/*
 * Copyright (c) 2020, Emanuel Sprung <emanuel.sprung@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include "RegexByteCode.h"
#include "RegexError.h"
#include "RegexLexer.h"
#include "RegexOptions.h"

#include <AK/Forward.h>
#include <AK/StringBuilder.h>
#include <AK/Types.h>
#include <AK/Vector.h>

namespace regex {

class PosixExtendedParser;
class ECMA262Parser;

template<typename T>
struct GenericParserTraits {
    using OptionsType = T;
};

template<typename T>
struct ParserTraits : public GenericParserTraits<T> {
};

template<>
struct ParserTraits<PosixExtendedParser> : public GenericParserTraits<PosixOptions> {
};

template<>
struct ParserTraits<ECMA262Parser> : public GenericParserTraits<ECMAScriptOptions> {
};

class Parser {
public:
    struct Result {
        ByteCode bytecode;
        size_t capture_groups_count;
        size_t named_capture_groups_count;
        size_t match_length_minimum;
        Error error;
        Token error_token;
    };

    explicit Parser(Lexer& lexer)
        : m_parser_state(lexer)
    {
    }

    Parser(Lexer& lexer, AllOptions regex_options)
        : m_parser_state(lexer, regex_options)
    {
    }

    virtual ~Parser() = default;

    Result parse(Optional<AllOptions> regex_options = {});
    bool has_error() const { return m_parser_state.error != Error::NoError; }
    Error error() const { return m_parser_state.error; }

protected:
    virtual bool parse_internal(ByteCode&, size_t& match_length_minimum) = 0;

    ALWAYS_INLINE bool match(TokenType type) const;
    ALWAYS_INLINE bool match(char ch) const;
    ALWAYS_INLINE bool match_ordinary_characters();
    ALWAYS_INLINE Token consume();
    ALWAYS_INLINE Token consume(TokenType type, Error error);
    ALWAYS_INLINE bool consume(const String&);
    ALWAYS_INLINE bool try_skip(StringView);
    ALWAYS_INLINE bool lookahead_any(StringView);
    ALWAYS_INLINE char skip();
    ALWAYS_INLINE void back(size_t = 1);
    ALWAYS_INLINE void reset();
    ALWAYS_INLINE bool done() const;
    ALWAYS_INLINE bool set_error(Error error);

    struct ParserState {
        Lexer& lexer;
        Token current_token;
        Error error = Error::NoError;
        Token error_token { TokenType::Eof, 0, StringView(nullptr) };
        ByteCode bytecode;
        size_t capture_groups_count { 0 };
        size_t named_capture_groups_count { 0 };
        size_t match_length_minimum { 0 };
        AllOptions regex_options;
        HashMap<int, size_t> capture_group_minimum_lengths;
        HashMap<FlyString, size_t> named_capture_group_minimum_lengths;
        HashMap<size_t, FlyString> named_capture_groups;

        explicit ParserState(Lexer& lexer)
            : lexer(lexer)
            , current_token(lexer.next())
        {
        }
        explicit ParserState(Lexer& lexer, AllOptions regex_options)
            : lexer(lexer)
            , current_token(lexer.next())
            , regex_options(regex_options)
        {
        }
    };

    ParserState m_parser_state;
};

class PosixExtendedParser final : public Parser {
public:
    explicit PosixExtendedParser(Lexer& lexer)
        : Parser(lexer)
    {
    }

    PosixExtendedParser(Lexer& lexer, Optional<typename ParserTraits<PosixExtendedParser>::OptionsType> regex_options)
        : Parser(lexer, regex_options.value_or({}))
    {
    }

    ~PosixExtendedParser() = default;

private:
    ALWAYS_INLINE bool match_repetition_symbol();

    bool parse_internal(ByteCode&, size_t&) override;

    bool parse_root(ByteCode&, size_t&);
    ALWAYS_INLINE bool parse_sub_expression(ByteCode&, size_t&);
    ALWAYS_INLINE bool parse_bracket_expression(ByteCode&, size_t&);
    ALWAYS_INLINE bool parse_repetition_symbol(ByteCode&, size_t&);
};

class ECMA262Parser final : public Parser {
public:
    explicit ECMA262Parser(Lexer& lexer)
        : Parser(lexer)
    {
    }

    ECMA262Parser(Lexer& lexer, Optional<typename ParserTraits<ECMA262Parser>::OptionsType> regex_options)
        : Parser(lexer, regex_options.value_or({}))
    {
        m_should_use_browser_extended_grammar = regex_options.has_value() && regex_options->has_flag_set(ECMAScriptFlags::BrowserExtended);
    }

    ~ECMA262Parser() = default;

private:
    bool parse_internal(ByteCode&, size_t&) override;

    enum class ReadDigitsInitialZeroState {
        Allow,
        Disallow,
    };
    StringView read_digits_as_string(ReadDigitsInitialZeroState initial_zero = ReadDigitsInitialZeroState::Allow, bool hex = false, int max_count = -1);
    Optional<unsigned> read_digits(ReadDigitsInitialZeroState initial_zero = ReadDigitsInitialZeroState::Allow, bool hex = false, int max_count = -1);
    StringView read_capture_group_specifier(bool take_starting_angle_bracket = false);

    bool parse_pattern(ByteCode&, size_t&, bool unicode, bool named);
    bool parse_disjunction(ByteCode&, size_t&, bool unicode, bool named);
    bool parse_alternative(ByteCode&, size_t&, bool unicode, bool named);
    bool parse_term(ByteCode&, size_t&, bool unicode, bool named);
    bool parse_assertion(ByteCode&, size_t&, bool unicode, bool named);
    bool parse_atom(ByteCode&, size_t&, bool unicode, bool named);
    bool parse_quantifier(ByteCode&, size_t&, bool unicode, bool named);
    bool parse_atom_escape(ByteCode&, size_t&, bool unicode, bool named);
    bool parse_character_class(ByteCode&, size_t&, bool unicode, bool named);
    bool parse_capture_group(ByteCode&, size_t&, bool unicode, bool named);
    Optional<CharClass> parse_character_class_escape(bool& out_inverse, bool expect_backslash = false);
    bool parse_nonempty_class_ranges(Vector<CompareTypeAndValuePair>&, bool unicode);

    // Used only by B.1.4, Regular Expression Patterns (Extended for use in browsers)
    bool parse_quantifiable_assertion(ByteCode&, size_t&, bool named);
    bool parse_extended_atom(ByteCode&, size_t&, bool named);
    bool parse_inner_disjunction(ByteCode& bytecode_stack, size_t& length, bool unicode, bool named);
    bool parse_invalid_braced_quantifier(); // Note: This function either parses and *fails*, or doesn't parse anything and returns false.
    bool parse_legacy_octal_escape_sequence(ByteCode& bytecode_stack, size_t& length);
    Optional<u8> parse_legacy_octal_escape();

    size_t ensure_total_number_of_capturing_parenthesis();

    // ECMA-262's flavour of regex is a bit weird in that it allows backrefs to reference "future" captures, and such backrefs
    // always match the empty string. So we have to know how many capturing parenthesis there are, but we don't want to always
    // parse it twice, so we'll just do so when it's actually needed.
    // Most patterns should have no need to ever populate this field.
    Optional<size_t> m_total_number_of_capturing_parenthesis;

    // Keep the Annex B. behaviour behind a flag, the users can enable it by passing the `ECMAScriptFlags::BrowserExtended` flag.
    bool m_should_use_browser_extended_grammar { false };
};

using PosixExtended = PosixExtendedParser;
using ECMA262 = ECMA262Parser;

}

using regex::ECMA262;
using regex::PosixExtended;