﻿/* 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 "TokenStream.h"

namespace antlr4 {

  /**
   * This implementation of {@link TokenStream} loads tokens from a
   * {@link TokenSource} on-demand, and places the tokens in a buffer to provide
   * access to any previous token by index.
   *
   * <p>
   * This token stream ignores the value of {@link Token#getChannel}. If your
   * parser requires the token stream filter tokens to only those on a particular
   * channel, such as {@link Token#DEFAULT_CHANNEL} or
   * {@link Token#HIDDEN_CHANNEL}, use a filtering token stream such a
   * {@link CommonTokenStream}.</p>
   */
  class ANTLR4CPP_PUBLIC BufferedTokenStream : public TokenStream {
  public:
    BufferedTokenStream(TokenSource *tokenSource);
    BufferedTokenStream(const BufferedTokenStream& other) = delete;

    BufferedTokenStream& operator = (const BufferedTokenStream& other) = delete;

    virtual TokenSource* getTokenSource() const override;
    virtual size_t index() override;
    virtual ssize_t mark() override;

    virtual void release(ssize_t marker) override;
    virtual void reset();
    virtual void seek(size_t index) override;

    virtual size_t size() override;
    virtual void consume() override;

    virtual Token* get(size_t i) const override;

    /// Get all tokens from start..stop inclusively.
    virtual std::vector<Token *> get(size_t start, size_t stop);

    virtual size_t LA(ssize_t i) override;
    virtual Token* LT(ssize_t k) override;

    /// Reset this token stream by setting its token source.
    virtual void setTokenSource(TokenSource *tokenSource);
    virtual std::vector<Token *> getTokens();
    virtual std::vector<Token *> getTokens(size_t start, size_t stop);

    /// <summary>
    /// Given a start and stop index, return a List of all tokens in
    ///  the token type BitSet.  Return null if no tokens were found.  This
    ///  method looks at both on and off channel tokens.
    /// </summary>
    virtual std::vector<Token *> getTokens(size_t start, size_t stop, const std::vector<size_t> &types);
    virtual std::vector<Token *> getTokens(size_t start, size_t stop, size_t ttype);

    /// Collect all tokens on specified channel to the right of
    ///  the current token up until we see a token on DEFAULT_TOKEN_CHANNEL or
    ///  EOF. If channel is -1, find any non default channel token.
    virtual std::vector<Token *> getHiddenTokensToRight(size_t tokenIndex, ssize_t channel);

    /// <summary>
    /// Collect all hidden tokens (any off-default channel) to the right of
    ///  the current token up until we see a token on DEFAULT_TOKEN_CHANNEL
    ///  or EOF.
    /// </summary>
    virtual std::vector<Token *> getHiddenTokensToRight(size_t tokenIndex);

    /// <summary>
    /// Collect all tokens on specified channel to the left of
    ///  the current token up until we see a token on DEFAULT_TOKEN_CHANNEL.
    ///  If channel is -1, find any non default channel token.
    /// </summary>
    virtual std::vector<Token *> getHiddenTokensToLeft(size_t tokenIndex, ssize_t channel);

    /// <summary>
    /// Collect all hidden tokens (any off-default channel) to the left of
    ///  the current token up until we see a token on DEFAULT_TOKEN_CHANNEL.
    /// </summary>
    virtual std::vector<Token *> getHiddenTokensToLeft(size_t tokenIndex);

    virtual std::string getSourceName() const override;
    virtual std::string getText() override;
    virtual std::string getText(const misc::Interval &interval) override;
    virtual std::string getText(RuleContext *ctx) override;
    virtual std::string getText(Token *start, Token *stop) override;

    /// Get all tokens from lexer until EOF.
    virtual void fill();

  protected:
    /**
     * The {@link TokenSource} from which tokens for this stream are fetched.
     */
    TokenSource *_tokenSource;

    /**
     * A collection of all tokens fetched from the token source. The list is
     * considered a complete view of the input once {@link #fetchedEOF} is set
     * to {@code true}.
     */
    std::vector<std::unique_ptr<Token>> _tokens;

    /**
     * The index into {@link #tokens} of the current token (next token to
     * {@link #consume}). {@link #tokens}{@code [}{@link #p}{@code ]} should be
     * {@link #LT LT(1)}.
     *
     * <p>This field is set to -1 when the stream is first constructed or when
     * {@link #setTokenSource} is called, indicating that the first token has
     * not yet been fetched from the token source. For additional information,
     * see the documentation of {@link IntStream} for a description of
     * Initializing Methods.</p>
     */
    // ml: since -1 requires to make this member signed for just this single aspect we use a member _needSetup instead.
    //     Use bool isInitialized() to find out if this stream has started reading.
    size_t _p;

    /**
     * Indicates whether the {@link Token#EOF} token has been fetched from
     * {@link #tokenSource} and added to {@link #tokens}. This field improves
     * performance for the following cases:
     *
     * <ul>
     * <li>{@link #consume}: The lookahead check in {@link #consume} to prevent
     * consuming the EOF symbol is optimized by checking the values of
     * {@link #fetchedEOF} and {@link #p} instead of calling {@link #LA}.</li>
     * <li>{@link #fetch}: The check to prevent adding multiple EOF symbols into
     * {@link #tokens} is trivial with this field.</li>
     * <ul>
     */
    bool _fetchedEOF;

    /// <summary>
    /// Make sure index {@code i} in tokens has a token.
    /// </summary>
    /// <returns> {@code true} if a token is located at index {@code i}, otherwise
    ///    {@code false}. </returns>
    /// <seealso cref= #get(int i) </seealso>
    virtual bool sync(size_t i);

    /// <summary>
    /// Add {@code n} elements to buffer.
    /// </summary>
    /// <returns> The actual number of elements added to the buffer. </returns>
    virtual size_t fetch(size_t n);

    virtual Token* LB(size_t k);

    /// Allowed derived classes to modify the behavior of operations which change
    /// the current stream position by adjusting the target token index of a seek
    /// operation. The default implementation simply returns {@code i}. If an
    /// exception is thrown in this method, the current stream index should not be
    /// changed.
    /// <p/>
    /// For example, <seealso cref="CommonTokenStream"/> overrides this method to ensure that
    /// the seek target is always an on-channel token.
    ///
    /// <param name="i"> The target token index. </param>
    /// <returns> The adjusted target token index. </returns>
    virtual ssize_t adjustSeekIndex(size_t i);
    void lazyInit();
    virtual void setup();

    /**
     * Given a starting index, return the index of the next token on channel.
     * Return {@code i} if {@code tokens[i]} is on channel. Return the index of
     * the EOF token if there are no tokens on channel between {@code i} and
     * EOF.
     */
    virtual ssize_t nextTokenOnChannel(size_t i, size_t channel);

    /**
     * Given a starting index, return the index of the previous token on
     * channel. Return {@code i} if {@code tokens[i]} is on channel. Return -1
     * if there are no tokens on channel between {@code i} and 0.
     *
     * <p>
     * If {@code i} specifies an index at or after the EOF token, the EOF token
     * index is returned. This is due to the fact that the EOF token is treated
     * as though it were on every channel.</p>
     */
    virtual ssize_t previousTokenOnChannel(size_t i, size_t channel);

    virtual std::vector<Token *> filterForChannel(size_t from, size_t to, ssize_t channel);

    bool isInitialized() const;

  private:
    bool _needSetup;
    void InitializeInstanceFields();
  };

} // namespace antlr4