input; // Pure reference, usually from statically allocated instance.

  protected:
    /// How to create token objects.
    Ref<TokenFactory<CommonToken>> _factory;

  public:
    /// The goal of all lexer rules/methods is to create a token object.
    ///  This is an instance variable as multiple rules may collaborate to
    ///  create a single token.  nextToken will return this object after
    ///  matching lexer rule(s).  If you subclass to allow multiple token
    ///  emissions, then set this to the last token to be matched or
    ///  something nonnull so that the auto token emit mechanism will not
    ///  emit another token.

    // Life cycle of a token is this:
    // Created by emit() (via the token factory) or by action code, holding ownership of it.
    // Ownership is handed over to the token stream when calling nextToken().
    std::unique_ptr<Token> token;

    /// <summary>
    /// What character index in the stream did the current token start at?
    ///  Needed, for example, to get the text for current token.  Set at
    ///  the start of nextToken.
    /// </summary>
    size_t tokenStartCharIndex;

    /// <summary>
    /// The line on which the first character of the token resides </summary>
    size_t tokenStartLine;

    /// The character position of first character within the line.
    size_t tokenStartCharPositionInLine;

    /// Once we see EOF on char stream, next token will be EOF.
    /// If you have DONE : EOF ; then you see DONE EOF.
    bool hitEOF;

    /// The channel number for the current token.
    size_t channel;

    /// The token type for the current token.
    size_t type;

    // Use the vector as a stack.
    std::vector<size_t> modeStack;
    size_t mode;

    Lexer();
    Lexer(CharStream *input);
    virtual ~Lexer() {}

    virtual void reset();

    /// Return a token from this source; i.e., match a token on the char stream.
    virtual std::unique_ptr<Token> nextToken() override;

    /// Instruct the lexer to skip creating a token for current lexer rule
    /// and look for another token.  nextToken() knows to keep looking when
    /// a lexer rule finishes with token set to SKIP_TOKEN.  Recall that
    /// if token == null at end of any token rule, it creates one for you
    /// and emits it.
    virtual void skip();
    virtual void more();
    virtual void setMode(size_t m);
    virtual void pushMode(size_t m);
    virtual size_t popMode();

    template<typename T1>
    void setTokenFactory(TokenFactory<T1> *factory)  {
      this->_factory = factory;
    }

    virtual Ref<TokenFactory<CommonToken>> getTokenFactory() override;

    /// Set the char stream and reset the lexer
    virtual void setInputStream(IntStream *input) override;

    virtual std::string getSourceName() override;

    virtual CharStream* getInputStream() override;

    /// By default does not support multiple emits per nextToken invocation
    /// for efficiency reasons. Subclasses can override this method, nextToken,
    /// and getToken (to push tokens into a list and pull from that list
    /// rather than a single variable as this implementation does).
    virtual void emit(std::unique_ptr<Token> newToken);

    /// The standard method called to automatically emit a token at the
    /// outermost lexical rule.  The token object should point into the
    /// char buffer start..stop.  If there is a text override in 'text',
    /// use that to set the token's text.  Override this method to emit
    /// custom Token objects or provide a new factory.
    virtual Token* emit();

    virtual Token* emitEOF();

    virtual size_t getLine() const override;

    virtual size_t getCharPositionInLine() override;

    virtual void setLine(size_t line);

    virtual void setCharPositionInLine(size_t charPositionInLine);

    /// What is the index of the current character of lookahead?
    virtual size_t getCharIndex();

    /// Return the text matched so far for the current token or any
    /// text override.
    virtual std::string getText();

    /// Set the complete text of this token; it wipes any previous
    /// changes to the text.
    virtual void setText(const std::string &text);

    /// Override if emitting multiple tokens.
    virtual std::unique_ptr<Token> getToken();

    virtual void setToken(std::unique_ptr<Token> newToken);

    virtual void setType(size_t ttype);

    virtual size_t getType();

    virtual void setChannel(size_t newChannel);

    virtual size_t getChannel();

    virtual const std::vector<std::string>& getChannelNames() const = 0;

    virtual const std::vector<std::string>& getModeNames() const = 0;

    /// Return a list of all Token objects in input char stream.
    /// Forces load of all tokens. Does not include EOF token.
    virtual std::vector<std::unique_ptr<Token>> getAllTokens();

    virtual void recover(const LexerNoViableAltException &e);

    virtual void notifyListeners(const LexerNoViableAltException &e);

    virtual std::string getErrorDisplay(const std::string &s);

    /// Lexers can normally match any char in it's vocabulary after matching
    /// a token, so do the easy thing and just kill a character and hope
    /// it all works out.  You can instead use the rule invocation stack
    /// to do sophisticated error recovery if you are in a fragment rule.
    virtual void recover(RecognitionException *re);

    /// <summary>
    /// Gets the number of syntax errors reported during parsing. This value is
    /// incremented each time <seealso cref="#notifyErrorListeners"/> is called.
    /// </summary>
    /// <seealso cref= #notifyListeners </seealso>
    virtual size_t getNumberOfSyntaxErrors();

  protected:
    /// You can set the text for the current token to override what is in
    /// the input char buffer (via setText()).
    std::string _text;

  private:
    size_t _syntaxErrors;
    void InitializeInstanceFields();
  };

} // namespace antlr4
