//

// Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)

//

// Distributed under the Boost Software License, Version 1.0. (See accompanying

// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

//

// Official repository: https://github.com/boostorg/json

//

#ifndef BOOST_JSON_SERIALIZER_HPP

#define BOOST_JSON_SERIALIZER_HPP

#include <boost/json/detail/config.hpp>

#include <boost/json/value.hpp>

#include <boost/json/detail/format.hpp>

#include <boost/json/detail/stack.hpp>

#include <boost/json/detail/stream.hpp>

namespace boost {

namespace json {

/** A serializer for JSON.

    This class traverses an instance of a library

    type and emits serialized JSON text by filling

    in one or more caller-provided buffers. To use,

    declare a variable and call @ref reset with

    a pointer to the variable you want to serialize.

    Then call @ref read over and over until

    @ref done returns `true`.

    @par Example

    This demonstrates how the serializer may

    be used to print a JSON value to an output

    stream.

    @code

    void print( std::ostream& os, value const& jv)

    {

        serializer sr;

        sr.reset( &jv );

        while( ! sr.done() )

        {

            char buf[ 4000 ];

            os << sr.read( buf );

        }

    }

    @endcode

    @par Thread Safety

    The same instance may not be accessed concurrently.

*/

class serializer

{

    enum class state : char;

    // VFALCO Too many streams

    using stream = detail::stream;

    using const_stream = detail::const_stream;

    using local_stream = detail::local_stream;

    using local_const_stream =

        detail::local_const_stream;

    using fn_t = bool (serializer::*)(stream&);

#ifndef BOOST_JSON_DOCS

    union

    {

        value const* pv_;

        array const* pa_;

        object const* po_;

    };

#endif

    fn_t fn0_ = &serializer::write_null<true>;

    fn_t fn1_ = &serializer::write_null<false>;

    value const* jv_ = nullptr;

    detail::stack st_;

    const_stream cs0_;

    char buf_[detail::max_number_chars + 1];

    bool done_ = false;

    inline bool suspend(state st);

    inline bool suspend(

        state st, array::const_iterator it, array const* pa);

    inline bool suspend(

        state st, object::const_iterator it, object const* po);

    template<bool StackEmpty> bool write_null   (stream& ss);

    template<bool StackEmpty> bool write_true   (stream& ss);

    template<bool StackEmpty> bool write_false  (stream& ss);

    template<bool StackEmpty> bool write_string (stream& ss);

    template<bool StackEmpty> bool write_number (stream& ss);

    template<bool StackEmpty> bool write_array  (stream& ss);

    template<bool StackEmpty> bool write_object (stream& ss);

    template<bool StackEmpty> bool write_value  (stream& ss);

    inline string_view read_some(char* dest, std::size_t size);

public:

    /// Move constructor (deleted)

    serializer(serializer&&) = delete;

    /** Destructor

        All temporary storage is deallocated.

        @par Complexity

        Constant

        @par Exception Safety

        No-throw guarantee.

    */

    BOOST_JSON_DECL

    ~serializer() noexcept;

    /** Constructor

        This constructs a serializer with no value.

        The value may be set later by calling @ref reset.

        If serialization is attempted with no value,

        the output is as if a null value is serialized.

        @par Complexity

        Constant.

        @par Exception Safety

        No-throw guarantee.

    */

    BOOST_JSON_DECL

    serializer() noexcept;

    /** Constructor

        This constructs a serializer with no value.

        The value may be set later by calling @ref reset.

        If serialization is attempted with no value,

        the output is as if a null value is serialized.

        @par Complexity

        Constant.

        @par Exception Safety

        No-throw guarantee.

        @param sp A pointer to the @ref memory_resource

        to use when producing partial output.

        Shared ownership of the memory resource

        is retained until the serializer is

        destroyed.

        @param buf An optional static buffer to

        use for temporary storage when producing

        partial output.

        @param buf_size The number of bytes of

        valid memory pointed to by `buf`.

    */

    BOOST_JSON_DECL

    serializer(

        storage_ptr sp,

        unsigned char* buf = nullptr,

        std::size_t buf_size = 0) noexcept;

    /** Returns `true` if the serialization is complete

        This function returns `true` when all of the

        characters in the serialized representation of

        the value have been read.

        @par Complexity

        Constant.

        @par Exception Safety

        No-throw guarantee.

    */

    bool

    done() const noexcept

    {

        return done_;

    }

    /** Reset the serializer for a new element

        This function prepares the serializer to emit

        a new serialized JSON representing `*p`.

        Any internally allocated memory is

        preserved and re-used for the new output.

        @param p A pointer to the element to serialize.

        Ownership is not transferred; The caller is

        responsible for ensuring that the lifetime of

        `*p` extends until it is no longer needed.

    */

    /** @{ */

    BOOST_JSON_DECL

    void

    reset(value const* p) noexcept;

    BOOST_JSON_DECL

    void

    reset(array const* p) noexcept;

    BOOST_JSON_DECL

    void

    reset(object const* p) noexcept;

    BOOST_JSON_DECL

    void

    reset(string const* p) noexcept;

    /** @} */

    /** Reset the serializer for a new string

        This function prepares the serializer to emit

        a new serialized JSON representing the string.

        Any internally allocated memory is

        preserved and re-used for the new output.

        @param sv The characters representing the string.

        Ownership is not transferred; The caller is

        responsible for ensuring that the lifetime of

        the characters reference by `sv` extends

        until it is no longer needed.

    */

    BOOST_JSON_DECL

    void

    reset(string_view sv) noexcept;

    /** Read the next buffer of serialized JSON

        This function attempts to fill the caller

        provided buffer starting at `dest` with

        up to `size` characters of the serialized

        JSON that represents the value. If the

        buffer is not large enough, multiple calls

        may be required.

\n

        If serialization completes during this call;

        that is, that all of the characters belonging

        to the serialized value have been written to

        caller-provided buffers, the function

        @ref done will return `true`.

        @par Preconditions

        @code

        this->done() == false

        @endcode

        @par Complexity

        Linear in `size`.

        @par Exception Safety

        Basic guarantee.

        Calls to `memory_resource::allocate` may throw.

        @return A @ref string_view containing the

        characters written, which may be less than

        `size`.

        @param dest A pointer to valid memory of at

        least `size` bytes.

        @param size The maximum number of characters

        to write to the memory pointed to by `dest`.

    */

    BOOST_JSON_DECL

    string_view

    read(char* dest, std::size_t size);

    /** Read the next buffer of serialized JSON

        This function allows reading into a

        character array, with a deduced maximum size.

        @par Preconditions

        @code

        this->done() == false

        @endcode

        @par Effects

        @code

        return this->read( dest, N );

        @endcode

        @par Complexity

        Linear in `N`.

        @par Exception Safety

        Basic guarantee.

        Calls to `memory_resource::allocate` may throw.

        @return A @ref string_view containing the

        characters written, which may be less than

        `size`.

        @param dest The character array to write to.

    */

    template<std::size_t N>

    string_view

    read(char(&dest)[N])

    {

        return read(dest, N);

    }

#ifndef BOOST_JSON_DOCS

    // Safety net for accidental buffer overflows

    template<std::size_t N>

    string_view

    read(char(&dest)[N], std::size_t n)

    {

        // If this goes off, check your parameters

        // closely, chances are you passed an array

        // thinking it was a pointer.

        BOOST_ASSERT(n <= N);

        return read(dest, n);

    }

#endif

};

} // namespace json

} // namespace boost

#endif