// Protocol Buffers - Google's data interchange format
// Copyright 2023 Google LLC.  All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd

#include "hpb_generator/gen_enums.h"

#include <algorithm>
#include <deque>
#include <limits>
#include <string>
#include <vector>

#include "google/protobuf/descriptor.pb.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/str_join.h"
#include "absl/strings/string_view.h"
#include "hpb_generator/context.h"
#include "hpb_generator/gen_utils.h"
#include "hpb_generator/keywords.h"
#include "hpb_generator/names.h"
#include "google/protobuf/descriptor.h"

namespace google {
namespace protobuf {
namespace hpb_generator {

using Sub = google::protobuf::io::Printer::Sub;

namespace {

std::string ContainingTypeNames(const google::protobuf::EnumDescriptor* enum_descriptor) {
  std::deque<absl::string_view> containing_type_names;
  auto containing_type = enum_descriptor->containing_type();
  while (containing_type != nullptr) {
    containing_type_names.push_front(containing_type->name());
    containing_type = containing_type->containing_type();
  }
  return absl::StrJoin(containing_type_names, "_");
}

}  // namespace

// Convert enum value to C++ literal.
//
// In C++, an value of -2147483648 gets interpreted as the negative of
// 2147483648, and since 2147483648 can't fit in an integer, this produces a
// compiler warning.  This works around that issue.
std::string EnumInt32ToString(int number) {
  if (number == std::numeric_limits<int32_t>::min()) {
    // This needs to be special-cased, see explanation here:
    // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52661
    return absl::StrCat(number + 1, " - 1");
  } else {
    return absl::StrCat(number);
  }
}

std::string EnumTypeName(const google::protobuf::EnumDescriptor* enum_descriptor) {
  const std::string containing_types = ContainingTypeNames(enum_descriptor);
  if (containing_types.empty()) {
    // enums types with no package name are prefixed with protos_ to prevent
    // conflicts with generated C headers.
    if (enum_descriptor->file()->package().empty()) {
      return absl::StrCat(kNoPackageNamePrefix,
                          ToCIdent(enum_descriptor->name()));
    }
    return ResolveKeywordConflict(ToCIdent(enum_descriptor->name()));
  } else {
    // Since the enum is in global name space (no package), it will have the
    // same classified name as the C header include, to prevent collision
    // rename as above.
    if (enum_descriptor->containing_type()->file()->package().empty()) {
      return ToCIdent(absl::StrCat(containing_types, "_", kNoPackageNamePrefix,
                                   enum_descriptor->name()));
    } else {
      return ToCIdent(
          absl::StrCat(containing_types, "_", enum_descriptor->name()));
    }
  }
}

std::string EnumValueSymbolInNameSpace(
    const google::protobuf::EnumDescriptor* desc,
    const google::protobuf::EnumValueDescriptor* value) {
  const std::string containing_types = ContainingTypeNames(desc);
  if (!containing_types.empty()) {
    return ToCIdent(
        absl::StrCat(containing_types, "_", desc->name(), "_", value->name()));
  } else {
    // protos enum values with no package name are prefixed with protos_ to
    // prevent conflicts with generated C headers.
    if (desc->file()->package().empty()) {
      return absl::StrCat(kNoPackageNamePrefix, ToCIdent(value->name()));
    }
    return ResolveKeywordConflict(ToCIdent(value->name()));
  }
}

void WriteEnumValues(const google::protobuf::EnumDescriptor* desc, Context& ctx) {
  std::vector<const google::protobuf::EnumValueDescriptor*> values;
  auto value_count = desc->value_count();
  values.reserve(value_count);
  for (int i = 0; i < value_count; i++) {
    values.push_back(desc->value(i));
  }
  std::stable_sort(values.begin(), values.end(),
                   [](const google::protobuf::EnumValueDescriptor* a,
                      const google::protobuf::EnumValueDescriptor* b) {
                     return a->number() < b->number();
                   });

  for (size_t i = 0; i < values.size(); i++) {
    auto value = values[i];
    ctx.Emit({{"name", EnumValueSymbolInNameSpace(desc, value)},
              {"number", EnumInt32ToString(value->number())},
              {"sep", i == values.size() - 1 ? "" : ","}},
             R"cc(
               $name$ = $number$$sep$
             )cc");
  }
}

void WriteEnumDeclarations(
    const std::vector<const google::protobuf::EnumDescriptor*>& enums, Context& ctx) {
  for (auto enumdesc : enums) {
    ctx.Emit({{"type", EnumTypeName(enumdesc)},
              Sub("enum_vals", [&] { WriteEnumValues(enumdesc, ctx); })
                  .WithSuffix(",")},
             R"cc(
               enum $type$ : int {
                 $enum_vals$,
               };
             )cc");
  }
}

}  // namespace hpb_generator
}  // namespace protobuf
}  // namespace google
