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// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_SEGMENTATION_PLATFORM_INTERNAL_DATABASE_SIGNAL_KEY_H_
#define COMPONENTS_SEGMENTATION_PLATFORM_INTERNAL_DATABASE_SIGNAL_KEY_H_
#include <cstdint>
#include <ostream>
#include <string>
#include "base/time/time.h"
namespace segmentation_platform {
// The SignalKey is used for identifying a particular record in the
// SignalDatabase. The format is defined in go/chrome-segmentation-storage-mvp.
//
// It provides functionality to convert to and from a binary format. The format
// for this binary key must never change on a single device, so an internal
// representation for this, SignalKeyInternal, is used.
//
// The SignalKey is not meant to be used by external clients in any way,
// and should be considered as an internal implementation detail of the
// SignalDatabase.
//
// The binary representation of the key does not store any resolution smaller
// than seconds, so any constructed SignalKey is immediately stripped of
// resolutions smaller than 1 second to ensure a SignalKey which has been
// converted to a binary key and back again matches the original SignalKey.
//
// Since the binary representation is not human readable, the struct also
// supports being streamed or by calling ToDebugString(), which will make it be
// presented using this format:
// {kind=..., name_hash=..., range_start=..., range_start=...} which is useful
// for debugging.
//
// The binary representation of a key can be lexicographically compared. The
// fields are in the following order: kind, name_hash, range_start, range_end.
class SignalKey {
public:
enum Kind {
UNKNOWN = 0,
USER_ACTION = 1,
HISTOGRAM_VALUE = 2,
HISTOGRAM_ENUM = 3,
};
SignalKey(Kind kind,
uint64_t name_hash,
base::Time range_start,
base::Time range_end);
SignalKey();
~SignalKey();
// Whether this object has been initialized and does not contain unknown data.
bool IsValid() const;
Kind kind() const { return kind_; }
uint64_t name_hash() const { return name_hash_; }
// The smallest resolution for range_start() and range_end() is 1 second, so
// any fraction of a second is dropped.
const base::Time& range_start() const { return range_start_; }
const base::Time& range_end() const { return range_end_; }
// A machine readable representation of the SignalKey.
// See ToDebugString and operator<< implementation for a human readable
// format.
std::string ToBinary() const;
// Parses a machine readable representation of a SignalKeyInternal into
// a SignalKey. Returns whether the conversion succeeded.
[[nodiscard]] static bool FromBinary(const std::string& input,
SignalKey* output);
// The SignalKey prefix in binary format.
std::string GetPrefixInBinary() const;
// Returns a human readable representation of the SignalKey.
std::string ToDebugString() const;
// Allow SignalKey to be a key in STL containers.
bool operator<(const SignalKey& other) const;
private:
// The type of record this key refers to.
Kind kind_;
// The name of the sample identifier, for example the hash of the histogram
// or user action.
uint64_t name_hash_;
// The first record timestamp this key refers to.
base::Time range_start_;
// The latest record timestamp this key refers to.
base::Time range_end_;
};
std::ostream& operator<<(std::ostream& os, const SignalKey& key);
} // namespace segmentation_platform
#endif // COMPONENTS_SEGMENTATION_PLATFORM_INTERNAL_DATABASE_SIGNAL_KEY_H_
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