#pragma once

#include <QByteArray>
#include <QElapsedTimer>
#include <QJsonObject>
#include <QObject>
#include <QString>
#include <QTimer>

// One HA entity (docs/DESIGN.md, D23): the base class of every entity type.
// It describes the entity for discovery, holds its current state, throttles
// state changes (SEN-14) and knows whether it has a value (SEN-15: without
// one, HA shows it as unavailable).
//
// It knows nothing about MQTT: HaDevice publishes what it reports.
class HaEntity : public QObject {
  Q_OBJECT
 public:
  struct Description {
    // Topic level and suffix of the unique id, e.g. "uptime".
    QString id;
    // Name shown in HA, e.g. "Uptime".
    QString name;
    // Optional: HA device class, unit, entity category ("diagnostic", …).
    QString deviceClass;
    QString unit;
    QString category;
    // Minimum time between two published states (SEN-14).
    int throttleMs = 1000;
  };

  // `platform`: the HA entity type, e.g. "sensor".
  HaEntity(QString platform, Description description,
           QObject* parent = nullptr);

  const QString& platform() const { return m_platform; }
  const Description& description() const { return m_description; }

  // The component for device-based discovery; topics are relative to the
  // device's base topic "~". `uniqueIdPrefix`: e.g.
  // "frameassistant_<device id>".
  virtual QJsonObject discoveryComponent(const QString& uniqueIdPrefix) const;

  // Topics relative to the device's base topic.
  QString stateTopic() const;
  QString availabilityTopic() const;

  bool hasValue() const { return m_hasValue; }
  // The state as published; empty without a value.
  QByteArray state() const { return m_hasValue ? m_state : QByteArray(); }

 signals:
  // A new state to publish, at most once per throttle interval (the newest
  // one wins). Emitted before availabilityChanged(true) for a first value.
  void stateChanged(const QByteArray& state);
  void availabilityChanged(bool available);

 protected:
  // For the concrete types: set or clear the state.
  void updateState(const QByteArray& state);
  void clearState();

 private:
  void emitState();

  const QString m_platform;
  const Description m_description;
  QByteArray m_state;
  bool m_hasValue = false;
  // The state last emitted, and when.
  QByteArray m_emittedState;
  QElapsedTimer m_sinceEmit;
  QTimer m_throttle;
};