//===- llvm/TableGen/TableGenBackend.h - Backend utilities ------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Useful utilities for TableGen backends.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_TABLEGEN_TABLEGENBACKEND_H
#define LLVM_TABLEGEN_TABLEGENBACKEND_H

#include "llvm/ADT/STLFunctionalExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/TableGen/Main.h"
#include "llvm/TableGen/Record.h"

namespace llvm {

class RecordKeeper;
class raw_ostream;

namespace TableGen::Emitter {

/// Represents the emitting function. Can produce a single or multple output
/// files.
struct FnT {
  using SingleFileGeneratorType = void(const RecordKeeper &Records,
                                       raw_ostream &OS);
  using MultiFileGeneratorType = TableGenOutputFiles(
      StringRef FilenamePrefix, const RecordKeeper &Records);

  SingleFileGeneratorType *SingleFileGenerator = nullptr;
  MultiFileGeneratorType *MultiFileGenerator = nullptr;

  FnT() = default;
  FnT(SingleFileGeneratorType *Gen) : SingleFileGenerator(Gen) {}
  FnT(MultiFileGeneratorType *Gen) : MultiFileGenerator(Gen) {}

  bool operator==(const FnT &Other) const {
    return SingleFileGenerator == Other.SingleFileGenerator &&
           MultiFileGenerator == Other.MultiFileGenerator;
  }
};

/// Creating an `Opt` object registers the command line option \p Name with
/// TableGen backend and associates the callback \p CB with that option. If
/// \p ByDefault is true, then that callback is applied by default if no
/// command line option was specified.
struct Opt {
  Opt(StringRef Name, FnT CB, StringRef Desc, bool ByDefault = false);
};

/// Convienence wrapper around `Opt` that registers `EmitterClass::run` as the
/// callback.
template <class EmitterC> class OptClass : Opt {
  static TableGenOutputFiles run(StringRef /*FilenamePrefix*/,
                                 const RecordKeeper &RK) {
    std::string S;
    raw_string_ostream OS(S);
    EmitterC(RK).run(OS);
    return {S, {}};
  }

public:
  OptClass(StringRef Name, StringRef Desc) : Opt(Name, run, Desc) {}
};

/// A version of the wrapper for backends emitting multiple files.
template <class EmitterC> class MultiFileOptClass : Opt {
  static TableGenOutputFiles run(StringRef FilenamePrefix,
                                 const RecordKeeper &RK) {
    return EmitterC(RK).run(FilenamePrefix);
  }

public:
  MultiFileOptClass(StringRef Name, StringRef Desc) : Opt(Name, run, Desc) {}
};

/// Apply callback for any command line option registered above. Returns false
/// is no callback was applied.
bool ApplyCallback(const RecordKeeper &Records, TableGenOutputFiles &OutFiles,
                   StringRef FilenamePrefix);

} // namespace TableGen::Emitter

/// emitSourceFileHeader - Output an LLVM style file header to the specified
/// raw_ostream.
void emitSourceFileHeader(StringRef Desc, raw_ostream &OS,
                          const RecordKeeper &Record = RecordKeeper());

} // namespace llvm

#endif // LLVM_TABLEGEN_TABLEGENBACKEND_H