// 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_

// If TINT_SYMBOL_STORE_DEBUG_NAME is 1, Symbol instances store a `debug_name_`
// member initialized with the name of the identifier they represent. This
// member is not exposed, but is useful for debugging purposes.
#ifndef TINT_SYMBOL_STORE_DEBUG_NAME
#define TINT_SYMBOL_STORE_DEBUG_NAME 0
#endif

#include <string>

#include "src/tint/program_id.h"

namespace tint {

/// A symbol representing a string in the system
class Symbol {
  public:
    /// Constructor
    /// An invalid symbol
    Symbol();
    /// Constructor
    /// @param val the symbol value
    /// @param program_id the identifier of the program that owns this Symbol
    Symbol(uint32_t val, tint::ProgramID program_id);
#if TINT_SYMBOL_STORE_DEBUG_NAME
    /// Constructor
    /// @param val the symbol value
    /// @param program_id the identifier of the program that owns this Symbol
    /// @param debug_name name of symbols used only for debugging
    Symbol(uint32_t val, tint::ProgramID pid, std::string debug_name);
#endif
    /// 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);

    /// Comparison operator
    /// @param o the other symbol
    /// @returns true if the symbols are the same
    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 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;

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

  private:
    uint32_t val_ = static_cast<uint32_t>(-1);
    tint::ProgramID program_id_;
#if TINT_SYMBOL_STORE_DEBUG_NAME
    std::string debug_name_;
#endif
};

/// @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_