// Copyright 2024 Google Inc. All Rights Reserved.

//

// 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.

#pragma once

#include <stdarg.h>

#include <stdio.h>

#include <string>

#include <unordered_map>

#include <vector>

/// A class used to record a list of explanation strings associated

/// with a given 'item' pointer. This is used to implement the

/// `-d explain` feature.

struct Explanations {

 public:

  /// Record an explanation for |item| if this instance is enabled.

  void Record(const void* item, const char* fmt, ...) {

    va_list args;

    va_start(args, fmt);

    RecordArgs(item, fmt, args);

    va_end(args);

  }

  /// Same as Record(), but uses a va_list to pass formatting arguments.

  void RecordArgs(const void* item, const char* fmt, va_list args) {

    char buffer[1024];

    vsnprintf(buffer, sizeof(buffer), fmt, args);

    map_[item].emplace_back(buffer);

  }

  /// Lookup the explanations recorded for |item|, and append them

  /// to |*out|, if any.

  void LookupAndAppend(const void* item, std::vector<std::string>* out) {

    auto it = map_.find(item);

    if (it == map_.end())

      return;

    for (const auto& explanation : it->second)

      out->push_back(explanation);

  }

 private:

  std::unordered_map<const void*, std::vector<std::string>> map_;

};

/// Convenience wrapper for an Explanations pointer, which can be null

/// if no explanations need to be recorded.

struct OptionalExplanations {

  OptionalExplanations(Explanations* explanations)

      : explanations_(explanations) {}

  void Record(const void* item, const char* fmt, ...) {

    if (explanations_) {

      va_list args;

      va_start(args, fmt);

      explanations_->RecordArgs(item, fmt, args);

      va_end(args);

    }

  }

  void RecordArgs(const void* item, const char* fmt, va_list args) {

    if (explanations_)

      explanations_->RecordArgs(item, fmt, args);

  }

  void LookupAndAppend(const void* item, std::vector<std::string>* out) {

    if (explanations_)

      explanations_->LookupAndAppend(item, out);

  }

  Explanations* ptr() const { return explanations_; }

 private:

  Explanations* explanations_;

};