// Copyright 2020 The Tint Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef SRC_TINT_SYMBOL_H_
#define SRC_TINT_SYMBOL_H_

#include <string>
#include <variant>

#include "src/tint/builtin/access.h"
#include "src/tint/builtin/address_space.h"
#include "src/tint/builtin/builtin.h"
#include "src/tint/builtin/builtin_value.h"
#include "src/tint/builtin/function.h"
#include "src/tint/builtin/interpolation_sampling.h"
#include "src/tint/builtin/interpolation_type.h"
#include "src/tint/builtin/texel_format.h"
#include "src/tint/program_id.h"

namespace tint {

/// A symbol representing a string in the system
class Symbol {
  public:
    /// The type of builtin this symbol could represent, if any.
    enum class BuiltinType {
        /// No builtin matched
        kNone = 0,
        /// Builtin function
        kFunction,
        /// Builtin
        kBuiltin,
        /// Builtin value
        kBuiltinValue,
        /// Address space
        kAddressSpace,
        /// Texel format
        kTexelFormat,
        /// Access
        kAccess,
        /// Interpolation Type
        kInterpolationType,
        /// Interpolation Sampling
        kInterpolationSampling,
    };

    /// Constructor
    /// An invalid symbol
    Symbol();
    /// Constructor
    /// @param val the symbol value
    /// @param pid the identifier of the program that owns this Symbol
    /// @param name the name this symbol represents
    Symbol(uint32_t val, tint::ProgramID pid, std::string_view name);

    /// Copy constructor
    /// @param o the symbol to copy
    Symbol(const Symbol& o);
    /// Move constructor
    /// @param o the symbol to move
    Symbol(Symbol&& o);
    /// Destructor
    ~Symbol();

    /// Copy assignment
    /// @param o the other symbol
    /// @returns the symbol after doing the copy
    Symbol& operator=(const Symbol& o);
    /// Move assignment
    /// @param o the other symbol
    /// @returns teh symbol after doing the move
    Symbol& operator=(Symbol&& o);

    /// Equality operator
    /// @param o the other symbol
    /// @returns true if the symbols are the same
    bool operator==(const Symbol& o) const;

    /// Inequality operator
    /// @param o the other symbol
    /// @returns true if the symbols are the different
    bool operator!=(const Symbol& o) const;

    /// Less-than operator
    /// @param o the other symbol
    /// @returns true if this symbol is ordered before symbol `o`
    bool operator<(const Symbol& o) const;

    /// @returns true if the symbol is valid
    bool IsValid() const { return val_ != static_cast<uint32_t>(-1); }

    /// @returns true if the symbol is valid
    operator bool() const { return IsValid(); }

    /// @returns the value for the symbol
    uint32_t value() const { return val_; }

    /// Convert the symbol to a string
    /// @return the string representation of the symbol
    std::string to_str() const;

    /// Converts the symbol to the registered name
    /// @returns the string_view representing the name of the symbol
    std::string_view NameView() const;

    /// Converts the symbol to the registered name
    /// @returns the string representing the name of the symbol
    std::string Name() const;

    /// @returns the identifier of the Program that owns this symbol.
    tint::ProgramID ProgramID() const { return program_id_; }

    /// @returns the builtin type
    BuiltinType Type() const { return builtin_type_; }

    /// @returns the builtin value
    template <typename T>
    T BuiltinValue() const {
        return std::get<T>(builtin_value_);
    }

  private:
    void DetermineBuiltinType();

    uint32_t val_ = static_cast<uint32_t>(-1);
    tint::ProgramID program_id_;
    std::string_view name_;

    BuiltinType builtin_type_ = BuiltinType::kNone;
    std::variant<std::monostate,
                 builtin::Function,
                 builtin::Builtin,
                 builtin::BuiltinValue,
                 builtin::AddressSpace,
                 builtin::TexelFormat,
                 builtin::Access,
                 builtin::InterpolationType,
                 builtin::InterpolationSampling>
        builtin_value_ = {};
};

/// @param sym the Symbol
/// @returns the ProgramID that owns the given Symbol
inline ProgramID ProgramIDOf(Symbol sym) {
    return sym.IsValid() ? sym.ProgramID() : ProgramID();
}

}  // namespace tint

namespace std {

/// Custom std::hash specialization for tint::Symbol so symbols can be used as
/// keys for std::unordered_map and std::unordered_set.
template <>
class hash<tint::Symbol> {
  public:
    /// @param sym the symbol to return
    /// @return the Symbol internal value
    inline std::size_t operator()(const tint::Symbol& sym) const {
        return static_cast<std::size_t>(sym.value());
    }
};

}  // namespace std

#endif  // SRC_TINT_SYMBOL_H_