// processWriteIntentError tries to push the conflicting
// transaction(s) responsible for the given WriteIntentError, and to
// resolve those intents if possible. Returns a new error to be used
// in place of the original.
//
// The returned error may be a copy of the original WriteIntentError,
// with or without the Resolved flag set, which governs the client's
// retry behavior (if the transaction is pushed, the Resolved flag is
// set to tell the client to retry immediately; otherwise it is false
// to cause the client to back off).
func (ir *intentResolver) processWriteIntentError(ctx context.Context,
	wiPErr *roachpb.Error, args roachpb.Request, h roachpb.Header,
	pushType roachpb.PushTxnType) *roachpb.Error {
	wiErr, ok := wiPErr.GetDetail().(*roachpb.WriteIntentError)
	if !ok {
		return roachpb.NewErrorf("not a WriteIntentError: %v", wiPErr)
	}

	if log.V(6) {
		log.Infof(ctx, "resolving write intent %s", wiErr)
	}

	method := args.Method()
	readOnly := roachpb.IsReadOnly(args) // TODO(tschottdorf): pass as param

	resolveIntents, pushErr := ir.maybePushTransactions(ctx, wiErr.Intents, h, pushType, false)

	if resErr := ir.resolveIntents(ctx, resolveIntents,
		false /* !wait */, pushType == roachpb.PUSH_ABORT /* poison */); resErr != nil {
		// When resolving without waiting, errors should not
		// usually be returned here, although there are some cases
		// when they may be (especially when a test cluster is in
		// the process of shutting down).
		log.Warningf(ctx, "asynchronous resolveIntents failed: %s", resErr)
	}

	if pushErr != nil {
		if log.V(1) {
			log.Infof(ctx, "on %s: %s", method, pushErr)
		}

		if _, isExpected := pushErr.GetDetail().(*roachpb.TransactionPushError); !isExpected {
			// If an unexpected error occurred, make sure it bubbles up to the
			// client. Examples are timeouts and logic errors.
			return pushErr
		}

		// For write/write conflicts within a transaction, propagate the
		// push failure, not the original write intent error. The push
		// failure will instruct the client to restart the transaction
		// with a backoff.
		if h.Txn != nil && h.Txn.ID != nil && !readOnly {
			return pushErr
		}

		// For read/write conflicts, and non-transactional write/write
		// conflicts, return the write intent error which engages
		// backoff/retry (with !Resolved). We don't need to restart the
		// txn, only resend the read with a backoff.
		return wiPErr
	}

	// We pushed all transactions, so tell the client everything's
	// resolved and it can retry immediately.
	wiErr.Resolved = true
	return wiPErr // references wiErr
}

// UpdateForBatch updates the first argument (the header of a request contained
// in a batch) from the second one (the batch header), returning an error when
// inconsistencies are found.
// It is checked that the individual call does not have a UserPriority
// or Txn set that differs from the batch's.
// TODO(tschottdorf): will go with #2143.
func updateForBatch(args roachpb.Request, bHeader roachpb.BatchRequest_Header) error {
	// Disallow transaction, user and priority on individual calls, unless
	// equal.
	aHeader := args.Header()
	if aPrio := aHeader.GetUserPriority(); aPrio != roachpb.Default_RequestHeader_UserPriority && aPrio != bHeader.GetUserPriority() {
		return util.Errorf("conflicting user priority on call in batch")
	}
	aHeader.UserPriority = bHeader.UserPriority
	aHeader.Txn = bHeader.Txn // reqs always take Txn from batch
	return nil
}

// processWriteIntentError tries to push the conflicting
// transaction(s) responsible for the given WriteIntentError, and to
// resolve those intents if possible. Returns a new error to be used
// in place of the original.
//
// The returned error may be a copy of the original WriteIntentError,
// with or without the Resolved flag set, which governs the client's
// retry behavior (if the transaction is pushed, the Resolved flag is
// set to tell the client to retry immediately; otherwise it is false
// to cause the client to back off).
func (ir *intentResolver) processWriteIntentError(ctx context.Context,
	wiErr roachpb.WriteIntentError, r *Replica, args roachpb.Request, h roachpb.Header,
	pushType roachpb.PushTxnType) *roachpb.Error {

	if log.V(6) {
		log.Infoc(ctx, "resolving write intent %s", wiErr)
	}

	method := args.Method()
	readOnly := roachpb.IsReadOnly(args) // TODO(tschottdorf): pass as param

	resolveIntents, pushErr := ir.maybePushTransactions(ctx, wiErr.Intents, h, pushType, false)

	if resErr := ir.resolveIntents(ctx, r, resolveIntents,
		false /* !wait */, true /* poison */); resErr != nil {
		// When resolving without waiting, errors should not
		// usually be returned here, although there are some cases
		// when they may be (especially when a test cluster is in
		// the process of shutting down).
		log.Warningf("asynchronous resolveIntents failed: %s", resErr)
	}

	if pushErr != nil {
		if log.V(1) {
			log.Infoc(ctx, "on %s: %s", method, pushErr)
		}

		// For write/write conflicts within a transaction, propagate the
		// push failure, not the original write intent error. The push
		// failure will instruct the client to restart the transaction
		// with a backoff.
		if h.Txn != nil && h.Txn.ID != nil && !readOnly {
			return pushErr
		}

		// For read/write conflicts, and non-transactional write/write
		// conflicts, return the write intent error which engages
		// backoff/retry (with !Resolved). We don't need to restart the
		// txn, only resend the read with a backoff.
		return roachpb.NewError(&wiErr)
	}

	// We pushed all transactions, so tell the client everything's
	// resolved and it can retry immediately.
	wiErr.Resolved = true
	return roachpb.NewError(&wiErr)
}

// SendWrappedAt is a convenience function which wraps the request in a batch
// and sends it via the provided Sender at the given timestamp. It returns the
// unwrapped response or an error. It's valid to pass a `nil` context;
// context.Background() is used in that case.
func SendWrappedAt(sender Sender, ctx context.Context, ts roachpb.Timestamp, args roachpb.Request) (roachpb.Response, error) {
	if ctx == nil {
		ctx = context.Background()
	}
	ba, unwrap := func(args roachpb.Request) (*roachpb.BatchRequest, func(*roachpb.BatchResponse) roachpb.Response) {
		ba := &roachpb.BatchRequest{}
		ba.Timestamp = ts
		{
			h := args.Header()
			ba.Key, ba.EndKey = h.Key, h.EndKey
			ba.CmdID = h.CmdID
			ba.Replica = h.Replica
			ba.RangeID = h.RangeID
			ba.UserPriority = h.UserPriority
			ba.Txn = h.Txn
			ba.ReadConsistency = h.ReadConsistency
		}
		ba.Add(args)
		return ba, func(br *roachpb.BatchResponse) roachpb.Response {
			unwrappedReply := br.Responses[0].GetInner()
			// The ReplyTxn is propagated from one response to the next request,
			// and we adopt the mechanism that whenever the Txn changes, it needs
			// to be set in the reply, for example to ratchet up the transaction
			// timestamp on writes when necessary.
			// This is internally necessary to sequentially execute the batch,
			// so it makes some sense to take the burden of updating the Txn
			// from TxnCoordSender - it will only need to act on retries/aborts
			// in the future.
			unwrappedReply.Header().Txn = br.Txn
			return unwrappedReply
		}
	}(args)
	br, pErr := sender.Send(ctx, *ba)
	if err := pErr.GoError(); err != nil {
		return nil, err
	}
	return unwrap(br), nil
}