Format.h

/*
 * Copyright (c) 2020, the SerenityOS developers.
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <AK/CheckedFormatString.h>

#include <AK/AllOf.h>
#include <AK/AnyOf.h>
#include <AK/Array.h>
#include <AK/GenericLexer.h>
#include <AK/Optional.h>
#include <AK/StringView.h>

#ifndef KERNEL
#    include <stdio.h>
#endif

namespace AK {

class TypeErasedFormatParams;
class FormatParser;
class FormatBuilder;

template<typename T, typename = void>
struct Formatter {
    using __no_formatter_defined = void;
};

constexpr size_t max_format_arguments = 256;

struct TypeErasedParameter {
    enum class Type {
        UInt8,
        UInt16,
        UInt32,
        UInt64,
        Int8,
        Int16,
        Int32,
        Int64,
        Custom
    };

    template<size_t size, bool is_unsigned>
    static consteval Type get_type_from_size()
    {
        if constexpr (is_unsigned) {
            if constexpr (size == 1)
                return Type::UInt8;
            if constexpr (size == 2)
                return Type::UInt16;
            if constexpr (size == 4)
                return Type::UInt32;
            if constexpr (size == 8)
                return Type::UInt64;
        } else {
            if constexpr (size == 1)
                return Type::Int8;
            if constexpr (size == 2)
                return Type::Int16;
            if constexpr (size == 4)
                return Type::Int32;
            if constexpr (size == 8)
                return Type::Int64;
        }

        VERIFY_NOT_REACHED();
    }

    template<typename T>
    static consteval Type get_type()
    {
        if constexpr (IsIntegral<T>)
            return get_type_from_size<sizeof(T), IsUnsigned<T>>();
        else
            return Type::Custom;
    }

    constexpr size_t to_size() const
    {
        i64 svalue;

        if (type == TypeErasedParameter::Type::UInt8)
            svalue = *static_cast<const u8*>(value);
        else if (type == TypeErasedParameter::Type::UInt16)
            svalue = *static_cast<const u16*>(value);
        else if (type == TypeErasedParameter::Type::UInt32)
            svalue = *static_cast<const u32*>(value);
        else if (type == TypeErasedParameter::Type::UInt64)
            svalue = *static_cast<const u64*>(value);
        else if (type == TypeErasedParameter::Type::Int8)
            svalue = *static_cast<const i8*>(value);
        else if (type == TypeErasedParameter::Type::Int16)
            svalue = *static_cast<const i16*>(value);
        else if (type == TypeErasedParameter::Type::Int32)
            svalue = *static_cast<const i32*>(value);
        else if (type == TypeErasedParameter::Type::Int64)
            svalue = *static_cast<const i64*>(value);
        else
            VERIFY_NOT_REACHED();

        VERIFY(svalue >= 0);

        return static_cast<size_t>(svalue);
    }

    // FIXME: Getters and setters.

    const void* value;
    Type type;
    void (*formatter)(TypeErasedFormatParams&, FormatBuilder&, FormatParser&, const void* value);
};

class FormatParser : public GenericLexer {
public:
    struct FormatSpecifier {
        StringView flags;
        size_t index;
    };

    explicit FormatParser(StringView input);

    StringView consume_literal();
    bool consume_number(size_t& value);
    bool consume_specifier(FormatSpecifier& specifier);
    bool consume_replacement_field(size_t& index);
};

class FormatBuilder {
public:
    enum class Align {
        Default,
        Left,
        Center,
        Right,
    };
    enum class SignMode {
        OnlyIfNeeded,
        Always,
        Reserved,
        Default = OnlyIfNeeded,
    };

    explicit FormatBuilder(StringBuilder& builder)
        : m_builder(builder)
    {
    }

    void put_padding(char fill, size_t amount);

    void put_literal(StringView value);

    void put_string(
        StringView value,
        Align align = Align::Left,
        size_t min_width = 0,
        size_t max_width = NumericLimits<size_t>::max(),
        char fill = ' ');

    void put_u64(
        u64 value,
        u8 base = 10,
        bool prefix = false,
        bool upper_case = false,
        bool zero_pad = false,
        Align align = Align::Right,
        size_t min_width = 0,
        char fill = ' ',
        SignMode sign_mode = SignMode::OnlyIfNeeded,
        bool is_negative = false);

    void put_i64(
        i64 value,
        u8 base = 10,
        bool prefix = false,
        bool upper_case = false,
        bool zero_pad = false,
        Align align = Align::Right,
        size_t min_width = 0,
        char fill = ' ',
        SignMode sign_mode = SignMode::OnlyIfNeeded);

#ifndef KERNEL
    void put_f64(
        double value,
        u8 base = 10,
        bool upper_case = false,
        Align align = Align::Right,
        size_t min_width = 0,
        size_t precision = 6,
        char fill = ' ',
        SignMode sign_mode = SignMode::OnlyIfNeeded);
#endif

    const StringBuilder& builder() const
    {
        return m_builder;
    }
    StringBuilder& builder() { return m_builder; }

private:
    StringBuilder& m_builder;
};

class TypeErasedFormatParams {
public:
    Span<const TypeErasedParameter> parameters() const { return m_parameters; }

    void set_parameters(Span<const TypeErasedParameter> parameters) { m_parameters = parameters; }
    size_t take_next_index() { return m_next_index++; }

private:
    Span<const TypeErasedParameter> m_parameters;
    size_t m_next_index { 0 };
};

template<typename T>
void __format_value(TypeErasedFormatParams& params, FormatBuilder& builder, FormatParser& parser, const void* value)
{
    Formatter<T> formatter;

    formatter.parse(params, parser);
    formatter.format(builder, *static_cast<const T*>(value));
}

template<typename... Parameters>
class VariadicFormatParams : public TypeErasedFormatParams {
public:
    static_assert(sizeof...(Parameters) <= max_format_arguments);

    explicit VariadicFormatParams(const Parameters&... parameters)
        : m_data({ TypeErasedParameter { &parameters, TypeErasedParameter::get_type<Parameters>(), __format_value<Parameters> }... })
    {
        this->set_parameters(m_data);
    }

private:
    Array<TypeErasedParameter, sizeof...(Parameters)> m_data;
};

// We use the same format for most types for consistency. This is taken directly from
// std::format. One difference is that we are not counting the width or sign towards the
// total width when calculating zero padding for numbers.
// https://en.cppreference.com/w/cpp/utility/format/formatter#Standard_format_specification
struct StandardFormatter {
    enum class Mode {
        Default,
        Binary,
        BinaryUppercase,
        Decimal,
        Octal,
        Hexadecimal,
        HexadecimalUppercase,
        Character,
        String,
        Pointer,
        Float,
        Hexfloat,
        HexfloatUppercase,
    };

    FormatBuilder::Align m_align = FormatBuilder::Align::Default;
    FormatBuilder::SignMode m_sign_mode = FormatBuilder::SignMode::OnlyIfNeeded;
    Mode m_mode = Mode::Default;
    bool m_alternative_form = false;
    char m_fill = ' ';
    bool m_zero_pad = false;
    Optional<size_t> m_width;
    Optional<size_t> m_precision;

    void parse(TypeErasedFormatParams&, FormatParser&);
};

template<typename T>
struct Formatter<T, typename EnableIf<IsIntegral<T>>::Type> : StandardFormatter {
    Formatter() = default;
    explicit Formatter(StandardFormatter formatter)
        : StandardFormatter(formatter)
    {
    }

    void format(FormatBuilder&, T value);
};

template<>
struct Formatter<StringView> : StandardFormatter {
    Formatter() = default;
    explicit Formatter(StandardFormatter formatter)
        : StandardFormatter(formatter)
    {
    }

    void format(FormatBuilder&, StringView value);
};
template<>
struct Formatter<const char*> : Formatter<StringView> {
    void format(FormatBuilder& builder, const char* value)
    {
        if (m_mode == Mode::Pointer) {
            Formatter<FlatPtr> formatter { *this };
            formatter.format(builder, reinterpret_cast<FlatPtr>(value));
        } else {
            Formatter<StringView>::format(builder, value);
        }
    }
};
template<>
struct Formatter<char*> : Formatter<const char*> {
};
template<size_t Size>
struct Formatter<char[Size]> : Formatter<const char*> {
};
template<>
struct Formatter<String> : Formatter<StringView> {
};
template<>
struct Formatter<FlyString> : Formatter<StringView> {
};

template<typename T>
struct Formatter<T*> : StandardFormatter {
    void format(FormatBuilder& builder, T* value)
    {
        if (m_mode == Mode::Default)
            m_mode = Mode::Pointer;

        Formatter<FlatPtr> formatter { *this };
        formatter.format(builder, reinterpret_cast<FlatPtr>(value));
    }
};

template<>
struct Formatter<char> : StandardFormatter {
    void format(FormatBuilder&, char value);
};
template<>
struct Formatter<bool> : StandardFormatter {
    void format(FormatBuilder&, bool value);
};

#ifndef KERNEL
template<>
struct Formatter<float> : StandardFormatter {
    void format(FormatBuilder&, float value);
};
template<>
struct Formatter<double> : StandardFormatter {
    Formatter() = default;
    explicit Formatter(StandardFormatter formatter)
        : StandardFormatter(formatter)
    {
    }

    void format(FormatBuilder&, double value);
};
#endif

template<>
struct Formatter<std::nullptr_t> : Formatter<FlatPtr> {
    void format(FormatBuilder& builder, std::nullptr_t)
    {
        if (m_mode == Mode::Default)
            m_mode = Mode::Pointer;

        return Formatter<FlatPtr>::format(builder, 0);
    }
};

void vformat(StringBuilder&, StringView fmtstr, TypeErasedFormatParams);

#ifndef KERNEL
void vout(FILE*, StringView fmtstr, TypeErasedFormatParams, bool newline = false);

template<typename... Parameters>
void out(FILE* file, CheckedFormatString<Parameters...>&& fmtstr, const Parameters&... parameters) { vout(file, fmtstr.view(), VariadicFormatParams { parameters... }); }

template<typename... Parameters>
void outln(FILE* file, CheckedFormatString<Parameters...>&& fmtstr, const Parameters&... parameters) { vout(file, fmtstr.view(), VariadicFormatParams { parameters... }, true); }

inline void outln(FILE* file) { fputc('\n', file); }

template<typename... Parameters>
void out(CheckedFormatString<Parameters...>&& fmtstr, const Parameters&... parameters) { out(stdout, move(fmtstr), parameters...); }

template<typename... Parameters>
void outln(CheckedFormatString<Parameters...>&& fmtstr, const Parameters&... parameters) { outln(stdout, move(fmtstr), parameters...); }

inline void outln() { outln(stdout); }

#    define outln_if(flag, fmt, ...)       \
        do {                               \
            if constexpr (flag)            \
                outln(fmt, ##__VA_ARGS__); \
        } while (0)

template<typename... Parameters>
void warn(CheckedFormatString<Parameters...>&& fmtstr, const Parameters&... parameters)
{
    out(stderr, move(fmtstr), parameters...);
}

template<typename... Parameters>
void warnln(CheckedFormatString<Parameters...>&& fmtstr, const Parameters&... parameters) { outln(stderr, move(fmtstr), parameters...); }

inline void warnln() { outln(stderr); }

#    define warnln_if(flag, fmt, ...)      \
        do {                               \
            if constexpr (flag)            \
                outln(fmt, ##__VA_ARGS__); \
        } while (0)

#endif

void vdbgln(StringView fmtstr, TypeErasedFormatParams);

template<typename... Parameters>
void dbgln(CheckedFormatString<Parameters...>&& fmtstr, const Parameters&... parameters)
{
    vdbgln(fmtstr.view(), VariadicFormatParams { parameters... });
}

inline void dbgln() { dbgln(""); }

void set_debug_enabled(bool);

#ifdef KERNEL
void vdmesgln(StringView fmtstr, TypeErasedFormatParams);

template<typename... Parameters>
void dmesgln(CheckedFormatString<Parameters...>&& fmt, const Parameters&... parameters)
{
    vdmesgln(fmt.view(), VariadicFormatParams { parameters... });
}

void v_critical_dmesgln(StringView fmtstr, TypeErasedFormatParams);

// be very careful to not cause any allocations here, since we could be in
// a very unstable situation
template<typename... Parameters>
void critical_dmesgln(CheckedFormatString<Parameters...>&& fmt, const Parameters&... parameters)
{
    v_critical_dmesgln(fmt.view(), VariadicFormatParams { parameters... });
}
#endif

template<typename T, typename = void>
inline constexpr bool HasFormatter = true;

template<typename T>
inline constexpr bool HasFormatter<T, typename Formatter<T>::__no_formatter_defined> = false;

template<typename T>
class FormatIfSupported {
public:
    explicit FormatIfSupported(const T& value)
        : m_value(value)
    {
    }

    const T& value() const { return m_value; }

private:
    const T& m_value;
};
template<typename T, bool Supported = false>
struct __FormatIfSupported : Formatter<StringView> {
    void format(FormatBuilder& builder, const FormatIfSupported<T>&)
    {
        Formatter<StringView>::format(builder, "?");
    }
};
template<typename T>
struct __FormatIfSupported<T, true> : Formatter<T> {
    void format(FormatBuilder& builder, const FormatIfSupported<T>& value)
    {
        Formatter<T>::format(builder, value.value());
    }
};
template<typename T>
struct Formatter<FormatIfSupported<T>> : __FormatIfSupported<T, HasFormatter<T>> {
};

// This is a helper class, the idea is that if you want to implement a formatter you can inherit
// from this class to "break down" the formatting.
struct FormatString {
};
template<>
struct Formatter<FormatString> : Formatter<String> {
    template<typename... Parameters>
    void format(FormatBuilder& builder, StringView fmtstr, const Parameters&... parameters)
    {
        vformat(builder, fmtstr, VariadicFormatParams { parameters... });
    }
    void vformat(FormatBuilder& builder, StringView fmtstr, TypeErasedFormatParams params);
};

} // namespace AK

#ifdef KERNEL
using AK::critical_dmesgln;
using AK::dmesgln;
#else
using AK::out;
using AK::outln;

using AK::warn;
using AK::warnln;
#endif

using AK::dbgln;

using AK::CheckedFormatString;
using AK::FormatIfSupported;
using AK::FormatString;

#define dbgln_if(flag, fmt, ...)       \
    do {                               \
        if constexpr (flag)            \
            dbgln(fmt, ##__VA_ARGS__); \
    } while (0)