// Copyright 2016 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.

#pragma once

#include <memory>
#include <mutex>
#include <string>
#include <thread>
#include <utility>
#include <vector>

#include "Common/CommonTypes.h"
#include "Common/Event.h"
#include "Common/FifoQueue.h"
#include "Common/Flag.h"

typedef void CURL;

// Utilities for analytics reporting in Dolphin. This reporting is designed to
// provide anonymous data about how well Dolphin performs in the wild. It also
// allows developers to declare trace points in Dolphin's source code and get
// information about what games trigger these conditions.
//
// This unfortunately implements Yet Another Serialization Framework within
// Dolphin. We cannot really use ChunkFile because there is precedents for
// backwards incompatible changes in the ChunkFile format. We could use
// something like protobuf but setting up external dependencies is Hard™.
//
// Example usage:
//
// static auto s_reporter = std::make_unique<AnalyticsReporter>();
// if (user_gave_consent)
// {
//     s_reporter->SetBackend(std::make_unique<MyReportingBackend>());
// }
// s_reporter->Send(s_reporter->Builder()
//     .AddData("my_key", 42)
//     .AddData("other_key", false));

namespace Common
{

// Generic interface for an analytics reporting backends. The main
// implementation used in Dolphin can be found in Core/Analytics.h.
class AnalyticsReportingBackend
{
public:
	virtual ~AnalyticsReportingBackend() {}

	// Called from the AnalyticsReporter backend thread.
	virtual void Send(std::string report) = 0;
};

// Builder object for an analytics report.
class AnalyticsReportBuilder
{
public:
	AnalyticsReportBuilder();
	~AnalyticsReportBuilder() = default;

	AnalyticsReportBuilder(const AnalyticsReportBuilder& other)
	{
		*this = other;
	}

	AnalyticsReportBuilder(AnalyticsReportBuilder&& other)
	{
		std::lock_guard<std::mutex> lk(other.m_lock);
		m_report = std::move(other.m_report);
	}

	const AnalyticsReportBuilder& operator=(const AnalyticsReportBuilder& other)
	{
		if (this != &other)
		{
			std::lock_guard<std::mutex> lk(m_lock);
			std::lock_guard<std::mutex> lk2(other.m_lock);
			m_report = other.m_report;
		}
		return *this;
	}

	// Append another builder to this one.
	AnalyticsReportBuilder& AddBuilder(const AnalyticsReportBuilder& other)
	{
		// Get before locking the object to avoid deadlocks with this += this.
		std::string other_report = other.Get();
		std::lock_guard<std::mutex> lk(m_lock);
		m_report += other_report;
		return *this;
	}

	template <typename T>
	AnalyticsReportBuilder& AddData(const std::string& key, const T& value)
	{
		std::lock_guard<std::mutex> lk(m_lock);
		AppendSerializedValue(&m_report, key);
		AppendSerializedValue(&m_report, value);
		return *this;
	}

	std::string Get() const
	{
		std::lock_guard<std::mutex> lk(m_lock);
		return m_report;
	}

	// More efficient version of Get().
	std::string Consume()
	{
		std::lock_guard<std::mutex> lk(m_lock);
		return std::move(m_report);
	}

protected:
	static void AppendSerializedValue(std::string* report, const std::string& v);
	static void AppendSerializedValue(std::string* report, const char* v);
	static void AppendSerializedValue(std::string* report, bool v);
	static void AppendSerializedValue(std::string* report, u64 v);
	static void AppendSerializedValue(std::string* report, s64 v);
	static void AppendSerializedValue(std::string* report, u32 v);
	static void AppendSerializedValue(std::string* report, s32 v);
	static void AppendSerializedValue(std::string* report, float v);

	// Should really be a std::shared_mutex, unfortunately that's C++17 only.
	mutable std::mutex m_lock;
	std::string m_report;
};

class AnalyticsReporter
{
public:
	AnalyticsReporter();
	~AnalyticsReporter();

	// Sets a reporting backend and enables sending reports. Do not set a remote
	// backend without user consent.
	void SetBackend(std::unique_ptr<AnalyticsReportingBackend> backend)
	{
		m_backend = std::move(backend);
		m_reporter_event.Set();  // In case reports are waiting queued.
	}

	// Gets the base report builder which is closed for each subsequent report
	// being sent. DO NOT use this builder to send a report. Only use it to add
	// new fields that should be globally available.
	AnalyticsReportBuilder& BaseBuilder() { return m_base_builder; }

	// Gets a cloned builder that can be used to send a report.
	AnalyticsReportBuilder Builder() const { return m_base_builder; }

	// Enqueues a report for sending. Consumes the report builder.
	void Send(AnalyticsReportBuilder&& report);

	// For convenience.
	void Send(AnalyticsReportBuilder& report) { Send(std::move(report)); }

protected:
	void ThreadProc();

	std::shared_ptr<AnalyticsReportingBackend> m_backend;
	AnalyticsReportBuilder m_base_builder;

	std::thread m_reporter_thread;
	Common::Event m_reporter_event;
	Common::Flag m_reporter_stop_request;
	FifoQueue<std::string> m_reports_queue;
};

// Analytics backend to be used for debugging purpose, which dumps reports to
// stdout.
class StdoutAnalyticsBackend : public AnalyticsReportingBackend
{
public:
	void Send(std::string report) override;
};

// Analytics backend that POSTs data to a remote HTTP(s) endpoint. WARNING:
// remember to get explicit user consent before using.
class HttpAnalyticsBackend : public AnalyticsReportingBackend
{
public:
	HttpAnalyticsBackend(const std::string& endpoint);
	~HttpAnalyticsBackend() override;

	void Send(std::string report) override;

protected:
	CURL* m_curl = nullptr;
};

}  // namespace Common
