/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef TRRService_h_
#define TRRService_h_

#include "mozilla/DataMutex.h"
#include "nsHostResolver.h"
#include "nsIObserver.h"
#include "nsITimer.h"
#include "nsWeakReference.h"
#include "TRRServiceBase.h"
#include "nsICaptivePortalService.h"
#include "nsTHashSet.h"
#include "TRR.h"

class nsDNSService;
class nsIPrefBranch;
class nsINetworkLinkService;
class nsIObserverService;

namespace mozilla {
namespace net {

class TRRServiceChild;
class TRRServiceParent;

class TRRService : public TRRServiceBase,
                   public nsIObserver,
                   public nsSupportsWeakReference,
                   public AHostResolver,
                   public SingleWriterLockOwner {
 public:
  NS_DECL_ISUPPORTS_INHERITED
  NS_DECL_NSIOBSERVER
  NS_DECL_NSIPROXYCONFIGCHANGEDCALLBACK

  TRRService();
  static TRRService* Get();

  bool OnWritingThread() const override { return NS_IsMainThread(); }

  nsresult Init();
  nsresult Start();
  bool Enabled(nsIRequest::TRRMode aRequestMode = nsIRequest::TRR_DEFAULT_MODE);
  bool IsConfirmed() { return mConfirmation.State() == CONFIRM_OK; }
  uint32_t ConfirmationState() { return mConfirmation.State(); }

  bool DisableIPv6() { return mDisableIPv6; }
  void GetURI(nsACString& result) override;
  nsresult GetCredentials(nsCString& result);
  uint32_t GetRequestTimeout();
  void RetryTRRConfirm();

  LookupStatus CompleteLookup(nsHostRecord*, nsresult, mozilla::net::AddrInfo*,
                              bool pb, const nsACString& aOriginSuffix,
                              TRRSkippedReason aReason,
                              TRR* aTrrRequest) override;
  LookupStatus CompleteLookupByType(nsHostRecord*, nsresult,
                                    mozilla::net::TypeRecordResultType&,
                                    uint32_t, bool pb) override;
  void AddToBlocklist(const nsACString& host, const nsACString& originSuffix,
                      bool privateBrowsing, bool aParentsToo);
  bool IsTemporarilyBlocked(const nsACString& aHost,
                            const nsACString& aOriginSuffix,
                            bool aPrivateBrowsing, bool aParentsToo);
  bool IsExcludedFromTRR(const nsACString& aHost);

  bool MaybeBootstrap(const nsACString& possible, nsACString& result);
  void RecordTRRStatus(TRR* aTrrRequest);
  bool ParentalControlEnabled() const { return mParentalControlEnabled; }

  nsresult DispatchTRRRequest(TRR* aTrrRequest);
  already_AddRefed<nsIThread> TRRThread();
  bool IsOnTRRThread();

  bool IsUsingAutoDetectedURL() { return mURISetByDetection; }

  void SetHeuristicDetectionResult(TRRSkippedReason aValue) {
    mHeuristicDetectionValue = aValue;
  }
  TRRSkippedReason GetHeuristicDetectionResult() {
    return mHeuristicDetectionValue;
  }

  nsresult LastConfirmationStatus() {
    return mConfirmation.LastConfirmationStatus();
  }
  TRRSkippedReason LastConfirmationSkipReason() {
    return mConfirmation.LastConfirmationSkipReason();
  }

  // Returns a reference to a static string identifying the current DoH server
  // If the DoH server is not one of the built-in ones it will return "(other)"
  static const nsCString& ProviderKey();
  static void SetProviderDomain(const nsACString& aTRRDomain);
  // Only called when TRR mode changed.
  static void SetCurrentTRRMode(nsIDNSService::ResolverMode aMode);

  void InitTRRConnectionInfo() override;

  void DontUseTRRThread() { mDontUseTRRThread = true; }

 private:
  virtual ~TRRService();

  friend class TRRServiceChild;
  friend class TRRServiceParent;
  static void AddObserver(nsIObserver* aObserver,
                          nsIObserverService* aObserverService = nullptr);
  static bool CheckCaptivePortalIsPassed();
  static bool GetParentalControlEnabledInternal();
  static bool CheckPlatformDNSStatus(nsINetworkLinkService* aLinkService);

  nsresult ReadPrefs(const char* name);
  void GetPrefBranch(nsIPrefBranch** result);
  friend class ::nsDNSService;
  void SetDetectedTrrURI(const nsACString& aURI);

  bool IsDomainBlocked(const nsACString& aHost, const nsACString& aOriginSuffix,
                       bool aPrivateBrowsing);
  bool IsExcludedFromTRR_unlocked(const nsACString& aHost);

  void RebuildSuffixList(nsTArray<nsCString>&& aSuffixList);

  nsresult DispatchTRRRequestInternal(TRR* aTrrRequest, bool aWithLock);
  already_AddRefed<nsIThread> TRRThread_locked();
  already_AddRefed<nsIThread> MainThreadOrTRRThread(bool aWithLock = true);

  // This method will process the URI and try to set mPrivateURI to that value.
  // Will return true if performed the change (if the value was different)
  // or false if mPrivateURI already had that value.
  bool MaybeSetPrivateURI(const nsACString& aURI) override;
  void ClearEntireCache();

  virtual void ReadEtcHostsFile() override;
  void AddEtcHosts(const nsTArray<nsCString>&);

  bool mInitialized{false};
  MutexSingleWriter mLock;

  nsCString mPrivateCred;  // main thread only
  nsCString mConfirmationNS MOZ_GUARDED_BY(mLock){"example.com"_ns};
  nsCString mBootstrapAddr MOZ_GUARDED_BY(mLock);

  Atomic<bool, Relaxed> mCaptiveIsPassed{
      false};  // set when captive portal check is passed
  Atomic<bool, Relaxed> mDisableIPv6;  // don't even try
  Atomic<bool, Relaxed> mShutdown{false};
  Atomic<bool, Relaxed> mDontUseTRRThread{false};

  // TRR Blocklist storage
  // mTRRBLStorage is only modified on the main thread, but we query whether it
  // is initialized or not off the main thread as well. Therefore we need to
  // lock while creating it and while accessing it off the main thread.
  DataMutex<nsTHashMap<nsCStringHashKey, int32_t>> mTRRBLStorage{
      "DataMutex::TRRBlocklist"};

  // A set of domains that we should not use TRR for.
  nsTHashSet<nsCString> mExcludedDomains MOZ_GUARDED_BY(mLock);
  nsTHashSet<nsCString> mDNSSuffixDomains MOZ_GUARDED_BY(mLock);
  nsTHashSet<nsCString> mEtcHostsDomains MOZ_GUARDED_BY(mLock);

  // The result of the TRR heuristic detection
  TRRSkippedReason mHeuristicDetectionValue = nsITRRSkipReason::TRR_UNSET;

  enum class ConfirmationEvent {
    Init,
    PrefChange,
    ConfirmationRetry,
    FailedLookups,
    RetryTRR,
    URIChange,
    CaptivePortalConnectivity,
    NetworkUp,
    ConfirmOK,
    ConfirmFail,
  };

  //                            (FailedLookups/RetryTRR/URIChange/NetworkUp)
  //                                    +---------------------------+
  // +-----------+                      |                           |
  // |   (Init)  |               +------v---------+               +-+--+
  // |           | TRR turned on |                | (ConfirmOK)   |    |
  // |    OFF    +--------------->     TRY-OK     +---------------> OK |
  // |           |  (PrefChange) |                |               |    |
  // +-----^-----+               +^-^----+--------+               +-^--+
  //       |    (PrefChange/CP)   | |    |                          |
  //   TRR +   +------------------+ |    |                          |
  //   off |   |               +----+    |(ConfirmFail)             |(ConfirmOK)
  // (Pref)|   |               |         |                          |
  // +---------+-+             |         |                          |
  // |           |    (CPConn) | +-------v--------+               +-+---------+
  // | ANY-STATE |  (NetworkUp)| |                |  timer        |           |
  // |           |  (URIChange)+-+      FAIL      +--------------->  TRY-FAIL |
  // +-----+-----+               |                | (Confirmation |           |
  //       |                     +------^---------+  Retry)       +------+----+
  //       | (PrefChange)               |                                |
  //       | TRR_ONLY mode or           +--------------------------------+
  //       | confirmationNS = skip                (ConfirmFail)
  // +-----v-----+
  // |           |
  // |  DISABLED |
  // |           |
  // +-----------+
  //
  enum ConfirmationState {
    CONFIRM_OFF = 0,
    CONFIRM_TRYING_OK = 1,
    CONFIRM_OK = 2,
    CONFIRM_FAILED = 3,
    CONFIRM_TRYING_FAILED = 4,
    CONFIRM_DISABLED = 5,
  };

  class ConfirmationContext final : public nsITimerCallback, public nsINamed {
    NS_DECL_ISUPPORTS_INHERITED
    NS_DECL_NSITIMERCALLBACK
    NS_DECL_NSINAMED

   private:
    static const size_t RESULTS_SIZE = 32;

    RefPtr<TRR> mTask;
    nsCOMPtr<nsITimer> mTimer;
    uint32_t mRetryInterval = 125;  // milliseconds until retry
    // The number of TRR requests that failed in a row.
    Atomic<uint32_t, Relaxed> mTRRFailures{0};

    // This buffer holds consecutive TRR failures reported by calling
    // RecordTRRStatus(). It is only meant for reporting event telemetry.
    char mFailureReasons[RESULTS_SIZE] = {0};

    // The number of confirmation retries.
    uint32_t mAttemptCount = 0;

    // The results of past confirmation attempts.
    // This is circular buffer ending at mAttemptCount.
    char mResults[RESULTS_SIZE] = {0};

    // Time when first confirmation started. Needed so we can
    // record the time from start to confirmed.
    TimeStamp mFirstRequestTime;
    // The network ID at the start of the last confirmation attempt
    nsCString mNetworkId;
    // Captive portal status at the time of recording.
    int32_t mCaptivePortalStatus = nsICaptivePortalService::UNKNOWN;

    // The reason the confirmation context changed.
    nsCString mContextChangeReason;

    // What triggered the confirmation
    nsCString mTrigger;

    // String representation of consecutive failed lookups that triggered
    // confirmation.
    nsCString mFailedLookups;

    Atomic<TRRSkippedReason, Relaxed> mLastConfirmationSkipReason{
        nsITRRSkipReason::TRR_UNSET};
    Atomic<nsresult, Relaxed> mLastConfirmationStatus{NS_OK};

    void SetState(enum ConfirmationState aNewState);

   public:
    // Called when a confirmation completes successfully or when the
    // confirmation context changes.
    void RecordEvent(const char* aReason, const MutexSingleWriterAutoLock&);

    // Called when a confirmation request is completed. The status is recorded
    // in the results.
    void RequestCompleted(nsresult aLookupStatus, nsresult aChannelStatus);

    enum ConfirmationState State() { return mState; }

    void CompleteConfirmation(nsresult aStatus, TRR* aTrrRequest);

    void RecordTRRStatus(TRR* aTrrRequest);

    // Returns true when handling the event caused a new confirmation task to be
    // dispatched.
    bool HandleEvent(ConfirmationEvent aEvent);
    bool HandleEvent(ConfirmationEvent aEvent,
                     const MutexSingleWriterAutoLock&);

    void SetCaptivePortalStatus(int32_t aStatus) {
      mCaptivePortalStatus = aStatus;
    }

    TRRSkippedReason LastConfirmationSkipReason() {
      return mLastConfirmationSkipReason;
    }
    nsresult LastConfirmationStatus() { return mLastConfirmationStatus; }

    uintptr_t TaskAddr() { return uintptr_t(mTask.get()); }

   private:
    // Since the ConfirmationContext is embedded in the TRRService object
    // we can easily get a pointer to the TRRService. ConfirmationContext
    // delegates AddRef/Release calls to the owning object since they are
    // guaranteed to have the same lifetime.
    TRRService* OwningObject() {
      return reinterpret_cast<TRRService*>(
          reinterpret_cast<uint8_t*>(this) -
          offsetof(TRRService, mConfirmation) -
          offsetof(ConfirmationWrapper, mConfirmation));
    }

    Atomic<enum ConfirmationState, Relaxed> mState{CONFIRM_OFF};

    // TRRService needs to be a friend class because it needs to access the
    // destructor.
    friend class TRRService;
    ~ConfirmationContext() = default;
  };

  // Because TRRService needs to be a friend class to ConfirmationContext that
  // means it can access member variables. In order to properly separate logic
  // and prevent direct access to its member variables we embed it in a wrapper
  // class.
  class ConfirmationWrapper {
   public:
    // Called when a confirmation completes successfully or when the
    // confirmation context changes.
    void RecordEvent(const char* aReason,
                     const MutexSingleWriterAutoLock& aLock) {
      mConfirmation.RecordEvent(aReason, aLock);
    }

    // Called when a confirmation request is completed. The status is recorded
    // in the results.
    void RequestCompleted(nsresult aLookupStatus, nsresult aChannelStatus) {
      mConfirmation.RequestCompleted(aLookupStatus, aChannelStatus);
    }

    enum ConfirmationState State() { return mConfirmation.State(); }

    void CompleteConfirmation(nsresult aStatus, TRR* aTrrRequest) {
      mConfirmation.CompleteConfirmation(aStatus, aTrrRequest);
    }

    void RecordTRRStatus(TRR* aTrrRequest) {
      mConfirmation.RecordTRRStatus(aTrrRequest);
    }

    bool HandleEvent(ConfirmationEvent aEvent) {
      return mConfirmation.HandleEvent(aEvent);
    }

    bool HandleEvent(ConfirmationEvent aEvent,
                     const MutexSingleWriterAutoLock& lock) {
      return mConfirmation.HandleEvent(aEvent, lock);
    }

    void SetCaptivePortalStatus(int32_t aStatus) {
      mConfirmation.SetCaptivePortalStatus(aStatus);
    }

    TRRSkippedReason LastConfirmationSkipReason() {
      return mConfirmation.LastConfirmationSkipReason();
    }
    nsresult LastConfirmationStatus() {
      return mConfirmation.LastConfirmationStatus();
    }

   private:
    friend TRRService* ConfirmationContext::OwningObject();
    ConfirmationContext mConfirmation;
  };

  ConfirmationWrapper mConfirmation;

  bool mParentalControlEnabled{false};
  // This is used to track whether a confirmation was triggered by a URI change,
  // so we don't trigger another one just because other prefs have changed.
  bool mConfirmationTriggered{false};
  nsCOMPtr<nsINetworkLinkService> mLinkService;
};

}  // namespace net
}  // namespace mozilla

#endif  // TRRService_h_