// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef LIB_INSPECT_CPP_VMO_TYPES_H_
#define LIB_INSPECT_CPP_VMO_TYPES_H_

#include <string>
#include <vector>

#include <lib/inspect/cpp/vmo/block.h>
#include <zircon/types.h>

namespace inspect {

class Node;
class State;

namespace internal {
// A property containing a templated numeric type. All methods wrap the
// corresponding functionality on |State|, and concrete
// implementations are available only for int64_t, uint64_t and double.
template <typename T>
class NumericProperty final {
 public:
  // Construct a default numeric metric. Operations on this metric are
  // no-ops.
  NumericProperty() = default;
  ~NumericProperty();

  // Allow moving, disallow copying.
  NumericProperty(const NumericProperty& other) = delete;
  NumericProperty(NumericProperty&& other) = default;
  NumericProperty& operator=(const NumericProperty& other) = delete;
  NumericProperty& operator=(NumericProperty&& other);

  // Set the value of this numeric metric to the given value.
  void Set(T value);

  // Add the given value to the value of this numeric metric.
  void Add(T value);

  // Subtract the given value from the value of this numeric metric.
  void Subtract(T value);

  // Return true if this metric is stored in a buffer. False otherwise.
  explicit operator bool() { return state_ != nullptr; }

 private:
  friend class ::inspect::State;
  NumericProperty(std::shared_ptr<State> state, BlockIndex name, BlockIndex value)
      : state_(std::move(state)), name_index_(name), value_index_(value) {}

  // Reference to the state containing this metric.
  std::shared_ptr<State> state_;

  // Index of the name block in the state.
  BlockIndex name_index_;

  // Index of the value block in the state.
  BlockIndex value_index_;
};

// A value containing an array of numeric types. All methods wrap the
// corresponding functionality on |State|, and concrete
// implementations are available only for int64_t, uint64_t and double.
template <typename T>
class ArrayValue final {
 public:
  // Construct a default array value. Operations on this value are
  // no-ops.
  ArrayValue() = default;
  ~ArrayValue();

  // Allow moving, disallow copying.
  ArrayValue(const ArrayValue& other) = delete;
  ArrayValue(ArrayValue&& other) = default;
  ArrayValue& operator=(const ArrayValue& other) = delete;
  ArrayValue& operator=(ArrayValue&& other);

  // Set the value of the given index of this array.
  void Set(size_t index, T value);

  // Add the given value to the value of this numeric metric.
  void Add(size_t index, T value);

  // Subtract the given value from the value of this numeric metric.
  void Subtract(size_t index, T value);

  // Return true if this metric is stored in a buffer. False otherwise.
  explicit operator bool() { return state_ != nullptr; }

 private:
  friend class ::inspect::State;
  ArrayValue(std::shared_ptr<State> state, BlockIndex name, BlockIndex value)
      : state_(std::move(state)), name_index_(name), value_index_(value) {}

  // Reference to the state containing this value.
  std::shared_ptr<State> state_;

  // Index of the name block in the state.
  BlockIndex name_index_;

  // Index of the value block in the state.
  BlockIndex value_index_;
};

template <typename T>
class LinearHistogram final {
 public:
  // Create a default histogram.
  // Operations on the metric will have no effect.
  LinearHistogram() = default;

  // Insert the given value once to the correct bucket of the histogram.
  void Insert(T value) { Insert(value, 1); }

  // Insert the given value |count| times to the correct bucket of the
  // histogram.
  void Insert(T value, T count) { array_.Add(GetIndexForValue(value), count); }

 private:
  friend class ::inspect::Node;

  // First slots are floor, step_size, and underflow.
  static const size_t kBucketOffset = 3;

  // Get the number of buckets, which excludes the two parameter slots and the
  // two overflow slots.
  size_t BucketCount() { return array_size_ - 4; }

  // Calculates the correct array index to store the given value.
  size_t GetIndexForValue(T value) {
    if (array_size_ == 0) {
      return 0;
    }
    size_t ret = kBucketOffset - 1;
    T current_floor = floor_;
    for (; value >= current_floor && ret < array_size_ - 1; current_floor += step_size_, ret++) {
    }
    return ret;
  }

  // Internal constructor wrapping an array.
  LinearHistogram(T floor, T step_size, size_t array_size, ArrayValue<T> array)
      : floor_(floor), step_size_(step_size), array_size_(array_size), array_(std::move(array)) {
    ZX_ASSERT(array_size_ > 4);
    array_.Set(0, floor_);
    array_.Set(1, step_size_);
  }

  const T floor_ = 0;
  const T step_size_ = 0;
  const size_t array_size_ = 0;
  ArrayValue<T> array_;
};

template <typename T>
class ExponentialHistogram final {
 public:
  // Create a default histogram.
  // Operations on the metric will have no effect.
  ExponentialHistogram() = default;

  // Insert the given value once to the correct bucket of the histogram.
  void Insert(T value) { Insert(value, 1); }

  // Insert the given value |count| times to the correct bucket of the
  // histogram.
  void Insert(T value, T count) { array_.Add(GetIndexForValue(value), count); }

 private:
  friend class ::inspect::Node;

  // First slots are floor, initial_step, step_multiplier, and underflow.
  static const size_t kBucketOffset = 4;

  // Get the number of buckets, which excludes the two parameter slots and the
  // two overflow slots.
  size_t BucketCount() { return array_size_ - 5; }

  // Calculates the correct array index to store the given value.
  size_t GetIndexForValue(T value) {
    if (array_size_ == 0) {
      return 0;
    }
    T current_floor = floor_;
    T current_step = initial_step_;
    size_t ret = kBucketOffset - 1;
    for (; value >= current_floor && ret < array_size_ - 1;
         current_floor += current_step, current_step *= step_multiplier_, ret++) {
    }
    return ret;
  }

  // Internal constructor wrapping a VMO type.
  ExponentialHistogram(T floor, T initial_step, T step_multiplier, size_t array_size,
                       ArrayValue<T> array)
      : floor_(floor),
        initial_step_(initial_step),
        step_multiplier_(step_multiplier),
        array_size_(array_size),
        array_(std::move(array)) {
    ZX_ASSERT(array_size_ > 5);
    array_.Set(0, floor_);
    array_.Set(1, initial_step_);
    array_.Set(2, step_multiplier_);
  }

  const T floor_ = 0;
  const T initial_step_ = 0;
  const T step_multiplier_ = 0;
  const size_t array_size_ = 0;
  ArrayValue<T> array_;
};

// A property containing a string value.
// All methods wrap the corresponding functionality on |State|.
template <typename T>
class Property final {
 public:
  // Construct a default property. Operations on this property are
  // no-ops.
  Property() = default;
  ~Property();

  // Allow moving, disallow copying.
  Property(const Property& other) = delete;
  Property(Property&& other) = default;
  Property& operator=(const Property& other) = delete;
  Property& operator=(Property&& other);

  // Return true if this property is stored in a buffer. False otherwise.
  explicit operator bool() { return state_ != nullptr; }

  // Set the value of this property.
  void Set(const T& value);

 private:
  friend class ::inspect::State;
  Property(std::shared_ptr<State> state, BlockIndex name, BlockIndex value)
      : state_(std::move(state)), name_index_(name), value_index_(value) {}

  // Reference to the state containing this property.
  std::shared_ptr<State> state_;

  // Index of the name block in the state.
  BlockIndex name_index_;

  // Index of the value block in the state.
  BlockIndex value_index_;
};

}  // namespace internal

using IntProperty = internal::NumericProperty<int64_t>;
using UintProperty = internal::NumericProperty<uint64_t>;
using DoubleProperty = internal::NumericProperty<double>;

using IntArray = internal::ArrayValue<int64_t>;
using UintArray = internal::ArrayValue<uint64_t>;
using DoubleArray = internal::ArrayValue<double>;

using LinearIntHistogram = internal::LinearHistogram<int64_t>;
using LinearUintHistogram = internal::LinearHistogram<uint64_t>;
using LinearDoubleHistogram = internal::LinearHistogram<double>;

using ExponentialIntHistogram = internal::ExponentialHistogram<int64_t>;
using ExponentialUintHistogram = internal::ExponentialHistogram<uint64_t>;
using ExponentialDoubleHistogram = internal::ExponentialHistogram<double>;

using StringProperty = internal::Property<std::string>;
using ByteVectorProperty = internal::Property<std::vector<uint8_t>>;

// An node under which properties, metrics, and other nodes may be nested.
// All methods wrap the corresponding functionality on |State|.
class Node final {
 public:
  // Construct a default node. Operations on this node are
  // no-ops.
  Node() = default;
  ~Node();

  // Allow moving, disallow copying.
  Node(const Node& other) = delete;
  Node(Node&& other) = default;
  Node& operator=(const Node& other) = delete;
  Node& operator=(Node&& other);

  // Create a new |Node| with the given name that is a child of this node.
  // If this node is not stored in a buffer, the created node will
  // also not be stored in a buffer.
  Node CreateChild(const std::string& name);

  // Create a new |IntProperty| with the given name that is a child of this node.
  // If this node is not stored in a buffer, the created metric will
  // also not be stored in a buffer.
  IntProperty CreateInt(const std::string& name, int64_t value);

  // Create a new |UintProperty| with the given name that is a child of this node.
  // If this node is not stored in a buffer, the created metric will
  // also not be stored in a buffer.
  UintProperty CreateUint(const std::string& name, uint64_t value);

  // Create a new |DoubleProperty| with the given name that is a child of this node.
  // If this node is not stored in a buffer, the created metric will
  // also not be stored in a buffer.
  DoubleProperty CreateDouble(const std::string& name, double value);

  // Create a new |StringProperty| with the given name and value that is a child of this node.
  // If this node is not stored in a buffer, the created property will
  // also not be stored in a buffer.
  StringProperty CreateString(const std::string& name, const std::string& value);

  // Create a new |ByteVectorProperty| with the given name and value that is a child of this node.
  // If this node is not stored in a buffer, the created property will
  // also not be stored in a buffer.
  ByteVectorProperty CreateByteVector(const std::string& name, const std::vector<uint8_t>& value);

  // Create a new |IntArray| with the given name and slots that is a child of this node.
  // If this node is not stored in a buffer, the created value will
  // also not be stored in a buffer.
  IntArray CreateIntArray(const std::string& name, size_t slots);

  // Create a new |UintArray| with the given name and slots that is a child of this node.
  // If this node is not stored in a buffer, the created value will
  // also not be stored in a buffer.
  UintArray CreateUintArray(const std::string& name, size_t slots);

  // Create a new |DoubleArray| with the given name and slots that is a child of this node.
  // If this node is not stored in a buffer, the created value will
  // also not be stored in a buffer.
  DoubleArray CreateDoubleArray(const std::string& name, size_t slots);

  // Create a new |LinearIntHistogram| with the given name and format that is a child of this
  // node. If this node is not stored in a buffer, the created value will also not be stored in
  // a buffer.
  LinearIntHistogram CreateLinearIntHistogram(const std::string& name, int64_t floor,
                                              int64_t step_size, size_t buckets);

  // Create a new |LinearUintHistogram| with the given name and format that is a child of this
  // node. If this node is not stored in a buffer, the created value will also not be stored in
  // a buffer.
  LinearUintHistogram CreateLinearUintHistogram(const std::string& name, uint64_t floor,
                                                uint64_t step_size, size_t buckets);

  // Create a new |LinearDoubleHistogram| with the given name and format that is a child of this
  // node. If this node is not stored in a buffer, the created value will also not be stored in
  // a buffer.
  LinearDoubleHistogram CreateLinearDoubleHistogram(const std::string& name, double floor,
                                                    double step_size, size_t buckets);

  // Create a new |ExponentialIntHistogram| with the given name and format that is a child of this
  // node. If this node is not stored in a buffer, the created value will also not be stored in
  // a buffer.
  ExponentialIntHistogram CreateExponentialIntHistogram(const std::string& name, int64_t floor,
                                                        int64_t initial_step,
                                                        int64_t step_multiplier, size_t buckets);

  // Create a new |ExponentialUintHistogram| with the given name and format that is a child of this
  // node. If this node is not stored in a buffer, the created value will also not be stored in
  // a buffer.
  ExponentialUintHistogram CreateExponentialUintHistogram(const std::string& name, uint64_t floor,
                                                          uint64_t initial_step,
                                                          uint64_t step_multiplier, size_t buckets);

  // Create a new |ExponentialDoubleHistogram| with the given name and format that is a child of
  // this node. If this node is not stored in a buffer, the created value will also not be
  // stored in a buffer.
  ExponentialDoubleHistogram CreateExponentialDoubleHistogram(const std::string& name, double floor,
                                                              double initial_step,
                                                              double step_multiplier,
                                                              size_t buckets);

  // Return true if this node is stored in a buffer. False otherwise.
  explicit operator bool() { return state_ != nullptr; }

 private:
  friend class ::inspect::State;
  Node(std::shared_ptr<State> state, BlockIndex name, BlockIndex value)
      : state_(std::move(state)), name_index_(name), value_index_(value) {}

  // Reference to the state containing this metric.
  std::shared_ptr<State> state_;

  // Index of the name block in the state.
  BlockIndex name_index_;

  // Index of the value block in the state.
  BlockIndex value_index_;
};

}  // namespace inspect

#endif  // LIB_INSPECT_CPP_VMO_TYPES_H_